Study on the excited states of zinc porphyrinogen and anisotropy of 2, 2, 6, 6-tetramethylpiperidinooxy by the technology of electron paramagnetic resonance

Abstract

To investigate the energy transfer and electron transfer of the photo-induced excited state in porphyrin sensitizers, we built the “zinc porphyrin-2, 2, 6, 6-tetramethylpiperidinooxy-xylene” experimental system. Zinc porphyrin's UV-visible spectrum shows that the characteristic absorption line of zinc porphyrin consists of bands B and Q, which are generated by the transition of elections from the ground state to the excited state in molecules of zinc porphyrin. The electron paramagnetic resonance spectrum of the experimental system is produced under the UV-visible light irradiation, at a temperature of 143 K; and we have detected the enhanced electron paramagnetic resonance spectrum of 2, 2, 6, 6-tetramethylpiperidinooxy. Based on the theory of the molecular excited states, and the photophysical and photochemical theory as well as the theory of the chemical-induced electron spin polarization, we also analyze the experimental results. Our conclusion is that the enhanced electron paramagnetic resonance spectrum of 2, 2, 6, 6-tetramethylpiperidinooxy is caused by the energy transfer and electron transfer of the photo-induced excited state in the porphyrin sensitizers. The anisotropic characteristics of the phenomenon of electron paramagnetic resonance spectrum of 2, 2, 6, 6-tetramethylpiperidinooxy at low temperatures are due to the anisotropic hyperfine interaction between nitroxide electrons and nitrogen nuclear.