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

The first singlet excited state lifetimes (τs) of asymmetric pentaazadentate porphyrin-like complexes, [(R-APPC)M]Cln, were measured by the time-correlated single photon counting method. Fluorescent decays of the first singlet excited state for all [(R-APPC)M]Cln were found to be shorter than 0.5ns. The intersystem crossing rates (kisc) were calculated from the τs values and previously measured triplet quantum yields (ϕT). Values for kisc for the complexes ranged from 0.68 to 3.04×109s−1 and are significantly greater than those of silicon naphthalocyanine (SiNc) and lead phthalocyanine (PbPc(CP)4). The values of τs and kisc of the [(R-APPC)M]Cln complexes are sensitive to variations in both the bridging R group and the metal center.

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