Complexation: Metal and Organic Molecular Complexes, Inclusion Compounds with Reference to Cyclodextrins, Methods of Analysis.

1. Complexation: Metal and Organic
Molecular Complexes, Inclusion
Compounds with Reference to
Cyclodextrins, Methods of Analysis.
CHAVAN KHUSHAL

2. CONTENTS
 Introduction to Complexation
 Characteristics of Metal-Organic
Complexes
 Types of Metal-Organic Complexes
 Applications of Metal-Organic Complexes
 Introduction to Inclusion Compounds
 Cyclodextrins: Versatile Host Molecules
 Methods of Analysis for Complexation
 UV-Vis Spectroscopy
 NMR Spectroscopy
 X-ray Crystallography
 Calorimetry
 Applications of Analytical Methods in
Complexation
 Conclusion: Complexation - A Fascinating
Chemical World
 References

3. Introduction to Complexation
• Complexation, also known as chelation or
adduction, is a chemical process in which
two or more molecules, called
ligands, form a bond with a central metal
ion.
• The ligands donate electron pairs to the
metal ion, creating a coordinate covalent
bond.
• The resulting complex has distinct
properties from the individual components.
metal ion surrounded by ligands

4. Complexation, also known as coordination complex formation, is a fundamental chemical phenomenon with diverse
applications across various fields. It involves the interaction and association of two or more species, typically:
• Central atom/ion: This is usually a metal ion with vacant orbitals capable of accepting electron pairs.
• Ligands: These are molecules or ions that donate electron pairs to the central atom/ion through lone pairs or negative
charges.
The resulting complex entity exhibits unique properties and behavior different from its individual components.
Key aspects of complexation:
• Types of ligands: Ligands can be monodentate (donating one electron pair), bidentate (donating two electron pairs), or
polydentate (donating more than two electron pairs). Chelating ligands, a specific type of polydentate ligands, form
multiple bonds with the central atom/ion, creating highly stable complexes.
• Coordination number: This refers to the maximum number of ligands that can bind to the central atom/ion. It depends
on the central atom's size and electronic configuration.
• Geometry: The arrangement of ligands around the central atom/ion determines the complex's geometry, which can be
octahedral, tetrahedral, square planar, etc.
• Bonding: Complexation involves various types of bonding, including covalent and dative (coordinate) covalent bonds.
• Properties: Complexation can significantly influence the properties of the central atom/ion and ligands, such as
solubility, stability, reactivity, color, and magnetism.

5. Characteristics of Metal-Organic Complexes
• Metal-organic complexes are formed
when organic ligands, such as
carboxylic acids, amines, or
phosphines, bind to a metal ion.
• The number of ligands that can bind to
a metal ion is determined by its
coordination number.
• The geometry of the complex depends
on the arrangement of ligands around
the metal ion.
3D structure of a metalorganic complex

6. Metal-organic complexes (MOCs) are a fascinating class of compounds exhibiting unique characteristics due to their hybrid nature,
combining organic ligands and metal ions. Here are some key characteristics of MOCs:
Structure and Bonding:
• Hybrid structure: MOCs are constructed from central metal ions coordinated with organic ligands through coordinate covalent bonds.
The ligands donate lone pairs of electrons to the metal center, forming a complex with specific geometry and stability.
• Variety of ligands: MOCs can utilize diverse organic ligands with different functionalities and coordination modes, significantly
impacting the overall properties of the complex.
• Tunable structure: The choice of metal and ligand allows for precise control over the complex's structure, leading to targeted properties
and functionality.
• Bonding: The metal-ligand interaction involves various types of bonding, including covalent, dative covalent (coordinate covalent), and
ionic contributions.
Properties:
• High stability: MOCs often exhibit high stability due to the strong metal-ligand interaction and chelating effects from polydentate
ligands.
• Tunable properties: The properties of MOCs, such as solubility, reactivity, color, magnetism, and luminescence, can be finely tuned by
varying the metal, ligand, and coordination sphere.
• Redox activity: Many MOCs exhibit diverse redox behavior, making them valuable for applications in energy storage and catalysis.
• Catalysis: The presence of metal centers and functional organic ligands can create highly active and selective catalysts for various
chemical reactions.
• Porosity: Some MOCs, known as metal-organic frameworks (MOFs), possess highly porous structures with large surface areas, making
them attractive for gas storage, separation, and drug delivery applications.
• Luminescence: Certain MOCs emit light of different colors, leading to potential applications in LEDs, sensors, and bioimaging.

