Syntheses, Structures, and Properties of a Series of Polyazaheteroaromatic Core-Based Zn(II) Coordination Polymers Together with Carboxylate Auxiliary Ligands

Six Zn(II) coordination polymers, [Zn(H2L)(Hipa-CH3)(2)]center dot 2H(2)O (1), [Zn-2(HL)(2)(ipa-CH3)] (2), [Zn-2(HL)(2)(ipa-NO2)]center dot 2H(2)O (3), [Zn-2(HL)(2)(ipa-NO2)] (4), [Zn-2(HL)(BTCA)(H2O)]center dot H2O (5), and [Zn-3(HL)(3)(BTCA)] (6), were synthesized by reactions of Zn(II) salts with rigid ligand 1-(1H-imidazol-4-yl)-4-(4H-tetrazol-5-yl)benzene (H2L) and different carboxylic acids, 5-methyl-isophthalic acid (H(2)ipa-CH3), 5-nitroisophthalic acid (H(2)ipa-NO2), and 1,2,4-benzenetricarboxylic acid (H(3)BTCA). Complexes 1 and 2 were formed under different pH values, and 1 is a onedimensional (1D) chain extended by hydrogen bonds and pi-pi stacking interactions to form a three-dimensional (3D) supramolecular polymer, while 2 exhibits a uninodal 6-connected 3D architecture with (4(12).6(3))-pcu topology based on the binuclear Zn(II) secondary building units (SBUs). Polymers 3 and 4 present a pair of pseudopolymorphs with layered-pillared framework. Polymer 3 possesses Zn-2(HL-)(2)(2+) sheets pillared by the ipa-NO22- ligand to form a 3D net, while 4 builds on the [Zn-2(HL)(ipa-NO2)](+) layer pillared by HL- ligand. Complex 5 is a (3,8)-connected tfz-d 3D net with point (Schlafli) symbol (4(3))(2)(4(6).6(18).8(4)) based on the tetranudear [Zn-4(COO)(4)] SBUs, while the BTCA(3-) ligands act as three-connector pillars to link adjacent [Zn-3(HL-)(3)](3-) layers into a 3D net for 6. Complexes 1-6 exhibit intense light blue emission in the solid state at room temperature, and activated sample 6 shows highly selective CO2 uptake over N-2 and H-2.