Metal transition complexes of tridentate Schiff base ligands derived from 2-hydrazinopyridine: synthesis, spectroscopic characterization and X-ray structures

Abstract

Mononuclear complexes of 1-(pyridin-2-ylmethylidene)-2-(pyridin-2-yl)hydrazine (HL1) and 1-(pyridin-2-yl)-2-(1-(pyridin-2-yl)ethylidene)hydrazine (HL2), [Mn(HL1)(Cl2)(H2O)] (1), [Zn(HL1)(CH3COO)2]·(H2O)3 (2), [Mn(HL2)2]·(ClO4)2 (3) and [Cu(HL2)(NO3)2(H2O)] (4) were synthesized and characterized by physicochemical and spectroscopic methods and X-ray structure determination. The mononuclear compounds 1, 2 and 4 contain one ligand molecule per metal atom while the manganese (II) atom in compound 3 is coordinated to two ligand molecules. Both ligands coordinated to the transition metal center in a tridentate fashion through two Npyridyl atoms and one Nimino atom. The chloride and acetate anions coordinate in monodentate manner, respectively, in complex 1 and in complex 2. In complex 3, the perchlorate groups remain uncoordinated. In complex 4, the nitrate anions act in unidentate fashion. The molar conductance value indicates that the complexes obtained from HL1 are non-electrolytes while those obtained from HL2 are 2:1 electrolytes in DMF solutions. The X-ray structures reveal octahedral geometry for complexes 1, 3, 4 and trigonal bipyramidal environment for 2.