A Highly Oxidized Cobalt Porphyrin Dimer: Spin Coupling and Stabilization of the Four‐Electron Oxidation Product

Abstract

A highly oxidized cobalt porphyrin dimer is reported. Each cobalt(II) ion and porphyrin ring underwent 1e oxidation with iodine as the oxidant to give a 4e-oxidized cobalt(III) porphyrin π-cation radical dimer. The bridging ethylene group allows for substantial conjugation of the porphyrin macrocycles, thus leading to a strong antiferromagnetic coupling between the π-cation radicals and to stabilization of the singlet state. X-ray crystallography clearly showed that the complex may be considered as a real supramolecule rather than two cobalt(III) porphyrin π-cation radicals that interact through space.

Intermacrocyclic Interaction Triggers Facile One‐Pot Synthesis of a Chlorin–Porphyrin Heterodimer

“…The spectral pattern between Pd 2 DEPR⋅I 3 and Cu 2 DEPR⋅I 3 is very much similar, but the low‐energy bands in the NIR region are more redshifted in Cu 2 DEPR⋅I 3 (Figure ). Moreover, the lowering of the Soret band intensity in M 2 DEPR⋅I 3 indicates the reduction of the overall aromaticity of the complex because of its extensive π‐conjugation through the bridge –. ESI‐MS spectra show the molecular ion peaks at m / z= 1334.6537 for [Cu 2 DEPR] + and at m / z= 1422.6019 for [Pd 2 DEPR] + supporting that three protons were removed as a result of intramolecular oxidative fusion (Figures S8 and S9 in the Supporting Information).…”

Silver(III)⋅⋅⋅Silver(III) Interactions that Stabilize the syn Form in a Porphyrin Dimer Upon Oxidation

“…Two rings are rather more slipped in syn ‐ 1 and syn ‐ 1 ⋅I 3 , while they are mostly on top of each other in the 2 e − ‐oxidized complex syn ‐ 1 ⋅(X) 2 . However, 2 e − ‐oxidation of the highly flexible ethane‐bridged porphyrin dimer and their complexes are known to stabilize in the anti form only –. Our investigation clearly demonstrates that metallophilic attractive interactions do play an essential role in bringing two porphyrin in syn ‐ 1 ⋅(X) 2 more cofacial as evident by the short Ag III ⋅⋅⋅Ag III distance, which also display intense emission peak at 546 nm at 77 K. We have shown here, for the first time, the X‐ray structural characterization of a Ag III porphyrin, a Ag II /Ag III mixed valent porphyrin dimer and a disilver(III) porphyrin dimer with an unprecedented Ag III ⋅⋅⋅Ag III metallophilic interaction.…”

“…Interestingly, the highly flexible ethane‐bridged porphyrin dimer and its complexes with different transition metals adopt a cofacial syn conformation in a variety of solvents owing to π–π interactions between the macrocycles . Experimental investigations have clearly demonstrated further closeness of two macrocycles after 1 e − oxidation, which however move far apart upon 2 e − oxidation, stabilizing the anti form of the complex owing to the repulsion between two positive charges –. Herein, we have investigated the effects of possible interactions upon stepwise oxidations between two Ag II porphyrins connected via a flexible ethane bridge, which provides ample flexibility to orient the macrocycles for the probable argentophilic interactions and thereby allowing significant modulation of their ground and excited‐state properties.…”

“…An electrochemical study was performed for syn ‐ 1 . The complex displays reversible couples of two 1 e − and one 2 e − oxidations (Supporting Information, Figure S11), which are indicative of strong through‐space electronic communication– between the two cofacial silver porphyrins. At 0.30 V, one Ag II porphyrin unit is oxidized to generate Ag III porphyrin at a potential much lower than that of its monomeric analogue.…”

Synergistic Dual‐Atom Molecular Catalyst Derived from Low‐Temperature Pyrolyzed Heterobimetallic Macrocycle‐N4 Corrole Complex for Oxygen Reduction

“…[18][19][20][21][42][43][44][45][46] Compared with recently reported bimetallic systems derived from two different metal precursors, a single molecular complex composed of heterobimetals in close proximity, resulting in a synergistic effect, is highly desirable for a facile oxygen reduction mechanism, similar to the natural ORR conducted by cytochrome c oxidase. [47][48][49][50][51] Lower symmetry structures of MN4 macrocycles, such as corrin and corroles, have been reported to show noteworthy ORR performance compared with symmetric porphyrins and phthalocyanines. [17][18][19][20] Furthermore, the effect of heterobimetals, particularly the combination of Co and Fe, along with their presence in a single MN4 macrocycle, can afford the additional advantage of providing both activity and stability.…”