Issue 17, 2024

Spectroscopic and thermodynamic characterization of a cobalt-verdazyl valence tautomeric system. influence of crystal structure, solvent and counterion

Abstract

Crystallization of the verdazyl-based valence tautomeric ion [Co(dipyvd)2]2+ (where dipyvd is the radical ligand 1-isopropyl-3,5-di(2′-pyridyl)-6-oxoverdazyl) with a variety of different counterions results in materials that show varying degrees of valence tautomeric (VT) transition in the solid state. The X-ray structure of the SbF6 salt at 150 K reveals a localized structure for the S = 1/2 tautomer, with a Co3+ cation and distinct anionic and radical ligands. Comparison with the structure of the same material at 300 K reveals large structural changes in the ligand as a result of the valence tautomeric equilibrium. Data for the S = 3/2 form is less conclusive; X-ray spectroscopy on the PF6 salt suggests a degree of low spin Co2+ character for the S = 3/2 tautomer at very low temperature though this is inconsistent with EPR data at similar temperatures and structural information at 150 K. Magnetic measurements on the [BArF4] and triflate salts in organic solvents show that the VT equilibrium is dependent on solvent and ion pairing effects.

Graphical abstract: Spectroscopic and thermodynamic characterization of a cobalt-verdazyl valence tautomeric system. influence of crystal structure, solvent and counterion

Supplementary files

Article information

Article type
Paper
Submitted
16 Febr. 2024
Accepted
01 Apr. 2024
First published
03 Apr. 2024
This article is Open Access
Creative Commons BY-NC license

Dalton Trans., 2024,53, 7536-7545

Spectroscopic and thermodynamic characterization of a cobalt-verdazyl valence tautomeric system. influence of crystal structure, solvent and counterion

D. J. R. Brook, J. DaRos, A. Ponnekanti, S. Agrestini and E. Pellegrin, Dalton Trans., 2024, 53, 7536 DOI: 10.1039/D4DT00465E

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