Syntheses, structures and fluorescence properties of a Zn and a Cd(II) coordination polymer based on the mixed ligands

Abstract

Two new compounds, [Zn(4-npa)(btmb)]n (1) and [Cd(4-npa)(btmb)0.5(H2O)2]n (2) (H24-npa = 4-nitrophthalic acid, btmb = 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene) have been achieved under hydrothermal conditions and structurally characterized by elemental analysis, IR spectroscopy and single-crystal x-ray diffraction. The compound 1 crystallizes in monoclinic crystal system, space group P21/c and is characterized by a two-dimensional layer structure containing 1 D Zn-carboxylate chains. Wherein the central Zn(II) ion is coordinated by two carboxylate O atoms and two N atoms to give a distorted tetrahedral [ZnO2N2] geometry. In compound 2, The hexa-coordinated Cd(II) ion forms a slightly distorted octahedral [CdNO5] geometry. The two Cd(II) centers are bridged by pair 4-npa dianions adopting bidentate-bridging mode to form a dinuclear unit. The dinuclear units are linked together by 4-npa dianions to form a Cd-carboxylate layer, and further extend by btmb molecules to form a 3 D pillared-layer metal–organic framework. The thermogravimetric analyses and luminescent properties of two compounds are also investigated.