Instantaneous emission spectra and molecular rotation of n-dimethylaminobenzonitrile fluorescing in the long-wavelength spectral range

The kinetics of the instantaneous luminescence spectra and of the polarization of luminescence of n-dimethylaminobenzonitrile in polar solutions are studied. The luminescence is excited by radiation at 403 nm from a picosecond laser, which populates states of strongly nonequilibrium forms of the compound under consideration. The behavior of the instantaneous emission spectra and the rotation of these forms upon recording of their luminescence radiation in different spectral ranges are analyzed. As the luminescence recording wave-length increases from 470 to 530 nm, the average time of rotational relaxation in a glycerol solution decreases from 25 to 15 ns. The results obtained indicate that, upon rotation of excited luminophore molecules, the boundary conditions of sticking of solvent molecules are satisfied in this solution. The calculated effective volume of rotation corresponds to that of a solvate that, apart from luminophore, involves the first coordination sphere of glycerol molecules.