Synthesis and characterization of Cu(II) and Ni(II) complexes of a tripodal ligand containing imidazoles

Abstract

Two complexes of the formula [MH 3L](ClO 4) 2 [M = Cu(II) ( 1), Ni(II) ( 2)] have been prepared by the reaction of M(ClO 4) 2 · 6H 2O with the ligand (H 3L) formed by the Schiff base condensation of tris(2-aminoethyl)amine (tren) with three molar equivalents of 4-methyl-5-imidazolecarboxaldehyde and structurally and magnetically characterized. The structures of 1 and 2 are isomorphous with each other and with the iron(II) complex of H 3L which has been reported previously. The ligand, while potentially heptadentate, forms six coordinate complexes with both metal centers forming three M–N imine and three M–N imidazole bonds. The tren central N atom is at a nonbonded distance from M of 3.261 Å for 1 and 3.329 Å for 2. The neutral complex CuHL 3 was prepared by reaction of H 3L with Cu(OCH 3) 2 and the ionic complex Na[NiL] 4 was prepared by deprotonation of 2 with aqueous sodium hydroxide. Magnetic measurements of 1– 3 are consistent with the spin-only values expected for S = 1/2 ( d 9, Cu(II)) and S = 1 ( d 8, Ni (II)) systems.