A series of complexes based on biphenyl-2,5,2′,5′-tetracarboxylic acid: syntheses, crystal structures, luminescent and magnetic properties

Five new metal complexes based on H(4)bptc: {[Cu-2(bptc)(H2O)(6)]center dot 11H(2)O}(n) (1), {[Ni-2(bptc)(H2O)(6)]center dot 11H(2)O}(n) (2), {[Co-2(H(2)bptc)(2)(4,4'-bpy)(2)(H2O)(2)]center dot 4H(2)O}(n) (3), [Ni-2(bptc) (2,2'-bpy)(2)(H2O)(6)]center dot 2H(2)O (4), [Zn-2(bptc)(2,2'-bpy)(2)(H2O)(6)]center dot 3H(2)O (5) (bptc = biphenyl-2,5,2',5'-tetracarboxylic acid, 2,2'-bpy = 2,2'-bipyridine, 4,4'-bpy = 4,4'-bipyridine) have been synthesized and structurally characterized by elemental analysis, IR spectra, powder X-ray diffraction, thermogravimetric analysis and X-ray crystallography. Complex 1 features a 2D sheet structure with (4, 4) grid units. The Cu(II) center in 1 is penta-coordinated in a square-pyramidal geometry. Complex 2 is isostructural with 1 excluding the metal ions. Complex 3 shows a 2D layer structure with rectangular windows. There exist parallel left-and right-handed helical chains in adjacent 2D sheets in complexes 1-3. Complex 4 exhibits a 3D supramolecular structure with a butterfly-shaped unit cell. Complexes 5 and 4 are isomers excluding the lattice water molecules. The non-covalent interactions (O-H center dot center dot center dot O, C-H center dot center dot center dot O, C-H center dot center dot center dot pi and pi center dot center dot center dot pi interactions) extend complexes 1-5 into 3D supramolecular networks. In addition, the photoluminescent properties for 1-5 and magnetic properties for 1, 3 have been investigated, respectively. Complexes 1 and 3 exhibit weak antiferromagnetic behaviour.