This document provides background information on rotaxanes and their potential applications. It discusses the nomenclature and synthesis strategies for rotaxanes, including statistical, templated, and transition metal mediated approaches. Applications described include use as molecular switches and machines, in nanorecording, and for asymmetric catalysis. One example highlighted is a helical peptide-based rotaxane that acts as a switch, changing conformations between recognition sites upon changing solvents. Rotaxanes offer possibilities for controlled molecular motion and transferring chirality to achieve enantioselective reactions.
Hindered Rotation of Dihydrogen on Synthesized Metal OxidesGeorge Rouvelas
This thesis discusses the synthesis of magnesium oxide and zinc oxide nanoparticles and examines the rotational eigenstates of molecular hydrogen interacting with metal oxide surfaces. Single morphology nanocubes of magnesium oxide were consistently produced. Zinc oxide synthesis resulted in a mixture of tetrapods, kites, and hexagonal pillars. A MATLAB program was used to calculate the rotational energies of hydrogen and deuterium molecules in the presence of an anisotropic hindering potential, meant to model interactions with a metal oxide surface. An increase in the hindering potential about the azimuthal angle was found to lift the degeneracy of the mj = ±1 states.
Molecular machines: Delving into the world of Supramolecualr ChemistryShreesha Bhat
This document provides an overview of molecular machines and supramolecular chemistry. It discusses how molecular machines are discrete assemblies designed to perform mechanical movements in response to stimuli. Natural molecular machines like biomotors are mentioned. The document also covers artificial molecular machines and how supramolecular chemistry utilizes non-covalent interactions and mechanical bonds to create interlocked structures like catenanes and rotaxanes. Efficient synthesis methods like template effects and click chemistry are summarized. Applications of molecular machines in drug delivery through molecular shuttling and switching are also highlighted.
Simple and Effective Method of the Synthesis of Nanosized Fe2O 3particlesIOSR Journals
Abstract: Nanosized Iron oxide is prepared by using precipitation method from iron nitrate and liquid ammonia. Thermal analysis shows that synthesized iron oxide shows some weight loss and oxide undergoing decomposition, dehydration or any physical change from TGA curve we observe that Iron oxide shows stable weight loss above 4000C. In DTA curve also, there is exothermic and endothermic peak. Which shows phase transition, solid state reaction or any chemical reaction occurred during heating treatment. Morphology is observed by scanning electron microscopy (SEM) shows particles are nanosized. Further morphology observation by Transmission Electron Microscopy (TEM) revels that Iron Oxide has the corundum (Al2O3) structure. Magnetic measurements shows that iron oxide has five unpaired electron and strongly paramagnetic character.
A study the effect of zr o3 on the electrical and mechanical propertiesAlexander Decker
This document summarizes a study on the effect of adding ZrO3 on the electrical and mechanical properties of PMMA-Cr2O3 polymer composites. The study found that adding ZrO3 increased the electrical conductivity and ultrasound velocity of the composites. It also increased the relaxation amplitude, relaxation time, and bulk modulus while decreasing the molar conductivity, disintegration degree, and compressibility. The changes in properties are due to interactions between the polymer matrix and ZrO3 filler on the molecular level that affect ion motion and polymer chain structure. The addition of ZrO3 thus improves both the electrical and mechanical properties of the PMMA-Cr2O3 composite for applications.
Gel-filtration chromatography, also known as size-exclusion chromatography, separates molecules based on their size. During the process, a resin with pores is selected that allows smaller molecules to pass through while excluding larger ones, causing the larger molecules to elute first. The ability to separate molecules by size depends on the highly porous structure of the gel, which presents both included and excluded volumes. Molecules' partition coefficients describe their affinity for these volumes, determining whether they pass through pores or around beads to elute earlier or later.
This document describes a study that uses an iron-squarate based 3D metal-organic framework (FeSq-MOF) as a heterogeneous catalyst for transforming tetrazines into oxadiazole derivatives at room temperature. The FeSq-MOF was found to efficiently catalyze the reaction of various tetrazine substrates to their corresponding oxadiazole products in yields ranging from 53-97% within 1-24 hours, depending on the substrate. Testing confirmed the heterogeneous nature of the catalysis and that no iron leaching occurred. The FeSq-MOF could be recycled for multiple reaction cycles with only a moderate decrease in yield after the third cycle. This new catalytic method provides a simple, mild, and
This dissertation investigates luminescence properties of rare earth and transition metal ion doped fluoride crystals for applications in mercury-free fluorescent lamps. Single crystals of LiCaAlF6 doped with Tm3+ and Mn2+ were grown and their spectroscopic properties studied using synchrotron radiation and laser excitation. Fine structure was observed in emission spectra of Tm3+ due to crystal field splitting. Absorption bands associated with 3d → 4s transitions of Mn2+ were analyzed in various fluoride hosts. This work presents the first systematic analysis of Mn2+ in fluorides using synchrotron radiation.
Preparation and Structural Properties of Aluminium Substituted Lithium Nano F...IOSR Journals
This document describes the preparation and structural properties of aluminum-substituted lithium nanoferrites synthesized using the citrate gel auto combustion method. Nanoferrites with the general formula Li0.5AlxFe2.5-xO4 (where x=0.0, 0.2, 0.4, 0.6, 0.8, 1.0) were prepared at low temperature (1800C). X-ray diffraction analysis confirmed the formation of a single-phase cubic spinel structure with particle sizes ranging from 13 to 27 nm. Lattice parameter, density, and porosity were calculated from the XRD data and showed decreases with increasing aluminum content. Scanning electron microscopy revealed the formation of
Hindered Rotation of Dihydrogen on Synthesized Metal OxidesGeorge Rouvelas
This thesis discusses the synthesis of magnesium oxide and zinc oxide nanoparticles and examines the rotational eigenstates of molecular hydrogen interacting with metal oxide surfaces. Single morphology nanocubes of magnesium oxide were consistently produced. Zinc oxide synthesis resulted in a mixture of tetrapods, kites, and hexagonal pillars. A MATLAB program was used to calculate the rotational energies of hydrogen and deuterium molecules in the presence of an anisotropic hindering potential, meant to model interactions with a metal oxide surface. An increase in the hindering potential about the azimuthal angle was found to lift the degeneracy of the mj = ±1 states.
Molecular machines: Delving into the world of Supramolecualr ChemistryShreesha Bhat
This document provides an overview of molecular machines and supramolecular chemistry. It discusses how molecular machines are discrete assemblies designed to perform mechanical movements in response to stimuli. Natural molecular machines like biomotors are mentioned. The document also covers artificial molecular machines and how supramolecular chemistry utilizes non-covalent interactions and mechanical bonds to create interlocked structures like catenanes and rotaxanes. Efficient synthesis methods like template effects and click chemistry are summarized. Applications of molecular machines in drug delivery through molecular shuttling and switching are also highlighted.
Simple and Effective Method of the Synthesis of Nanosized Fe2O 3particlesIOSR Journals
Abstract: Nanosized Iron oxide is prepared by using precipitation method from iron nitrate and liquid ammonia. Thermal analysis shows that synthesized iron oxide shows some weight loss and oxide undergoing decomposition, dehydration or any physical change from TGA curve we observe that Iron oxide shows stable weight loss above 4000C. In DTA curve also, there is exothermic and endothermic peak. Which shows phase transition, solid state reaction or any chemical reaction occurred during heating treatment. Morphology is observed by scanning electron microscopy (SEM) shows particles are nanosized. Further morphology observation by Transmission Electron Microscopy (TEM) revels that Iron Oxide has the corundum (Al2O3) structure. Magnetic measurements shows that iron oxide has five unpaired electron and strongly paramagnetic character.
A study the effect of zr o3 on the electrical and mechanical propertiesAlexander Decker
This document summarizes a study on the effect of adding ZrO3 on the electrical and mechanical properties of PMMA-Cr2O3 polymer composites. The study found that adding ZrO3 increased the electrical conductivity and ultrasound velocity of the composites. It also increased the relaxation amplitude, relaxation time, and bulk modulus while decreasing the molar conductivity, disintegration degree, and compressibility. The changes in properties are due to interactions between the polymer matrix and ZrO3 filler on the molecular level that affect ion motion and polymer chain structure. The addition of ZrO3 thus improves both the electrical and mechanical properties of the PMMA-Cr2O3 composite for applications.
Gel-filtration chromatography, also known as size-exclusion chromatography, separates molecules based on their size. During the process, a resin with pores is selected that allows smaller molecules to pass through while excluding larger ones, causing the larger molecules to elute first. The ability to separate molecules by size depends on the highly porous structure of the gel, which presents both included and excluded volumes. Molecules' partition coefficients describe their affinity for these volumes, determining whether they pass through pores or around beads to elute earlier or later.
This document describes a study that uses an iron-squarate based 3D metal-organic framework (FeSq-MOF) as a heterogeneous catalyst for transforming tetrazines into oxadiazole derivatives at room temperature. The FeSq-MOF was found to efficiently catalyze the reaction of various tetrazine substrates to their corresponding oxadiazole products in yields ranging from 53-97% within 1-24 hours, depending on the substrate. Testing confirmed the heterogeneous nature of the catalysis and that no iron leaching occurred. The FeSq-MOF could be recycled for multiple reaction cycles with only a moderate decrease in yield after the third cycle. This new catalytic method provides a simple, mild, and
This dissertation investigates luminescence properties of rare earth and transition metal ion doped fluoride crystals for applications in mercury-free fluorescent lamps. Single crystals of LiCaAlF6 doped with Tm3+ and Mn2+ were grown and their spectroscopic properties studied using synchrotron radiation and laser excitation. Fine structure was observed in emission spectra of Tm3+ due to crystal field splitting. Absorption bands associated with 3d → 4s transitions of Mn2+ were analyzed in various fluoride hosts. This work presents the first systematic analysis of Mn2+ in fluorides using synchrotron radiation.
Preparation and Structural Properties of Aluminium Substituted Lithium Nano F...IOSR Journals
This document describes the preparation and structural properties of aluminum-substituted lithium nanoferrites synthesized using the citrate gel auto combustion method. Nanoferrites with the general formula Li0.5AlxFe2.5-xO4 (where x=0.0, 0.2, 0.4, 0.6, 0.8, 1.0) were prepared at low temperature (1800C). X-ray diffraction analysis confirmed the formation of a single-phase cubic spinel structure with particle sizes ranging from 13 to 27 nm. Lattice parameter, density, and porosity were calculated from the XRD data and showed decreases with increasing aluminum content. Scanning electron microscopy revealed the formation of
This document summarizes the mechanochemical synthesis of isoreticular metal-organic frameworks (IRMOFs) and their potential for nitrobenzene sensing. Specifically, it discusses:
1) The liquid-assisted grinding synthesis of IRMOF-1 and halogen-substituted IRMOF-2 frameworks containing chlorine, bromine, or iodine.
2) Characterization of the frameworks by powder X-ray diffraction and scanning electron microscopy, which confirmed their structures.
3) Investigation of the frameworks' fluorescence properties, which revealed IRMOF-1 is a highly sensitive and selective fluorescence quenching agent for nitrobenzene detection.
