Tuning of Cr-Cr Magnetic Exchange through Chalcogenide Linkers in Cr2 Molecular Dimers

A set of three Cr-dimer compounds, Cr2Q2(en)4X2(Q: S, Se;X: Br, Cl;en: ethylenediamine), with monoatomicchalcogenide bridges have been synthesized via a single-step solvothermal route. Chalcogenide linkers mediate magnetic exchangebetween Cr3+centers, while bidentate ethylenediamine ligands complete the distorted octahedral coordination of Cr centers. Unlikethe compounds previously reported, none of the chalcogenide atoms are connected to extra ligands. Magnetic susceptibility studiesindicate antiferromagnetic coupling between Cr3+centers, which are moderate in Cr2Se2(en)4X2and stronger in Cr2S2(en)4Cl2.Fitting the magnetic data requires a biquadratic exchange term. High-frequency EPR spectra showing characteristic signals due tocoupledS= 1 spin states could be interpreted in terms of thegiant spinHamiltonian. A fourth compound, Cr2Se8(en)4, has asingle diatomic Se bridge connecting the two Cr3+centers and shows weak ferromagnetic exchange interactions. This workdemonstrates the tunability in strength and type of exchange interactions between metal centers by manipulating the interatomic distances and number of bridging chalcogenide linkers.

Automated summary

A series of Cr-dimer compounds with monoatomic chalcogenide bridges have been synthesized. The chalcogenide linkers mediate magnetic exchange between Cr3+ centers, and the ethylenediamine ligands complete the coordination of Cr centers. Antiferromagnetic coupling is observed between Cr3+ centers, and the strength of coupling can be controlled by adjusting the interatomic distances and number of chalcogenide linkers.