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5th East Asian Polymer Conference
- 1. Toward to Highly Efficient Near-Infrared Chiroptically Switching Materials: -- Design, Synthesis and Properties Reporter: Jian Deng Supervisor: Naiheng Song (Peking University) Zhixing Su (Lanzhou University) 5 th East-Asian Polymer Conference_ June 3-6, 2008, Shanghai, China.
- 3. Chirality “ I call any geometrical figure, or group of points, chiral, and say that it has chirality, if its image in a plane mirror, ideally realized, cannot be brought to coincide with itself.” Lord Kelvin, Baltimore Lectures, 1904
- 6. Chiral Waveguide and Polarization Control NIR Chiroptically Active Materials Strong Signal Changes (Ellipticity or Optical Rotation ) Control of External Field (e.g., Electric or Light Filed)
- 7. Huang, X.F.; Rickman, B.H.; Borhan, B.; Berova, N.; Nakanishi, K. J.Am.Chem.Soc. , 1998, 120 , 6185. Structure Factors Rosenfeld Equation
- 8. Appropriate introduction of electro/photochromic chromophores into a suitable chiral structure should lead to Electrically or Optically controllable chiroptical properties. Structural Design I Molecular Design
- 9. Conformational Differences Relationship between Structure and Properties Structural Design II 60 o - 120 o
- 10. Synthesis of Model Compounds
- 11. CV UV-vis Spectroelectrochemisty Chiroptical Properties CS
- 12. Optimized Geometries Zentel, R.;Muller, M. Macromolecules , 1994, 27 , 4404. Polymer Design
- 14. 1H NMR
- 15. UV-vis Spectroelectrochemisty Chiroptical Properties CD CD CV UV-vis
- 16. 手性光学性质
- 17. Different Sign Different Magnitude Different Wavelength
- 19. Thanks for your attentions !
Editor's Notes
- Good morning, everyone! Very glad to have this chance to give my presentation. Today, my topic is “Towards to Highly Efficient Near-Infrared Chiroptical Switching Matertials”. My talk will include
- five parts: introduction of background, molecular design, synthesis of model compounds, properties of model compounds, polymer, and conclusions.
- What is chirality? If an object can’t be coincided with its mirror image, we can call it chiral and say it has chirality. For examples, your right and left hand, a molecule with an asymmetric carbon atom.Chirality is a very common phenomena in Natrue.Including asymmetric molecules, like alanine; supermolecules, like DNA double helix structure; macroscopic objects, like helical nebula. Chiral materials are important in living organism, but also have charming chiroptical properties.
- Chiroptical properties include mainly optical rotation and circular dichroism. When chiral light transmits the chiroptical materials, the different rates and absorbance of the right and left circularly polarized light produce the optical rotatino and ciucular dichroism, respectively. Generally, specific rotation and molar ellipticiy are used to describe the magnitude of chiroptical propertities. They are related with electronic structure of molecules and external conditions, such as, temperature and concentration.
- Indicated by the National Research Council of US, optics have changed our lives in 21th century, such as communication and data storage. Chiral photonics focuses on chiroptical phenomena produced from asymmetric structures and their applications in chiral liquid crystalline, chiroptical switches, chirally-fluorescent sensor, chiral wave-guide, and so on. Today, I will focus my attentions on Chiroptical Switches.
- But, most of researches focused on the chitoptical properties in the region of UV-vis wavelength.Therefore, Our aims is to develop materials with chiroptical properties in the region of Near-Infrared wavelength. Such materials have important applications in waveguide and control of polarization in Near-Infrared region.
- In 1,1’-binaphthyl, vertical distance of 2,2’ positions is about 3 angstrom, and anlge between naphthyls can be changed from 60 to 120 degree depending on the different substituent groups. Therefore, we designed open-cycling (R)-BEBPB and cyclic (R)-CBEBPB based on 1,1-bynaphthyl and viologen. The optimized geometies shew they would exhibit dramatic chiroptical properties in the region of near-infrared wavelength. Moreover, the magnitude of cyclic molecule is more lager than open-cycling molecule. After find the molecules with near-infrared chiroptical properties, we must synthesize them and characterize their properties to test our model.
- The model compounds were synthesized according to the procedures as the scheme. The molecular structures were affirmed by nuclear magnetic resonance and mass spectra techniques.
- The electrochemical behavior was studied firstly. Similar to the methyl viologen, (R)-1 exhibited two redox processes, but very differently, (R)-2 exhibited three redox processes. Considering the geometries, the more closer distance between viologens, the more stronger electronic interaction between viologens led to the process form DRC to DQ divided into two processes.
- More larger chiroptical properties
- Therefore, the polymer P4 was design based on (R)-1 and synthesized according to the scheme. The structures were characterized by nuclear magnetic resonance spectra.
- The signal of hydroxy hydrogen in P1 disappeared and the signal of methyl hydrogen appeared, which revealed that the methyl sulfonate is complete. Similarly, the iodidation is complete. The hydrogen signals in the range from 9 to 10 ppm revealed that the viologen grafting was successful, and the grafting yield is 100% from the integral of NMR.
- and CD spectral changes. In contrast to that of ( R )-BEBPB, the reduced polymer (i.e., in the violene state) showed a blue shift of the CD band, opposite sign and much weaker CD signals, which may be attributed to the overlap of multiple electronic interactions between viologen units and between viologen and polymer backbone.
- a structural model correlating geometric structures of a chiral molecule with the magnitude of chiroptical properties was come up with based on exciton coupling theory and modern quantum mechanical computation techniques. 2. Based on the model, a novel type of redox-based molecular chiroptical switches containing electrochromic viologens and axially dissymmetric 1,1’-binaphthyl-2,2’-diyl and with open-ring or cyclic structures was designed. 3.