7. Applications:
• Catalysis: MOCs serve as efficient catalysts for a wide range of organic and inorganic transformations,
including olefin hydrogenation, oxidation reactions, and polymerization reactions.
• Gas storage and separation: MOFs with high porosity and tunable pore sizes are ideal candidates for
capturing and separating gases like CO2, H2, and CH4.
• Drug delivery: MOCs can be designed to deliver drugs to specific target sites in the body, enhancing their
efficacy and reducing side effects.
• Sensors: MOCs can be used to detect various analytes due to their ability to selectively bind to specific
molecules and alter their properties.
• Energy storage: MOCs with redox-active metal centers can be utilized for developing new battery
materials and fuel cell technologies.
• Biomaterials: MOCs have the potential for application in biomaterials due to their biocompatibility and
tailorable properties, offering potential in tissue engineering and regenerative medicine.
Overall, the unique and versatile characteristics of metal-organic complexes make them a promising platform
for research and development across various scientific and technological fields.

8. Types of Metal-Organic Complexes
• Metal-organic complexes can be classified
based on the type of ligands involved:
• Chelate complexes: These complexes involve
ligands that can bind to the metal ion through
multiple sites, forming a ring structure.
• Monodentate complexes: These complexes
involve ligands that can only bind to the metal
ion through a single site.
different types of metalorganic complexes

9. 1. Based on Ligand Structure:
• Monodentate Ligands: These
ligands donate only one electron
pair to the metal center, forming
simple complexes. Examples
include water (H2O) and
ammonia (NH3).
• Bidentate Ligands: These
ligands donate two electron pairs
through two separate donor
atoms, often forming more stable
and well-defined complexes.
Examples include
ethylenediamine (en) and
bipyridine (bipy).
• Polydentate Ligands: These
ligands can donate three or more
electron pairs, often forming
highly stable chelate complexes
with ring structures. Examples
include EDTA
(ethylenediaminetetraacetic acid)
and porphyrins.
2. Based on Metal Ion:
• Transition Metal Complexes:
These are the most common type
of MOCs, formed by transition
metals like Fe, Cu, Ni, Co, and
Zn. These metals possess
partially filled d-orbitals,
allowing them to form various
coordination geometries and
exhibit diverse properties.
• Main Group Metal Complexes:
These involve metals from the
main groups of the periodic
table, such as Mg, Al, and Be.
They often exhibit different
coordination behavior compared
to transition metals.
• Lanthanide and Actinide
Complexes: These involve f-
block elements with unique
electronic configurations and
coordination preferences. They
are often used in luminescent
materials and magnetic devices.
3. Based on Coordination
Geometry:
• Octahedral: This is a common
geometry observed in MOCs
with six ligands surrounding the
metal center. Examples include
Fe(CO)6 and [Cr(H2O)6]3+.
• Tetrahedral: This geometry
involves four ligands arranged
tetrahedrally around the metal
center. Examples include
[ZnCl4]2- and [CoCl4]2-.
• Square planar: This geometry
has four ligands surrounding the
metal center in a planar square
arrangement. Examples include
[Ni(CN)4]2- and [PtCl4]2-.
• Trigonal bipyramidal: This
geometry has five ligands
arranged in a trigonal
bipyramidal fashion, with three
in the plane and two
perpendicular to it. Examples
include [Fe(CO)5] and
[Mo(CO)5]2-.
4. Special Types of MOCs:
• Metal-Organic Frameworks
(MOFs): These are porous
materials constructed from metal
ions and organic ligands,
forming highly ordered
structures with large surface
areas. MOFs have various
potential applications in gas
storage, separation, and
catalysis.
• Organometallic Complexes:
These involve metal centers
directly bonded to carbon atoms,
often exhibiting unusual and
highly reactive properties. They
are used in various catalysts and
organic synthesis reactions.
• Bioinorganic Complexes:
These are MOCs found in
biological systems, playing
crucial roles in various metabolic
processes and protein functions.
Examples include the iron center
in hemoglobin and the
magnesium center in
chlorophyll.
Metal-organic complexes (MOCs) exhibit a remarkable diversity in their structure and properties due to the
wide range of possible combinations between metal ions and organic ligands. Here's a breakdown of the
different types of MOCs based on various criteria:

