An Inorganic Helix [Mn(IPG)(MeOH)]n[PF6]n[‡]: Structural and Magnetic Properties of asyn-anti Carboxylate-Bridged Manganese(II) Chain Involving a Tetradentate Ligand

Abstract

The crystal structure of an infinite inorganic chain consisting of MnII and an N-centered tripodal ligand N,N-(2-pyridylmethyl)[(1-methylimidazol-2-yl)-methyl]glycinate is presented. It exhibits a chiral helical structure with a pitch of two monomeric units (each monomeric unit containing one Mn atom). Each manganese is connected to its neighbor through a carboxylate bridge in a syn-anti geometry. Around each manganese center, two carboxylates bind in a cis geometry. This peculiar bridging geometry (syn-anticis) provides a broken-line chain, running in a zig-zag manner along the b axis of the P21 space group. The magnetic properties have been investigated. They show a pseudo-2D magnetic structure, with one major pathway along the chain and an inter-chain minor one. The intrachain coupling is a weak antiferromagnetic interaction (J/k = –0.25). This low value is entirely consistent with the geometry of the bridge. The interchain coupling is a weaker antiferromagnetic coupling (J′/k = –0.11) and could be mediated through π-π interactions between pyridine and imidazole from two adjacent helixes.