Four New Cd(II) Coordination Polymers with Mixed Multidentate N-Donors and Biphenyl-Based Polycarboxylate Ligands: Syntheses, Structures, and Photo luminescent Properties

Four new cadmium(II) coordination polymers (CPs), {[Cd(Hpptpd)(H(2)bptta)]center dot 8H(2)O}(n) (1), {[Cd-2(Hpptpd)(2)(bptta)(H2O)2]center dot 4H(2)O}(n) (2), {[Cd-2(pptpz)(bpta)(H2O)]center dot H2O}(n) (3), and {[Cd(Hpptpz)(bpba)]center dot 2H(2)O}(n) (4) (Hpptpd = 2-(3-(4-(pyridin-4-yl)phenyl)-1H-1,2,4-triazol-5-yl)pyridine, Hpptpz = 2-(3-(4-(pyridin-4-yl)phenyl)-1H-1,2,4-triazol-5-yl)pyrazine, H(4)bptta = 3,3',5,5'-biphenyltetracarboxylic acid, H(3)bpta = 3,4',5-biphenyltricarboxylic acid, H(2)bpba = 3,4'-biphenylbicarboxylic acid), were synthesized under hydrothermal conditions. The CPs were structurally characterized by single-crystal X-ray diffraction analyses and further characterized by infrared spectra (IR), elemental analyses, powder X-ray diffraction (PXRD), and thermogravimetric analyses (TGA). Complex 1 exhibits an unusual 2D + 2D -> 2D parallel interpenetrated 63-hcb network. The adjacent 2D networks are interdigitated with each other to form the resulting three-dimensional (3D) supramolecular architecture through the interbilayer pi center dot center dot center dot pi stacking between Hpptpd ligands and nonclassical C-H center dot center dot center dot O hydrogen bonds. Complex 2 is a one-dimensional (1D) molecular ladder along the a direction and further extended via hydrogen bonds into the 3D supramolecular framework. Complex 3 exhibits a novel complicated 3D (3,4,4,5)-connected framework with the Schlafli symbol of (4.6(5))(4.6(7).8(2))(6(3))(6(4).8(2)). Complex 4 manifests an intriguing layered structure with 5-connected cadmium atom as a unique node and can be simplified to an Archimedean (3(3).4(4).5(3)) cem topology with triangular and rectangular circuits. The topology of 4 could be alternately simplified to a 3,4-connected binodal layer with a V2O5-type network. The thermal stabilities and photoluminescence behaviors of them were also discussed.