Complexation Study of Synthesized Pharmacological Organic Ligands with Samarium

This research describes the formation of samarium complexation with organic ligands (Schiff bases of anti-mycobacterial agent isonicotinic acid hydrazide) through pH-metric technique at 25, 35, and 45°C in 70% (v/v) ethanol/water medium at 1M (NaClO4) ionic strength. Organic ligands have been synthesized and their structures have been confirmed by various characterization techniques such as TLC, MP, IR, 1H NMR, 13C NMR, UV-Vis spectroscopies and elemental analysis. They have been evaluated for biological activity against gram positive, gram negative bacteria, and fungi showing moderate to significant results. Complexation study of these binary complexes has been evaluated and calculated using Calvin–Bjerrum technique. The order of stability constant has been found to be as follows N-[(E)-(4-hydroxy-3-methoxyphenyl)methylene]isonicotinohydrazide (L2) < N-[(E)-(4-chlorophenyl)methylene]isonicotinohydrazide (L1) < N-[(E)-(4-hydroxyphenyl)methylen]isonicotinohydrazid (L4) < N-[(E)-(2-hydroxyphenyl)methylen]isonicotinohydrazid (L5) < N-[(E)-(2-nitrophenyl)methylen]isonicotinohydrazide (L3). Thermodynamic parameters associated with the samarium complexation have been observed to be negative in ΔH and ΔG. This indicates the exothermic reaction in complexation.