基于电子顺磁共振的ZnTPP激发态及其TEMPO各向异性的研究

为了研究卟啉类敏化剂的光致激发态能量转移和电子转移问题,本文基于紫外可见光谱仪和电子顺磁共振波谱仪,构建了以锌卟啉为研究对象的"锌卟啉-稳态自由基-二甲苯"实验体系.锌卟啉的紫外可见光谱显示,在可见光谱的B带和Q带出现明显的特征峰,是锌卟啉分子中电子由基态能级跃迁至激发态能级产生的.低温条件下受紫外可见光辐照的实验体系的电子顺磁共振波谱,检测到了稳态自由基四甲基哌啶氧化物的增强吸收电子顺磁共振波谱.根据分子激发态相关理论、光化学物理反应理论和化学诱导电子自旋极化理论对实验结果进行了分析,结果表明,四甲基哌啶氧化物稳态自由基电子顺磁共振波谱的增强吸收对应于锌卟啉光致激发态的能量转移和电子转移;四甲基哌啶氧化物在低温(143 K)下的电子顺磁共振波谱表现出的各向异性特征现象来源于氮氧自由基电子与氮核的各向异性超精细相互作用.

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

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.
Keywords：ZnTPPphoto-induced excited stateUV-visible spectrumelectronic paramagnetic resonance