4) The role of
Magnetic chitosan nanoparticles for removal of cr(vi) from aqueous solutionhbrothers
This document describes research on using magnetic chitosan nanoparticles for removing Cr(VI) from aqueous solutions. The researchers introduced a simple method to prepare magnetic chitosan nanoparticles via co-precipitation and epichlorohydrin cross-linking. Characterization showed the nanoparticles were spherical and around 30 nm in size. Adsorption experiments found Cr(VI) removal was highly dependent on pH, with maximum adsorption of 55.80 mg/g occurring at pH 3. Kinetic data fit a pseudo-second order model and isotherm data fit the Langmuir model well. The magnetic chitosan nanoparticles showed potential for use in wastewater treatment applications to remove Cr(VI).
Growth and Characterization of Morpholium Cadmium Acetoperchlorate Single Cry...IJERA Editor
In the search for novel crystal with promising nonlinear optical properties an attempt is made to grow
morpholium cadmium aceto-perchlorate single crystals. The title compound is synthesized by slow evaporation
technique at room temperature. The powder X-ray diffraction pattern has been recorded and the various planes
of reflections are identified. The transmittance spectrum of the crystal in the UV–Vis region has been obtained.
Using the FTIR spectrum, the vibrational modes of the crystal is analysed and the presence of cadmium in the
crystal is confirmed. Thermogravimetric analysis and differential thermal analysis studies have been done to
assess the thermal stability of the grown crystal. The dielectric measurement for the crystal is carried out in the
range of 50 Hz to 5 MHz for three different temperatures 40ºC, 80ºC and 120ºC to study the electrical nature of
the grown crystal. The nonlinear optical property of the grown crystal is confirmed
The document summarizes research on the synthesis and characterization of a new nonlinear organic single crystal called urea L-asparagine. Key findings include:
1) Urea L-asparagine crystals were grown using a slow evaporation solution method and yielded bright, transparent crystals measuring 11 x 0.7 x 0.3 cm3.
2) Elemental analysis and powder X-ray diffraction confirmed the crystalline nature and stoichiometric composition of the compound.
3) Single crystal X-ray diffraction showed the crystal has an orthorhombic structure with space group P.
4) Optical and vibrational spectroscopy showed the crystal has good transmittance in the visible range
This document discusses photoluminescence studies of Eu3+ doped La0.6Y0.4PO4 phosphor codoped with Tb3+ and Gd3+. The phosphors were prepared by solid state diffusion reaction and characterized using XRD, SEM, and photoluminescence techniques. XRD analysis confirmed the monoclinic crystal structure. SEM images showed irregularly shaped particles ranging from submicron to microns in size. Photoluminescence emission was observed from 530-630 nm under 254 nm excitation. Codoping with Tb3+ and Gd3+ increased the intensity of the 612 nm emission peak from the Eu3+ ions, likely due to a cross relaxation
Size exclusion chromatography, also known as gel filtration chromatography, separates molecules based on their size and molecular weight. Larger molecules pass through the porous beads of the stationary phase more quickly than smaller molecules that can enter the pores. This document discusses the basic principles, history, applications, and factors affecting size exclusion chromatography such as column length and packing. It is commonly used to purify proteins and other biomolecules.
Synthesis and charaterization of la1 x srxmno3 perovskite nanoparticlesMai Trần
In recent times perovskite materials are extensively studied and have attracted much attention because they exhibit interesting the properties, showing potential applications in commercial, technical and biomedical. In Vietnam, perovskite materials be of interest research and applications are strong but with major research direction is to go deep into the electrical properties and the magnetic properties. The Lanthanum Strontium manganite is a perovskite-based crystal-structured ceramic material with the formula of La1-xSrxMnO3, where x describes the doping ratio. It has attracted much attention due to its good magnetic, electrical, and catalytic properties and is becoming an attractive possibility material in several biomedical applications, particularly with nano-size. In industry, this material is commonly used in as a cathode material in commercially produced solid oxide fuel cells. In this thesis, we present the Perovskite nanoparticles La1-xSrxMnO3 were successfully synthesized of the nanosize La1-xSrxMnO3 at x = 0; 0.1; 0.2; 0.3 and 0.4 which prepared by a modified sol-gel method. Structure and magnetic properties of them were systematically investigated in dependence on doped Sr ratio x. The structure was investigated by XRD and show slightly changed but magnetic properties varied strongly with changing the doping ratio x. Magnetic properties of samples were studied by Vibrating Sample Mode of Physical Properties Measurement System show at the room temperature, the samples show superparamagnetic properties with high saturated magnetization MS of 57 emu/g which strongly dependents on the doped Sr ratio x.
The document discusses barium perovskites as potential humidity sensing materials. Three key points:
1) Samples of BaMO3 (M=Ti, Zr, Hf, Sn) were prepared via wet chemical synthesis or solid state reaction and tested for their electrical response to humidity.
2) All samples showed an increase in capacitance and conductivity with increasing humidity, indicating interaction between water vapor and the crystal surfaces. Sensitivity was highest at low frequencies and decreased with increasing humidity.
3) Time response to humidity changes was typically 10-100 seconds for intermediate humidity levels. Response time was influenced by the amount of mesopores in the material, with shorter response times associated with less mesoporous
Characterization of Clay/Chitosan Nanocomposites and their Use for Adsorption...Editor IJCATR
The document describes a study that prepared nanocomposite films from chitosan biopolymer and montmorillonite nanoclay (MMT) at various weight percentages. XRD and FTIR were used to characterize the structural properties of the nanocomposites and showed an intercalated structure formed. The nanocomposites were then used to adsorb Mn(II) ions from aqueous solution. Parameters like pH, contact time, adsorption mass, initial concentration, and temperature were investigated. Adsorption isotherms and kinetics as well as thermodynamic properties of the process were analyzed.
The recent spike in solar cell failures experienced by TIR Solar Energy has been attributed to inconsistent titanium dioxide particles used in solar cell production. To institute proper quality controls of this material and to minimize further failures, the Quality Control department has proposed purchasing a Rigaku MiniFlex600 Benchtop XRD Instrument for just under $95,000. An X-ray diffractometer would allow them to characterize the crystal phase of the titanium dioxide nanoparticles, determining whether they have the desired anatase phase or the less effective rutile phase. This testing is needed to improve quality control over the production process and prevent further costly defects.
Super Critical Fluid Chromatography was first proposed in 1958 and involves using fluids above their critical temperature and pressure to separate mixtures. Carbon dioxide is commonly used as the mobile phase due to its stability and ability to dissolve large molecules. SFC provides faster analysis than HPLC and can analyze non-volatile compounds without derivatization like GC. It finds applications in pharmaceuticals, natural products, lipids, pesticides and more due to its mild conditions and speed.
Structural and magnetic properties on F-doped LiVO2 with two-dimensional tria...Yang Li
The layered oxide LiVO2 recently has received more attention due to its interesting structural and magnetic behaviors involving the two-dimensional magnetic frustration in these systems. We synthesized a series of F-doped LiVO2 samples, and reported the F-doping effect on the structure and transition temperature Tt. The samples LiVO2-xFx (x=0, 0.1, 0.2 and 0.3) were characterized by X-ray diffraction, scanning electron microscope (SEM), differential scanning calorimetry (DSC), magnetic susceptibility and specific heat measurement. The structural analysis shows that with increasing x, the ratio of lattice parameter c/a increasing, i.e. in the a-b plane the lattice is compressed while in the c-axis direction the lattice expands. The DSC measurements show that a first-order phase transition happens at around 500 K, and the thermal hysteresis around phase transition temperature Tt increases with increasing x. Substitution of O with F ions results in a change of two dimensional characteristics and the distortion of the VO6 block in structure, which significantly influence the magnetic ordering transition temperature Tt.
The document summarizes four new heterometallic molecular aggregates containing cobalt and lanthanide metals. Compounds 1 and 2 have the formula [(CoII)3(CoIII)2Ln3(μ3-OH)5(O2CtBu)12(L)2]·2H2O and feature distorted cubane cores, while compounds 3 and 4 have the formula [(CoIII)3Ln3(μ3-OH)4(O2CtBu)6(L)3](NO3)2·2CH3CN·2H2O and display hemicubane-like metallic cores. Magnetic studies show significant magnetic entropy changes for 1 and 3, and single molecule magnetic
This document describes a lattice model for simulating the nematic-isotropic phase transition in liquid crystals. The model uses rod-shaped particles arranged on a simple cubic lattice. An original computer code was written to implement the Monte Carlo method and Metropolis algorithm. The code calculates properties like energy, heat capacity, and order parameter during the phase transition. Simulation results agree well with literature, validating the computer code. The code provides a basis for extending the model to handle helicoidal particles and study chiral nematic liquid crystal phases exhibited by such particles.
Role of αc–relaxation in high-temperature polymer deformation.
Proceedings of the American Society for Composites 2009-Twenty-Fourth Technical ConferenceWith the Canadian Association for Composite Structures and Materials (Joint Canadian-American International Conference), September 15-17, Newark, DE
Rotaxanes are supramolecular assemblies consisting of a macrocyclic molecule threaded onto a linear molecule capped with bulky stoppers. They can be synthesized through template-directed methods like clipping, threading, and snapping. Switchable rotaxanes have applications in logic gates and memory due to their ability to shuttle between binding stations. Rotaxanes can also be used to enhance or reduce reactivity, act as molecular muscles, and self-assemble into structures that can slowly release dye.
The superconductor accelerator cavity is one of the most important and perspective technology for an advance accelerator. For example, the International Committee for Future Accelerators decided that the Linear Collider design had been based on the superconductor technology. Moreover, the accelerator operating with continue wave (CW) mode must use the superconductor technology in stead of the normal conductor technology, such as the Accelerator-driven sub-critical reactor system (ADS), the Accelerator Transmutation of Waste (ATW), the Accelerator Production of Tritium (APT), and so on.
In order to meet all kinds of application, the scientific world interest is now focus on further developments of new resonant cavities fabrication techniques to reduce cost and improve the performance of the accelerator cavity. To realize this object, one of the important methods is to pursue research on new materials. The goal will be the achievement of superconducting cavity working better the Nb ones at 4.2K. For example, the better parameters of the Tc, the surface resistance, the critical field Hc and the Q value are needed.
Up to now, the most possible candidate is Nb3Sn. The Nb3Sn has not only the better superconductivity parameters, but also the stable property and the easy fabrication. There are two methods to fabricate the superconductor cavity with the Nb3Sn, which are including the diffusion method and the multilayer deposition method. In the thesis, we focus on the multilayer deposition method, and ......
Dynamics of cold atoms in moving optical lattices (Version Dek8)Nadal Sarkytbayev
This document discusses the dynamics of cold atoms in moving optical lattices. It begins with introducing relevant theoretical concepts like de Broglie hypothesis, band theory, and Bloch's theorem. It then describes different methods for cooling atoms, such as laser cooling and magneto-optical traps. The main body of the document analyzes cold atom transport through optical lattices under different regimes defined by the field strength and lattice velocity. It finds transitions between wave dragging and Bloch oscillation regimes that are sensitive to field variations. In conclusion, the document demonstrates control over cold atom transport in optical lattices.
