Highly Oxidized Cobalt Porphyrin Dimer: Control of Spin Coupling via a Bridge

A cobalt porphyrin dimer is constructed in which two Co­(II)­porphyrins are connected covalently through a redox-active diethylpyrrole moiety via a flexible but “nonconjugated” methylene bridge. Upon oxidation with even a mild oxidant such as iodine, each cobalt­(II) center and porphyrin ring underg...

Full description

Saved in:
Bibliographic Details
Published in:Inorganic chemistry 2022-06, Vol.61 (22), p.8419-8430
Main Authors: Sanfui, Sarnali, Usman, Mohammad, Sarkar, Sabyasachi, Pramanik, Subhadip, Garribba, Eugenio, Rath, Sankar Prasad
Format: Article
Language:English
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:A cobalt porphyrin dimer is constructed in which two Co­(II)­porphyrins are connected covalently through a redox-active diethylpyrrole moiety via a flexible but “nonconjugated” methylene bridge. Upon oxidation with even a mild oxidant such as iodine, each cobalt­(II) center and porphyrin ring undergo 1e– oxidation, leading to the formation of a 4e–-oxidized cobalt­(III)­porphyrin dication diradical complex. Other oxidants such as Cl2 and Br2 also produce similar results. To stabilize such highly oxidized dication diradicals, the “nonconjugated” methylene spacer undergoes a facile and spontaneous oxidation to form a methine group with a drastic structural change, thereby making the bridge fully π-conjugated and enabling through-bond communication. This results in a strong spin coupling between two π-cation radicals which stabilizes the singlet state. The experimental observations are also strongly supported by extensive density functional theory calculations. The present study highlights the crucial role played by the nature of the bridge in the long-range electronic communication.
ISSN:0020-1669
1520-510X
DOI:10.1021/acs.inorgchem.1c03807