10. Applications of Metal-Organic Complexes
• Metal-organic complexes have a wide range of
applications in various fields:
• Analytical chemistry: Metal-organic complexes
are used in chelatometric titration to quantify
metal ions.
• Materials science: Metal-organic complexes are
used as catalysts, sensors, and magnetic materials.
• Medicine: Metal-organic complexes are used as
therapeutic agents, such as cisplatin for cancer
treatment and radiocontrast agents for medical
imaging.
metalorganic complex used as a catalyst

11. Metal-organic complexes (MOCs) hold immense potential in various fields due to their unique properties like tunable structure, high stability, diverse
functionality, and reactivity. Here's an overview of their applications across different domains:
Catalysis:
• Homogeneous Catalysis: MOCs are widely employed as homogeneous catalysts for various organic and inorganic reactions, including olefin hydrogenation,
oxidation reactions, polymerization, and carbon dioxide fixation. Their ability to form specific complexes with substrates and intermediates allows for
efficient and selective catalysis.
• Heterogeneous Catalysis: MOCs can be immobilized on support materials to create heterogeneous catalysts with improved stability and ease of separation.
They are used in various industrial processes like hydrogenation, dehydrogenation, and hydroformylation.
Gas Storage and Separation:
Metal-Organic Frameworks (MOFs): Due to their high surface areas and tunable pore sizes, MOFs are ideal candidates for storing and separating gases like
CO2, H2, CH4, and other valuable molecules. Their potential applications include carbon capture and storage, gas purification, and renewable energy storage.
Drug Delivery:
MOCs can be designed to encapsulate and deliver drugs to specific target sites in the body, improving their efficacy and reducing side effects. They can also be
used to control the release rate of drugs, offering sustained therapeutic effects.
Metal-based anticancer drugs like cisplatin and carboplatin are examples of MOCs used in chemotherapy.
Sensors and Imaging:
MOCs can be used to design sensors for detecting various analytes due to their ability to selectively bind to specific molecules and alter their properties. They
have applications in environmental monitoring, food safety analysis, and medical diagnostics.
MOCs are also employed as contrast agents in magnetic resonance imaging (MRI) and other medical imaging techniques.
Energy Storage and Conversion:
MOCs are promising materials for developing new battery technologies due to their ability to store and release energy through redox reactions. They are also
being explored for their potential in solar energy conversion and photocatalysis applications.
Other Applications:

12. Other Applications:
MOCs are used in various other applications, including:
• Dye-sensitized solar cells
• Luminescent materials
• Magnetic materials
• Cosmetic pigments
• Food additives
• Water purification materials
As research progresses, new applications for MOCs are continually being discovered. Their versatility and tunability
make them a valuable tool for scientists and engineers to address challenges in various fields.

