title: Effect of solvent and protonation/deprotonation on electrochemistry, spectroelectrochemistry and electron-transfer mechanisms of N-confused tetraarylporphyrins in nonaqueous media.
abstract: A series of N-confused free-base meso-substituted tetraarylporphyrins was investigated by electrochemistry and spectroelectrochemistry in nonaqueous media containing 0.1 M tetra-n-butylammonium perchlorate (TBAP) and added acid or base. The investigated compounds are represented as (XPh)4 NcpH2 , in which "Ncp" is the N-confused porphyrin macrocycle and X is a OCH3 , CH3 , H, or Cl substituent on the para position of each meso-phenyl ring of the macrocycle. Two distinct types of UV/Vis spectra are initially observed depending upon solvent, one corresponding to an inner-2H form and the other to an inner-3H form of the porphyrin. Both forms have an inverted pyrrole with a carbon inside the cavity and a nitrogen on the periphery of the π-system. Each porphyrin undergoes multiple irreversible reductions and oxidations. The first one-electron addition and first one-electron abstraction are located on the porphyrin π-ring system to give π-anion and π-cation radicals with a potential separation of 1.52 to 1.65 V between the two processes, but both electrogenerated products are unstable and undergo a rapid chemical reaction to give new electroactive species, which were characterized in the present study. The effect of the solvent and protonation/deprotonation reactions on the UV/Vis spectra, redox potentials and reduction/oxidation mechanisms is discussed with comparisons made to data and mechanisms for the structurally related free-base corroles and porphyrins.
authors.affiliation: School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China).
authors.forename: Songlin
authors.initials: S
authors.lastname: Xue
authors.forename: Zhongping
authors.initials: Z
authors.lastname: Ou
authors.forename: Lina
authors.initials: L
authors.lastname: Ye
authors.forename: Guifen
authors.initials: G
authors.lastname: Lu
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Fang
authors.forename: Xiaoqin
authors.initials: X
authors.lastname: Jiang
authors.forename: Karl M
authors.initials: KM
authors.lastname: Kadish
keywords: deprotonation; electrochemistry; porphyrinoids; protonation; spectroelectrochemistry