A. A. Ishchenko

Pyrylocyanines. 11. Symmetrical tetraphenyl-substituted pyrylo-2-cyanines

Symmetrical polymethine dyes (monomethylidyne, carbo-, and dicarbocyanines), viz., 4,6-diphenylpyrylium, -thiopyrylium, and -pyridinium derivatives, were synthesized. It follows from a comparison of the absorption spectra of pyrylo-2-cyanines and their heteroanalogs with the spectra of the corresponding 4 isomers that these dyes differ from one another with respect to the positions, intensities, and forms of the bands. The pyrylocarbo- and -dicarbocyanines and their sulfur analogs are more deeply colored than their γ isomers, while the reverse regularity is observed in the pyridocyanine series. The long-wave bands in the spectra of all of the α isomers are accompanied by more intensive transitions to the vibrational sublevels than in the case of the γ isomers.

Pyrylocyanines. 21. Unsymmetrical α-pyrylo- and α-pyridocyanines

Abstract(2-Pyrylo)- and (2-pyrido)(indo)trimethinecyanines containing both electron donor and electron acceptor substituants in the heterocyclic rings have been synthesized. It has been shown that the 4,6-diphenyl-2H-pyran nucleus confers less basicity (electron donor characteristics) than the 1,3,3-trimethylindoline segment. It has also been shown that the introduction of substituents to the heterocyclic residues of unsymmetrical dyes allows one to manipulate their electronic asymmetry over a wide range up to a change in the distribution of charge from one ring to another.

Pyrylocyanines. 16. Tetraphenyl-substituted (2-pyrylo) (4-pyrylo) cyanines

Unsymmetrical tetraphenyl-substituted (2-pyrylo) (4-pyrylo) monomethylidyne-, carbo-, and dicarbocyanines and their thiopyrylium and pyridinium analogs were synthesized. The absorption spectra of these dyes were studied. The spectral characteristics of their long-wave absorption bands have values that are intermediate between the analogous characteristics of the corresponding symmetrical isomers of the α and α series.

Pyrylocyanines. 15. Benzopyrylo-2-cyanines

Symmetrical 4,4′-diphenyl-substituted benzopyrylo-2-monomethylidyne, carbo-, and dicarbocyanines and their thio analogs, as well as unsymmetrical carbocyanines that contain, in addition to 4-phenylbenzopyrylium or 4-phenylbenzothiopyrylium rings, 3-ethylbenzothiazolium or 1,3,3-trimethyl-3H-indolium residues, were synthesized. The indicated dyes were more highly colored than their isomers that contain flavylium or thioflavylium residues. On the basis of the deviations calculated from the centers of the absorption bands it was concluded that the benzopyran residues in the dyes of the α series have greater electron donor character than those in the dyes of the γ series.