Issue 29, 2023

Valence tautomerism in a cobalt–dioxolene complex containing an imidazolic ancillary ligand

Abstract

This work reports the synthesis, structural, spectroscopic and magnetic investigation of two complexes, [Co(bmimapy)(3,5-DTBCat)]PF6·H2O (1) and [Co(bmimapy)(TCCat)]PF6·H2O (2), where bmimapy is an imidazolic tetradentate ancillary ligand and 3,5-DTBCat and TCCat are the 3,5-di-tert-butyl-catecholate and tetrachlorocatecholate anions, respectively. Their structures have been elucidated using single crystal X-ray diffraction, showing a pseudo-octahedral cobalt ion bound to a chelating dioxolene ligand and the ancillary bmimapy ligand in a folded conformation. Magnetometry displayed an entropy-driven, incomplete, Valence Tautomeric (VT) process for 1 in the 300–380 K temperature range, while 2 displayed a temperature independent, diamagnetic low-spin cobalt(III)–catecholate charge distribution. This behaviour was interpreted on the basis of the cyclic voltammetric analysis, allowing the estimation of the free energy difference associated with the VT interconversion of +8 and +96 kJ mol−1 for 1 and 2, respectively. A DFT analysis of this free energy difference highlighted the ability of the methyl-imidazole pendant arm of bmimapy favouring the onset of the VT phenomenon. This work introduces the imidazolic bmimapy ligand to the scientific community working in the field of valence tautomerism, increasing the library of ancillary ligands to prepare temperature switchable molecular magnetic materials.

Graphical abstract: Valence tautomerism in a cobalt–dioxolene complex containing an imidazolic ancillary ligand

Supplementary files

Article information

Article type
Paper
Submitted
15 5 2023
Accepted
22 6 2023
First published
04 7 2023
This article is Open Access
Creative Commons BY license

RSC Adv., 2023,13, 20050-20057

Valence tautomerism in a cobalt–dioxolene complex containing an imidazolic ancillary ligand

A. Moledo Vicente Guedes, L. Sodré de Abreu, I. A. V. Maldonado, W. S. Fernandes, T. M. Cardozo, R. A. Allão Cassaro, M. Scarpellini and G. Poneti, RSC Adv., 2023, 13, 20050 DOI: 10.1039/D3RA03235C

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