Chromotropism Behavior and Biological Activity of some Schiff Base-Mixed Ligand Transition Metal Complexes

Abstract

We report about a series of mono-nuclear and bi-nuclear complexes with acyclic as well as macro-cyclic ligands, which have been synthesized with Schiff base ligands in tri- tetra and pentadentate forms. The bonding sites on complex formation are mainly the azomethine groups and/or imide nitrogen, ketonic oxygen or sulphur atoms. Complexes of two series of Schiff base ligands, H 2 L a and H 2 L b derived from the reaction of 2,6-diacetyl pyridine with semicarbazide, replaced by or thiosemicarbazide with the metal ions, Co(II), Ni(II), Cu(II), VO(IV) and UO 2 (VI) have been prepared. Mono-nuclear complexes with tetradentate macrocyclic Schiff base ligands, derived from the condensation of 1,1′ -diacetylferrocene with 1,3-diaminopropanein in the molar ratio 1:1 and 1:2 have been also synthesized and react with the transition metal ions, copper(II), nickel(II), cobalt(II), and Zinc(II) in the molar ratio 1:1. The structures of these ligands as well as the related complexes are elucidated by different spectroscopic methods. Solvatochromic behavior of copper(II) mixed ligand complexes of 3-acetylcoumarine (3-ACoum) and dinitrogen bases (L), with the general formula Cu(3-ACoum)(L)Xn; where n = 2, L = N,N,N′, N″-tetramethylethylenediamine (tmen), 1,10-phenanthroline (phen), 2,2′ -bipyridine (bipy) and X = ClO 4 −, BF 4 − or NO 3 − their synthesis and characterization by elemental analysis, IR, UV-Vis, electron spin resonance spectra, magnetic susceptibility and conductivity measurements is reported. The d-d absorption bands of tmen-complexes in weak donor solvents show the formation of square planar or square pyramidal geometries, whilst the strong donor solvents yield octahedral complexes. The observed solvatochromism is mainly due to the solute-solvent interaction between the chelate cation and the solvent molecules and the spectra displayed the possibility of using these complexes as Lewis base indicators. The Coats-Redfern equation can be used to calculate the kinetic and thermodynamic parameters for the different thermal decomposition steps of some complexes. Cyclic voltagrammes of Co(II) and Ni(II) show quasi-reversible peaks and characterize the redox properties and the nature of the electroactive species of the complexes. Biochemically, both the ligands and the complexes show growth inhibitory activity against pathogenic bacteria and plant pathogenic fungi.