13. Introduction to Inclusion Compounds
• Inclusion compounds, also known as clathrates or
host-guest complexes, are a type of complex in
which a host molecule encapsulates a guest
molecule within its cavity.
• The host molecule typically has a rigid, hollow
structure, while the guest molecule is a smaller
molecule that can fit into the host's cavity.
• The interaction between the host and guest is
driven by weak forces, such as van der Waals
forces and hydrogen bonding.
guest molecule encapsulated within a host molecule

14. Introduction to Inclusion Compounds:
Inclusion compounds, also known as inclusion complexes, are a fascinating class of molecular adducts formed by the
interaction of two or more components:
• Host molecule: This molecule possesses a cavity or framework capable of encapsulating another molecule.
• Guest molecule: This molecule is smaller than the host cavity and fits snugly inside it.
The interaction between host and guest is primarily driven by weak intermolecular forces like van der Waals forces,
hydrogen bonding, and π-π interactions. There is no formation of covalent bonds between the host and guest molecules.
Key characteristics of inclusion compounds:
• Geometric complementarity: The host cavity must be of a suitable size and shape to accommodate the guest molecule
efficiently.
• Non-covalent interactions: The interaction between host and guest is dominated by weak forces, allowing for reversible
complexation and release of the guest molecule.
• Varied composition: Both host and guest molecules can be organic, inorganic, or a combination of both, leading to a
vast array of possible inclusion compounds.
• Tailorable properties: The properties of the inclusion compound depend on the specific host and guest molecules,
allowing for the design of materials with targeted functionalities.

15. Types of inclusion compounds:
• Clathrates: These compounds are formed by a lattice of host molecules, creating cavities that encapsulate guest
molecules. Examples include gas hydrates and cyclodextrin inclusion complexes.
• Intercalation compounds: In these compounds, guest molecules are inserted between the layers of a layered host
structure. Examples include graphite intercalation compounds and layered double hydroxides.
• Channel inclusion compounds: These compounds possess channels or tunnels through their structure, where guest
molecules are accommodated. Zeolites and nanotubes are examples.
Applications of inclusion compounds:
• Separation and purification: Inclusion compounds can be used to selectively capture and separate specific molecules
from mixtures, based on size and shape complementarity.
• Drug delivery: Encapsulation of drugs within inclusion compounds can improve their solubility, bioavailability, and
targeted delivery to specific tissues.
• Catalysis: Inclusion compounds can act as microreactors, providing an environment for specific reactions to occur within
the host cavity.
• Gas storage: Clathrate compounds are efficient for storing gases like methane and hydrogen, offering potential for
renewable energy storage.
• Sensors and biosensors: Inclusion compounds can be designed to selectively bind to specific molecules, making them
useful for sensing and detection applications.
The study of inclusion compounds provides insights into molecular recognition, self-assembly, and the design of functional
materials with diverse applications.

16. Cyclodextrins: Versatile Host Molecules
• Cyclodextrins are a family of cyclic
oligosaccharides derived from starch. They have a
truncated cone-shaped structure with a hydrophilic
exterior and a hydrophobic interior.
• This unique structure makes cyclodextrins
excellent host molecules for inclusion compounds.
• Cyclodextrins can encapsulate a wide variety of
guest molecules, including drugs, flavors,
• Food science: Cyclodextrins are used to improve
the stability, flavor, and bioavailability of food
ingredients.
• Environmental science: Cyclodextrins are used to
remove pollutants from water and soil.
cyclodextrin molecule with a guest molecule

