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    Synthesis and characterization of naphthalene-tethered Schiff bases and corresponding poly(phenoxy-imine)s: A potent and highly selective “turn-on” chemosensor for Sn2+ ions
    (Korean Society of Industrial Engineering Chemistry, 2025) Kaya, İsmet; Kolcu, Feyza; Yılmaz, Zumre Nur; Yağmur, Hatice Karaer
    In this study, a series of naphthalene-tethered Schiff bases and their corresponding poly(phenoxy-imine) derivatives were synthesized through condensation and oxidative polycondensation reactions. Quantitative comparison revealed that only SB2 exhibited a remarkable 28-fold enhancement in fluorescence intensity upon coordination with Sn2+ ions, ascribed to by a chelation-enhanced fluorescence (CHEF) mechanism accompanied by the suppression of ?C=N- isomerization. The chemosensor exhibited excellent selectivity, a low detection limit of 45 nM, and a high association constant (2.86 × 1010 M?2). Moreover, Interference experiments performed with competing metal (Ag+, K+, Cd2+, Co2+, Cu2+, Hg2+, Mn2+, Ni2+, Pb2+, Zn2+, Al3+, Cr3+, Fe3+, and Cr6+) five times greater than that of SB2 confirmed the selectivity of its sensing performance. All poly(phenoxy-imine)s displayed substantial char yields and high limiting oxygen index (LOI) values, indicating their potential as impressive flame-retardant properties (LOI ' 33 %). Furthermore, polymers P-SB1 and P-SB2 displayed blue and violet photoluminescence, respectively, under UV excitation, suggesting their utility in light-emitting materials. The novelty of this work lies in the integration of a highly selective “turn-on” fluorescent chemosensor (SB2) for Sn2+ ions with the synthesis of thermally stable, flame-retardant poly(phenoxy-imine)s, establishing a new class of multifunctional materials that combine environmental sensing capability with exceptional thermal and optical performance. © 2025 The Korean Society of Industrial and Engineering Chemistry.
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    Synthesis of poly (4-aminosalicylic acid) through enzymatic and oxidative polycondensation by H2O2 oxidant
    (Springer Science and Business Media Deutschland GmbH, 2022) Kaya, İsmet; Yağmur, Hatice Karaer
    Aromatic compounds containing hydroxyl and amine groups in their structure are converted into oligomers or polymers through oxidative polymerization in water or organic solvent media. Again, aromatic amine or aromatic hydroxyl compounds are converted into oligomers or polymers by horseradish peroxidase (HRP) enzyme at different pH values in water or organic solvent media. Since the enzymatic oligomerization or polymerization of such compounds is environmentally sensitive, they are referred to as green chemistry. Poly(4-aminosalicylic acid) was synthesized by both enzymatic (PASA-E) and oxidative polycondensation (PASA-O) reactions. The structure and characterization were determined by FTIR, UV–vis, NMR, TGA, fluorescence and SEM measurements.PASA-O from 4-aminosalicylic acid was obtained by chemical oxidative polycondensation in glacial acetic acid by H2O2 (35% aqueous solution) as an oxidant. Enzymatic oxidative polymerizationof 4-aminosalicylic acid was performed by HRP. It has important advantages such as mild reaction conditions, mainly in terms of temperature and toxicity.The optical bandgap (Eg) values of ASA, PASA-O and PASA-E polymers were calculated to be 3.72, 2.40, and 2.73 eV, respectively. The electrochemical properties of compounds were determined by CV. The electrochemical bandgap (E′g) values of PASA-O and PASA-E were determined as 2.16 and 2.68 eV, respectively. The residual amount of PASA-O was higher than that of ASA and PASA-E at 1000 °C.