Solvent Dependent Linear and Nonlinear Optical Properties of Triphenylamine Unit Incorporated Difluoroboron Β-Diketonate Complexes

In this work, four intramolecular charge transfer (ICT) compounds, TBT, TVBVT, TSBST and TSVBVST, with difluoroboron β-diketonate as the electron acceptor, triphenylamine unit as the electron donor and different π-conjugated bridges have been synthesized. The linear absorption and emission spectra in different organic solvents indicate a positive solvato-chromism. The multilinear regression analyses of the linear optical spectra in different solvents indicate that the solvato-chromism is mainly caused by the polarity/dipolarity properties of the solvents and possibly the halogen-halide interaction. Time-dependent density functional theory (TD-DFT) calculations were used to investigate the charge density difference between the ground and excited states of the complex molecules of interest and the ICT processes of the excited molecules were verified. The nonlinear optical properties of the molecules were studied using a Z-scan technique. It is found that not only the structure of the molecules influences the nonlinear optical properties, but that also the solvent-solute interaction plays an important role.