Dichroism induced

A general theory of dichroism induced by strain in polymeric networks Is developed by adaptation of methods developed earlier for treating strain birefringence. It is generally applicable to dichrolc bands associated with any specified conformation involving sequences of one or more consecutive bonds. The transition dipole moment is introduced in the local framework of the skeletal bonds associated therewith. Possible differences in transition moments for various conformations and repeat units are taken into account. Numerical calculations for PE chains show gauche bonds, rather than trans, to be more favorably oriented with respect to the chain vector r. 

The circular dichroism induced in achiral compounds upon complexation with a chiral material can be used to characterize the nature of the interaction responsible for the association. Studies of this type may be conveniently classified as being the optical activity induced upon dissolution of a solute in a chiral solvent, through association of the species of interest with a co-dissolved chiral solute, or through association of the solute with chiral polymers. 

Fig. 23 TDDFT sector maps calculated at the B3LYP/aug-cc-pVDZ level of theory for the circular dichroism induced in the carbonyl centered n-to-n transition of formaldehyde. The scan was performed 1.3 A above the chromophore plane using point charges of —O.le and +0.3e, respectively...

FIQtIRE 3.10 Relaxation in the dark of the dichroism induced by linearly polarized 3( 0 nm light irradiation in the Pjjo azo-polyglutamate. The spectra were obtained after 2 minutes unpolarized 450 nm irradiation (I and I and after 6 days relaxation in the dark (2// and 2jj. None that the absorbances have shifted to higher values due to the cis->trans isomerization, while tlte initial dichroism was increased.The inset is an expanded view of of the region around 450 nm. After reference 22, redrawn by permission of ACS. 

The methods were straightforward to use for chiral molecules generally, as discussed in sec 6, [116], and for particular applications such as circular dichroism induced by a chiral neighbour [138]. 

Induced circular dichroism. Induced circular dichroism is observable for electronic transitions of an achiral molecule when, for example, it is associated in the form of a coordination complex with a chiral molecule. In the example given by Stang of a tetranuclear platinum complex where two achiral fragments are linked by two S,S)-tartrate anions (2.36) (Figure 2.59), a Cotton effect is observed for the transitions of the achiral anthracene unit. 

Wu, Y, Seo, T., Maeda, S., Sasaki, T., Irie, S., and Sakurai, K. (2005). Circular dichroism induced by the helical conformations of acylated chitosan derivatives bearing cinnamate chromophores, /. Polym. Sci. Polym. Phys., 43,1354-1364. 

The determination of the absolute configuration of a chiral substance is a very important part of the characterization of that molecule. That is also true for chiral solvents. Circular dichroisms induced in the UV spectra of metal complexes solvated by a chiral solvent can be used for the determination of the absolute configuration of the solvent [Br 80]. This method is attractive in that the experiments are easy to carry out. 

Weigert, F. (1919). Dichroism Induced in a Fine-Grain Silverchloride Emulsion by a Beam of Linearly Polarized Light. Verh. Dtsch. Phys. Ges., 1919, 21,479-483. 

Linear polarized radiation of He-Cd laser (1 = 441,6 run) was used as an actinic light. The birefringence and the dichroisme induced by the linear polarized actinic light can be calculated by means of formulae (Kakichashvili Shaverdova, 1982) ... 

See also Biochemical Applications of Raman Spectroscopy Biomacromolecular Applications of Circular Dichroism and ORD Carbohydrates Studied by NMR Circularly Polarized Luminescence and Fluorescence Detected Circular Dichroism Induced Circular Dichroism Magnetic Circular Dichroism, Theory Nucleic Acids and Nucleotides Studied Using Mass Spectrometry Organometallics Studied Using Mass Spectrometry Polymer Applications of IR and Raman Spectroscopy Proteins Studied Using NMR Spectroscopy Vibrational CD Spectrometers Vibrational CD, Theory. 

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