Transition metal complexes of pyrazole head 24-membered polyazamacrocyclic bimetal cores: synthesis, characterization, electrochemistry and spectral study

A series of new 24-membered macrocyclic Co^II, Ni^II, Cu^II and Zn^II complexes of the ligands L¹H₂ and L²H₂ were prepared by the non-template and template methods respectively. The ligand L¹H₂ was formed by the condensation of pyrazole-3,5-dicarbohydrazide and glyoxal and all attempts to isolate the ligand L²H₂ were unsuccessful. These, ligand and transition metal complexes were characterized on the basis of elemental analysis, IR, ¹HNMR, UV–Visible, magnetic susceptibility measurements, ESR, conductivity measurements, FAB-mass and thermal analysis. The redox behavior of metal ions in the polyazamacrocyclic ligand field is also studied. Electroreduction of carbon dioxide to carbon monoxide is mainly focused on using polydentate azamacrocyclic ligands with amine and imine functionalities, based on the electrochemical behavior of nickel (II) ion in the macrocyclic territory.