Interaction of Co(II), Ni(II), Cu(II), and Zn(II) with 12-and 14-membered macrocycles containing O2N2 donors

The 12- and 14-membered diazadioxo macrocyclic ligands, 1,2 : 7,8-diphenyl-6,9-diaza-3,12-dioxocyclododecane (L1) and 1,2 : 8,9-diphenyl-7,10-diaza-3,14-dioxocyclotetradecane (L2), were synthesized by condensation between o-phenylenediamine, 1,2-dibromoethane/1,3-dibromopropane, and catechol. Metal complexes [ML1Cl2] and [ML2Cl2] [M = Co(II), Ni(II), Cu(II), and Zn(II)] were prepared by interaction of L1 or L2 with metal(II) chlorides. The ligands and their complexes were characterized by elemental analyses, IR, 1H, and 13C NMR, EPR, UV-Vis spectroscopy, magnetic susceptibility, conductivity measurements, and Electrospray ionization-mass spectral (ESI-MS) studies. The results of elemental analyses, ESI-MS, Job's method, and conductivity measurements confirmed the stoichiometry of ligands and their complexes while absorption bands and resonance peaks in IR and NMR spectra confirmed the formation of ligand framework around the metal ions. Stereochemistry was inferred from the UV-Vis, EPR, and magnetic moment studies.