Synthesis, structural analysis, in vitro antioxidant, antimicrobial activity and molecular docking studies of transition metal complexes derived from Schiff base ligands of 4-(benzyloxy)-2-hydroxybenzaldehyde

• Published in: Research on chemical intermediates 2022-04, Vol.48 (4), p.1541-1576
• Main Authors: Devi, Jai, Kumar, Sanjeev, Kumar, Binesh, Asija, Sonika, Kumar, Ashwani
• Format: Article
• Language: English
• Subjects: Aminophenol; Antiinfectives and antibacterials; Antimicrobial agents; Antioxidants; Catalysis; Chemical analysis; Chemistry; Chemistry and Materials Science; Condensates; Coordination compounds; Copper; Copper compounds; Decoloring; Dilution; Enzymes; Fluorescence; Fungicides; Hydrophobicity; Hydroxybenzaldehydes; Imines; Inorganic Chemistry; Ligands; Mass spectrometry; Melting points; Metal oxides; Nickel; Nitrophenol; Oxygen atoms; Physical Chemistry; Sterols; Structural analysis; Thermal decomposition; Zinc
• ISSN: 0922-6168; 1568-5675
• DOI: 10.1007/s11164-021-04644-y

Sixteen Co(II), Ni(II), Cu(II) and Zn(II) complexes were synthesized by four Schiff base ligands 4-((4-(benzyloxy)-2-hydroxybenzylidene)amino)-[1,1'-biphenyl]-3-ol (H 2 L 1 ), 6-((4-(benzyloxy)-2-hydroxybenzylidene)amino)-4,6-dichloro-3-methylphenol (H 2 L 2 ), 2-((4-(benzyloxy)-2-hydroxybenzylidene)amino)-6-chloro-4-nitrophenol (H 2 L 3 ), 5-(benzyloxy)-2-(((2-hydroxyphenyl)imino)methyl)phenol (H 2 L 4 ) obtained from condensation reaction of 4-(benzyloxy)-2-hydroxybenzaldehyde with various aminophenol derivatives and well characterized by various spectroscopic techniques (FT-IR, UV–Vis, NMR, ESR, SEM, fluorescence), mass spectrometry, elemental analysis (CHN) and physical studies (TGA, XRD, molar conductance, melting point). The various characterization data suggested that the Schiff base ligands coordinated via nitrogen of azomethine and deprotonated phenolic oxygen atoms (ONO) with metal ions in 1:1 molar ratio having general formula [M(L 1−4 )(H 2 O) 2 (CH 3 COO)]. Low values of molar conductance of compounds suggested their non-electrolytic nature. The thermal decomposition of complexes indicated that metal complexes are stable up to 150 °C and give metal oxide as end product. Using SEM analysis, the surface morphology of the synthesized compound was determined. The compounds (1–20) were evaluated for their in vitro antioxidant activity and found that the synthesized metal(II) complexes are highly potent and also show good efficiency for decolourizing the purple-coloured solution of DPPH compared to free Schiff base ligands and Cu(II) complexes were most potent having IC 50 value from 2.98 to 3.89 µM range. The compounds (1–20) were assayed for their in vitro antimicrobial activities against four bacterial strains ( S. aureus , B. subtilis , P. aeruginosa, E. coli) and two fungal strains ( A. niger, C. albicans) by serial dilution method, and it was found that the metal(II) complexes are more noxious than free Schiff base ligands. The antimicrobial activity results showed that the complexes 10, 11, 14 and 15 were most active compounds. Antifungal activity of complex 11 (Cu(L 2 )(CH 3 COO)(H 2 O) against C. albicans was found to be comparable to standard drug. The molecular docking of ligand H 2 L 2 (2) and its Cu(II) complex (11) with enzyme C. albicans sterol 14-alpha demethylase suggested the hydrophobic binding. Furthermore, in silico study stressed that the compounds may be used as orally active drugs. Graphical abstract The synthesized compounds