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Öğe Chromogenic sensing, biological, and optical properties of Schiff bases of 2-amino-6-methoxybenzothiazole(Elsevier B.V., 2024) Akhüseyin Yıldız, Elif; Pepe, Yasemin; Erdener, Diğdem; Karatay, Ahmet; Boyacıoğlu, Bahadır; Ünver, Hüseyin; Yapar, Gönül; Demir, Neslihan; Yıldız, MustafaIn this study, a new series of Schiff base benzothiazole derivatives were synthesized and their structures were characterized by elemental analysis, FTIR, UV–VIS and NMR spectroscopy. The biological, sensory and photophysical properties of the benzothiazole derivatives were investigated. The sensing properties of the compounds were investigated UV–VIS spectroscopically, calorimetrically and theoretically. All compounds showed colorimetric, fluorometric and spectroscopic sensor properties for F−, CN−, AcO−, H2PO4− and OH− anions. Furthermore, DNA binding, DNA cleavage and antioxidant activities of compounds 1-4 were investigated. All compounds affected pBR322 DNA both hydrolytically and oxidatively, interacted with DNA in electrostatic mode, and also compounds 1 and 2 exhibited antioxidant activity close to standard BHT. In addition, the effects of electron donating and accepting substituents on the emission properties and charge transfer dynamics were investigated by fluorescence and femtosecond transient absorption spectroscopy measurements, respectively. According to fluorescence measurements, compounds 3 and 4 showed emission signal, while compounds 1 and 2 showed fluorescence quenching and weaker emission signal.Öğe Colorimetric chemical sensing properties of 3-amino-4-hydroxybenzene- sulfonic acid-based Schiff bases containing electron donor-acceptor groups(Elsevier, 2023) Akhüseyin Yıldız, Elif; Pepe, Yasemin; Erdener, Diğdem; Karatay, Ahmet; Boyacıoğlu, Bahadır; Ünver, Hüseyin; Yapar, Gönül; Yıldız, Mustafa; Demir, NeslihanA new series of aminobenzene sulfonic acid-based Schiff bases (1-3) were synthesized from the reaction of 3-amino-4-hydroxybenzenesulfonic acid with 5-methyl, 5-nitro and 5-bromo-salicylaldehyde. The colorimetric and UV-Vis spectroscopic responses of compounds in DMSO to addition of equivalent number of anions (F-, Br-, I-, CN-, SCN-, ClO4-, HSO4-, AcO-, H2PO4-, N3- and OH-) were investigated. Additionally, biological activities of the compounds; antimicrobial and DNA binding properties, were investigated. A DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) free radical method was used to measure antioxidant activity, and 4-hydroxy-3-(2-hydroxy-5-methylbenzylideneamino)benzene sulfonic acid (1) displayed greater antioxidant activity than butylated hydroxytoluene (BHT). Studied compounds demonstrated emission properties over a wide range of visible spectrum, and compound 4-hydroxy-3-(2-hydroxy-5-nitrobenzylideneamino)benzenesulfonic acid (2) has hyp-sochromic shift by incorporating NO2 in comparison with other compounds. Femtosecond transient absorption spectroscopy measurements showed that compounds 4-hydroxy-3-(2-hydroxy-5-nitrobenzylideneamino)benze-nesulfonic acid (2) and 3-(5-bromo-2-hydroxybenzylideneamino)-4-hydroxybenzenesulfonic acid (3), incorpo-rated nitro and bromine groups and possessing electron accepting features have fast triplet transition. This study provides a novel design strategy for biological activity and colorimetric probing features of aminobenzene sul-fonic acid-based Schiff bases.