Ambidentate behavior of pentadentate N,N′-bis(2-hydroxyphenyl)-pyridine-2,6-dicarboxamide towards transition metal(II) salts

Complexes of Co(II), Ni(II), Cu(II), Mn(II), Zn(II) and Cd(II) with N,N'-bis(2-hydroxyphenyl)pyridine-2,6-dicarboxamide have been synthesized and characterized by elemental analysis, conductivity measurements, spectral (electronic, i.r., n.m.r. and e.p.r.), electrochemical and thermal studies. I.r. studies show that the ligand behaves in an ambidentate way. It coordinates through the pyridine nitrogen, two amide oxygens and two phenolic oxygens in the Co(II), Ni(II), and Cu(II) complexes, whereas in the Mn(II), Zn(II) and Cd(II) complexes it coordinates through the pyridine nitrogen, two uncharged amide nitrogens and two-phenolic oxygens under similar experimental conditions.[PUBLICATION ABSTRACT]