EPR, magnetic and spectral studies of copper(II) and nickel(II) complexes of Schiff base macrocyclic ligand derived from thiosemicarbazide and glyoxal

A new macrocylic Schiff base 1,2,5,6,8,11-hexaazacyclododeca-7,12-dithione-2,4,8,10-tetraene(H2L4) containing thiosemicarbazone moiety is readily prepared and characterized for the first time with fairly good yield. Macrocylic ligand (H2L4) is prepared from the mesocyle 6-ethoxy-4-thio-2,3,5-triazine(H2L3) in ethanol with copper chloride acting as template using high dilution technique. The complexes of macrocylic ligand with a general composition M(H2L4)X-2 [where M = Cu(II) or Ni(II); H2L4 = 1,2,5,6,8,11-hexaazacyclododeca-7,12-dithione-2,4,8, 10-tetraene; X = Cl-, NO3-, (1)/2SO42-] and ML4 (where metal salt used to synthesize complex is copper acetate and nickel thiocyanate) have been synthesized. The complexes were characterized on the basis of elemental analysis, molar conductance, magnetic susceptibility, IR, electronic, H-1 NMR, mass and EPR spectral studies. The complexes from H2L4 show different stoichiometry ratio and with a variable grade of deprotonation in the ligand, depending upon the salt used and working conditions. (C) 2003 Elsevier B.V. All rights reserved.