Öğe Effect of group electronegativity on spectroscopic, biological, chromogenic sensing and optical properties of 2-formyl-benzene sulfonic acid sodium salt-based Schiff bases(Elsevier B.V., 2023) Akhüseyin Yıldız, Elif; Pepe, Yasemin; Erdener, Diğdem; Karatay, Ahmet; Boyacıoğlu, Bahadır; Ünver, Hüseyin; Yapar, Gönül; Demir, Neslihan; Yıldız, Mustafa; Elmalı, AyhanIn this study, 2-formylbenzenesulfonic acid sodium salt-based Schiff bases were synthesized from the reactions of 2-formylbenzenesulfonic acid sodium salt with 2-amino-4-chlorophenol and 2-amino-4-methylphenol. The structure of the compounds was determined by FTIR, UV–Vis and NMR spectroscopy methods using both experimental and DFT methods. The anion sensor properties of the compounds were investigated both UV–Vis spectroscopically and calorimetrically. In addition, the antimicrobial activities, interactions with DNA, DNA cleavage and antioxidant activities of Schiff bases were investigated. Additionally, the effects of group electronegativity on the spectroscopic, biological, chromogenic sensing and optical properties of chlorine and methyl side groups and sodium 2-sulfobenzalidene-aminophenol-based Schiff bases were investigated.Öğe Exploring Charge Transfer Mechanisms in Schiff Base-Modified N-Doped GQDs: Insights from DFT and Pump-Probe Spectroscopy for Bioimaging Applications(Wiley-V C H Verlag Gmbh, 2024) Hance, Saadet; Erdener, Diğdem; Özturk, Berfin İlayda; Akhüseyin Yıldız, Elif; Karatay, Ahmet; Boyacıoğlu, Bahadır; Ünver, Hüseyin; Yıldız, MustafaIn recent developments, graphene quantum dots (GQDs) have emerged as valuable tools for imaging and biosensing. Various modifications on the GQDs with any desired functionality and attachment of organic molecules and/or nanostructures allow tuning their photophysical properties as well as charge transfer dynamics for bioimaging applications. This study focuses on synthesizing and characterizing of polyethyleneimine-functionalized nitrogen-doped GQDs (NC1), Schiff base- functionalized nitrogen-doped GQDs (NC2), and silver nanocomposites of these Schiff base-functionalized nitrogen-doped GQDs (NC3). We explore their absorption and emission properties to understand their interactions in the ground state. Furthermore, ultrafast transient absorption spectroscopy measurements reveal that the presence of NC3 shortens the excited state lifetime of NC1 due to charge transfer, resulting in reduced fluorescence intensity. Both experimental and DFT results suggest the potential of NC3 for bioimaging and sensing applications, making them promising candidates for phototheranostic purposes.Öğe Spectroscopic studies, antimicrobial activities, and crystal structure of N-[2-hydroxy-1-naphthylidene]3,5-bis(trifluoromethyl)aniline(Springer/Plenum Publishers, 2006) Ünver, Hüseyin; Yıldız, Mustafa; Kiraz, Aşkın; İskeleli, Nazan Ocak; Erdönmez, Ahmet; Dülger, Başaran; Durlu, Tahsin NuriA new Schiff base compound has been synthesized by the reaction of 2-hydroxy-1-naphthaldehyde with 3,5-bis(trifluoromethyl)aniline.The title compound was characterized by elemental analysis, IR, H-1 NMR, C-13 NMR, and UV-Visible techniques.Its UV-Vis spectra was examined in polar and nonpolar solvents and in acidic and basic media. The crystal structure of the compound showed the OH group to be ortho to the imine group. It crystallizes in the monoclinic space group P2(1) with a = 11.328(2), b = 6.125(1), c = 11.937(2) angstrom, V = 825.1(2) angstrom(3), D (x) = 1.543 g cm(-3) and Z = 2. An intramolecular O1- H center dot center dot center dot N1 [2.558(7) angstrom] hydrogen bond stabilizes the molecule. The compound has also been