Synthesis, characterisation, in vitro antimicrobial, antioxidant and anti-inflammatory activities of diorganotin(IV) complexes derived from salicylaldehyde Schiff bases

Abstract

A new series of diorganotin(IV) complexes of 4-((2-hydroxybenzylidene)amino)-[1,1′-biphenyl]-3-ol (H2L1), 4-((2-hydroxy-5-nitrobenzylidene)amino)-[1,1′-biphenyl]-3-ol (H2L2), 4-((3-bromo-2-hydroxy-5-nitrobenzylidene)amino)-[1,1′-biphenyl]-3-ol (H2L3) and 4-((3,5-dibromo-2-hydroxybenzylidene)amino)-[1,1′-biphenyl]-3-ol (H2L4) Schiff base ligands with general formula R2SnL (where R = Me, Et, Bu and Ph) were synthesized. Structural aspect of these synthesized compounds have been described with the help of elemental analysis and spectroscopic techniques like FT-IR, UV–Vis, NMR, Mass and fluorescence. Schiff bases coordinated to tin metal as dibasic tridentate ligand through imine nitrogen and two phenolic oxygen atoms forming pentacoordinated complexes. Metal complexes gave low molar conductance value describing their non-electrolytic nature. Thermal decomposition of the complexes resulted in the formation of SnO2 as end product. The in vitro antimicrobial activities have been evaluated against Gram positive bacteria, Gram-negative bacteria and two fungal strains. The screening evaluation showed that organotin(IV) complexes have better antimicrobial activity. The free radical scavenging ability of the compounds was invest by in vitro antioxidant assay involving DPPH radical and was found to be moderately good. The anti-inflammatory activity was done by egg albumin method and percentage inhibition of protein denaturation was calculated. By comparing the biological activities of the synthesized compounds it was found that metal complexes were more potent than the free ligands and compounds 16, 20 were having more potential as drugs.