A series of coordination complexes based on unsymmetrical multicarboxylate ligands: syntheses, structures and properties

Six new coordination polymers, namely, [Zn-2(L-1)(2)phen(2)(H2O)(2)] (1), [M-3(L-1)(2)(OH)(2) (4,4'-bpy)(H2O)(2)]center dot 2H(2)O (M = Cd (2), Co(3)), [Cd-5(L-1)(2)(OH)(2)(trz)(4)(L-3)]center dot 2H(2)O (4), [Zn(HL2)(4,4'-bpy)] (5) and [Cd-3(L-2)(2)(L-3)(2)(H2O)(5)]center dot H2O (6) (H2L1 = 4-(1-carboxy-ethoxy)-benzoic acid, H3L2 = 5-(1-carboxy-ethoxy)-isophthalic acid, L-3 = 1,2-bis(1,2,4-triazole-1-yl)ethane, phen = 1,10-phenanthroline, 4,4'-bpy = 4,4'-bipyridine, Htrz = 1,2,4-triazole), have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction. Compound 1 is a molecular square composed by two Zn ions, two L-1 and two phen ligands. Compounds 2 and 3 are isostructural and display 3D frameworks constructed by 1D M-O-M chains. Compound 4 exhibits a 3D 8-connected network with hex topology based on the pentanuclear Cd cluster and the point symbol is (3(6).4(18).5(3).6). Compound 5 shows a 2D wavelike layer with sql topology. Compound 6 reveals a 3D threefold interpenetrating architecture having (3,4)-connected dmd topology with the point symbol of (4.10(2))(2)(4(2).10(4)). These compounds have been characterized by infrared spectroscopy (IR) and thermal gravimetric analyses (TGA). In addition, the photoluminescent behaviour of 1, 2, and 4-6 has been investigated in detail.