Synthesis and studies of ionic chelates of hafnocene with guanine

Abstract

Ionic chelates of hafnocene with guanine (<b>I</b>) of the type [(η⁵-C₅H₅)₂HfL]⁺X^- (<b>II</b>) [X = CuCl₃ , ZnCl₃, CdCl₃, HgCl₃, C₆H₅NHNHCS₂; HL = guanine] have been synthesized. Spectral studies (IR, UV, ¹H NMR and ¹³C NMR) indicate that the guanine moiety acts as a bidentate group, binding to the hafnium(IV) ion through carbonyl oxygen at C(6) and deprotonation of N(7). Conductance measurements reveal that the compounds are 1:1 electrolytes. Fluorescence studies have been carried out for the complex containing mercury in the anionic moiety and relevant photochemical parameters have been elucidated. The thermal behaviour of the complexes has been studied by thermogravimetric and differential thermal analytical techniques. Thermodynamic parameters of the thermal decomposition process have been computed by the Coats-Redfern method and their variations have been correlated with some structural parameters of the complexes. The ligands, as well as their hafnium(IV) complexes, exhibit appreciable antibacterial and antifungal activity against <i>E.coli,</i> <i>P.aeruginosa </i>and <i>Z.mobilis </i>bacterial strains, and <i>versus A.awamori </i>and <i>A. niger </i>fungal strains, respectively.