Excited state lifetime and intersystem crossing rate of asymmetric pentaazadentate porphyrin-like metal complexes

摘要

The first singlet excited state lifetimes (τ_(s)) of asymmetric pentaazadentate porphyrin-like complexes, [(R-APPC)M]Cl_(n), were measured by the time-correlated single photon counting method. Fluorescent decays of the first singlet excited state for all [(R-APPC)M]Cl_(n) were found to be shorter than 0.5 ns. The intersystem crossing rates (k_(isc)) were calculated from the τ_(s) values and previously measured triplet quantum yields (φ_(T)). Values for k_(isc) for the complexes ranged from 0.68 to 3.04×10~(9) s~(-1) and are significantly greater than those of silicon naphthalocyanine (SiNc) and lead phthalocyanine (PbPc(CP)_(4)). The values of τ_(s) and k_(isc) of the [(R-APPC)M]Cl_(n) complexes are sensitive to variations in both the bridging R group and the metal center.