THERMOCHROMISM OF INTRAMOLECULAR CHARGE TRANSFER EMISSION BANDS - PROBING THE TEMPERATURE DEPENDENCE OF FRANCK-CONDON FACTORS

摘要

The temperature dependence of the charge transfer emission band, Franck-Condon maximum has been determined for two donor-spacer-acceptor molecules in six solvents with dielectric constants between 4 and 10. The CT band maximum shifted to higher energies (27 cm(-1) K-1 in Et(2)O, 14 cm(-1) K-1 in ClCH2CH2Cl) with increasing temperature. Analysis of the thermochromism solvent dependence using a continuum model yielded values of the geometric factor, e(2)(1/r(A) + 1/r(D)-2/R(cc)), of 22.9 and 28.5 kK for DSAs 1 and 2. Solvent-independent thermochromism of approximate to 8 cm(-1) K-1 was found in both DSA molecules. Possible sources of this thermochromism are discussed. [References: 27]