Spectral and physicochemical properties of difluoroboranyls containing N,N-dimethylamino group studied by...

The solvatochromism of the dyes was analyzed based on the four-parameter scale including: polarizability (SP), dipolarity (SdP), acidity (SA) and basicity (SB) parameters by method proposed by Catalán. The change of solvent to more polar caused the red shift of absorption and fluorescence band position. The frequency shifts manifest the change in the dipole moment upon excitation. The ground-state dipole moment of the difluoroboranyls was estimated based on changes in molecular polarization with temperature. Moreover, the Stokes shifts were used to calculate the excited state dipole moments of the dyes. For the calculation, the ground-state dipole moments and Onsager cavity radius were also determined theoretically using density functional theory (DFT). The experimentally determined excited-state dipole moments for the compounds are higher than the corresponding ground-state values. The increase in the dipole moment is described in terms of the nature of the excited state.