Imidazolate Bridges Enable Spin Communication in Diiron(III) Porphyrin Dimers: A Bioinspired Model of the Diheme Enzyme MauG.

Authors

Subhadip Pramanik, Rupesh Kumar Tiwari, Sarnali Sanfui, Priyajit Tudu, Gopalan Rajaraman, Sankar Prasad Rath

Published in

Inorganic chemistry. Volume 65. Issue 36. Pages 20987-20999. Sep 14, 2026.

Abstract

Inspired by the long-range electron-transfer pathways in diheme enzymes such as MauG and bacterial diheme cytochrome c peroxidases, where an intervening tryptophan residue mediates electronic communication between spatially separated heme centers, we report a rare class of imidazolate-bridged Fe(III) porphyrin dimers that emulate this biological architecture. The redox-active imidazolate bridge directly couples two iron porphyrin centers, enabling efficient electronic communication. To probe the role of structural flexibility, dimers incorporating rigid cis-ethene and flexible diethyl pyrrole linkers were systematically investigated. Stepwise chemical oxidation modulates the electronic structure and magnetic coupling through the bridge. Paramagnetic 1H NMR spectroscopy reveals oxidation-dependent shifts of the imidazolate proton resonances, providing direct evidence for spin delocalization onto the bridging ligand. Magnetic studies show a nonmonotonic dependence of the JFe-Fe exchange interaction on the oxidation state, weakening after one-electron oxidation but strengthening upon further oxidation. Complementary structural, spectroscopic, and DFT analyses attribute this behavior to subtle changes in Fe-Nμim and Fe-Np bond lengths, axial ligand orientation, and spin density redistribution, which collectively regulate orbital overlap between the iron centers. Overall, this work establishes a structure-property relationship linking the bridge geometry, redox state, and magnetic exchange, providing a molecular design strategy for tuning electronic communication in bioinspired diheme architectures.

PMID:
42734398
Bibliographic data and abstract were imported from PubMed on 14 Sep 2026.

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