Concentration mediated structural modulation in a family of mixed-ligand coordination polymers: Structure, sorption and luminescence study

Abstract

A series of mixed-ligands Zn(II) coordination polymers (CPs) have contracted by varying the relative ratio of two ligands. A linear N,N′-donor ligand, trans 4,4′-azobispyridine (azbpy) and a sodium salt of tri carboxylic acid, 1,3,5-benzenetricarboxylate (Na3btc) have been used in different ratio, along with Zn(II) salt to synthesize three different mixed ligands multifunctional hydroxy bridged CPs, namely {[Zn2(μ2-OH)(azbpy)(btc)(H2O)]. (H2O)(MeOH)}n (1), {[Zn2(μ3-OH)(azbpy)1.5(btc)(H2O)].(azbpy)0.5(H2O)4}n (2), and {[Zn2.5(azbpy)(Hbtc)2(μ2-OH)(H2O)3].(H2O)3.5(MeOH)}n (3). All these CPs 1, 2 and 3 have been characterized by single crystal X-ray diffraction (SCXRD), elemental analysis, infrared (IR) spectroscopy, thermogravimetric (TG) analysis, UV–visible spectroscopy and powder X-ray diffraction (PXRD). The desolvated frameworks of 1 and 2 adsorb CO2 better, over N2, whereas, complex 3 shows reverse phenomenon. Solid state luminescence studies of these CPs display attentive fluorescence emission at room temperature. Change in those properties has been observed, which has been discussed here with structural correlation.