This document summarizes a study on dehydrogenation of methylcyclohexane (MCH) over 3 wt% Pt/V2O5 and 3 wt% Pt/Y2O3 catalysts for hydrogen delivery applications. The catalytic activity was tested using a spray-pulse mode reactor, which creates alternating wet and dry conditions on the catalyst surface. 3 wt% Pt/Y2O3 achieved a hydrogen evolution rate of 958 mmol/g/min at 350°C and nearly 100% hydrogen selectivity. 3 wt% Pt/V2O5 achieved 98% MCH conversion at 60 minutes using the spray-pulse reactor. The catalysts were characterized using techniques such as XRD, CO-chemisorption
Analysis Of Carbon Nanotubes And Quantum Dots In A Photovoltaic DeviceM. Faisal Halim
Analysis of Carbon Nanotubes and Quantum Dots in a Photovoltaic Device
A poster prepared by Francis and me; presented by Francis. I modified on of the photographs used, in this copy.
The document summarizes the scientific background on the 2016 Nobel Prize in Chemistry, which was awarded for the design and synthesis of molecular machines. It discusses how Jean-Pierre Sauvage, Sir James Fraser Stoddart, and Bernard Feringa helped develop molecular machines through their work on topological entanglement using mechanical bonds and controlled motion in molecular components. Specifically, it highlights Sauvage's development of template synthesis to produce interlocked molecular structures like catenanes and rotaxanes, Stoddart's demonstration of translational motion in a molecular shuttle, and their combined work in 1994 to demonstrate externally controlled translational and rotational motion in mechanically interlocked molecules.
This document summarizes the mechanochemical synthesis of isoreticular metal-organic frameworks (IRMOFs) and their potential for nitrobenzene sensing. Specifically, it discusses:
1) The liquid-assisted grinding synthesis of IRMOF-1 and halogen-substituted IRMOF-2 frameworks containing chlorine, bromine, or iodine.
2) Characterization of the frameworks by powder X-ray diffraction and scanning electron microscopy, which confirmed their structures.
3) Investigation of the frameworks' fluorescence properties, which revealed IRMOF-1 is a highly sensitive and selective fluorescence quenching agent for nitrobenzene detection.
4) The role of
Magnetic chitosan nanoparticles for removal of cr(vi) from aqueous solutionhbrothers
This document describes research on using magnetic chitosan nanoparticles for removing Cr(VI) from aqueous solutions. The researchers introduced a simple method to prepare magnetic chitosan nanoparticles via co-precipitation and epichlorohydrin cross-linking. Characterization showed the nanoparticles were spherical and around 30 nm in size. Adsorption experiments found Cr(VI) removal was highly dependent on pH, with maximum adsorption of 55.80 mg/g occurring at pH 3. Kinetic data fit a pseudo-second order model and isotherm data fit the Langmuir model well. The magnetic chitosan nanoparticles showed potential for use in wastewater treatment applications to remove Cr(VI).
Growth and Characterization of Morpholium Cadmium Acetoperchlorate Single Cry...IJERA Editor
In the search for novel crystal with promising nonlinear optical properties an attempt is made to grow
morpholium cadmium aceto-perchlorate single crystals. The title compound is synthesized by slow evaporation
technique at room temperature. The powder X-ray diffraction pattern has been recorded and the various planes
of reflections are identified. The transmittance spectrum of the crystal in the UV–Vis region has been obtained.
Using the FTIR spectrum, the vibrational modes of the crystal is analysed and the presence of cadmium in the
crystal is confirmed. Thermogravimetric analysis and differential thermal analysis studies have been done to
assess the thermal stability of the grown crystal. The dielectric measurement for the crystal is carried out in the
range of 50 Hz to 5 MHz for three different temperatures 40ºC, 80ºC and 120ºC to study the electrical nature of
the grown crystal. The nonlinear optical property of the grown crystal is confirmed
The document summarizes research on the synthesis and characterization of a new nonlinear organic single crystal called urea L-asparagine. Key findings include:
1) Urea L-asparagine crystals were grown using a slow evaporation solution method and yielded bright, transparent crystals measuring 11 x 0.7 x 0.3 cm3.
2) Elemental analysis and powder X-ray diffraction confirmed the crystalline nature and stoichiometric composition of the compound.
3) Single crystal X-ray diffraction showed the crystal has an orthorhombic structure with space group P.
4) Optical and vibrational spectroscopy showed the crystal has good transmittance in the visible range
This document discusses photoluminescence studies of Eu3+ doped La0.6Y0.4PO4 phosphor codoped with Tb3+ and Gd3+. The phosphors were prepared by solid state diffusion reaction and characterized using XRD, SEM, and photoluminescence techniques. XRD analysis confirmed the monoclinic crystal structure. SEM images showed irregularly shaped particles ranging from submicron to microns in size. Photoluminescence emission was observed from 530-630 nm under 254 nm excitation. Codoping with Tb3+ and Gd3+ increased the intensity of the 612 nm emission peak from the Eu3+ ions, likely due to a cross relaxation
Size exclusion chromatography, also known as gel filtration chromatography, separates molecules based on their size and molecular weight. Larger molecules pass through the porous beads of the stationary phase more quickly than smaller molecules that can enter the pores. This document discusses the basic principles, history, applications, and factors affecting size exclusion chromatography such as column length and packing. It is commonly used to purify proteins and other biomolecules.
Synthesis and charaterization of la1 x srxmno3 perovskite nanoparticlesMai Trần
In recent times perovskite materials are extensively studied and have attracted much attention because they exhibit interesting the properties, showing potential applications in commercial, technical and biomedical. In Vietnam, perovskite materials be of interest research and applications are strong but with major research direction is to go deep into the electrical properties and the magnetic properties. The Lanthanum Strontium manganite is a perovskite-based crystal-structured ceramic material with the formula of La1-xSrxMnO3, where x describes the doping ratio. It has attracted much attention due to its good magnetic, electrical, and catalytic properties and is becoming an attractive possibility material in several biomedical applications, particularly with nano-size. In industry, this material is commonly used in as a cathode material in commercially produced solid oxide fuel cells. In this thesis, we present the Perovskite nanoparticles La1-xSrxMnO3 were successfully synthesized of the nanosize La1-xSrxMnO3 at x = 0; 0.1; 0.2; 0.3 and 0.4 which prepared by a modified sol-gel method. Structure and magnetic properties of them were systematically investigated in dependence on doped Sr ratio x. The structure was investigated by XRD and show slightly changed but magnetic properties varied strongly with changing the doping ratio x. Magnetic properties of samples were studied by Vibrating Sample Mode of Physical Properties Measurement System show at the room temperature, the samples show superparamagnetic properties with high saturated magnetization MS of 57 emu/g which strongly dependents on the doped Sr ratio x.
The document discusses barium perovskites as potential humidity sensing materials. Three key points:
1) Samples of BaMO3 (M=Ti, Zr, Hf, Sn) were prepared via wet chemical synthesis or solid state reaction and tested for their electrical response to humidity.
2) All samples showed an increase in capacitance and conductivity with increasing humidity, indicating interaction between water vapor and the crystal surfaces. Sensitivity was highest at low frequencies and decreased with increasing humidity.
3) Time response to humidity changes was typically 10-100 seconds for intermediate humidity levels. Response time was influenced by the amount of mesopores in the material, with shorter response times associated with less mesoporous
Characterization of Clay/Chitosan Nanocomposites and their Use for Adsorption...Editor IJCATR
The document describes a study that prepared nanocomposite films from chitosan biopolymer and montmorillonite nanoclay (MMT) at various weight percentages. XRD and FTIR were used to characterize the structural properties of the nanocomposites and showed an intercalated structure formed. The nanocomposites were then used to adsorb Mn(II) ions from aqueous solution. Parameters like pH, contact time, adsorption mass, initial concentration, and temperature were investigated. Adsorption isotherms and kinetics as well as thermodynamic properties of the process were analyzed.
The recent spike in solar cell failures experienced by TIR Solar Energy has been attributed to inconsistent titanium dioxide particles used in solar cell production. To institute proper quality controls of this material and to minimize further failures, the Quality Control department has proposed purchasing a Rigaku MiniFlex600 Benchtop XRD Instrument for just under $95,000. An X-ray diffractometer would allow them to characterize the crystal phase of the titanium dioxide nanoparticles, determining whether they have the desired anatase phase or the less effective rutile phase. This testing is needed to improve quality control over the production process and prevent further costly defects.
Super Critical Fluid Chromatography was first proposed in 1958 and involves using fluids above their critical temperature and pressure to separate mixtures. Carbon dioxide is commonly used as the mobile phase due to its stability and ability to dissolve large molecules. SFC provides faster analysis than HPLC and can analyze non-volatile compounds without derivatization like GC. It finds applications in pharmaceuticals, natural products, lipids, pesticides and more due to its mild conditions and speed.
Structural and magnetic properties on F-doped LiVO2 with two-dimensional tria...Yang Li
The layered oxide LiVO2 recently has received more attention due to its interesting structural and magnetic behaviors involving the two-dimensional magnetic frustration in these systems. We synthesized a series of F-doped LiVO2 samples, and reported the F-doping effect on the structure and transition temperature Tt. The samples LiVO2-xFx (x=0, 0.1, 0.2 and 0.3) were characterized by X-ray diffraction, scanning electron microscope (SEM), differential scanning calorimetry (DSC), magnetic susceptibility and specific heat measurement. The structural analysis shows that with increasing x, the ratio of lattice parameter c/a increasing, i.e. in the a-b plane the lattice is compressed while in the c-axis direction the lattice expands. The DSC measurements show that a first-order phase transition happens at around 500 K, and the thermal hysteresis around phase transition temperature Tt increases with increasing x. Substitution of O with F ions results in a change of two dimensional characteristics and the distortion of the VO6 block in structure, which significantly influence the magnetic ordering transition temperature Tt.
The document summarizes four new heterometallic molecular aggregates containing cobalt and lanthanide metals. Compounds 1 and 2 have the formula [(CoII)3(CoIII)2Ln3(μ3-OH)5(O2CtBu)12(L)2]·2H2O and feature distorted cubane cores, while compounds 3 and 4 have the formula [(CoIII)3Ln3(μ3-OH)4(O2CtBu)6(L)3](NO3)2·2CH3CN·2H2O and display hemicubane-like metallic cores. Magnetic studies show significant magnetic entropy changes for 1 and 3, and single molecule magnetic
This document describes a lattice model for simulating the nematic-isotropic phase transition in liquid crystals. The model uses rod-shaped particles arranged on a simple cubic lattice. An original computer code was written to implement the Monte Carlo method and Metropolis algorithm. The code calculates properties like energy, heat capacity, and order parameter during the phase transition. Simulation results agree well with literature, validating the computer code. The code provides a basis for extending the model to handle helicoidal particles and study chiral nematic liquid crystal phases exhibited by such particles.
Role of αc–relaxation in high-temperature polymer deformation.