characterized by its antimicrobial activities. The ligand has been screened in vitro against the organisms Escherichia coli ATCC 11230, Staphylococcus aureus ATCC 6538, Klebsiella pneumoniae UC57, Micrococcus luteus La 2971, Proteus vulgaris ATCC 8427, Pseudomonas aeruginosa ATCC 27853, Mycobacterium smegmatis CCM 2067, Bacillus cereus ATCC 7064, and Listeria monocytogenes ATCC 15313, the yeast cultures Candida albicans ATCC 10231, Kluyveromyces fragilis NRRL 2415, Rhodotorula rubra DSM 70403, Debaryomyces hansenii DSM 70238, and Hanseniaspora guilliermondii DSM 3432.Öğe Synthesis, characterization and applications of (E)-3- ((5-bromo-2-hydroxy-3-methoxycyclohexa-1,3-dienyl) methyleneamino)-6-(hydroxymethyl)-tetrahydro-2hpyran-2,4,5-triol(Open Access House of Science and Technology, 2016) Tadesse, Solomon; Alpaslan, Yelda Bingöl; Yıldız, Mustafa; Ünver, Hüseyin; Aslan, KadirWe present the synthesis, characterization, biological and sensing applications of a Schiff base, (E)- 3-((5-bromo-2-hydroxy-3-methoxycyclohexa-1, 3-dienyl)methyleneamino)-6-(hydroxymethyl)- tetrahydro-2H-pyran-2,4,5-triol. Characterization of the title compound was carried out using theoretical quantum-mechanical calculations and experimental spectroscopic methods. The molecular structure of the title compound was confirmed using NMR and FTIR, which was in good agreement with the structure predicted by the theoretical calculations. The title compound was evaluated for its ability to detect anions in DMSO and on a solid surface and for its antimicrobial activity against several common microorganisms. © 2016 Solomon Tadesse, Yelda Bingöl Alpaslan, Mustafa Yildiz, Hüseyin ünver and Kadir Aslan.Öğe Synthesis, characterization, and application of a novel water-soluble polyethyleneimine-based Schiff base colorimetric chemosensor for metal cations and biological activity(Elsevier Science Sa, 2017) Yıldız, Mustafa; Demir, Neslihan; Ünver, Hüseyin; Şahiner, NurettinA novel colorimetric cation sensor based on polyethyleneiminehydrochloride (PEI.HCl) as Schiff base was synthesized. The molecular structure of the PEI.HCl-Schiff base was characterized via FT-IR, H-1 NMR, C-13 NMR, LC-MS and UV-vis spectroscopic methods The chromogenic sensing ability of PEI.HCl-Schiff base was investigated with colorimetric and UV-vis spectroscopy. The designed sensor exhibited highly selective recognition for Fe2+, Co2+, Cu2+, Cr3+, and Fe3+ amongst a wide range of metal ions tested in water. In the presence of these cations, the sensor underwent a dramatic colour change from yellow to green, while the presence of other metal cations such as Mn2+, Ni2+, Zn2+, Cd2+, Hg2+ and Pb2+ produced no effect on the colour. The absorption spectral changes were observed upon the addition of Fe2+, Co2+, Cu2+, Cr3+, and Fe3+ with impressive naked eye detectable colour change from yellow to dark-gray, light-brown, green, light-green and brown, respectively. The most discernable colour change in the PEI.HCl-Schiff base was caused by Fe2+, Co2+, Cu2+, Cr3+, and Fe3+ suggesting the selective detection of these metal cations. Surprisingly, PEI.HCl-Schiff base behaves as highly selective chemical sensor for the oxidation of Fe2+ to Fe3+ cations. Moreover, the antimicrobial activity of PEI.HCl-Schiff base was tested for its minimum inhibitory concentration (MIC), and the interaction with calf thymus DNA (CT-DNA) was investigated using UV-vis spectroscopy. DNA cleavage study showed that PEI.HCl-Schiff base can successfully cleave DNA without any external agents. (C) 2017 Elsevier B.V. All rights reserved.