Studies on cluster, salt and molecular complex of zinc-quinolinate

Abstract

Reactions of zinc halides with 8-hydroxyquinoline (hydroxQ) in equimolar ratio were carried out in different solvents. Respective solvates of tetranuclear clusters, namely [Zn4(oxyQ)6 X 2].(solvent)2, (when X = Cl, Solvent = dimethylformamide (1), dimethylacetamide (2) and dimethysulphoxide (3); X = Br, solvent = dimethylformamide (4), oxyQ = quinolinate anion) were obtained. Bond parameters of these isostructural clusteres 1-4 are compared from their single crystal structures. Anhydrous forms of these complexes have porous packing and are thermally stable below 250∘C. Surface area of the complexes 1 and 4 are 8.933 and 6.172 m2/g, respectively. Complexes 1 and 4 can be reversibly hydrated, which is reflected in colour changes. The reaction of zinc chloride with 8-hydroxyquinoline in equimolar ratio followed by crystallization from water gave salt (HhydroxQ)2[ZnCl4] (5) and a similar reaction followed by crystallisation from 3-methylpyridine (3mepy) resulted in the molecular complex [Zn(oxyQ)2(3mepy)]. [Zn(oxyQ)2(3mepy)2].3H2O (6). Complex 5 is formed from a hydrolytic equilibrium of water with zinc chloride yielding tetrachloro zinc anion and zinc hydroxide. Taking advantage of this reaction, a composite material of ZnO@complex 5 exhibiting dual fluorescence at 450 and 575 nm on excitation at 390 nm was prepared. Fluorescence emission properties of all the complexes in solid state are compared with fluorescence emission of the ligand.