The tridentate (NNO) Schiff base (HL), has been prepared by the condensation of 2-(aminomethyl)pyridine with 5-chloro-salicylaldehyde. The mononuclear [N-(2-pyridylmethyl)-3-chloro-salicylaldiminato] (azido) copper(II) complex of general formula [Cu(L)(N-3)] (1) has been synthesized by the treatment of HL and CuCl2 center dot 2H(2)O with sodium azide. The ligand and complex have been investigated by various methods including IR, TG-DTA and X-ray diffraction techniques. The complex crystallizes in monoclinic space group P2(1/c), with unit cell dimensions a = 6.7369(4), b = 11.6058(8), c = 17.1379(11) angstrom, beta = 93.823(2)degrees. The distorted square-planar Cu(II) ion in complex is chelated by one imino N, one phenolic O and one pyridine N atoms of Schiff base ligand and one N atom of azide ion. The electrochemical behavior of the mononuclear copper azido complex was studied with cyclic voltammetry. Tautomer stability of the ligand and the complex has been determined by molecular modeling techniques. It has been concluded that the HL is more stable than its tautomeric form (THL) both as ligand and complex structures. (C) 2015 Elsevier B.V. All rights reserved.