The complexing tendency of vanadium with nifoxipam and lorazepam were carried out by pH metric titration technique in aqueous acid media at different temperatures (298, 308 and 318 K) and an ionic strength of 0.2 M. The degree of complexation was investigated at different pH values. Potentionmetric measurement of hydrogen ion concentration was also studied with the degree of complex formation. The proton-ligand and metal-ligand stability constants were resolved by modified Calvin-Bjerrum pH titration technique (Irving and Rossitti) using computer programming. The important thermodynamic parameters such as Gibb's free energy change (ΔG), entropy change (ΔS) and enthalpy change (ΔH) for the complexation reactions were calculated. The formation of metal complexes was found to be spontaneous, exothermic and conducive in nature at lower temperatures.

Hexamethyldibenzotetraaza[14]annulene type macrocyclic complexes of Ni(II) and Cu(II) have been synthesized by template method. These macrocyclic complexes were characterized by molar conductance, elemental analysis, IR, UV-visible, mass spectra and cyclic voltammetry. On the basis of electronic studies saddle shape distorted octahedral structure have been assigned to these macrocyclic complexes. The redox behaviour of Ni(II) and Cu(II) macrocyclic complexes showed reversible and quasi-irreversible redox process that supported by the ipc/ipa ratio which is in good agreement with Randles-Sevcik equation. These macrocyclic complexes were also studied for the antimicrobial activity against E. coli, P. aeruginosa, B. subtilis, S. aureus and C. albicans compared with gentamycin as standard drug.

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