Browsing by Author "Kurt B.Z."

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New Schiff bases based on isatin and (thio)/carbohydrazone: preparation, experimental–theoretical spectroscopic characterization, and DFT approach to antioxidant characteristics
(2023-04-01) Muğlu H.; Sönmez F.; Çavuş M.S.; Kurt B.Z.; Yakan H.
In this study, synthesis, spectroscopic elucidation, and investigation of antioxidant properties of new Schiff bases based on isatin and (thio)/carbohydrazone derivatives have been reported for the first time. The structures of the synthesized compounds were elucidated by FT-IR, 1H-NMR, and 13C-NMR spectroscopic methods and elemental analysis. Their DPPH, ABTS, and CUPRAC activities were evaluated as antioxidant properties. Electronic and spectral data of the compounds were obtained by DFT calculations at the B3LYP/6–311+ +G(2d,2p) level of theory. Intramolecular interactions and charge densities on the bonds were analyzed by QTAIM and IRI calculations. In addition to parameters such as frontier molecular orbital energy eigenvalues, electronegativity, nucleophilicity index, and electrodonating power, the changes in the enthalpy of the compounds for the reactions realized through the SET mechanism were calculated to elucidate the antioxidant reactions of the compounds. Most of synthesized compounds exhibited antioxidant activities with the IC50 values ranging from 27.13 to 43.35 µM for DPPH, from 6.47 to 24.96 µM for ABTS and with the A0.50 values ranging from 9.04 to 47.52 µM for CUPRAC. Among them, compound 3, containing two hydroxyl groups, showed the strongest antioxidant activity for each assay (IC50 = 27.13 µM for DPPH, 6.47 µM for ABTS, and A0.50 = 9.04 µM for CUPRAC). The antioxidant activities of compound 3 were almost two or threefold weaker than that of BHA (IC50 = 9.55 µM for DPPH, 3.42 µM for ABTS, and A0.50 = 2.24 µM for CUPRAC), used as a standard. In addition, thiocarbohydrazone compounds exhibited higher antioxidant activity than carbohydrazones. Electron donating ability and single electron transfer enthalpy calculations predicted that thiocarbohydrazone compounds can perform SET reactions more easily than carbohydrazones.
Preparation, antioxidant activity, and theoretical studies on the relationship between antioxidant and electronic properties of bis(thio/carbohydrazone) derivatives
(2022-05-01) Muğlu H.; Kurt B.Z.; Sönmez F.; Güzel E.; Çavuş M.S.; Yakan H.
A series of novel bis(thio/carbohydrazone) compounds has been prepared from (thio)/carbohydrazide and various aldehyde derivatives. FTIR, 1H and 13C NMR spectroscopy, and elemental analysis have been used to elucidate the structures of synthesized compounds. Their antioxidant properties have been assessed using the DPPH, ABTS, and CUPRAC methods. Most of the synthesized compounds exhibited antioxidant activity in each assay. The effects of the electronic and structural properties of urea/thiourea groups on the antioxidant properties of the compounds have been investigated, and it was observed that thiourea-based compounds showed better antioxidant activity than structurally similar urea-based compounds. Among them, N′,N‴-1,4-phenylene-bis(methaneylylidene)-bis(N′-2-hydroxybenzylidene)methane-bis(thiohydrazide) (9) and N′,N‴-(1,4-phenylene-bis(methaneylylidene)-bis(N′-2,4-dihydroxybenzylidene)methane-bis(thiohydrazide) (11) showed higher ABTS activity (IC50 = 2.69 μM and 3.24 μM, respectively) than the reference butylated hydroxyanisole (BHA, IC50 = 3.42 μM). Moreover, compound 11 showed the strongest DPPH activity with an IC50 value of 5.77 μM, almost twofold higher than that of BHA (IC50 = 9.55 μM). Structural, spectral, and electronic analyses of the compounds have also been performed by DFT calculations at the B3LYP/6–311++g(2d,2p) level of theory. EDR, NCI, DOS, and QTAIM calculations have been carried out to analyze the bond properties of electronegative atoms and to investigate intramolecular interactions. DFT simulations have also been carried out in order to study the relationship between electronic characteristics and antioxidant activity.