Microwave-assisted synthesis, crystal structure and fluorescence of novel coordination complexes with Schiff base ligands

Abstract

The reactions of the ligand 2-hydroxy-3-methoxy-benzaldehyde (Hhmb) and methylamine, or 25% ammonia with varied metal salts of Zn(II), Mn(II), Ni(II) result in formation of three new coordination complexes, [M 7(OH) 6(mimmp) 6]X 2 (M = Zn, X = NO 3 - (1); M = Mn, X = ClO 4 - ), [Ni(immp) 2]·(H 2O) 2 ( 3) (mimmp is the anion of 2-methoxy-6-methyliminomethyl-phenolic and immp is the anion of 2-iminomethyl-6-methoxyphenolic) and their structures were determined by X-ray crystallography. Complexes 1 and 2 with octahedral metal centers have similar disperse heptanuclear clusters, while complex 3 displays a 3-D network structure through N–H⋯O and O–H⋯O hydrogen bonds containing an interesting six-membered water ring; Herein, the Ni(II) has planar coordination geometry. Ligand mimmp acts as a tetradentate bridging ligand in 1 and 2 while ligand immp acts as bidentate chelated ligand in 3. The photoluminescent properties of Hmimmp ligand and complexes 1 and 2 were studied in the solid state at room temperature.