Thermal cis-trans isomerization of solvatochromic merocyanines: linear correlations between solvent polarity and adiabatic and diabatic transition energies | Zendy

Shakir T. AbdelHalim | Zendy; Mahmoud H. AbdelKader | Zendy; Ulrich E. Steiner | Zendy

Open Access

Thermal cis-trans isomerization of solvatochromic merocyanines: linear correlations between solvent polarity and adiabatic and diabatic transition energies

Author(s) -

Shakir T. AbdelHalim,

Mahmoud H. AbdelKader,

Ulrich E. Steiner

Publication year - 1988

Publication title -

the journal of physical chemistry

Language(s) - English

Resource type - Journals

eISSN - 1541-5740

pISSN - 0022-3654

DOI - 10.1021/j100326a017

Subject(s) - solvatochromism , adiabatic process , isomerization , diabatic , computer science , chemistry , physics , solvent , thermodynamics , organic chemistry , catalysis

The correlation between solvatochromy and the solvent-polarity-dependent rate constant k, of thermal cis-trans isomerization (solvatokinetic behavior) has been investigated for a stilbazolium-type merocyanine and an amphiphilic analogue in a polarity series of eight neat solvents (protic and aprotic). At room temperature k,, varies over 7 orders of magnitude, decreasing with increasing solvent polarity. It has been demonstrated that the first transition energy AEand the free activation enthalpy AG*, of thermal cis-trans isomerization are linearly correlated with each other and with Dimroth’s solvent polarity parameter ET. These observations and the solvent-polarity-dependent increase of absorption band width are explained in terms of a model emphasizing the strong coupling between molecular conformation, electronic charge distribution, and solvent polarization.

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