Proceedings of the American Society for Composites 2009-Twenty-Fourth Technical ConferenceWith the Canadian Association for Composite Structures and Materials (Joint Canadian-American International Conference), September 15-17, Newark, DE
Rotaxanes are supramolecular assemblies consisting of a macrocyclic molecule threaded onto a linear molecule capped with bulky stoppers. They can be synthesized through template-directed methods like clipping, threading, and snapping. Switchable rotaxanes have applications in logic gates and memory due to their ability to shuttle between binding stations. Rotaxanes can also be used to enhance or reduce reactivity, act as molecular muscles, and self-assemble into structures that can slowly release dye.
The superconductor accelerator cavity is one of the most important and perspective technology for an advance accelerator. For example, the International Committee for Future Accelerators decided that the Linear Collider design had been based on the superconductor technology. Moreover, the accelerator operating with continue wave (CW) mode must use the superconductor technology in stead of the normal conductor technology, such as the Accelerator-driven sub-critical reactor system (ADS), the Accelerator Transmutation of Waste (ATW), the Accelerator Production of Tritium (APT), and so on.
In order to meet all kinds of application, the scientific world interest is now focus on further developments of new resonant cavities fabrication techniques to reduce cost and improve the performance of the accelerator cavity. To realize this object, one of the important methods is to pursue research on new materials. The goal will be the achievement of superconducting cavity working better the Nb ones at 4.2K. For example, the better parameters of the Tc, the surface resistance, the critical field Hc and the Q value are needed.
Up to now, the most possible candidate is Nb3Sn. The Nb3Sn has not only the better superconductivity parameters, but also the stable property and the easy fabrication. There are two methods to fabricate the superconductor cavity with the Nb3Sn, which are including the diffusion method and the multilayer deposition method. In the thesis, we focus on the multilayer deposition method, and ......
Dynamics of cold atoms in moving optical lattices (Version Dek8)Nadal Sarkytbayev
This document discusses the dynamics of cold atoms in moving optical lattices. It begins with introducing relevant theoretical concepts like de Broglie hypothesis, band theory, and Bloch's theorem. It then describes different methods for cooling atoms, such as laser cooling and magneto-optical traps. The main body of the document analyzes cold atom transport through optical lattices under different regimes defined by the field strength and lattice velocity. It finds transitions between wave dragging and Bloch oscillation regimes that are sensitive to field variations. In conclusion, the document demonstrates control over cold atom transport in optical lattices.
This document summarizes a study on dehydrogenation of methylcyclohexane (MCH) over 3 wt% Pt/V2O5 and 3 wt% Pt/Y2O3 catalysts for hydrogen delivery applications. The catalytic activity was tested using a spray-pulse mode reactor, which creates alternating wet and dry conditions on the catalyst surface. 3 wt% Pt/Y2O3 achieved a hydrogen evolution rate of 958 mmol/g/min at 350°C and nearly 100% hydrogen selectivity. 3 wt% Pt/V2O5 achieved 98% MCH conversion at 60 minutes using the spray-pulse reactor. The catalysts were characterized using techniques such as XRD, CO-chemisorption
Analysis Of Carbon Nanotubes And Quantum Dots In A Photovoltaic DeviceM. Faisal Halim
Analysis of Carbon Nanotubes and Quantum Dots in a Photovoltaic Device
A poster prepared by Francis and me; presented by Francis. I modified on of the photographs used, in this copy.
The document summarizes the scientific background on the 2016 Nobel Prize in Chemistry, which was awarded for the design and synthesis of molecular machines. It discusses how Jean-Pierre Sauvage, Sir James Fraser Stoddart, and Bernard Feringa helped develop molecular machines through their work on topological entanglement using mechanical bonds and controlled motion in molecular components. Specifically, it highlights Sauvage's development of template synthesis to produce interlocked molecular structures like catenanes and rotaxanes, Stoddart's demonstration of translational motion in a molecular shuttle, and their combined work in 1994 to demonstrate externally controlled translational and rotational motion in mechanically interlocked molecules.
Photophysical properties of light harvesting molecules: three different approaches (of increasing complexity and accuracy) to foresee the harvesting behaviour are reviewed with a highly didactic flow. Design principles are highlighted.
A supplementary set of slides is available among my uploads.
This document is a self-made research I did for a photochemistry course. I don't own part of the shown material and references for many public images are reported at the end.
An Experimental Enquiry into The Growth of Mordenite Nanocrystals Sans Seed A...Mohammad Hassnain
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But we have mainly focused on Mordenite synthesis in nanosize without adding seed and incorporating its effect on Mordenite morphology by comparing with standard Mordenite.
Synthesis of Mordenite nanocrystals was mainly divided into three steps. The first step covered the procedure for preparation of gel without adding seed. The gel is then converted into raw Mordenite under hydrothermal conditions in the second step. Finally, in third step raw Mordenite product is recovered into pure Mordenite crystals by applying washing with distilled water and drying techniques. The effect of sans adding seed and distilled water in the sample is then studied with the help of X-ray diffraction (XRD) and scanning electron microscopy (SEM).
Vast range of laboratorial and industrial applications of Mordenite are summarized into three major uses. These includes the use of Mordenite as a catalyst, as an adsorbent and as an ion exchanging sieve. Other uses of Mordenite are also discussed.
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Annotated BibliographyYour annotated bibliography should be .docxfestockton
Annotated Bibliography
Your annotated bibliography should be prepared according to ACS format, using The ACS Style Guide: Effective Communication of Scientific Information, 3rd edition. One or more copies of this book are held on reserve in the library.
The Purdue Online Writing Lab (OWL) at http://owl.english.purdue.edu/owl/resource/614/01/ offers further information regarding annotated bibliographies.
This annotated bibliography, along with a correctly formatted citation, should include a summary of the content of the source and a two-pronged critical analysis of the source. The first part of the critical analysis will be your objective evaluation of the source and the second part will be your subjective evaluation. Even if a source is found to be credible, if it does not contribute to your research question, it should not be included.
Prepare your annotated bibliographic entry according to the following guidelines:
1. Bibliography Entry: Include the complete bibliographic information correctly formatted according to the ACS style guidelines
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Objective Evaluation: Objectively evaluate the credibility of the source using the criteria that are most relevant. Use the questions presented in the TRAAP criteria found under “Evaluate Sources” at
https://youtu.be/zzTBBm1HXvM
1. to stimulate your ideas, but don’t feel as if you need to address each criteria as a checklist. Use the criteria that are appropriate for your source. When relevant, address such things as bias or lack of bias, outdated material or current material, author’s point of view, and author’s credentials and qualifications to write on the topic. What is the author’s purpose in writing the information? Is the information presented without prejudice? Or does the author, publisher, or research funding organization have a stake in the outcome or the controversy you are investigating?
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Photochemistry Assignment #2
This assignment covers material from Chapter 2 section 1 to Chapter 2 Section 14.
1) According to the principles of quantum mechanics, what is the wave function?
2) What is the Born-Oppenheimer approximation?
3) Under what two types of interactions does the approximation given in equation 2.4
break down?
4) (a) What is the four-letter abbreviation for the highest energy occupied molecular
orbital?
(b) What is the four-letter abbreviation for the lowest energy unoccupied molecular
orbital?
5) To what does the square of a wave function relate?
6) What is an expectation value?
7) What is meant by an electronic configuration?
8) An alken ...
Annotated BibliographyYour annotated bibliography should be .docxSHIVA101531
This document provides guidelines for preparing an annotated bibliography entry for a photochemistry assignment. The annotated bibliography should include a bibliography entry in ACS format, a summary of the source content, and a two-part critical analysis consisting of an objective evaluation and subjective evaluation of how the source relates to the research topic. The guidelines specify how to structure each part of the annotated bibliography entry. A sample assignment on photochemistry is also provided that requires answers to multiple questions.
Nanotechnology involves working with materials at the nanoscale, between 1 to 100 nanometers. There are top-down and bottom-up approaches to creating nanoparticles. Top-down involves breaking bulk materials into nanoparticles while bottom-up involves building nanoparticles from individual atoms or molecules. Nanoparticles can be created through various methods including attrition, pyrolysis, and liquid phase techniques like sol-gel and microemulsions. Nanoparticles find applications in areas like batteries and 3D printing.
This document summarizes an experiment investigating high-temperature superconductivity in Yttrium Barium Copper Oxide samples. The experiment aimed to demonstrate the Meissner effect and zero resistance in the samples using liquid nitrogen. The document provides theoretical background on superconductivity, including the Meissner effect, Ginzburg-Landau theory, BCS theory, and the structure of Yttrium Barium Copper Oxide. It describes the experimental methods, results from Meissner effect tests, magnetic field experiments, X-ray diffraction analysis, and resistance measurements. The results are then discussed in relation to the theories of superconductivity.
This document summarizes research on using boron-doped carbon nanotubes (B-CNTs) as a catalyst for oxygen dissociation in proton exchange membrane fuel cells (PEMFCs). Density functional theory (DFT) calculations were performed to model oxygen adsorption and dissociation on a (5,5) single-walled carbon nanotube (SWCNT) with one hexagon replaced by B3C3 (B3SWCNT). The nudged elastic band (NEB) method was used to calculate minimum energy reaction paths and activation barriers. The results show an average activation barrier of 1.01 eV for oxygen dissociation on the B3SWCNT, with the most favorable path having a barrier
1. TOWARDS THE SYNTHESIS OF CYCLOCHIRAL ROTAXANES
BSc IV Dissertation project
Gordon J. Lister
Supervisor Dr Ai-Lan Lee
2010/2011
1
2. Declaration
I, Gordon J. Lister confirm that this work submitted for assessment is my own work and
is expressed in my own words. Any uses made within it of the work of other authors in
any form are properly acknowledged at the point of use.
Signed:
Dated:
2
3. Contents
Contents............................................................................................................................3
1.0 Abstract......................................................................................................................5
2.0 Introduction...............................................................................................................6
2.1 Interlocked molecular architectures .......................................................................6
2.2 Nomenclature of Rotaxanes......................................................................................7
2.3 Applications for Rotaxanes.......................................................................................8
2.4 Overview of strategies for synthesising rotaxanes................................................11
2.4.1 Early statistical approach....................................................................................13
2.4.2 Directed synthesis via covalent bond formation................................................14
2.4.3 Hydrogen bond mediated templating synthesis.................................................16
2.4.4 π-electron donor/ π-electron acceptor interactions...........................................17
2.4.5 Transition metal template synthesis of rotaxanes ............................................18
2.5 Active metal synthesis of rotaxanes.......................................................................20
2.5.1 CuAAc active metal template for rotaxane synthesis.......................................20
2.5.2 Copper mediated alkyne-alkyne heterocoupling...............................................24
2.6 Cyclochirality in rotaxanes ....................................................................................25
3.0 Aim of this project...................................................................................................28
4.0 Results and Discussion ...........................................................................................30
4.1 Synthesis of macrocycle precursor 44....................................................................30
4.2 Synthesis of macrocycle 41.....................................................................................32
5.0 Conclusion................................................................................................................33
6.0 Experimental section...............................................................................................34
6.1 Synthesis of macrocycle precursor.........................................................................34
6.2 Synthesis of macrocycle 41.....................................................................................38
3
4. Abbreviations
δ - chemical shift
mL – millilitres
mmol – millimoles
g – grams
mins – minutes
hrs – hours
EtOAc – ethyl acetate
PE – petroleum ether 40 – 60%
NMR – nuclear magnetic resonance
Hz – Hertz
MHz – mega Hertz
J – NMR coupling constant
s – singlet
d- doublet
t – triplet
q – quartet
m – multiplet
R.T – room temperature (between 12 and 20 o
C)
Me – methyl
Et – ethyl
tBu – tert-butyl
THF – tetrahydrofuran
DMF – dimethylformide
DCM – dichloromethane
TLC – thin layer chromatography
Ph – phenyl
OTf – triflate
Ts – tosyl
OTs – tosylate
o
C – degree Celsius
4
5. 1.0 Abstract
Cyclochirality in rotaxane systems is becoming increasingly important as their uses
become more widespread in nanotechnology. As such, methods of producing pure
samples of one cyclochiral form of a rotaxane are being highly sought after. So far two
methods for producing cyclochiral rotaxanes have so far been found, one where the
rotaxane is synthesised and then reacted to make it cyclochiral. The second method is
to impart the cyclochirality when forming the rotaxane, however this method can
sometimes lead to a racemic mixture of both cyclochiral forms.
