Nonspecific solvation and oscillator strengths for the long-wavelength vibronic absorption band of 4-dimethylaminochalcone solutions

The 4-dimethylaminochalcone molecule is one of the most efficient spectral-luminescent probes widely used in various medical and biological studies. Experimental data on the oscillator strengths in the long-wavelength vibronic band of 4-dimethylaminochalcone solutions in a series of individual solvents of different chemical nature are analyzed using the earlier derived refined equation describing the influence of nonspecific solvation processes on the matrix elements of the dipole moment of a purely electronic transition in organic dye molecules. It is shown that the semiempirical theory developed gives a satisfactory quantitative explanation to experimentally observed regularities indicative of a relatively weak influence of the solvent reaction field (orientation and induction forces) and dispersion interactions on the integrated intensity of the studied band belonging in the category of intramolecular charge transfer bands.