Excitation energy transfer processes in BODIPY based donor-acceptor system - Synthesis, photophysics, NLO and DFT study

摘要

Excited state intramolecular proton transfer (ESIPT) meso flanked BODIPY dyad are synthesized and investigated by using spectroscopic, fluorescence lifetime decay, electrochemical and DFT method. Excitation (lambda(exc) = 290 nm) of the Bn-OH-BDY dyad leads to emission (lambda(emi) = 545 nm) totally directed by the BODIPY subunits pointing to excitation energy transfer (EET) from the ESIPT to BODIPY core. A large shift of 255 nm has been observed between excitation and emitted light. Attachment of ESIPT unit does not cause any perturbation in the low-energy absorption band of the Bn-OH-BDY dyad. The electrochemical study shows an irreversible peak of single-electron oxidation of ESIPT core at 0.38 eV and reduction of BODIPY core at 1.023 eV. DFT calculation studies show the existence of charge transfer (CT) state from ESIPT to BODIPY core. The results obtained from photophysics, electrochemical study and DFT support EET from excited ESIPT core to BODIPY subunits. The DFT results show dominating electronic contribution to the linear polarizability (alpha) and first hyperpolarizability (beta). NLO response was measured using Z scan technique. The values obtained for nonlinear absorption coefficient (beta) in DMSO is -5.95 x 10(-12) (m/W) and for third-order susceptibility (chi)(3) it is 14.19 x 10(-13) (e.s.u). The geometries of the dyad were optimized by using B3LYP/6-311 + + G (d,p) level of theory.