K. V. Fedotov

A study of the vinylene shifts in polymethine dyes with sulphur-containing end-groups

Abstract A series of polymethine dyes with sulphur-containing end-groups have been investigated by spectral and quantum-chemical methods. The shift in absorption maximum with lengthening of the polymethine chain has been shown to depend on the nature of the first member of the vinylene series. Possible causes of this are discussed and a correlation between the first vinylene shift and the electron density change on excitation at the sulphur atoms has been established.

Pyrylocyanines. 27. Symmetrical polymethine dyes with an indeno[2,1-b]pyrylium nucleus

A number of symmetrical dyes with an indeno[2,1-b]pyrylium nucleus were synthesized. It is shown that the peculiarities of their absorption spectra are due to the specific characteristics of the condensed heteroring.

Mesoionic compounds with a bridged nitrogen atom. 6. Polymethine dyes of the thiazolo[3,2-α] quinolinium 1-oxide series

Mesoionic compounds formed from (2-quinolylthio)acetic acids readily give polymethine dyes. The structures of the synthesized compounds were confirmed by data from the PMR spectra and the results of elementary analysis.

Pyrylocyanines. 28. Unsymmetrical pyrylo-2-cyanines based on an indeno[2,1-b]pyrylium salt

A number of unsymmetrical pyrylo-2-cyanines with an indeno[2,1-b]pyrylium ring were synthesized. It was established that their absorption spectra contain, in the visible region, two bands, the locations, intensities, and forms of which depend markedly on the nature of the second terminal group.

Mesoionic compounds with a bridge nitrogen atom. 11. ?-Electron structures and absorption spectra of aza analogs of thiazolo[3,2-a]pyridinium 3-oxide

The π-electron structures and energies of the first electronic transitions of a number of mesoionic thiazoloazinium oxides were calculated by the Pariser-Parr-Pople method. An analysis of the data obtained showed that in the case of annelation of the heterorings and the introduction of a phenyl group in the 2 position the first absorption band should be shifted bathochromically, in agreement with the experimental data. In the case of replacement of the methylidyne groups by a trivalent nitrogen atom, however, one should have expected both bathochromic and hypsochromic effects, depending on the position into which the nitrogen atom was introduced. However, it was found experimentally that the first band is shifted to the long-wave region in all cases.

Mesoionic compounds with a bridged nitrogen atom. 7. Investigation of the cyclization of (2-pyrimidinylthio) phenylacetic acids

It is shown that mesoionic thiazolopyrimidines are formed by the action of acetic anhydride on (2-pyrimidinylthio)phenylacetic acids. The structures of these products were established, and their reactions with nucleophilic and electrophilic reagents were studied.