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

Molecular and electronic structures of So, S-1 and T-1 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 Si state is a charge-separated (CS) state, which is suggested to suppress the fluorescence, in the polar solvent. The T-1 state has a quite similar structure to the Si state; however the energy difference between Si and T-1 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. (C) 2017 Elsevier Ltd. All rights reserved.