Chromophores association

Reaction is thought to be a result of a a transition associated with the Cl atom chromophore, while reaction 78 is the result of excitation of the it chromophore associated with the it bond. 

The major historical interest in oligosaccharide-chromophore associations is as a source of information on the three dimensional structure of the oligosaccharide using the bi-chromophoric exciton coupling methods... 

Creed et al. [125]. The 2,6-di-substitution pattern was chosen so that the anthracene moiety would be more likely to be elongated and to act as a mesogen. This polymer has an LC mesophase that is most probably N. Evidence was reported for chromophore association in this polymer even when it is highly diluted in a good solvent such as dichloromethane, but spectral perturbations due to aggregation are especially noticeable in films. Aggregation, as evidenced by a strongly blue-shifted band at 235 nm (the isolated chromophore absorbs at... 

Local motions of a, a)-bis( 1-pyrene) alkanes and pyrene -labelled poly(methyl methacrylate) in solution have been measured by pico-second excimer fluorescence spectroscopy In this study the formation of the polymers during polymerisation could be accurately maintained by measuring excimer fluorescence lifetime. The photophysical properties of poly (N-vinylcarbazole) have been interpreted on the basis of a study in diastereoisomers of 2,4-di(N-carbazolyl)t In this work it is concluded that 95% of the excitation energy occurs with chromophores associated with specific excimer sites. Excimer formation in various polyvinyl carbazole... 

Figure 5. Schematic difference absorbance curves to exemplify absorption curve intensity and energy shifts. The monomeric state is in the reference beam and the associated state is in the sample beam, with the same number of monomers as in the reference beam. The difference curves are a sensitive measure of the changes in absorption that can occur when identical chromophores associate in a regular way. A, Hypochromism with a shift in the band to shorter wavelengths. B, Hyperchromism with a shift in the band to longer wavelengths. C, Band splitting with either a hypochromism (solid curve) or a hyperchromism (dashed curve). Aj is the monomer band center.

H. Fluorescence characteristics, formation mechaiusm and chromophore association of o)-(l-pyrenyl)alkanoic acid films prepared by vacuum deposition. Thin Solid Films 1989, 169, 323-332. 

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