SYNTHESIS AND SPECTROSCOPIC CHARACTERIZATION OF BIVALENT LEAD MACROCYCLIC COMPLEXES

Abstract

Lead(II) macrocyclic complexes of some 12- and 13-membered tetraazamacrocycles have been synthesized by the template process using bis(benzil)ethylenediamine as precursor. The change in ring size has been achieved solely by varying the number of methylene carbon that link adjacent benzil nitrogen atoms. Bis(benzil)ethylenediamine (L) reacts with PbCl₂ or Pb(OAc)₂ and primary diamines, i.e., 1,2-diaminoethane (1,2-en) or 1,3-diaminopropane (1,3-pn) in a 1:1:1 molar ratio in methanol to give several solid complexes of the general composition [Pb(L)X₂] (L = macrocyclic ligand, X = Cl or OAc). The precursor and the metal complexes of the macrocycles have been characterized by elemental analyses, molecular weight determinations, molar conductances, IR, ¹H NMR, ¹³C NMR, electronic and mass spectral studies. On the basis of the IR and NMR spectral data the involvement of amido nitrogen in coordination to the central metal ion has been confirmed. An octahedral geometry around the metal ion is suggested for the complexes. Based on molecular weights and conductivity measurements, their monomeric and non-electrolytic nature has been confirmed.

ACKNOWLEDGNEMT

The authors are thankful to the Government of India, Ministry of Science and Technology, New Delhi, India, for financial assistance through Grant No. SP/S1/F06/96.