Gadolinium (III) trinuclear salen capped Complexes of a series of N2O2 Donor Ligands: Synthesis, Characterization and Antimicrobial Studies

Abstract

Novel Gadolinium (III) trinuclear salen capped complexes of N₂O₂ donor ligands, [{Gd(OH)₂(salen)}₃(TT/TTPS)].3H₂O were synthesized.  Characterization of the compounds were done using UV-Visible, IR, ¹H, and ¹³C NMR spectroscopies, elemental analysis, and molar conductivity measurements. The spectral studies indicate that the ligands are hexadentate and coordinate to the Gd(III) ions through the oxygen atoms of the carboxylic group. The trinuclear Gd(III)salen capped complexes were characterized as being bridged by carboxylate anions to the Gd(III)salen centers and displays a coordination number of eight by involving two hydroxyl groups in the coordination sphere. The in vitro antimicrobial activities of the ligands and complexes were investigated against Gram-negative bacteria: Escherichia coli (ATCC 6749) and Pseudomonas aeruginosa (ATCC 9027), Gram-positive bacteria: Staphylococcus aureus (ATCC 6538P) and Bacillus cereus (ATCC 14579), and fungi: Candida albicans and Aspergillus niger by the agar well diffusion technique. In vitro antimicrobial test indicate that TTPS and [{Gd(OH)₂(salen)}₃(TTPS)].3H₂O showed higher activity against the test organisms investigated relative to TT and  [{Gd(OH)₂(salen)}₃(TT)].3H₂O.   The in vivo antimalarial assay carried out on Plasmodium berghei  shows a general dose-dependent significant parasitemia inhibition compared with the negative control with [{Gd(OH)₂(salen)}₃(TTPS)].3H₂O  having highest  inhibition of 72.20% at 50 mg/kg and 70.28% at 25 mg/kg close to the value (87.22%) of the standard drug artesunate 5 mg/kg. Hence, [{Gd(OH)₂(salen)}₃(TTPS)].3H₂O can serve as an antimalarial  drug at doses less than 2154 mg/kg.