Synthesis, structure and magnetic properties of hydroxychlorides A3Cu3(OH)Cl8 (A = Cs, Rb) with isolated tricopper

Abstract

Two copper hydroxychlorides, A₃Cu₃(OH)Cl₈ (A = Cs, Rb), were synthesized by a hydrothermal method, which crystallize in the space group P2₁/c. All copper atoms are coordinated with three Cl atoms and one OH group forming quite distorted squares of CuCl₃(OH), which further share one edge and one corner to form an isolated triangle unit of [Cu₃(OH)Cl₈]³⁻ with μ₂-Cl and μ₃-OH cores. Interestingly, the two isostructural compounds exhibit antiferromagnetic ordering at low temperature and the dominant exchange coupling in the isolated triangle is found to be of ferromagnetic type, ruling out geometrical frustration effects. The origin of such a ferromagnetic interaction is suggested to arise likely from the folded [Cu(2)Cu(3)(OH)Cl₅]²⁻ dimers with a Cu(2)–Cl(5)–Cu(3) route.