5
6. 2.0 Introduction
2.1 Interlocked molecular architectures
Mechanically interlocked molecular architectures are a ubiquitous class of “entwined”
molecules, which exist due to the stability of their topologies. They can neither be
classified as truly supramolecular nor complex-type species, due to the requirement of
covalent bond cleavage to afford their component parts.
Figure 1. Morphology of (a) rotaxane and (b) catenane
There are four main classes of mechanically interlocked molecular architectures, these
are; rotaxanes, catenanes, molecular knots and borromean rings though the latter two
will not be discussed. The term rotaxane is derived from the Latin rota meaning
“wheel” and axle meaning “axis”. Rotaxanes consist of a thread with a bulky stopper
group situated on each end. The resulting dumbbell is threaded through the cavity of a
macrocycle. The stopper groups are present to stop de-threading and the decomposition
into its component parts. Catenane, is derived from the Latin term catena, meaning
“chain”, comprising mechanically interlocked ring systems, which can adopt many
different topologies, however the assembly of extended chain systems is more
synthetically challenging.
6
7. 2.2 Nomenclature of Rotaxanes
The most basic rotaxane morphology (Figure 1) consists of a dumbbell shaped molecule
threaded through a single cyclic moiety. In this case the system is defined as a
[2]rotaxane, characterising the number of interlocked components inherent in the
structure. In more general terms, a [n]rotaxane contains [n-1] ring systems, threaded
onto the dumbbell component. In the case of more elaborate structures, the naming
convention proposed by Vögtle and co-workers is employed.1
Figure 2 shows two
further rotaxane topologies.
The earliest example of a cyclic moiety threaded by a linear chain was first proposed by
Frisch and Wasserman in 1961, when they claimed that a structure of this type could be
kinetically stable. In 1967, both the Harrison and Schill2
groups simultaneously
extended this concept to the synthesis of rotaxanes.
Figure 2. Illustration showing a [4]rotxane and a branched chain rotaxane
7
8. 2.3 Applications for Rotaxanes
The interesting chemical and structural properties of rotaxanes lead to a increased
amount of academic research. Their inherent ability to allow controlled mechanical
motion on the molecular scale has meant they have been exploited for use in the field of
nanotechnology.
Two such applications are molecular switches and molecular machines. In these
examples, an external stimuli controls the mechanical motion of the molecules towards
achieving some overall task. Various external stimuli can be applied to initiate this
movement, examples of this stimuli that have been studied include pH, redox of a co-
ordinated metal centre and light.
Figure 3. Illustration of a [2]rotaxane acting as a molecular switch
One such method for transforming a rotaxane into a molecular switch is by inserting a
copper ion into the macrocycle ring system of the rotaxane. The axle of the rotaxane
system will have one or more “recognition” sites. To make the ring system move from
site to site, the oxidation state of the copper is changed, which in turn would affect the
environment in which the copper resides.
In a 2009 study by Moretto and co-workers showed the use of a helical peptide axle in a
[2]rotaxane3
molecular machines. This study showed how rotaxanes can be “forced”
into making changes in their structure by altering the solvent and the temperature.
They have shown that by changing the solvent that the rotaxane has been dissolved in,
from chloroform to acetonitrile, the macrocycle ring system moves from one
“recognition” site to the other. The reason behind this switch from one “recognition”
site to another upon changing the solvent from chloroform to acetonitrile, is due to the
8
9. hydrogen bonds that are present between the acetonitrile solvent and the nitrogen link
station in the axle.
O
NH
O
N
H
N
H
NH
O
O
O
NH
H
O
NH
H
H
O
NH
H
H
O
NH
O
NH
O
NH
O
NH
O
NH
O
NH
O
O NH
O
O
NH
H
O
NH
1, macrocycle
stopper
stopper
C - terminal station
N - terminal station
amido - ester junction
310 -helix peptide linker
2, helical peptide axle with stoppers
Figure 4: Chemical structures of macrocycle and helical peptide axle with stopper groups attatched.
Scheme 1: Computer generated structures showing rotaxane switching and a space filling representation
of rotaxane.
However, rotaxanes have also been utilised in the field of nanorecording, where the
rotaxane is applied to a indium-tin oxide coated glass surface as a Langmuir-Blodgett
film.4
When a voltage is applied from the end of a scanning tunnelling microscope
probe, the macrocycle rings present in the area of contact switch to another
“recognition” site and the new overall conformation extrudes the surface by 0.2
nanometres, which is sufficient for a memory dot.
9
10. A final, and more recent, application for rotaxanes is in asymmetric catalysis. The first
example of such an application was developed by Takata and co-workers (shown below
in Scheme 2)5
, in which they utilised rotaxane 3 to catalyse an enantioselective
condensation reaction. They showed that the chemical field of the rotaxanes
components provided a chiral transfer field via non covalent bonding. The study also
showed that axial chirality from the macrocycle can be transferred to the achiral
catalytic site (thiazolium moiety) on the axle. Takata likened the rotaxane field to that
of an enzyme asymmetric reaction field. Although they only achieved a ee of 32% at
this stage, it illustrated the potential of rotaxanes for use in chiral reactions.
Cl
-
OO
OO
OO
OO
N
O
N
+
S
O
O
O
H
O
OH
Et3N
3, catalytic
Up to 90% yield
Up to 32% ee
Scheme 2. Asymmetric benzoin condensation catalysed by chiral rotaxane 1 "through space" chirality
transfer
However, the Nishibayashi group went on to develop a chelating bidentate chiral ligand
which was based on a pseudorotaxane structure, these ligands can be used in rhodium-
catalysed enantioselective hydrogenation of enamides. Their “lassoed” pseudorotaxane
is able to catalyse reactions to high conversions (>99%) and high enantioselectivities
(90-96%).6
Fan and co-workers also reported related pseudorotaxanes for rhodium-catalysed
enantioselective hydrogenation of enamides, the reduced products they report however
are with slightly lower enantioselectivities (68-88% ee) when compared with
Nishibayashi’s “lassoed” pseudorotaxane.7
The synthesis of the Fan “lassoed
pseudorotaxane” 4 is show below in Scheme 3.
10
12. bulky stopper groups to prevent de-threading, thus producing the desired interlocked
species.
Figure 5. Illustration of the threading process.
In a similar way the slipping process requires a macrocycle ring to be threaded onto a
pre-existing stoppered chain (Figure 6). To achieve this requires the cavity of the
macrocycle ring to be able to expand enough to pass over the stopper groups, then
contract once it has reached the desired “recognition” site on the chain, often this
process is thermal in nature. When heated, the macrocycle ring system is able to
expand and pass over the stopper, then upon cooling contracts such that the cavity is
now too small to pass over the stopper groups present in the system.
Figure 6. Illustration of the slipping process.
A third approach used is called clipping, this involves a turn (a large segment of the
macrocycle ring) that has been threaded onto a chain containing both stopper groups, a
macrocyclisation reaction is then carried out to implant the rest of the ring system and
complete the rotaxane (Figure 7).
Figure 7. Illustration of the clipping process.
12
13. Finally the most widely used synthesis process, active metal template, this process
involves a metal ion(active template), this metal ion causes and catalyses the formation
of covalent bonds between two pre-stoppered parts of the “axle” while still threading
the “axle” through the macrocycle cavity simultaneously.
Figure 8. Illustration of the active metal template process.
2.4.1 Early statistical approach
With Frisch and Wasserman first proposing the idea of mechanically interlocked
molecular structures and then their synthesis of the first [2]catenane relying on the
probability of threading through a macrocycles cavity. However it was the Harrison
group which first transferred this concept to rotaxane synthesis, however their approach
of repeatedly treating a Merrifield resin bound macrocycle with decane-1,10-diol and
triphenylmethyl chloride on a column, albeit resulting in a 6% yield of a [2]rotaxane
(reaction show below in Scheme 4).8
O
O
O
O
Resin
O
26
OH
OH
Cl
1. Repeated 70 times
2. NaHCO3, MeOH
O O
26
OH
O
6% yield
Scheme 4. The first synthesis of a [2]rotaxane by the Harrison Group using a Merrifield resin.8
13
14. 2.4.2 Directed synthesis via covalent bond formation
The term “directed synthesis” was first used by Schill and co-workers in 1964 to
describe employing covalent bonding at key stages to template the formation of
[2]catenane in the correct topology, key intermediates of the reaction are shown below
in Scheme 5. This technique although still giving a low yielding (30%) had overcame
the disadvantage of relying only on chance to form interlocked structures, and since this
development many other template strategies have since been developed.
O
O
(H2C)12
(H2C)12
Cl
Cl
NH2
(CH2)24
O
O N
(CH2)11
(CH2)11
(CH2)24
OH
O
O
O(CH2)25
(CH2)11
(CH2)11
Scheme 5. Key intermediates in the synthesis of a [2]catenane by Schill and co-workers.
This method of “directed synthesis” has been transferred and utilised in rotaxane
synthesis. In this synthesis Hiratani and co-workers first synthesised their macrocycle
ring system which as a polyether, contained many oxygen donor atoms, two of the
donor O atoms lay between aromatic ring systems and an unsaturated C-C double bond.
These two donor atoms were easily converted to phenolic hydroxyl groups via tandem
Claisen rearrangements. To obtain this rearrangement a thermal reaction of the
macrocyclic system was carried out in decalin at 160 o
C for 3 hrs, to give one phenolic
hydroxyl group (71% yield obtained), to obtain the second hydroxyl group a further
thermal reaction needed to be carried out, this time no solvent was used, the reaction
was carried out at 195 o
C and under vacuum conditions for 6hrs. This afforded the
required bi-phenolic hydroxyl containing macrocycle, these hydroxyl groups are then
available for the introduction of the axis of the rotaxane system.
