Copper(II) and zinc(II) complexes with Schiff-base ligands derived from salicylaldehyde and 3-methoxysalicylaldehyde: Synthesis, crystal structures, magnetic and luminescence properties

The following Schiff bases were employed as ligands in synthesizing copper(II) and zinc(II) complexes: N-[(2-pyridyl)-methyl]-salicylimine (Hsalampy), N-[2-(N,N-dimethyl-amino)-ethyl]-salicylimine (Hsaldmen), and N-[(2-pyridyl)-methyl]-3-methoxy-salicylimine (Hvalampy). The first two ligands were obtained by reacting salicylaldehyde with 2-aminomethyl-pyridyne and N,N-dimethylethylene diamine, respectively, while the third one results from the condensation of 3-methoxysalicylaldehyde with 2-aminomethyl-pyridine. Four new coordination compounds were synthesized and structurally characterized: [Cu(salampy)(H2O)(ClO4)] 1, [Cu2(salampy)2(H2trim)2] 2 (H2trim− = the monoanion of the trimescic acid), [Cu4(valampy)4](ClO4)4 · 2CH3CN 3, and [Zn3(saldmen)3(OH)](ClO4)2 · 0.25H2O 4. The crystal structure of 1 consists of supramolecular dimers resulted from hydrogen bond interactions established between mononuclear [Cu(salampy)(H2O)(ClO4)] complexes. Compound 2 is a binuclear complex with the copper ions connected by two monoatomic carboxylato bridges arising from two molecules of monodeprotonated trimesic acid. The crystal structure of 3 consists of tetranuclear cations with a heterocubane {Cu4O4} core, and perchlorate ions. Compound 4 is a trinuclear complex with a defective heterocubane structure. The magnetic properties of complexes 1–3 have been investigated. Compound 4 exhibits solid-state photoluminescence at room temperature.