Synthesis and magnetic properties of two Mn-based coordination polymers constructed by a mixed-ligand strategy

Abstract

Two novel coordination polymers (CPs), namely, {[Mn₂(HL)(DMF)₂(H₂O)]·H₂O}_n (1) and {[Mn₂(HL)(bibp)(H₂O)]·H₂O}_n (2) {H₅L = 2,4-di(2′,5′-dicarboxylphenyl)benzoic acid, bibp = 4,4′-bis(imidazolyl)biphenyl}, were prepared under solvothermal conditions by a mixed-ligand strategy. The structural analysis shows that 1 has a 2D sheet structure with a 2-nodal (3,5)-connected {3·4·5}{3²·4·5·6²·7⁴} topology, which is further expanded into a 3D supermolecular framework by hydrogen bonding between 2D layers, while 2 exhibits a 3D framework with a 3-nodal (3,3,12)-connected network with a point Schläfli symbol of {3·4·5}₂{3·5²}₂{3²·4¹⁴·5¹⁰·6²⁶·7⁶·8⁶·9²}. Moreover, temperature dependent magnetic susceptibility and magnetization measurements revealed that 1 and 2 show weak antiferromagnetic interactions in the Mn chains with different spin topologies, which consist of repeating sequences of –J₁J₂– for 1 and –J₁J₂J₃J₂– for 2. Meanwhile, their superexchange coupling constants obtained using the PHI program further indicate that the magnetic interactions have an –AF–AF– repeating sequence for 1 and an –F–AF–F–AF– repeating sequence for 2, which are attributed to the structural differences of CPs 1 and 2 and are consistent with the magnetic results of structural analysis.