14
15. O
O
ONa
Cl
Cl
O O
O
Cl
O
O
OH
NaH, DMF
OH
O
O
OH
O
O
O
TsO
O
TsO
O
O
O
O
O
O
O
O
O
OH
O
O
O
O
O
O
Decalin
160
o
C
3 hrs
O
OH
OH
O
O
O
O
O
195
o
C
6 hrs
5 6 7
CsCO3, KI, DMF
Scheme 6: Synthesis of macrocycle used by Hiratani and co-workers.
This macrocycle 7 is then reacted with an acid chloride 8 in THF at room temperature
(35% yield), giving a racemic mixture of monoesters 9 at either of the previously
hydroxyl positions. These monoester systems, were then reacted via an aminolysis
reaction with 10 carried out in a small amount of DMF at room temperature to afford
the desired rotaxane products 11.
NH
O
O
Cl
7
8
t-BuOK, THF
O
O
OH
O
O
O
O
O
NH
O
O
O
OH
O
O
O
O
O
O
NH
O
O
monoester isomers, 9
NH210
DMF
O
OH
OH
O
O
O
O
O
NH
O
O
NH
O
OH
OH
O
O
O
O
O
NH
O
O
NH
racemic mix of [2]rotaxanes 11
Scheme 7: Synthesis of [2]rotaxane 11 used by Hiratani and co-workers utilising covalent bond formation
to template the rotaxane formation.
15
16. 2.4.3 Hydrogen bond mediated templating synthesis
The first report of hydrogen bonding in connection with the templating of mechanically
interlocked structures was by Hunter, when they discovered a [2]catenane, in a 34%
yield, as a by-product of a macrocyclisation reaction.11
The [2]catenane results from
the macrocyclic precursors clipping around an existing molecule of the targeted
macrocycle, hydrogen bonding between the precursors amide groups and the
macrocycles carbonyl groups held the precursor in place while macrocyclisation
occurred to afford a [2]catenane.
The Leigh group also went on to utilise this phenomenon in the synthesis of a
[2]rotaxane, containing an amide macrocycle over an amide axle, using the clipping
methodology.12
The [2]rotaxane 12 formed satisfies the hydrogen bonding
requirements of both the axle and the macrocycle, this leads to the rotaxane being 105
times more soluble in chloroform than the free macrocycle.
R
O
Cl
O
Cl
NH2NH2
OO
NHNH
O O
O
O
CHPh2
CHPh2
R
O
N
H
O
N
H
NH
N
O
O H
O
O
NH
O
O
N
H
O
O
Ph2HC
NEt3
CHCl3
12
Scheme 8. Hydrogen bond assisted clipping of a macrocycle around an axle to afford corresponding
[2]rotaxane.12
16
17. 2.4.4 π-electron donor/ π-electron acceptor interactions
During the design of a receptor unit for parquat (a molecule containing π-electron
deficient bipyridinium rings), Stoddart and co-workers discovered that certain
bipyridinium salts complex efficiently with benzo crown ethers.13, 14
The parallel
aromatic rings of the π-electron rich benzo crown ethers coordinate with the π-electron
deficient paraquat-based salts, resulting in the production of pseudorotaxane type
structures, which can then be stoppered to give the equivalent rotaxane 13 (Scheme 7).
OO O O OHOOOH
SiTfO
N
N
+
N
+
N
+
N
+
4PF6
-
N
+
N
+
N
+
N
+
OO O OOOSi Si
5% yield
13
Scheme 9. Synthesis of a [2]rotaxane 13 by Stoddart and co-workers utilising π-π interactions.14
The development of π-π interactions as a viable route towards mechanically interlocked
structures has led to a large library of catenane and rotaxane systems being synthesised
with two15-20
, three21-25
and more23, 26
aromatic donor sites, thus with the potential to be
used as a molecular switch.
17
18. 2.4.5 Transition metal template synthesis of rotaxanes
The use of a transition metal to hold ligands in the precise orientation, directing bond
formation to favour an interlocked product, is extremely attractive to the synthetic
chemist. As well as the interactions being strong, the nature of the resulting
supramolecular complexes are frequently highly ordered, and often dictated by the
preferred geometry of the transition metal. The transition metal in this methodology
only aids the formation of the molecule but it is not essential once the molecule has
been synthesised.
The use of a metal template was first introduced by Sauvage and co-workers in 1983,
when they used tetrahedral Cu(I) to hold two 1,10-phenanthroline fragments orthogonal
to each other to allow the formation of a [2]catenane27
. When they first proposed this,
they were using a Williamson ether synthesis to close the ring systems27
,with this first
synthesis process they were obtaining a catenane yield of 27% which was surprising as
various other routes to catenanes at the time were only obtaining yields of <1%, they
then followed up this work by investigating the use of ring closing metathesis and first
published this in 199728
and then a fully completed paper was published on the subject
in 199929
reaction shown below in Scheme 10.
N
N
OH
OH
[Cu(NCCH3)4]+
N
N
OH
OH
N
N
OH
OH
Cu
+
[CH2(CH2OCH2)4CH2]
Cs2CO3
N
N
O
O
N
N
O
Cu
+
O
O
O
O
O
O
O
O
O27% yield
14
Scheme 10. [2]catenane 14 formation using a transition metal template methodology as employed by
Sauvage and co-workers.29
However it was Gibson and co-workers who first extended this concept to rotaxane
synthesis, using a similar Cu(I)-phenanthroline type ligand complex. They reported that
they obtained a [2]rotaxane, 15, in a 42% yield (Scheme 11).30
Since then the technique
has grown to not only incorporate copper but also to include many over transition
metals such as Fe, Co, Ni, Zn, Cd and Hg. The study of all these systems has led to a
much greater understanding of the mechanism associated with the synthesis.
18
20. 2.5 Active metal synthesis of rotaxanes
Although the introduction of transition metal template synthesis revolutionised the
synthesis of catenanes, rotaxanes and various other mechanically interlocked structures,
they did not fully utilise the chemistry intrinsically available to metal ions. As
previously discussed, the metal is only used to hold the reactive precursors in position
for as to allow for covalent bond formation. In the case of active metal template
synthesis, which is an extension of the previous concept, the metal has a dual role in the
synthesis, the metal acts as a template for holding the precursors together and to
catalyse the covalent bond formation which interlock the structure.
When synthesising rotaxanes using this methodology a metal is chosen such that it
promotes the formation of covalent bonds between two pre-functionalised “half-thread”
units, while still threading those “half-threads” through the cavity of the macrocycle.
The first active metal template synthesis was reported by the Leigh group in 2006, they
utilised a copper(I)-catalysed terminal alkyne-azide 1,3-cycloaddition (CuAAc) to
synthesis a [2]rotaxane, this model has now been extended to include other reactions
that utilise transition metals (Scheme 12).
2.5.1 CuAAc active metal template for rotaxane synthesis
Even with there being little knowledge of the mechanism of the CuAAc reaction at the
time, the mild reaction conditions and high yields obtained made it encouraging for
investigation, which lead to the gathering of proof of the active metal template concept.
However it was already known that the addition of Cu(I) exponentially accelerated the
reaction rate, as a result of this it was thought that the coordination of a tetrahedral Cu(I)
ion to the inner cavity of a monodentade or bidentate macrocycle would improve
coordination of an azide and terminal alkyne to the copper ion, through either face of
the macrocycle, the resulting coupling reaction results in the formation of a [2]rotaxane.
20
21. The Leigh group have reported yields of up to 94% for selected [2]rotaxanes, when the
reactions were carried out using a stoichiometric amount of the copper active species.31
With this they then investigated the use of sub-stoichiometric amounts of the copper
active species, while investigating this they found that the copper was able to both
template the reaction and also catalyse the cycloaddition reaction, when the reaction
mixture has a competitive ligand present (such as pyridine). Once optimised the sub-
stoichiometric reaction led to a slightly lower yield of 82% however this was achieved
using only 4mol% of the Cu(I) catalyst with respect to each “half-thread” precursor.32
The synthesis of [2]rotaxane 16 by CuAAc template is shown below in Scheme 12.
N
OO
(CH2)n
N
OOHO
(CH2)n
Cu
+
L4 F P
F
F-
-L
H
OR
Cu
+(IV)
L
L
L
N
OO
(CH2)n
ORCu
+(IV)
L
L-L
-HPF6
N3 OR
N
OO
(CH2)n
N
+
N
N
-
RO
OR
Cu
+(IV)
L
N
OO
(CH2)n
+L
+HPF6
L
Cu
+(IV)
L
N
RO
N
N
OR
+ pyridine
R = (t
-
BuC6H4)3CC6H4
-
L = MeCN, H2O, CH2Cl2, alkyne, azide, pyridine (catalytic version) or a donor from another rotaxane, macrocycle or thread.
N
OOHO
(CH2)n
N
N
N
O
O
16
Scheme 12. Cycle of a CuAAc reaction conducted by the Leigh group, used to investigate the effect of
macrocycle ring size on [2]rotaxane formation.
21
22. A study by Stoddart and co-workers in 2008 showed that consecutive CuAAc reactions
can be used to synthesis branched [4]rotaxanes in one pot reactions with reasonable
yield 44% (Scheme 13).33
The macrocycle used in the reaction is the charged species
CBPQT4+
, with a counter ion that is PF6
-
. Before being placed into the reaction the
stopper 19 and central axle unit 17 must first be activated from their corresponding
chlorides (shown below in Figure 9).
N3
N3
N3
O
O
O
OSiMe3
O
O
O
O
17
18
N
+
N
+
N
+
N
+
20
4PF6
-
N3
O
O
O
O
O
O
O
OMe
O
OMe
O
MeO
19
Figure 9: Starting materials for rotaxane synthesis, central axle component, 17, axle chain, 18, stopper
group, 19, macrocycle and counter ion, 20.
22
23. CH3
O
O
O
O
CH3
O
O
O
O
X =
N
N
N
N
N
N
N
N N
X
R
X
R
X
R
21 R = SiMe3
22 R = H
17 + 18
O
O
O
O
O
O
O
OMe
O
OMe
O
MeO
Y =
CuSO4.5H2O
Ascorbic acid
DMF
25
o
C
AgPF6
H2O
DMF
40
o
C
N
N
N
Y
N
N
N Y
N
N
N
N
N
N
N
N N
O
O
(CH2CH2O)3
O
O
(CH2CH2O)3
O
O
(CH2CH2O)3
(OH2CH2C)3
(OH2CH2C)3(CH2CH2O)3
N
N
N
Y
N
+
N
+
N
+
N
+
N
+
N
+
N
+
N
+
N
+
N
+
N
+
N
+
23
19 + 20
Cu nanopowder
[Cu(MeCN)4]PF6
DMF
-5
o
C
Scheme 13: One-pot rotaxane synthesis by Stoddart and co-workers.
23
24. 2.5.2 Copper mediated alkyne-alkyne heterocoupling
After their successful application of the CuAAc reaction, the Leigh group went on to
develop a copper-catalysed alkyne-alkyne heterocoupling active template synthesis,
which has its basis in a Cadiot-Chodkiewicz procedure (Scheme 14).32
Importantly, the
rotaxane products obtained contain unsymmetrical axles and unlike products of the
classical synthetic procedures, do not leave strong intercomponent binding motifs in the
final product. With this reaction procedure the group were able to synthesis rotaxanes
with excellent selectivity (>98%) and high yields (up to 85%), which makes the Cadiot-
Chodkiewicz one of, if not the most, efficient active template syntheses available to the
synthetic chemist to date.
