NEW NICKEL(II) COMPLEXES INCORPORATING DISSYMMETRIC TETRADENTATE SCHIFF BASE LIGANDS DERIVED FROM AMINOTHIOETHER PYRIDINE WITH N₂OS CHROMOPHORES: SYNTHESIS, SPECTROSCOPIC CHARACTERIZATION AND CRYSTAL STRUCTURES OF [Ni(pytIsal)]ClO₄ and [Ni(pytAzosal)]ClO₄.H₂O

 

Nezamaddin Daneshvar,*^a Lotf A. Saghatforoush,^b Ali A. Khandar,^c and
Ali A. Entezami ^d

 

^a,b,c Department of Inorganic Chemistry , Faculty of Chemistry, Univrsity of Tabriz, Tabriz, Iran

^d Department of Organic Chemistry, Faculty of Chemistry, University of Tabriz

* Corresponding author. fax: +98-411-3340191, Tel: +98-411-3393146, e-mail: nezam_daneshvar@yahoo.com

 

Abstract

The synthesis of nickel (II) complexes with five dissymmetric Schiff base ligands (abbreviataed pytIsalH, pytBrsalH, pytNO₂salH, pytOMesalH, and pytAzosalH) which were prepared from aminothioether pyridine and a salicylaldehyde derivative, are described. The ligands were characterized by ¹H,¹³C NMR, FTIR and elemental analysis. The complexes of these ligands were synthesized by treating an ethanolic solution of appropriate ligand with equimolar amount of Ni(ClO₄)₂.6H₂O and methanolic NaOH or alternatively by a more direct route in which the two reactants are added to a solution of the ligand immediately after formation of the ligand and prior to any isolation. The complexes were characterized by elemental analysis, FTIR, electronic spectra and molar conductivity. The complex [Ni(pytIsal)]ClO₄ (6) crystallizes in triclinc space group  with a = 12.188(2) Å, b = 13.312(3) Å , c = 13.348(3) Å, a = 115.48(3)^o, b = 90.78(3)^o, g = 90.90(3), Z = 4, R₁ = 0.0617 for 4276 reflections with I>2σ(I). The complex [Ni(pytAzosal)]ClO₄.H₂O (10) crystallizes in orthorhombic space group P2₁2₁2₁ with a = 7.093(5) Å, b = 9.277(6) Å, c = 34.62(3) Å, a = 90^o, b = 90^o, g = 90^o, Z = 4, R₁ = 0.0635 for 2185 reflections with I>2σ(I). The coordination geometry of nickel ions in the complexes with mixed N, S and O donor atoms is square planar with a slight tetrahedron distortion. All of the complexes were found to be 1:1 electrolyte systems in acetonitrile. Cyclic voltammetry studies indicates that the complexes [Ni(pytXsal)]ClO₄ (X = I and OMe) show quasi-reversible reduction to Ni(I) while this process for X = Azo and NO₂ is reversible and irreversible, respectively.