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Solvatochromism of dyes. Part I. Solvatochromism of merocyanines. Derivatives of the 7 H ‐indolo [1,2‐ a ] quinolinium system. A new model of solvatochromism
Author(s) -
Soroka Jacek A.,
Soroka Krystyna B.
Publication year - 1991
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.610041003
Subject(s) - solvatochromism , chemistry , excited state , photochemistry , ground state , solvent , organic chemistry , atomic physics , physics
A new approximate model of the solvatochromism of merocyanines is presented. In solution merocyanines exist in the electronic ground state as a mixture of three different structures. Since only one longest wavelength band is observed in the UV—visible absorption spectra of such merocyanines, their lowest excited states are roughly assumed to be represented by a single structure. The molar fraction of each of the three structures of merocyanines in the ground state is a function of the solvent polarity. This (VBHB) model has been verified using merocyanines prepared from 5‐(hydroxyaryl)‐7,7‐dimethyl‐7 H ‐indolo [1,2‐ a ] quinolinium perchlorates. The analysis of the experimental data suggests that the three ground‐state structures of merocyanines are the vinylogous amide (V) and the betaine as the free (B) or hydrogen‐bonded (HB) form.