Dipole Moments and Polarizabilities of Benzophenones Estimated from Spectroscopic Measurements *

The electric and optical properties of molecules are commonly investigated by measurements of their absorption and fluorescence spectra, both in pure solvents of different polarities [1] and in mixed solvents [2]. The molecules benzophenone (BF), 2-aminobenzophenone (2ABF) and 4-aminobenzophenone (4ABF) investigated in this paper show no fluorescence at room temperature. Their absorption spectra, however, are shifted depending on the polarity of the solvent. Figure 1 shows the maxima of the absorption bands as functions of the content of n-butyl alcohol in n-heptane. In the case of benzophenone (n-^71* transition) an increase in the solvent polarity results in a shift of the spectrum to the short-wave side, whereas the absorption spectra of 2-aminobenzophenone and 4-aminobenzophenone (71transitions) are shifted to the longwave side. Therefore measurements of absorption spectra in mixtures of polar and nonpolar solvents were carried out to determine the composition of the first coordination solvent shell, the Onsager cavity radius and the mean energy of interaction between the solvent and solute molecules in the ground state.