Electrochemical and Spectrochemical Studies of Diphosphorylated Metalloporphyrins: Unusual Formation of Phlorin Anion

Tuesday, 26 May 2015: 09:00
Lake Erie (Hilton Chicago)
Y. Fang, P. Chen, X. Jiang, M. Manowong (University of Houston), Y. G. Gorbunova, A. Sinelshchikova, Y. Y. Enakieva, A. Tsivadze (Frumkin Inst. of Physical Chem. and Electrochem. of RAS), C. Stern, A. Bessmertnykh-Lemeune, R. Guilard (Université de Bourgogne, ICMUB), and K. M. Kadish (University of Houston)
Two series of diphosphoryl-substituted porphyrins were synthesized and characterized by electrochemistry and spectroelectrochemistry in benzontrile, dichloromethane and pyridine containing 0.1 M tetra-n-butylammonium perchlorate. The investigated compounds are represented as 5,15-bis(diethoxyphosphoryl)-10,20-diphenylporphyrins and 5,15-bis-(diethoxyphosphoryl)-10,20-di(p-carbomethoxyphenyl) porphyrins (Chart). The porphyrins with non-redox active metal centers undergo two ring centered oxidations and two ring centered reductions, the latter of which is followed by a chemical reaction to give a phlorin anion. The phlorin anion is electroactive and can be reoxidized to give back the starting porphyrin or reversibly reduced to give a phlorin dianion. Each redox reaction was monitored by thin-layer UV-visible spectroelectrochemistry and an overall reduction mechanism is proposed.