RO
Cu
+
L
N N
O O
O O
RO
Cu
+
L
N
+
N
+
O O
O O
Br RO
Oxidative addition
RO
Cu
3+
N
+
N
+
O O
O O
RO
Br
Reductive elimination
-CuBr
N N
O O
O O
O
O
R = (t-BuC6H4)3CC6H4
L = I, THF
24
Scheme 14. Stoichiometric Cadiot-Chodiewicz active template synthesis of [2]rotaxane 24.32
24
25. 2.6 Cyclochirality in rotaxanes
Cyclochirality as a feature of mechanically interlocked systems has not as yet been
exploited to a great degree. The concept of cyclochirality is closely linked to that of
chirality in covalently linked systems, however in a covalent system a chiral molecule is
described as one that cannot be deformed to give its mirror image without the breaking
of chemical bonds. Whereas in a rotaxane system the macrocycle ring can be caused to
expand its cavity to allow the macrocycle ring to pass over the stopper group and allow
de-threading and re-threading to produce its mirror image, thus the rotaxane is not
topologically chiral but is instead termed cyclochiral. A graphical representation of
cyclochirality is show below in Figure 10.
Figure 10. Graphical representation of cyclochirality.
The first reported synthesised racemic mixture of pure cyclochiral rotaxanes was by
V gtle and co-workers in 1997.ӧ 34
The cyclochirality of their produced rotaxanes comes
from differing sequences of sulphonamide and amine groups on the macrocycle ring.
This, along with unsymmetrical stopper groups gives directionality to the rotaxane
system and as such cyclochirality. The resulting racemic mixture ([2]rotaxanes 25a and
25b) was able to be separated by HPLC with a chiral column.
25
26. Figure 11: Cyclochiral [2]rotaxanes synthesised by V gtle and co-workers which were then separated byӧ
HPLC with a chiral column.
In a more recent study by Hiratani and co-workers they were able to synthesis and
resolve the mixture of rotaxane 11 (shown in Scheme 7)35
that has the ability to
recognise chirality in covalent species so they can be exploited as amino acid chiral
sensors. However they also reported that not all racemic mixtures of rotaxanes could be
resolved using chiral HPLC, they propose that this stems from the structure of the
rotaxane “axle”, with the stopper and chain length being the primary factor that
influences the efficiency of the separation by this technique. This approach to
producing cyclochiral rotaxanes does have its drawbacks, in that the maximum yield
that is applicable is 50%, which limits the scale on which cyclochiral rotaxanes can be
produced.
NH
SO2
NH
O
NH
SO2
NH
O
O O
NH NH
NH
S
O
NH
OO
NHNH
NH
S
O
NH
26
27. A more promising possible strategy is to adopt an asymmetric synthesis, where only the
desired enantiomer is synthesised, which therefore does not then have the same
problems in purification and yield as the racemic mixture strategy. However the
synthesis of a single enantiomer is extremely challenging and only one success has so
far been reported (synthesis shown below in Scheme 15)36
. The yield however is not
impressive (48%) shows that this strategy is a reasonable alternative, with an
enantiomeric excess of only 4.4% also being produced shows that although in theory it
is possible to produce just one enantiomer it is very hard to reproduce synthetically.
O
O
O
O
O
O
O
O
NHCOCH3
NH2
+
OH
PF6
-
+
CO O
2
P
P
catalyst, 99% ee
NH2
+
O
O
OO
O
O
OO
O O
NHCOCH3
PF6
-
26
Scheme 15: Synthesis of cyclochiral [2]rotaxane 26 by Takata and co-workers.
27
28. 3.0 Aim of this project
Previous work within the Lee group has led to the synthesis of the macrocycle shown
below in Scheme 16.
O
O
O
O
O
O
O
O
O
O O
OHOH
O O
O
I I
O
I I
O
N N
O O
O
O
OO
N N
O O
OH OH
N N
O O
O O
N
H
+
N
OH OH
Cl
-
Br
O
OH
O
OH
OH
N BrBr NBr
O
H
NBr
OH
N
H
+
N
OH OHCl
-
(i) n-BuLi, THF, -78
o
C
(ii) DMF, -78
o
C to R.T
74 %
86 % 85 %
79 % 83 %
80 % 82 %
76 % 90 %
82 %
82 %19 %
NaBH4, MeOH, 0
o
C
(i) NiCl2.6H2O, PPh3, Zn, 50
o
C
(ii) 29
(iii) HCl(g), DCM
K2CO3, Allyl bromide, KI
Acetone, Reflux
48% HBr(aq), DCM
Pd(PPh3)4, Aniline, THF, 50
o
C
In(OTf)3, Ethylene glycol,
Benzene, Dean-Stark,
Reflux LiAlH4, THF, 0
o
C to R.T
PPh3, I2, Toluene,
Reflux
In(OTf)3, Ethylene glycol,
Benzene, Dean-Stark,
Reflux
NaH, 33, DMF, 0
o
C to R.T
35, K2CO3
DMF (0.0024 molL
-1
), 80
o
C
27
28
29 30
31 32 33
30
34
35
36 37
38
39
40
41
Scheme 16: Synthesis of macrocycle and its precursors used within Lee group
28
29. The problems with this synthesis are that when forming the diiodo compound 39. The
compound upon formation (as shown in Scheme 16) loses the acetal group and therefore
requires re-acetylation. Although the formation of 40 is high yielding the compound is
not stable enough to be stored for long periods of time.
This project was set up to synthesis a new macrocycle precursor to replace 40. The
conditions that must be satisfied for the new macrocycle precursor are:
a) There must have 7 carbons between leaving groups as a shorter chain hinders
macrocycle formation.
b) The leaving groups X must be easily removable.
c) A five-membered acetal must be present to protect the ketone, as the ketone reactivity
is needed for making the rotaxane cyclochiral.
The new macrocycle precursor must be either formed in one step from the acetal diol 38
shown in Scheme 16 and Scheme 17, or be much higher yielding than the previous
precursor 40.
OO
OH OH
OO
X X
N N
O O
O
O
OO
N N
O O
OH
OH
OO
X X
+
38
35
41
Scheme 17: Overall aim of the project
29
30. 4.0 Results and Discussion
4.1 Synthesis of macrocycle precursor 44
The overall synthetic strategy adopted for the formation of a macrocycle precursor is
shown below in Scheme 18.
OO
O O
O O
O
O O
O O
OO
OH OH
OO
TsO OTs
O
BrBr
O
Br Br
O
383736
42 43
44
Scheme 18: Overall synthetic route explored for macrocycle precursor.
Many different acetals are possible in synthesis, however in this case a five-membered
acetal was chosen because of its ease of cleavage, this is important for revealing
cyclochirality in a rotaxane system comprising the precursor formed.
OO
O O
O O
O
O O
O O
36 37
Scheme 19: 2 mol% In(OTf)3, Ethylene Glycol, Benzene, Dean Stark reflux, 100 o
C, 18 hrs, 88%
The first step of the synthesis is an acetalation, of commercially available Diethyl 4-
oxopimelate, this reaction was carried out under normal Dean Stark conditions. This
reaction proceeded with an 88% yield after purification by column chromatography.
OO
O O
O O
OO
OH OH
37 38
Scheme 20: LiAlH4, dry THF, N2, 18 hrs, R.T, 64%
30
31. With the acetal ester successfully synthesised the next step was to reduce the ester to an
alcohol using LiAlH4 as the reducing agent. The reaction went to completion however a
Fieser workup (1 mL of H2O for every gram of LiAlH4 used followed by 1 mL of 15%
NaOH for every gram of LiAlH4 used then finally 3 mL of H2O for every gram of
LiAlH4 used) was necessary as the acetal diol is soluble in water. After filtration to
remove the salts the solvent was removed using a rotary evaporator, once all solvent had
been removed the pure product would crystallise.
OO
OH OH
O
BrBr
38 42
Scheme 21: PPh3, Br2, Toluene, 18 hrs, 21%
Following on from previous work within the group, the acetal diol was reacted with
bromine to form a dibromo compound (shown above in Scheme 15), however due to the
acidic conditions of the reaction the acetal of the diol is cleaved, because the acetal is
vital for the macrocycle the dibromo compound has to be re-acetalised.
O
BrBr
O
Br Br
O
42 43
Scheme 22: 2 mol% In(OTf)3, Ethylene Glycol, Benzene, Dean Stark reflux, 100 o
C, 18 hrs, 43%
This reaction utilised normal Dean-Stark conditions also, however in this case a poor
yield of only 43% was obtained, I think this may have been due to the relative
instability of the dibromo ketone at the temperatures required for the reaction to
proceed.
OO
OH OH
OO
TsO OTs
38 44
Scheme 23: KOH, TsCl, dry THF, -10 - 0 o
C, 66%
The new shorter final step of the synthesis is the conversion from an alcohol group to a
tosylate group without removing the acetal. This was performed under extremely mild
31
32. conditions to protect the acetal from being removed. The reaction proceeds via a
deprotonation of the alcohol to produce an alkoxide this then reacts via an SN2
mechanism to produce the OTs group from reaction with TsCl. The product was
recrystallised from MeOH/hexane to give a 66% yield of pure product.
4.2 Synthesis of macrocycle 41
N N
O O
O
O
OO
N N
O O
OH OH
OO
TsO OTs
+
413544
Scheme 24: Cs2CO3, dry DMF, N2, high dilution, 18 hrs, 37%
A high dilution set up was used for the macrocyclisation reaction. Both macrocycle
precursors (44 and 35) were dissolved up in dry DMF and transferred into syringes.
The Cs2CO3 was dissolved in dry DMF in a 3 necked round bottom flask with the
syringes containing the macrocycle precursors on an injection pump set to add into the
flask. This method compared with the previous method of adding all reactants in at
once gave a twice as high yield of 37% (versus the 21% yield obtained within group).
The macrocycle product was characterised by 1
H and 13
C-NMR, with a 1
H-13
C
correlation taken to resolve the many overlapping peaks.
32
33. 5.0 Conclusion
The main aim of the project was to synthesis a new macrocycle precursor which was
able to be stored for long periods unlike the precursor used by the group at the moment
(compound 40) this aim was achieved with the formation of precursor 44 as this is
stable for long periods and is able to be stored under air with no problems.
The secondary aim of the project was to make the precursor in fewe steps, this was also
successfully achieved with the formation of 44, because of the mild conditions the Ts
group can be added under the acetal is not cleaved and as such saves one step from the
synthesis.
Finally and most importantly the new precursor 44 was reacted with the other premade
precursor 35 to give the desired macrocycle, this process was also an improvement over
previous methods within the group, such that an almost doubled percentage yield was
obtained from the reaction (37% compared with 21% from previous work within the
group).
33
34. 6.0 Experimental section
1
H NMR spectra were recorded on Bruker AVIII and DPX 400 at 300 MHz and 400
MHz respectively and referenced to the residual solvent. 13
C NMR spectra were
recorded at 75.5 MHz and 100 MHz on the same spectrometers. Chemical shift data is
given in parts per million (δ in ppm), J values are given in Hz.
