Synthesis, Anion Sensing And Dna Binding Properties Of Schiff Base Derivatives Of 2-Amino-6-Methoxybenzothiazole And Other Commercially Available Reagents
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Date
2016
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Department
Chemistry
Program
Doctor of Philosophy
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This item is made available by Morgan State University for personal, educational, and research purposes in accordance with Title 17 of the U.S. Copyright Law. Other uses may require permission from the copyright owner.
Abstract
The anion sensing properties and DNA binding properties of 1-7 were investigated. Receptors 1-3 (5-nitro-2-hydroxy-benzaldehyde, 2-hydroxy-1,4-naphthoquinone (lawsone dye) and IR 786 perchlorate) are commercially available and were used as purchased. Receptors 4-7 were synthesized as Schiff base derivatives of 2-amino-6-methoxybenzothiazole and an appropriate salicyaldehyde derivative in methanol by reflux method. These receptors were experimentally characterized by FT-IR, 1HNMR and 13CNMR. The anion sensing properties of 1-7 against common anions (CN-, F-, AcO- , OH-, H2PO4-, Br-, Cl-, ClO4-, N3-, and HSO4-) were studied in both organic and aqueous media by optical techniques (colorimetry and fluorescence). In addition, the binding properties of 1-7 were determined by Job’s plots and their respective binding constants calculated using the Benesi-Hildebrand equation. When observed by the naked eye, 1-3 lacked colorimetric selectivity for the most basic anions while under UV illumination they were selective to CN- in both organic and aqueous media. For the same media, 4-7 visually discriminated CN- from other basic anions. Under UV illuminations, 4-7 displayed distinct fluorescence between CN- and OH-. The binding mechanisms for CN- to 4-7 as determined by 1H-NMR was different from other basic anions. CN- was bound through nucleophilic addition reaction while OH-, F-, AcO- and H2PO4- was by deprotonation. Attempts to investigate 4-7 in aqueous media were only successful upto 25% dilution; since the receptors were barely soluble in water. For DNA binding studies, the UV/vis spectroscopy of receptors 4 and 7, showed that Ct-DNA exhibited intercalative binding. This is attributed to inter ligand π-π* transitions via hydrogen bonding to G and C base. In summary, the commercially available reagents (1-3) could be used as anion sensors. However, under the experimental conditions, 1-3 lacked selectivity for the basic anions. The anion sensing properties was further improved by designing 4-7, affording them better selectivity and sensitivity.