Toxicity, Spectroscopic Characterization and Electrochemical Behaviour of New Macrocclic Complexes of Lead(II) and Palladium(II) Metals

Abstract

Tetraazamacrocyclie complexes of lead and palladium have been synthesized by the template process using the bis(benzil)ethylenediamine precursor. The tetradentate macrocycle (maL) reacts with PbCl₂, PdCl₂ and different diamines in a 1:1:1 molar ratio in methanol to give several solid complexes of the types [Pb(maL)(R)Cl₂] and [Pd(maL)(R)]Cl₂ (where R = 2,6-diaminopyridine or 1,2-phenylenediamine). The macrocycle and its metal complexes have been characterized by elemental analysis, molecular weight determinations, molar conductivity, IR, ¹H NMR, ¹³C NMR, electronic, mass and electrochemical studies. The macrocyclic ligand coordinates through the four azomethine nitrogen atoms which are bridged by benzil moieties. IR spectra suggest that the pyridine nitrogen is not coordinating. The palladium complexes exhibit tetracoordinated square-planar geometry, whereas a hexacoordinated octahedral geometry is suggested for lead complexes. The macrocycle along with its complexes have been screened in vitro against a number of pathogenic fungi and bacteria to assess their growth inhibiting potential.