Öğe Synthesis, spectroscopic studies and structure of 2-[(Benzo[d]thiazol-2- ylamino)methyl]phenol(Springer New York LLC, 2010) Yıldız, Mustafa; Özay, Hava; Ünver, Hüseyin; İskeleli, Nazan Ocak; Mehmet Zengin, D.; Durlu, Tahsin NuriSchiff base (E)-2-[(benzo[d]thiazol-2-ylimino)methyl]phenol (1) has been synthesized from the reaction of 2-hydroxy-benzaldehyde with 2-aminobenzothiazole. The 2-[(benzo[d]thiazol-2-ylamino)methyl]phenol (2) was prepared reduction of the Schiff base 1 with sodium borohydride. The compounds 1 and 2 have been characterized by elemental analysis, FT-IR, 1 H-NMR, 13 C-NMR and UV-visible spectroscopic techniques. The structure of the compound 2 has also been examined crystallographically. The compound 2 crystallizes in the monoclinic space group P2/c. The unit cell parameters were found as a = 10.017(1), b = 11.725(1), c = 10.341(1) Å, V = 1208.1(1) Å 3 , D x = 1.409 g cm -3 and Z = 4. The crystal structure was solved by direct methods and refined by the full-matrix least squares method and found as R 1 = 0.0308 and wR 2 = 0.0818 for 2032 for the observed reflections [I > 2?(I)]. Graphical Abstract: Crystal and molecular structure of the compound 2-[(benzo[d]thiazol-2- ylamino)methyl]phenol have been studied in order to reveal the presence of either the enol-imine or keto-amine forms related with hydrogen bonding by using FT-IR, 1 H-NMR, 13 C-NMR, UV-visible spectroscopic and X-ray crystallographic techniques.[Figure not available: see fulltext.] © 2010 Springer Science+Business Media, LLC.Öğe UV-Vis spectroscopic and colorimetric anion detection and fluorescence properties of new 3-amino-4-hydroxybenzenesulfonic acid-based Schiff bases depending on the strength and position of the electron donor substitution(Iop Publishing Ltd, 2023) Akhüseyin Yıldız, Elif; Pepe, Yasemin; Erdener, Diğdem; Karatay, Ahmet; Boyacıoğlu, Bahadır; Ünver, Hüseyin; Yapar, Gönül; Yıldız, Mustafa; Demir, NeslihanIn this study, 3-amino-4-hydroxybenzenesulfonic acid-based imine compounds; 3-(2,5-dihydroxybenzylideneamino)-4-hydroxybenzenesulfonic acid (1), 3-(2,4-dihydroxybenzylideneamino)-4-hydroxybenzenesulfonic acid (2) and 4-hydroxy-3-(2-hydroxy-3-methoxybenzylideneamino)-4-hydroxybenzenesulfonic acid (3) was synthesized. The compounds were analyzed using various spectroscopy methods, and the experimental UV-vis data matched the theoretical predictions. The compound 1 displayed lower stability, higher reactivity, and easier photoexcitation due to a smaller HOMO-LUMO energy gap. The investigated compounds 1-3 showed promise as chemosensors for anions, providing visible detection in daylight conditions. The compound 3 exhibited selective fluorescence at specific wavelengths. The compounds 1-3 interacted with DNA through electrostatic interactions. Also, compounds 1-3 showed higher antioxidant activity than BHT. However, fluorescence measurements indicated that the emission signals were strongly influenced by the position and strength of the electron-donating group. Adding a hydroxy or methoxy moiety near the -OH group on the phenyl ring decreased the fluorescence signal due to intersystem crossing and intramolecular charge transfer mechanisms, respectively. These findings were supported by femtosecond transient absorption spectroscopy measurements. The results emphasize the significance of substituents in imines derived from 3-amino-4-hydroxybenzenesulfonic acid in determining their biological activities, as well as their optical and sensor properties.
