Electrochemical and spectroelectrochemical studies of tetraparadiethylaminophenylporphyrins, metalloporphyrins, metallophthalocyanines, micellar porphyrins and 4(a), 5-substituted flavins.

摘要

Electrochemical and spectroelectrochemical techniques were used to characterize the electron transfer reactions of (i) parasubstituted free base tetraphenylporphyrins; (ii) monomeric, dimeric and trimeric metalloporphyrins containing Nb, Rh, Th and U central metals; (iii) metallophthalocyanines; (iv) micellar porphyrins; and (iv) 4{dollar}sp{lcub}rm a{rcub}{dollar}-5 substituted Flavins.; The free base diethylamino para-substituted tetraphenylporphyrin, (T(p-Et{dollar}sb2{dollar}N)PP) H{dollar}sb2{dollar}, exhibits a two-electron reversible ring centered oxidation followed by a two-electron irreversible oxidation centered at the diethylamino substituents.; The investigated monomeric Nb(V) porphyrins involve an irreversible metal centered reduction. The Nb(V) dimers, ((P)Nb) {dollar}sb2{dollar}O{dollar}sb3{dollar}, (where P is one of several porphyrin rings) may undergo up to three ring centered reductions and three ring centered oxidations.; The electrochemistry of 17 different tetraphenylporphinato-rhodium(III) complexes of the form (TPP)Rh(R) and (TPP)Rh(RX) are also reported. The bound alkyl halide could be reduced without cleavage of the metal-carbon bond and this results in an electrochemically initiated conversion of (TPP)Rh(RX) to (TPP)Rh(R). Bimetallic Rh(III) complexes of the form ((P)RhCl) {dollar}sb2{dollar}L where L is a conjugated bridging nitrogen-heterocycle show an interaction between the two porphyrin units.; Monomeric Th(IV) and U(IV) porphyrin and phthalocyanine complexes generally undergo only ring centered reductions and oxidations. The only noted exception was (P)U(acac){dollar}sb2{dollar} which undergoes a metal centered oxidation. Trimeric Th(IV) complexes of the form ((P)Th(OH){dollar}sb2rbrack sb3{dollar} can be reversibly reduced in up to six one-electron transfer steps and oxidized by up to six electrons. Each trimeric Th(IV) complex is oxidized or reduced at porphyrin ring based orbitals.; The formation of micelles for (hTriP)H{dollar}sb2{dollar} and the Ni, Cu and VO metallated derivatives of these porphyrins in EtOH/H{dollar}sb2{dollar}O mixtures was demonstrated by UV-visible and ESR spectroscopy. The electrochemistry was carried out in nonaqueous solvent and H{dollar}sb2{dollar}O/DMF mixture.; 4{dollar}sp{lcub}rm a{rcub}{dollar}, 5-substituted flavin radical cations are electrochemically generated from 5-ethyl-4{dollar}sp{lcub}rm a{rcub}{dollar} hydroxy-3-methyl-4{dollar}sp{lcub}rm a{rcub}{dollar},5-dihydrolumiflavin or 5-ethyl-4{dollar}sp{lcub}rm a{rcub}{dollar}-methoxy-3-methyl-4{dollar}sp{lcub}rm a{rcub}{dollar},5-dihydrolumiflavin. The electrogenerated radical cations can undergo a one-electron oxidation and, after a subsequent chemical transformation, lead to the formation of a 5-ethyl-3-methyllumiflavinium cation.