A novel dinuclear manganese(II) compound incorporating two bis(imidazolyl) based ligands with single μ2-η1:η1-carboxylato bridges. Molecular and crystal structure and magnetic properties of [Mn2Cl(BIP)(HBIMAM)(H2O)5]Cl3·4H2O (BIP = 3,3-di(2-1H-2-imidazolyl)propanoate; BIMAM = N-methyldi(1H-2-imidazolyl)methanamine)

Abstract

This paper reports the synthesis, X-ray structure and magnetic characterization of [Mn2Cl(BIP) (HBIMAM)(H2O)5]Cl3·4H2O a novel dinuclear manganese(II) incorporating two related bis(imidazolyl)-based ligands, BIP (3,3-di(2-1H-2-imidazolyl)propanoate) and BIMAM (N-methyldi(1H-2-imidazolyl)methanamine). The metal atoms in the dinuclear entity are bridged by a μ2-η1:η1 carboxylate group (from the propionate arm of the BIP ligand) acting in an anti–anti coordination bridging mode, with an intramolecular Mn⋯Mn distance of 6.47Å. The coordination around the Mn(II) ions shows a distorted octahedral geometry for both MnClN2O3 and MnN2O4 chromophores. Between the imidazole rings of neighbouring dinuclear units there significant aromatic–aromatic interactions. The propagation of these interactions generates chains of π-stacked dinuclear units, roughly running along the [100] direction. Magnetic susceptibility measurements in the range 2–300K show weak antiferromagnetic exchange interactions which were analysed by means of the isotropic S1=S2=5/2 spin-coupled dimer model Hˆ=-2J(Sˆ1·Sˆ2). Finally, the observed magnetic behavior (2J=−0.38(1)cm−1) is compared with that observed in related manganese(II) compounds with single [Mn(μ2-η1:η1-carboxylato)Mn] core.