Faraggi M, Carmichael A, Riesz P
Int J Radiat Biol Relat Stud Phys Chem Med. 1984 Dec;46(6):703-13. doi: 10.1080/09553008414551941.
Radical production during the photolysis of deaerated aqueous alkaline solutions (pH 11) of some water-soluble porphyrins was investigated. Metal-free and metallo complexes of tetrakis (4-N-methylpyridyl)porphyrin (TMPyP) and tetra (4-sulphonatophenyl)porphyrin (TPPS4) were studied. Evidence for the formation of OH radicals during photolysis at 615, 545, 435, 408 and 335 nm of Fe(III) TPPS4 is presented. Fe(III) TMPyP, Mn(III) TPPS4 and Mn(III) TMPyP also gave OH radicals but only during photolysis at 335 nm. The method of spin trapping with 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) and 4-pyridyl-1-oxide-N-tert-butylnitrone (POBN) combined with e.s.r. was used for the detection of OH, H and hydrated electrons. With the spin trap DMPO, photolysis generated DMPO-OH adducts under certain conditions but no DMPO-H adducts could be observed. With POBN, no POBN-H adducts were found. The formation of OH was confirmed by studying competition reactions for OH between the spin traps and OH scavengers (formate, isopropanol) and the concomitant formation of the CO-2 adduct and the (CH3)2COH adduct with both DMPO and POBN. The photochemical generation of OH radicals was pH dependent; at pH 7.5 no OH radicals could be detected. Photolysis (615-335 nm) of dicyanocomplexes of the Fe(III) porphyrins did not produce OH radicals. When corresponding Cu(II), Ni(II), Zn(II) and metal-free porphyrins were photolysed at 615 and 335 nm, no OH radicals could be spin trapped. These results tend to associate the well-known phenomenon of photoreduction of Fe(III) and Mn(III) porphyrins with the formation of OH radicals. This process is described mainly as the photoreduction of the metal ion by the ligand-bound hydroxyl ion via an intramolecular process.
研究了一些水溶性卟啉的脱气碱性水溶液（pH 11）在光解过程中的自由基生成情况。研究了四（4 - N - 甲基吡啶基）卟啉（TMPyP）和四（4 - 磺酸钠苯基）卟啉（TPPS4）的无金属和金属配合物。给出了在615、545、435、408和335 nm光照下Fe(III) TPPS4光解过程中OH自由基形成的证据。Fe(III) TMPyP、Mn(III) TPPS4和Mn(III) TMPyP也能产生OH自由基，但仅在335 nm光照时产生。采用5,5 - 二甲基 - 1 - 吡咯啉 - 1 - 氧化物（DMPO）和4 - 吡啶基 - 1 - 氧化物 - N - 叔丁基硝酮（POBN）自旋捕集法结合电子自旋共振（e.s.r.）用于检测OH、H和水合电子。使用自旋捕集剂DMPO时，光解在某些条件下生成DMPO - OH加合物，但未观察到DMPO - H加合物。使用POBN时，未发现POBN - H加合物。通过研究自旋捕集剂与OH清除剂（甲酸、异丙醇）之间对OH的竞争反应以及同时形成的DMPO和POBN的CO₂加合物和(CH₃)₂COH加合物，证实了OH的形成。OH自由基的光化学生成与pH有关；在pH 7.5时未检测到OH自由基。Fe(III)卟啉的二氰配合物在615 - 335 nm光解时不产生OH自由基。当相应的Cu(II)、Ni(II)、Zn(II)和无金属卟啉在615和335 nm光解时，未捕集到OH自由基。这些结果倾向于将Fe(III)和Mn(III)卟啉的光还原这一众所周知的现象与OH自由基的形成联系起来。该过程主要描述为通过分子内过程由配体结合的氢氧根离子对金属离子进行光还原。
