EXCITED-STATE PROPERTIES OF ASYMMETRIC PENTAAZADENTATE EXPANDED PORPHYRINS

The research results of the excited-state properties of asymmetric pen taazadentate expanded-porphyrins are reported. The results show that t he emission spectra appear in the 770-820 nm region in accord with the different substituents on the benzene ring. The quantum yield of fluo rescence is less than 0.02, and the lifetime of the first singlet exci ted state (S-1) is shorter than ins. There are excellent linear relati onships between the energy of the S-1 and the Hammett constants as wel l as the quantum yield of fluorescence and the electrophilic substitue nt constants sigma(+). The energies of the lowest excited triplet stat e (T-1) of the complexes are in the range of 94-130 KJ/mol. The lifeti me of T-1 is as long as tens of microseconds. The T-1-T-n transient ab sorption spectra appear in 450-550 nm region. And the quantum yield of title compounds for generating singlet oxygen is as high as 0.9.