A three-dimensional mixed-valence CuII/CuIcoordination polymer constructed from biphenyl-3,4′,5-tricarboxylate and 1,4-bis(1H-imidazol-1-yl)benzene ligands

Abstract

Coordination polymers (CPs) built by coordination bonds between metal ions/clusters and multidentate organic ligands exhibit fascinating structural topologies and potential applications as functional solid materials. The title coordination polymer, poly[diaquabis(μ4-biphenyl-3,4′,5-tricarboxylato-κ4O3:O3′:O4′:O5)tris[μ2-1,4-bis(1H-imidazol-1-yl)benzene-κ2N3:N3′]dicopper(II)dicopper(I)], [CuII2CuI2(C15H7O6)2(C12H10N4)3(H2O)2]n, was crystallized from a mixture of biphenyl-3,4′,5-tricarboxylic acid (H3bpt), 1,4-bis(1H-imidazol-1-yl)benzene (1,4-bib) and copper(II) chloride in a water–CH3CN mixture under solvothermal reaction conditions. The asymmetric unit consists of two crystallographically independent Cu atoms, one of which is CuII, while the other has been reduced to the CuIion. The CuIIcentre is pentacoordinated by three O atoms from three bpt3−ligands, one N atom from a 1,4-bib ligand and one O atom from a coordinated water molecule, and the coordination geometry can be described as distorted trigonal bipyramidal. The CuIatom exhibits a T-shaped geometry (CuN2O) coordinated by one O atom from a bpt3−ligand and two N atoms from two 1,4-bib ligands. The CuIIatoms are extended by bpt3−and 1,4-bib linkers to generate a two-dimensional network, while the CuIatoms are linked by 1,4-bib ligands, forming one-dimensional chains along the [20\overline{1}] direction. In addition, the completely deprotonated μ4-η1:η1:η1:η1bpt3−ligands bridge one CuIand three CuIIcations along thea(or [100]) direction to form a three-dimensional framework with a (103)2(10)2(42.6.102.12)2(42.6.82.10)2(8) topologyviaa 2,2,3,4,4-connected net. An investigation of the magnetic properties indicated a very weak ferromagnetic behaviour.