17. Cyclodextrins (CDs) are a fascinating class of cyclic oligosaccharides formed by the enzymatic degradation of starch. These molecules are
doughnut-shaped, with a hydrophilic outer surface and a hydrophobic, truncated cone-shaped cavity. This unique structure makes them
ideal host molecules for forming inclusion complexes with a wide variety of guest molecules.
Properties of cyclodextrins:
• High water solubility: Their hydrophilic exterior allows them to readily dissolve in water.
• Non-toxic and biodegradable: CDs are considered safe for use in various applications.
• Tunable cavity size: Different types of CDs exist, with varying cavity sizes to accommodate diverse guests.
• Chiral recognition: CDs can distinguish between enantiomers of guest molecules, making them valuable for separation and purification.
• Formation of inclusion complexes: CDs can encapsulate guest molecules within their cavity, altering their physicochemical properties.
Applications of cyclodextrins:
• Drug delivery: CDs can improve the solubility, stability, and bioavailability of drugs, enhancing their therapeutic effect and reducing
side effects.
• Food and cosmetics: CDs are used to prevent the degradation of flavors and fragrances, improve the texture of food, and encapsulate
active ingredients in cosmetics.
• Environmental remediation: CDs can remove pollutants from water and soil by selectively binding to them.
• Separation and purification: CDs can separate specific molecules from mixtures based on size and shape, enabling the isolation of
valuable compounds.
• Analytical chemistry: CDs are employed in various analytical techniques like chromatography and spectroscopy due to their ability to
form inclusion complexes with specific analytes.
• Catalysis: CD-based catalysts can be designed to provide microenvironments for specific reactions, enhancing their efficiency and
selectivity.

18. Types of cyclodextrins:
• α-cyclodextrin: This is the smallest CD with six glucopyranose units and a cavity size of 0.5 nm.
• β-cyclodextrin: This CD has seven glucopyranose units and a cavity size of 0.7 nm, making it the most widely
used type.
• γ-cyclodextrin: This CD has eight glucopyranose units and a cavity size of 0.9 nm, accommodating larger guest
molecules.
Derivatives of cyclodextrins:
• To improve their properties and expand their applications, CDs can be chemically modified to introduce various
functionalities, such as:
• Hydroxyl groups can be modified to increase solubility or enhance specific interactions with guest molecules.
• Cationic groups can be introduced for binding negatively charged molecules.
• Fluorescent tags can be attached for visualization and tracking purposes.
Overall, cyclodextrins are versatile host molecules with a wide range of applications in various fields. Their unique
properties, tunable cavity size, and ability to form inclusion complexes make them valuable tools for scientists and
engineers to develop innovative and functional materials.

19. Methods of Analysis for Complexation
 Various analytical techniques can be used to
characterize and study complexation
phenomena. These methods provide valuable
information about the structure, properties, and
stability of complexes and inclusion
compounds.
laboratory setup with various analytical instruments

20. Methods of Analyzing Complexation
Analyzing complexation involves determining the formation of a complex between a central atom/ion and ligands, measuring its stability
constant, and understanding the stoichiometry and geometry of the complex. Various techniques are employed depending on the specific
complex and the desired information.
Here are some commonly used methods for analyzing complexation:
1. Spectroscopic methods:
• UV-Vis spectroscopy: This technique measures the absorption of light by the complex, providing information about the electronic
transitions between energy levels. Changes in the absorption spectrum upon complexation can confirm its formation and reveal details
about the bonding interactions.
• Infrared (IR) spectroscopy: This technique measures the vibrational frequencies of bonds in the complex. Shifts in the IR spectrum
upon complexation indicate changes in bond strength and geometry, providing information about the coordination mode of the ligands.
• Nuclear magnetic resonance (NMR) spectroscopy: This technique provides information about the chemical environment of atoms in
the complex. Changes in the chemical shifts of NMR signals upon complexation can reveal the binding sites of the ligands and the
geometry of the complex.
2. Titration methods:
• pH titration: This technique measures the change in pH of a solution upon addition of a complexing agent. The resulting titration curve
can be used to determine the stoichiometry of the complex and the stability constant.
• Conductometric titration: This technique measures the change in electrical conductivity of a solution upon addition of a complexing
agent. Changes in conductivity can indicate the formation of the complex and provide information about the charge of the complex
species.
• Isothermal titration calorimetry (ITC): This technique measures the heat absorbed or released during complexation. The
thermodynamic parameters such as enthalpy and entropy change can be calculated, providing insights into the nature of the forces
driving the complexation process.

