Syntheses, crystal structures and fluorescences of two novel 2D Cd(II) coordination polymers

Two novel Cd(II) coordination polymers, [Cd-2(C10H2O8)(.)(H2O)(6)](n) (1) and [Cd-4(C6H4O2N)(8)(H2O)(4)](n)(2) (C10H2O8 = 1, 2, 4, 5-benzenetetracarboxyl and C6H4O2N = nicotinato), were hydrothermally synthesized and characterized by X-ray diffraction of the single-crystal and fluorescence spectra. Complex 1 crystallizes in triclinic system, space group P (1) over bar with a = 0.559 62(7) nm, b = 0.777 58(6) nm, c = 0.969 75(10) nm, alpha = 111.981(5)degrees, beta = 101.649(6)degrees, gamma = 98.240(5)degrees, and Z = 1. Final R = 0.024 8(wR = 0.078 5). Complex 2 belongs to orthorhombic system, space group Pbca with unit cell dimensions a = 1.144 94(19) nm, b = 1.209 69(6) nm, c = 1.740 73(8) nm and Z = 8. Final R = 0.018 5(wR = 0.034 8). Both the two complexes are coordination polymers with a two-dimensional infinite structure, the repeat unit is [Cd-2(C10H2O8)(H2O)(6)] (1) and [Cd-4(C6H4O2N)(8)(H2O)(4)] (2) which are bridged by the ligands of 1,2,4,5-benzenetetracarboxyl(C10H2O8) and nicotinato(NA), respectively. The two polymers show strong fluorescence with gamma(em) = 433 nm (gamma(ex) = 333 nm, 1) and gamma(em) = 423 nm (gamma(em) = 330 rim, 2) in the solid state at room temperature. The emissions observed in the polymers are tentatively assigned to the ligands fluorescence (LLCT).