Akademik Veri Yönetim Sistemi
JOURNAL OF MOLECULAR STRUCTURE, cilt.1356, 2026 (SCI-Expanded, Scopus)
New 2,6-dimethylphenyl-derived thiosemicarbazones (1-10) were synthesized through the condensation of various aldehydes with N-(o-tolyl)hydrazinecarbothioamide. The key thiosemicarbazide intermediate was obtained from the reaction of 2,6-dimethylphenyl isothiocyanate with hydrazine monohydrate. The chemical structures and purity of all newly synthesized compounds were confirmed by standard spectroscopic techniques, including proton and carbon nuclear magnetic resonance (H-1 and C-1(3) NMR), Fourier-transform infrared spectroscopy (FT-IR), and elemental analysis. The antioxidant activities of the compounds were evaluated using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging assay. Based on the calculated IC50 values from percent inhibition data, the antioxidant efficacy of the compounds followed the order: Ascorbic acid > 9 > 7 > 5 > 3 > 2 > 6 > 8 > 10 > 4 > 1. The DPPH radical scavenging capacities of compounds 9, 7, and 5 (7.52 +/- 0.11, 9.25 +/- 0.12, and 9.27 +/- 0.12 mu M, respectively) were found to be rather close to those of standard ascorbic acid (6.39 +/- 0.11 mu M). This indicates that these compounds possess free radical scavenging ability similar to that of ascorbic acid, even at low concentrations. Compounds 9, 7, and 5 contain both -OCH3 and -OH groups, which contribute to their high antioxidant activity by donating electrons to the medium, thereby increasing the stability of the resulting radicals. Additionally, the reducing power of the compounds was assessed using the potassium ferricyanide reduction method, and the absorbance values of all compounds were found to be lower than that of gallic acid. The study examined the influence of structural variations on antioxidant activity, with particular emphasis on the role of different functional groups in modulating radical scavenging efficiency. The structural and electronic characteristics of the compounds were analysed using DFT calculations, which showed a clear correlation with antioxidant activity. The compounds possessing low O-H BDE values and wide spin delocalization stabilized radicals more effectively, leading to enhanced antioxidant behaviour.