The photophysical characteristics of 2- butylamino-2-demethoxy-hypocrellin B

2- Butylamino-2-demethoxy-hypocrellin B (BAHB), is an efficient photodynamic sensitizer, excited singlet-state energies are determined from the overlap of the normalized from absorption and emission spectra to be 176.4 kJ mol−1 (ESCT) and 202.8 kJ mol−1 (ES1), respectively. The quantum yields of BAHB fluorescence are 0.0098 (Φf1) and 0.0076 (Φf2), respectively. The energies and quantum yields of excited triplet states of BAHB are examined from the external effect of heavy atom on its florescence emission in the mixture of n-propyl iodide and benzene. The energies of excited triplet states of BAHB are 134.4±10.5 kJ mol−1 (ETCT) and 158.6±10.5 kJ mol−1 (ET1), respectively. The quantum yields of excited triplet states of BAHB are 0.73±0.04 (ΦTCT) and 0.56±0.04 (ΦT1), respectively. Meanwhile, the kinetic constants of fluorescence emission, intersystem crossing and internal conversion are also calculated from relative equations.