Synthesis, characterization and antioxidant activity of new β-benzylselenated Schiff bases and their palladium complexes

Abstract

Three new β-benzylselenated Schiff bases, (S)-L1H, (R)-L2H and (R)-L3H, were synthesized from three chiral β-benzylselenated amines, (S)-2a, (R)-2b and (R)-2c, respectively, on condensation with salicylaldehyde. The corresponding palladium complexes, (S)-1, (R)-2 and (R)-3, were synthesized by reactions of these ligands with Na2[PdCl4]. The ligands and their complexes were characterized by spectroscopic (1H, 13C{1H} NMR and FT-IR), polarimetric and elemental analysis. The crystal structure of (S)-1 was determined by single-crystal X-ray diffraction. The ligands bind palladium(II) as deprotonated ((S)-L1 , (R)-L2 and (R)-L3 ) tridentate (Se,N,O-) chelates resulting in complexes of composition [Pd(L1-3 )Cl]. All these compounds have been screened for in vitro DPPH radical scavenging activity using vitamin-C as a reference standard. The DPPH radical scavenging activity was assessed by varying the concentration of each of these compounds. The results of antioxidant activity studies demonstrated that these compounds are good-to-excellent radical scavenging agents. The antioxidant activity was quantitatively expressed as their IC50 values which revealed that the activity of palladium complexes were 50% higher than those of corresponding ligands and very close to that of the standard reference vitamin-C.