21. 3. Other methods:
• Distribution method: This method relies on the different partitioning behavior of free and complexed ligands between
two immiscible phases. By measuring the distribution of the ligand in each phase, the stability constant of the complex
can be determined.
• Solubility method: This method measures the change in solubility of the central atom/ion upon complexation. The
change in solubility can be used to determine the stability constant and the stoichiometry of the complex.
• X-ray crystallography: This technique provides information about the three-dimensional structure of the complex,
including the bond lengths, bond angles, and coordination geometry.
The choice of method for analyzing complexation depends on several factors, including:
• The nature of the complex: This includes the identity of the central atom/ion and ligands, their charge, and their
complexation properties.
• The desired information: Whether the goal is to confirm complexation, determine the stoichiometry, measure the
stability constant, or understand the geometry of the complex.
• The available instrumentation and expertise: Some techniques require specialized equipment and training..
By combining various analytical methods, scientists can gain a comprehensive understanding of the complexation process
and develop new applications for these fascinating and versatile molecular adducts.

22. UV-Vis Spectroscopy
• UV-Vis spectroscopy is a technique that
measures the absorption of ultraviolet or visible
light by a molecule or complex.
• In the context of complexation, UV-Vis
spectroscopy can be used to:
• Determine the electronic structure of metal-
organic complexes.
• Study the formation and dissociation of
complexes.
• Monitor the encapsulation of guest molecules in
inclusion compounds.
Schematic drawing of the optical setup of a
monochromatic UV/Vis spectrophotometer

23. NMR Spectroscopy
• NMR spectroscopy is a technique that utilizes
nuclear magnetic resonance to probe the
structure and dynamics of molecules.
• In the context of complexation, NMR
spectroscopy can be used to:
• Determine the coordination geometry of metal-
organic complexes.
• Identify the types of ligands involved in
complexation.
• Study the rotational dynamics of guest
molecules in inclusion compounds.
NMR spectrometer

24. X-ray Crystallography
• X-ray crystallography is a technique that
determines the three-dimensional structure of
molecules or complexes by analyzing the
diffraction of X-rays from a crystalline sample.
• In the context of complexation, X-ray
crystallography can be used to:
• Determine the precise arrangement of atoms in
a metal-organic complex.
• Identify the positions and orientations of
ligands.
• Visualize the encapsulation of guest molecules
in inclusion compounds.
crystal structure

25. Calorimetry
• Calorimetry is a technique that measures the
heat released or absorbed during a chemical
reaction, such as complex formation.
• In the context of complexation, calorimetry can
be used to:
• Determine the enthalpy and entropy of complex
formation.
• Study the thermodynamics of ligand exchange
reactions.
• Evaluate the stability of inclusion compounds.
calorimeter

26. Applications of Analytical Methods in
Complexation
• The analytical methods discussed in this presentation
play a crucial role in various fields:
• Analytical chemistry: These methods are used to identify,
quantify, and characterize metal ions and complexes in
various samples, such as environmental samples,
industrial products, and biological fluids.
• Materials science: These methods are used to study the
structure, properties, and behavior of metal-organic
complexes and inclusion compounds in materials such as
catalysts, sensors, and functional materials.
• Medicine: These methods are used to develop new
therapeutic agents, understand the mechanisms of drug
action, and monitor the pharmacokinetics of drugs in the
body.
scientist analyzing a complex molecule

27. Conclusion: Complexation - A Fascinating
Chemical World
• The world of complexation is a fascinating
realm of chemistry, filled with intricate
interactions between molecules.
• The ability of molecules to form complexes
with tailored properties has opened up a vast
array of applications in diverse fields.
• Understanding complexation phenomena is
crucial for developing new materials, designing
novel therapeutic agents, and unraveling the
complexities of biological systems.
complex chemical formula with various ligands

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