Electrochemical and Spectroelectrochemical Studies of Diphosphorylated Metalloporphyrins. Generation of a Phlorin Anion Product

Two series of diphosphoryl-substituted porphyrins were synthesized and characterized by electrochemistry and spectroelectrochemistry in non-aqueous media containing 0.1 M tetra-n-butylammonium perchlorate (TBAP). The investigated compounds are 5, 15-bis(diethoxyphosphoryl)-10, 20-diphenylporphyrins (Ph)[sub 2](P(O)(OEt)[sub 2])[sub 2]PorM and 5, 15-bis(diethoxyphosphoryl)-10,20-di(para-carbomethoxyphenyl)porphy r ins (PhCOOMe)[sub 2](P(O) (Oet)[sub 2])[sub 2]PorM where M = 2H, Co(II), Ni(II), Cu(II), Zn(II), Cd(II), or Pd(II). Calculations of the electronic structure were performed on the Ni(II) porphyrin dianion, and the most favorable atoms for electrophilic attack were determined to be the two phosphorylated carbon atoms. Each redox reaction was monitored by thin-layer UV-visible spectroelectrochemistry, and an overall mechanism for each electron transfer is proposed on the basis of these data.