Mono- and dinuclear Zn(II) complexes of Schiff-base ligands: syntheses, characterization and studies of photoluminescence

Six Schiff-bases HL1-HL4, L5 and L6 [HL1 = 2,6-bis[1-(2-aminoethyl)pyrolidine-iminomethyl]-4-methyl-phenol, HL2 = 2,6-bis[1-(2-aminoethyl)piperidine-iminomethyl]-4-methyl-phenol, HL3 = N-{1-(2-aminoethyl)pyrolidine}salicylideneimine, HL4 = N-{1-(2-aminoethyl)piperidine}salicylideneimine, L5 = 2-benzoyl pyridine-N-{1-(2-aminoethyl)pyrolidine}, L6 = 2-benzoylpyridine-N-{1-(2-aminoethyl)piperidine}] have been synthesized and characterized. Zn(II) complexes of those ligands have been prepared by conventional sequential route as well as by template synthesis. The same complexes are obtained from the two routes as evident from routine physicochemical characterizations. All the Schiff-bases exhibit photoluminescence originating from intraligand (-*) transitions. Metal mediated fluorescence enhancement is observed on complexation of HL1-HL4 with Zn(II), whereas metal mediated fluorescence quenching occurs in Zn(II) complexes of L5 and L6.