Optics and Spectroscopy

, Volume 101, Issue 1, pp 90–97

Thermochromism and thermofluorochromism of merocyanines with a positive solvatochromism

  • A. A. Ishchenko
  • A. V. Kulinich
  • S. L. Bondarev
  • V. N. Knyukshto
  • A. A. Turban
Condensed-Matter Spectroscopy

DOI: 10.1134/S0030400X06070162

Cite this article as:
Ishchenko, A.A., Kulinich, A.V., Bondarev, S.L. et al. Opt. Spectrosc. (2006) 101: 90. doi:10.1134/S0030400X06070162

Abstract

The thermochromism and thermofluorochromism of ethanol solutions of di-, tetra-, and hexamethine merocyanines based on 1,3-dihydro-1,3,3-trimethyl-(2H)-indol-2-yliden and malonodinitrile, having a positive solvatochromism as compared to the corresponding cationic and anionic symmetric dyes, are studied at T = 348, 293, and 4.2 K. It is found that, upon a decrease in the temperature, the absorption spectra exhibit bathochromic shifts of bands, an increase in the vinylene shifts, and a decrease in deviations, whereas the fluorescence spectra exhibit opposite changes. In this case, the differences in the shapes of the absorption and luminescence bands decrease so considerably that the bands become virtually mirror-symmetric. It is shown that the spectral and luminescent effects observed arise because, at high temperatures, the electronic structure of the ground state of merocyanines approaches that of neutral polyenes, whereas, at low temperatures, this structure is similar to the structure of ideal polymethine. Such a transformation of the structure is caused by an increase in specific electrostatic interactions (nucleophilic and electrophilic solvations) with a solvent, as a result of which the alternation of the charges of a chromophore increases, while its bond orders become equalized.

PACS numbers

33.50 

Copyright information

© Pleiades Publishing, Inc. 2006

Authors and Affiliations

  • A. A. Ishchenko
    • 1
  • A. V. Kulinich
    • 1
  • S. L. Bondarev
    • 2
  • V. N. Knyukshto
    • 2
  • A. A. Turban
    • 2
  1. 1.Institute of Organic ChemistryNational Academy of Sciences of UkraineKievUkraine
  2. 2.Institute of Molecular and Atomic PhysicsNational Academy of Sciences of BelarusMinskBelarus

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