Synthesis, structure, and magnetic properties of Fe3+ and Ru3+ metal chalcogenide (O,S) complexes with bidentate ligands

Abstract

Hydroxypyridinones represent a versatile class of bidentate ligands for the construction of coordination compounds with tuneable structural and magnetic properties. In this work, we systematically investigate the coordination chemistry and magnetic behaviour of two group VIII trivalent transition metals (Fe³⁺ and Ru³⁺) with 1,2-dimethyl-3-hydroxy-4-pyridinone and its thione analogue, 1,2-dimethyl-3-hydroxy-4-pyridinethione. Tris-chelated octahedral complexes are readily obtained with the oxygen-donor ligand, yielding isostructural compounds stabilized by extended hydrogen-bond networks in the solid state. Substitution of the ketonic oxygen with sulphur markedly alters the reactivity, leading to the formation of a tris-chelated Fe³⁺ complex and an unprecedented sodium-bridged binuclear Ru³⁺ species. Magnetic measurements reveal high-spin (S = 5/2) Fe³⁺ behaviour with significant intermolecular antiferromagnetic interactions, while the Ru³⁺ derivatives exhibit a low-spin S = 1/2 character. In the sulphur-containing Ru system, the data suggest partial spin delocalization onto the ligand framework. These results elucidate how subtle changes in the donor atom identity and metal electronic structure govern coordination modes, solid-state organization, and magnetic properties, providing valuable insights for the rational design of hydroxypyridinone-based molecular magnetic materials.