Flash chromatography was carried out using Matrix silica gel 60a from Fisher
Chemicals and TLC was performed using Merck silica gel 60 F254 pre-coated sheets
with detection by CAM or permanganate dips depending upon reaction being studied.
The inference room temperature (RT) refers to an ambient temperature of 12 – 20 o
C.
All chemicals used were purchased from either Aldrich or Fischer chemical companies.
THF was dried by distillation from sodium as was toluene and DMF was dried using
vacuum distillation from sodium. PE refers to petroleum ether (40-60%). EtOAc refers
to ethyl acetate.
6.1 Synthesis of macrocycle precursor
Preparation of diethyl 3,3'-(1,3-dioxolane-2,2-diyl)dipropanoate 37
OO
O O
O O
Ha
Hb
Hb
Hc Hc
HdHd
He
He
He
Ha
O
O O
O O
36 37
Solution of diethyl 4-oxoheptanedioate (16.5 g, 71.5 mmol) and ethylene glycol (20
mL/22.3 g) in Benzene (330 mL) was stirred before indium triflate (0.819 g, 1.46
mmol) was added to the solution. The reaction mixture was then heated at reflux until
the reaction was complete (approximately 18 hrs) before being cooled to room
temperature. The solvent was then removed in vacuo to afford a crude yellow oil
product which was subsequently dissolved in a minimum amount of EtOAc. The
organics were then washed consecutively with H2O, saturated NaHCO3, H2O and brine
before being dried over Na2SO4. This was concentrated to a pale yellow oil, the oil was
pre-adsorbed onto silica and then purified by flash chromatography eluting with a
mixture of PE:EtOAc of 15:1 to 6:1 to yield (17.3 g, 63 mmol, 88%) of clean product
37 as a colourless oil.
34
35. δ H (300 MHz, CDCl3) 4.11 (4 H, q, J 7.1, Ha), 3.92 (4 H, s, Hb ), 2.40 – 2.31 (4 H, m,
Hc/Hd), 2.00 – 1.91 (4 H, m, Hc/Hd), 1.28 – 1.20 (6 H, m, He).
δ C (75 MHz, CDCl3) 173.4 (C x2), 110.1 (C), 65.1 (CH2 x2), 60.3 (CH2 x2), 32.4 (CH2
x2), 28.9 (CH2 x2), 14.2 (CH3 x2).
Preparation of 3,3'-(1,3-dioxolane-2,2-diyl)dipropan-1-ol 38
OO
O O
O O
OO
OH OHk
Hf
Hf
Hg
Hg
Hi Hi
Hj Hj
37 38
Solution of 37 (3.054 g, 11.1 mmol) in dry THF (130 mL) was stirred under N2, LiAlH4
(2.14 g, 56.3 mmol) was added portion wise at 0 o
C. The reaction was then stirred for
18 hrs at room temperature. The reaction was quenched using a minimum volume of
saturated Na2SO4 followed by EtOAc (20mL). The solution was then filtered and the
salts were washed with EtOAc, the solvent was removed from the filtrate in vacuo. The
residue obtained was dissolved in DCM (75 mL) and dried over Na2SO4. This was
concentrated to afford crude product, the crude product was pre-adsorbed onto silica
and then purified by flash chromatography eluting with a mixture of PE:EtOAc of 9:1 to
1:1 to yield (1.37 g, 7.2 mmol, 64%) of clean product 38 as a white solid.
δ H (300 MHz, CDCl3) 3.90 (4 H, s, Hf), 3.55 (4 H, t, J 6.1, Hg), 2.95 (2 H, s, Hk), 1.71 –
1.62 (4 H, m, Hi/Hj), 1.62 – 1.51 (4 H, m, Hi/Hj).
δ C (75 MHz, CDCl3) 111.8 (C), 65.2 (CH2 x2), 63.3 (CH2 x2), 33.8 (CH2 x2), 27.3 (CH2
x2).
Preparation of 1,7-dibromoheptan-4-one 42
OO
OH OH
O
BrBr
Hl
Hm Hm
Hn HnHl
38 42
A solution of 38 (0.502 g, 2.64 mmol) in dry toluene (40 mL) was stirred under an N2
atmosphere. PPh3 (1.81 g, 6.91 mmol) was added and reaction was heated to 130 o
C
and the Br2 (0.2 mL/0.62 g, 7.77 mmol) was added portion wise. The reaction was then
refluxed in darkness for 18 hrs. Absolute ethanol (0.25 mL) was added in 2 portions, 30
mins apart from each other. The solvent was then removed in vacuo before the residue
35
36. was taken up in a minimum DCM. The crude product was pre-adsorbed onto silica and
then purified by flash chromatography eluting with a mixture of PE:EtOAc of 10:1 to
yield (0.149 g, 0.55 mmol) of clean product 42 as a dark yellow/brown oil.
δ H (300 MHz, CDCl3) 3.47 (2 H, t, J 6.4, Hn), 2.66 (2 H, t, J 7.0, Hl), 2.15 (2 H, p, J 6.7,
Hm).
δ C (75 MHz, CDCl3) 110.5 (C), 35.7 (CH2 x2), 34.1 (CH2 x2), 27.4 (CH2 x2).
Preparation of 2,2-bis(3-bromopropyl)-1,3-dioxolane 43
O
BrBr
O
Br Br
O
Ho
Ho
Hp Hp
Hq Hq
Hr Hr
42 43
Solution of 42 (0.26 g, 0.96 mmol) and ethylene glycol (0.25 mL/0.28 g) in Benzene (7
mL) was stirred before indium triflate (0.013 g, 0.023 mmol) was added to the solution.
The reaction mixture was now heated at reflux until completion of the reaction
(approximately 18 hrs) before being cooled to room temperature. The solvent was then
removed in vacuo and the crude product dissolved in a minimum amount of EtOAc.
The organics were then washed consecutively with H2O, saturated NaHCO3, H2O and
brine before being dried over NaSO4. This was concentrated to a pale yellow oil, the oil
was pre-adsorbed onto silica and then purified by flash chromatography eluting with a
mixture of PE:EtOAc of 15:1 to yield (0.13 g, 0.41 mmol, 43%) of clean product 43 as a
brown solid.
δ H (300 MHz, CDCl3) 3.96 (4 H, s, Ho), 3.44 (4 H, t, J 6.6, Hr), 2.02 – 1.90 (4 H, m,
Hp), 1.81 – 1.72 (4 H, m, Hq).
δ C data was not obtained as not enough product was formed for analysis.
36
37. Preparation of 2,2-bis(3-tosyloxypropyl)-1,3-dioxolane 44
OO
OH OH
OO
TsO O
Hs
Hs
Ht Ht
Hu Hu
Hv Hv S
O
O
Hw
Hw
Hx
Hx
Hy
Hy
Hy
38 44
A solution of 38 (1.73 g, 9.07 mmol) in dry THF (20 mL) was cooled to -10 o
C under an
N2 atmosphere, TsCl (4.35 g, 22.8 mmol) and powdered KOH (5.1 g, 90.9 mmol) were
then added over portion wise over 20 mins. The reaction was allowed to stir for 30
mins before being allowed to reach 0 o
C and left to stir for 18 hrs. The solution was
then added to an ice/water mixture and extracted with EtOAc, the solution were then
washed 3 times with EtOAc. The organics were then washed with brine and dried with
MgSO4. The solvent was then removed in vacuo to afford a crude solid product, the
crude product was then recrystallised from hot MeOH and extracted using hexane to
yield (2.97 g, 5.97 mmol, 66%) of pure crystalline macrocycle precursor 44.
δ H (300 MHz, CDCl3) 7.76 (4 H, d, J 8.3, Hw), 7.32 (4 H, d, J 8.0, Hx), 4.00 (4 H, t, J
6.3, Hv), 3.82 (4 H, s, Hs), 2.43 (6 H, s, Hy), 1.69 – 1.61 (4 H, m, Ht/Hu), 1.58 – 1.53 (4
H, m, Ht/Hu).
δ C (75 MHz, CDCl3) 145.0 (C x2), 133.4 (C x2), 130.1 (CH x4), 128.1 (CH x4), 110.6
(C), 70.7 (CH2 x2), 65.2 (CH2 x2), 33.1 (CH2 x2), 23.6 (CH2 x2), 21.9 (CH3 x2).
37
38. 6.2 Synthesis of macrocycle 41
N N
O O
O
O
OO
Haa Hbb
Hcc
Hdd
Hdd
Hee
Hee
Hff
Hgg
Hff
Hgg
Hhh
Hhh
HiiHii
Hjj
Hjj
Hkk
Hkk
N N
O O
OH OH
OO
TsO OTs
+
413544
A solution of CsCO3 (0.383 g, 1.17 mmol) in dry DMF (50 mL) at 65 o
C was stirred
under N2. 44 (0.059 g, 0.012 mmol) was dissolved in dry DMF (5 mL) and put in
syringe, macrocycle precursor 35 (0.0502 g, 0.012 mmol) was dissolved in dry DMF (5
mL) and put in a syringe. Both syringes were put on a syringe pump set with a flow
rate of 0.5 mL/hr. Once all starting material had been added solution was stirred for a
further 24 hrs. The solvent was removed in vacuo then the residue was taken up in
EtOAc (100 mL). This solution was then washed with H2O (100 mL) and the aqueous
re-extracted using DCM (300 mL). This was concentrated to a brown oil, the oil was
pre-adsorbed onto silica and then purified by flash chromatography eluting with a
changing solvent system (DCM to DCM:MeOH 99.5:0.5 to DCM:MeOH 99:1) to yield
(0.025 g, 0.043 mmol, 37%) of clean macrocycle product 41 as a white solid.
δ H (400 MHz, CDCl3) 7.88 (2 H, d, J 7.7, Haa/Hcc), 7.70 (2 H, t, J 7.8, Hbb), 7.40 (2 H, d,
J 7.7, Haa/Hcc), 7.20 – 7.11 (4 H, m, Hgg), 6.75 – 6.68 (4 H, m, Hff), 4.63 (8 H, d, J 4.3,
alkyl CH2’s), 3.97 – 3.89 (8 H, m, alkyl CH2’s), 1.79 – 1.66 (8 H, m, alkyl CH2’s).
δ C (101 MHz, CDCl3) 159.0 (C x2), 158.6 (C x2), 137.5 (CH x2) , 130.3 (CH x4),
130.0 (C x2), 121.5 (CH x2), 120.5 (CH x2), 114.9 (CH x4), 111.5 (C x2), 77.4 (C),
73.0 (CH2 x2), 72.1 (CH2 x2), 68.1 (CH2 x2), 65.2 (CH2 x2), 33.6 (CH2 x2), 23.6 (CH2
x2).
38
39. Acknowledgements
I would like to thank my supervisor Dr Ai-Lan Lee for a very interesting project and all
the feedback I have received throughout it. I would also like to thank James O’Neill for
his considerable contribution during my time in the lab. Also thanks are extended to
Jamie Jordan-Hore and Pauline Glen for guidance when I have required it.
39
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