Highly effective aldose reductase mimetics: Catalytic transfer hydrogenation of D-Glucose to D-Sorbitol with novel azo-azomethine based Ru(II) complexes

Five types of azo-azomethine-based Schiff base ligands ( 2-6 ) have been synthesized from the reaction of (E)-5-((4-ethylphenyl)diazenyl)-2-hydroxybenzaldehyde 1 with aniline derivatives. Structures of the syn-thesized ligand were characterized with 13C-NMR, 1H-NMR, UV-Visible spectroscopy, elemental analysis, and FT-IR. The Ru(II) complexes were synthesized from the reaction of free ligands with Dichloro(p-cymene)ruthenium(II) dimer. From FTIR, UV-Visible, 13C-NMR, 1H-NMR, and elemental analysis results, it was understood that Ru metal is bound by N and O atoms in the ligands. In addition to these analyses, single-crystal X-Ray diffraction studies determined solid-state structures of 5 and 6 . The antimicrobial activity of the ligand and complexes against Gram-negative and Gram-positive bacteria was evaluated by the broth microdilution method. According to the results of our study, 2 had no antibacterial effect against Staphylococcus aureus (ATCC 25923). 5, 7, 8, 9 and 10 showed more antibacterial effect (MIC = 0.125 mg/mL, MBC = 0.25 mg/mL) than other compounds used in the study. Besides, the synthesized complexes were tried as catalysts in the transfer hydrogenation of D-glucose to D-sorbitol in isopropyl alcohol un-der microwave power. All the synthesized Ru(II)-complexes containing azo-azomethine ligands showed the very efficient, in fact, the best effective and selective catalytic activities in the catalytic transfer hy-drogenation of D-glucose to D-sorbitol compared to Ru(II)-complexes having hydride and phosphine or other ligands. Especially, complex 10 showed the best catalytic activity with 94.32 % selectivity in the conversion of 98.12 %.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

Five types of azo-azomethine-based Schiff base ligands were synthesized and characterized. The synthesized ligand showed Ru metal coordination with N and O atoms based on the analysis of various spectroscopy techniques. The antimicrobial activity of the ligand and complexes were evaluated, and certain complexes exhibited significant antibacterial effects. The synthesized Ru(II)-complexes with azo-azomethine ligands demonstrated excellent catalytic activity in the transfer hydrogenation reaction.