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    Öğe
    Analysis of tautomeric equilibrium in (E)-4,6-dibromo-2-[(4-fluorophenylimino)methyl]-3-methoxyphenol compound
    (Pergamon-Elsevier Science Ltd, 2015) Kastas, Cigdem Albayrak; Kastas, Gokhan; Gur, Mahmut; Muglu, Halit; Buyukgungor, Orhan
    In this study, the tautomeric equilibrium between the phenol-imine and keto-amine structural forms of (E)-4,6-dibromo-2-[(4-fluorophenylimino)methyl]-3-methoxyphenol compound has been investigated with experimental (XRD, UV-vis and NMR) and theoretical (DFT and TD-DFT) methods. The results clearly show that structural preference of the compound is definitely depended on its state. Namely, the compound exists in phenol-imine form in the solid state while one or both of these forms can be seen in solvent media. For example, the compound prefers phenol-imine form in benzene while both forms exist in EtOH and DMSO solvents. Coexistence of two forms has been quantified with NMR studies, giving a ratio of 11:9 for phenol and keto structures of the compound in acetone-d(6) solvent. (C) 2015 Elsevier B.V. All rights reserved.
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    Öğe
    New 5-methylisatin including thiocarbohydrazones: preparation, structure elucidation and antimicrobial activity
    (Springer, 2022) Yakan, Hasan; Cakmak, Sukriye; Buruk, Osman; Veyisoglu, Aysel; Muglu, Halit; Karakullukcu, Nalan Turkoz
    New 5-methylisatin including thiocarbohydrazones (1-5) have been synthesized. The chemical structure of synthesized compounds was elucidated with IR, H-1 NMR, C-13 NMR spectroscopic methods, and elemental analysis. Moreover, the synthesized compounds have been screened for antimicrobial activity. Their antibacterial activities were tested against Gram-positive (Bacillus subtilis ATCC 6623, Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 29212), Gram-negative (Escherichia coli ATCC 25922, Klebsiella pneumoniae ATCC 70060, Pseudomonas aeruginosa ATCC 27853), and fungal (Candida albicans ATCC 10231, Aspergillus niger ATCC 16404) microbial strains using the microdilution method. In the isatin series, particularly the compound 2 showed the best antimicrobial activity against E. faecalis strain with MIC values of 64 mu g/mL compared to other compounds. This high activity of compound 2 is due to the presence of two electron-donating methoxy groups in its structure. The remaining substituted compounds have shown good and moderate antimicrobial activity compared to standard drugs. The results may provide insights into the target compounds' structure-activity relationships, which may facilitate the development of pharmacological and biological applications for the target compounds. Graphical abstract New isatins bearing thiocarbohydrazone were synthesized. Structures of all com- pounds were elucidated with spectroscopic approaches. The antimicrobial activities of the tested compounds presented promising antimicrobial activity against the eight tested microorganisms.
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    Öğe
    Synthesis, structure elucidation, biological activity, enzyme inhibition and molecular docking studies of new Schiff bases based on 5-nitroisatin-thiocarbohydrazone
    (Elsevier, 2023) Yakan, Hasan; Omer, Hiba-H. S.; Buruk, Osman; Cakmak, Sukriye; Marah, Sarmad; Veyisoglu, Aysel; Muglu, Halit
    New Schiff bases bearing 5-nitroisatin-thiocarbohydrazone ( 1-9 ) have been prepared. The chemical structures of these compounds have been clarified by spectroscopic methods (IR, 1 H NMR, and 13 C NMR), and elemental analysis. Besides, they have been tested for antimicrobial activity. The antimicrobial activities of the novel compounds have been evaluated using a twofold serial dilution method for Minimum Inhibitory Concentration (MIC) against three gram-positive bacteria, three gram-negative bacteria, and two fungal pathogens. The obtained data showed that compound 7 has excellent activity against gram-strain positive and gram-strain-negative bacteria. Compound 7 showed better activity than amoxicillin, which is one of the standard drugs used against the E. faecalis pathogen, but showed the same activity as tetracycline. Synthesized compounds could be formed the basis for the development of better antibacterial agents. The total antioxidant activity of compounds 3 and 5 showed better antioxidant activity than standard BHT, while compounds 4, 8, 7, 2 , and 6 showed better antioxidant activity than standard Trolox. The urease inhibitory effect of compound 7 was better than thiourea. Also, the structure-activity relationship study showed that the scores of molecular models revealed that the compounds with the highest number of binding with urease enzyme were compounds 3 and 7 with total bond numbers of 19 and 18, respectively.(c) 2022 Elsevier B.V. All rights reserved.