Twelve Cadmium(II) Coordination Frameworks with Asymmetric Pyridinyl Triazole Carboxylate: Syntheses, Structures, and Fluorescence Properties

Based on an asymmetric pyridinyl triazole carboxylate ligand 1-(4-pyridinylmethyl)-1H-1,2,4-triazole-3-carboxylic acid (Hpmtc), 12 cadmium(II) polymers {Cd1.5(pmtc)2(NO3)]·H2O}n (1), {[Cd2(pmtc)2(μ2-SO4)(H2O)]}n (2), [Cd(pmtc)(SCN)]n (3), [Cd2(pmtc)2(SCN)2]n (4), {[Cd1.5(pmtc)2(N3)]·H2O}n (5),{[Cd(pmtc)2]}n (6), [Cd(pmtc)(NO2)(CH3OH)]n (7), {[Cd2(ppmtc)3(NO2)]}n (8), {[Cd2(pmtc)2(Cl)2(H2O)2]}n (9),{[Cd(pmtc)(Br)(H2O)]·CH3OH}n (10), {Cd(pmtc)(I)(H2O)]}n (11), and [Cd(pmtc)(I)]n (12) have been synthesized and structurally characterized. Employment of different anions has resulted in different architectures and topological structures, ranging from two-dimensional (2D) to three-dimensional (3D) frameworks, in which 2 and 4 present a new (42·6·103)(42·63·8)2(42·6) topology. Through calculations to the frontier molecular orbital (FMOs) of 9–11, their photoluminescence should be assigned as the n → π* transition. Moreover, the photoluminescent properties of 1–12 indicate that the coordination anions make great contribution to fluorescent emission of Cd(II) polymers.