Year 2007, Month 10 (Section Full Articles, Page 2021)
Spectral properties and conformations of nonlinear ketocyanines
L. A. Shvedova, A. S. Tatikolov, A. S. Shashkov, V. Ya. Artyukhov, and Zh. A. Krasnaya
The electronic transitions in molecules of the ketocyanine dyes (polyenic ω,ω´bisamino ketones) were calculated by quantum chemical methods. Satisfactory agreement was obtained between the experimental bands of the S—S absorption spectra and calculated electronic transitions for the ketocyanine with the central pyranone moiety and the corresponding salt assuming an acute angle between the chromophores and for the ketocyanine with the central pyridone moiety assuming an obtuse angle between the chromophores. Such molecular conformations were confirmed by the gNOESY 1Í NMR data for these dyes. The difference in the conformations of the dyes with the pyranone and pyridone moieties is due, most likely, to steric hindrance created by the central methyl groups in the molecules of the latter. The salts corresponding to these dyes have similar conformational differences.
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