Structure And Solid Fluorescent Properties Of Metal Complexes With Azo Ligands

Azo compounds with good fluorescent properties have been attracting much attention in past decades. Due to their relatively low thermal stability, the application of azo compounds is limited. In this work, sixteen sorts of novel coordination polymers by solvothermal (hydrothermal) method have been prepared by reacting three types of azo-containing derivatives as the ligands with I/IIB metal ion. The structures of crystals were characterized by elemental analysis, single-crystal X-ray diffraction, infrared (IR) spectra and powder X-ray diffractions (PXRD). Thermal stability and fluorescent performance of coordination polymers were measured, calculated and analyzed. The synthetic conditions, the coordination model of ligand, hydrogen bonding and π-π stacking interactions were discussed to reveal the effects on azo coordination polymers applications in order to obtain stable azo compounds under high temperature. The emission spectra of coordination polymers move to the direction of visible light caused by the interaction of metals and ligands, which provides a wider application prospect for the practical application of azo compounds.4-[(8-hydroxy-5-quinolinyl)azo]-benzenesulfonic acid (H2L1) as ligand reacts with Cu, Cd and Zn to synthesize ten sorts of novel coordination polymers:[Cu(L1)(en)]·0.5H2O (1),[Cu(L1)2][Cu(en)2]·2H2O (2),[Zn(L1)(H2O)4](3),{[Cd(L1)(en)]·EtOH}n (4),{[Cd(L1)(H2O)2]·H2O}n (5),{[Cd2(L1)2(en)2(H2O)2]·3H2O}n (6),{[Cd(L1)(en)]·DMF}n (7),[Zn3(L1)2(OH)2(H2O)6]n (8),[Zn(L1)(H2O)]n (9) and [Zn(M1)2](10). Compounds1,2,3and10exhibit zero-dimensional (0D) structure. Compounds4and5display infinite one-dimensional (1D) ladder-shaped chain structures. Compound6is1D zig-zag chain structure. Compounds7and8exhibit infinite1D double-metal chain structures. Compound9is a three-dimensional (3D) structure. Compounds1~8and10are further connected through hydrogen bonding and π-π interactions into3D supramolecular networks. The coordination model of ligand was discussed the effect of compound structure. From the description of the structure, the coordination model of sulfonate groups plays an important role in the structure of coordination compounds. Compound10was synthesized under the alkaline condition, which ligand was in situ reaction. The thermal stabilities of compounds1~9have an obvious enhancement with respect to H2L1ligand. The fluorescent properties of compounds1~2mainly come from the ligand-to-metal charge transfer, which have blue shift to H2L1ligand, showing violet fluorescence. The reaction between H2L1ligand and copper(II) ion leads to a sensitive fluorescent, visible to the naked eye and simple effective method of the detection of copper ion. The fluorescent properties of compounds3~9mainly come from the ligand-to-ligand charge transfer. The fluorescent data of compounds1~9indicate that the emission spectra of coordination compounds slightly inclined to blue shift to the H2L1ligand. The theoretical calculation of fluorescent spectra of compounds1,2,3and10were performed.4-[(8-hydroxy-5-quinolinyl)azo]-benzoic acid (H2L2) as ligand reacts with Zn and Cd to synthesize two sorts of novel coordination polymers:[Zn(L2)(H2O)2]n (11) and {[Cd(L2)(H2O)]·H2O}n (12). Compound11exhibits1D zig-zag chain structure. Compound12is two-dimensional (2D) layer structure. Compounds11~12are further connected through hydrogen bonding and π-π interactions into3D supramolecular networks. The coordination model of ligand was studied to reveal the effect on compound structure. The thermal satbility properties of compounds11~12have an obvious enhancement to H2L2ligand. The emission spectra of compounds11~12have scarcely change to H2L2ligand. The fluorescent properties of compounds11~12mainly come from the charge transfer from ligand to ligand.Azobenzene-4,4’-dicarboxylate (H2L3) as ligand reacts with Cd, Cu and Ag to synthesize four sorts of novel coordination polymers:{[Cd2(L3)2(en)2]·DMF}n (13),[Cu(L3)(en)]n (14),{[Cu(L3)(phen)(H2O)]·DMA}n (15) and [Ag(L3)0.5]n (16). Compounds13~15exhibit1D zig-zag chain structures, which are further connected through hydrogen bonding and π-π interactions into3D supramolecular networks. Compound16is3D structure. Ethylenediamine and1,10-phenanthroline as auxiliary ligands were studied to reveal the effect on compound structure. The thermal stability properties of compounds13~15have an obvious enhancement to H2L3ligand. The fluorescent properties of compounds13~15mainly come from the charge transfer from ligand to metal, which have red shift with respect to H2L3ligand, showing blue fluorescence.