Synthetic, spectral, thermal and biological studies of lanthanide(III) complexes with a Schiff base derived from 3-N-methylpiperidino-4-amino-5-mercapto-1,2,4-triazole

A series of Ln(III) complexes of the type [Ln(HPSMT)(2)- NO3].nH(2)O (where Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Yb, Y; HPSMT = 3-N-methylpipe ridino-4-salicylideneamino-5-mercapto-1,2,4-triazole and n = 1-3) have been synthesized by the direct reaction of 3-N-methylpiperidino-4-salicylidenea mino-5-mercapto-1,2,4-triazole with Ln(III) nitrate in dry alcohol. The com plexes have been characterized by elemental analyses, molar conductance, 1 magnetic measurements, electronic, infrared, and H-1 NMR studies. The eleme ntal analyses reveal 1:2 stoichiometry with respect to metal:ligand. Molar conductance studies indicate the non-electrolytic nature of the complexes. The spectral studies show the ligand HPSMT and nitrate groups bound to the Ln(III) ion in a bidentate fashion. It is proposed that the complexes exhib it the coordination number six. Thermal studies have been carried out for t he La(III), Nd(III) and Dy(III) complexes. The parameters, such as energy o f activation (Ea), change in enthalpy (Delta H double dagger), change in en tropy (Delta S double dagger) and change in free energy (Delta G double dag ger) were established for the above completes. The ligand and its Ln(III) c omplexes were screened for antibacterial and antifungal activity. It was fo und that in few of the Ln(III) complexes activity of the ligand gets increa sed.