Two magnetic Δ-chain-based Mn(ii) and Co(ii) coordination polymers with mixed carboxylate–phosphinate and μ3-OH− bridges

Abstract

The hydrothermal reaction of Mn(II) or Co(II) ions with 2-carboxyethyl(phenyl)phosphinic acid (H₂L) afforded Mn(II) and Co(II) carboxylate–phosphinates containing μ₃-OH⁻ as a co-ligand, namely [M₃(L)₂(OH)₂] (M = Mn (1) or Co (2)). Such two compounds feature a new layered structure in which Δ-type chains built from alternating corner- and edge-sharing M₃(μ₃-OH) triangles are further connected via the Y-shaped “–(CH₂)₂–C(–O–)–” spacers. Magnetic studies reveal that there are dominant antiferromagnetic interactions between the metal ions. In 1, the complicated magnetic couplings in the Δ-type chains result in spin competition, displaying spin-glass behaviors. In 2, spin fluctuation behavior was observed and the critical field at 2 K is 25 kOe.