Metal-centered photoinduced electron transfer reduction of a gold(III) porphyrin cation linked with a zinc porphyrin to produce a long-lived charge-separated state in nonpolar solvents

Photoexcitation of an electron donor-acceptor linked dyad containing gold(III) and zinc(II) porphyrins (ZnPQ-AuIIIPQ+) results in electron transfer from the singlet excited state of ZnPQ to the metal center of AuPQ+ to produce the charge-separated state (ZnPQ*+-AuIIPQ) which has a long lifetime (10 mus) in nonpolar solvents such as cyclohexane and toluene.     

Synthesis, characterization, and electrochemical studies of beta,beta'-fused metallocenoporphyrins

Beta,beta'-Fused monoruthenocenylporphyrins, Cp*Ru(III)[1,2-[M(II)-5,10,15,20-tetrakis(3,5-di-tert-butylphenyl)-porphyrinato]-3-methyl-cyclopentadienide] (M = Ni (20), Cu (21), Zn (22)), and bisferrocenoporphyrins, Fe(II) bis[1,2-[M(II)-5,10,15,20-tetraphenylporphyrinato]-3-methyl-cyclopentadienide] (M = Ni (24), Cu (25), Zn (26)), were synthesized and characterized. A novel synthetic approach to beta,beta'-fused porphyrins through Pd(0)-catalyzed [3 + 2] cycloaddition was implemented in this work. UV-vis spectra of these compounds show largely broadened and red-shifted bands (relative to their precursors) indicating potential electronic communication between the attached organometallic moiety and the porphyrin core. The electrochemistry of these molecules suggests significant electronic interactions between the metallocene and metalloporphyrin in molecules 20 and 24. The crystal structure of the bisferrocenoporphyrin 26, Fe(II) bis[1,2-[Zn(II)-5,10,15,20-tetraphenylporphyrinato]-3-methyl-cyclopentadienide], was determined: [Cp2Fe[ZnTPP(THF)]2][Cp2Fe[ZnTPP(THF)ZnTPP(MeOH)]].3MeOH.6THF, M = 3804.35, monoclinic, space group P21/c, a = 33.327(5) A, b = 19.145(3) A, c = 29.603(5) A, beta = 106.309(2) degrees , V = 18128(5) A3, Z = 4. In this molecule, one porphyrin ring is rotated by about 72 degrees with respect to the other in the 5-fold axis of the Cp ring.     

Redox behavior of cyclo[6]pyrrole in the formation of a uranyl complex

A uranyl complex, the first metal complex to be formed from the cyclo[n]pyrrole series of expanded porphyrins, is formed when cyclo[6]pyrrole is treated with the uranyl cation under aerobic conditions. Spectroscopic, spectroelectrochemical, and electron spin resonance data of this species are consistent with the ligand in the complex being oxidized to an antiaromatic form.     

非水介质中金属卟啉电化学

本文概述在非水介质中合成金属卟啉络合物的电化学。总结反应机理与金属卟啉的氧化和还原的关系,阐明半波电位及电子转移途径与一些因数的关系,如取代基效应,与氮基的轴向配位体配位,与卤素阴离子的轴向配位体配位,与二原子分子的轴向配位体配位,卟啉环体系的特性结构(即立栅式卟啉等),卟啉环的碱度,与溶剂的氢离子键合等。     

First electrogeneration of a platinum(IV) porphyrin: elucidation of the Pt(II/IV) and Pt(IV/II) oxidation-reduction processes in nonaqueous media

The first example for electrogeneration of a Pt(IV) porphyrin from its Pt(II) form is presented and the Pt(II/IV) and reverse Pt(IV/II) oxidation-reduction processes are elucidated by electrochemistry and thin-layer UV-visible spectroelectrochemistry. Three products, [(TPP˙(+))Pt(II)](+), [(TPP)Pt(IV)](2+) and [(TPP˙(+))Pt(IV)](3+), produced by electrooxidation of the Pt(II) porphyrin have been characterized by in situ spectroelectrochemistry and ESR measurements after controlled potential bulk electrolysis. The first definitive evidence for the electrochemical conversion of a Pt(iv) porphyrin to its Pt(II) form is also presented. The potential for this electroreduction is highly dependent upon the nature of the anion, ClO(4)(-) or Cl(-). A mechanism for the reversible conversion between Pt(II) and Pt(IV) tetraphenylporphyrins is proposed.     

Effect of Solvent and Protonation/Deprotonation on Electrochemistry,Spectroelectrochemistry and Electron‐Transfer Mechanisms of N‐Confused Tetraarylporphyrins in Nonaqueous Media

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)₄NcpH₂, 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.     

Synthesis and Characterization of Carbazole‐Linked Porphyrin Tweezers

Herein the synthesis, spectroscopic characterization, two‐photon absorption and electrochemical properties of 3,6‐disubstituted carbazole tweezers is reported. A dimer resulting from a Glaser homocoupling was isolated during a Sonogashira coupling reaction between a diethynyl‐carbazole spacer and a 5‐bromo‐triarylporphyrin and the properties of this original compound were compared with the 3,6‐disubstituted carbazole bisporphyrin tweezers. The dyads reported herein present a two‐photon absorption maximum at 920 nm with two‐photon absorption cross‐section in the 1200 GM range. Despite a strong linear absorption in the Soret region and moderate fluorescence quantum yield, they both lead to a high brightness reaching 30 000 M ^?1 cm^?1.