Theoretical study on S1 and T1 states of homoleptic bis(dipyrrinato)zinc(II) model complex

Abstract

Molecular and electronic structures of S0, S1 and T1 states of homoleptic bis(dipyrrinato)zinc(II) complexes are examined by density functional theory (DFT) and time-dependent (TD) DFT calculations using the simplest model complex in order to elucidate a decrease of their fluorescence quantum yield in polar solvents. The results indicate that the S1 state is a charge-separated (CS) state, which is suggested to suppress the fluorescence, in the polar solvent. The T1 state has a quite similar structure to the S1 state; however the energy difference between S1 and T1 states seems too large to conclude that the dominant path is the intersystem crossing. From those results, the deexcitation, which causes the decrease of the fluorescence quantum yield, is predicted to proceed dominantly through the CS state.