Synthesis and studies of ionic chelates of hafnocene with guanine

Ionic chelates of hafnocene with guanine (1) of the type [(eta(5) -C5H5)(2HfL)]X-+(-) (II) [X = CuCl3, ZnCl3, CdCl3, HgCl3 C6H5NHNHCS2; HL = guanine] have been synthesized. Spectral studies (IR, UV, H-1 NMR and C-13 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 E.coli, P.aeruginosa and Z.mobilis bacterial strains, and versus A.awamori and A.niger fungal strains, respectively.