Deakin University
Browse

File(s) under permanent embargo

Thiosemiquinoid Radical-Bridged CrIII2 Complexes with Strong Magnetic Exchange Coupling

Version 2 2024-06-13, 14:47
Version 1 2021-10-25, 08:13
journal contribution
posted on 2024-06-13, 14:47 authored by C Hua, JA Degayner, TD Harris
Semiquinoid radical bridging ligands are capable of mediating exceptionally strong magnetic coupling between spin centers, a requirement for the design of high-temperature magnetic materials. We demonstrate the ability of sulfur donors to provide much stronger coupling relative to their oxygen congeners in a series of dinuclear complexes. Employing a series of chalcogen donor-based bis(bidentate) benzoquinoid bridging ligands, the series of complexes [(TPyA)2Cr2(RL4–)]2+ (OLH4 = 1,2,4,5-tetrahydroxybenzene, OSLH4 = 1,2-dithio-4,5-dihydroxybenzene, SLH4 = 1,2,4,5-tetrathiobenzene, TPyA = tris(2-pyridylmethyl)amine) was synthesized. Variable-temperature dc magnetic susceptibility data reveal the presence of weak antiferromagnetic superexchange coupling between CrIII centers in these complexes, with exchange constants of J = −2.83(3) (OL4–), –2.28(5) (OSL4–), and −1.80(2) (SL4–) cm–1. Guided by cyclic voltammetry and spectroelectrochemical measurements, chemical one-electron oxidation of these complexes gives the radical-bridged species [(TPyA)2Cr2(RL3–•)]3+. Variable-temperature dc susceptibility measurements in these complexes reveal the presence of strong antiferromagnetic metal–semiquinoid radical coupling, with exchange constants of J = −352(10) (OL3–•), – 401(8) (OSL3–•), and −487(8) (SL3–•) cm–1. These results provide the first measurement of magnetic coupling between metal ions and a thiosemiquinoid radical, and they demonstrate the value of moving from O to S donors in radical-bridged metal ions in the design of magnetic molecules and materials.

History

Journal

Inorganic Chemistry

Volume

58

Pagination

7044-7053

Location

Washington, D.C.

ISSN

0020-1669

eISSN

1520-510X

Language

English

Publication classification

C1.1 Refereed article in a scholarly journal

Issue

10

Publisher

American Chemical Society