Browsing by Author "Kigga, M."

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A new colorimetric receptor for selective detection of maleate vs. fumarate and ratiometric detection of F- ions
(Royal Society of Chemistry, 2014) Kigga, M.; Trivedi, D.R.
Two new receptors, R1 and R2, were designed and synthesized for the isomeric discrimination of maleate ions over fumarate ions. Receptor R1 showed high selectivity with a significant color change from colorless to orange red with ??max of 104 nm. This was owing to the hydrogen bonded electrostatic interactions of maleate ions with receptor R1. The formation of hydrogen bond between receptor R1 and maleate ions was confirmed by 1H NMR titrations, where the signal at ? 12.25 corresponding to the benzohydrazide -NH proton showed a downfield shift upon binding with the anion. Receptor R3 did not show any binding with maleate ions or fumarate ions due to steric hindrance. Receptors R1 and R2 detected F- ions with color changes from colorless to orange and colorless to pale yellow, respectively. Upon incremental addition of F- ions, the color was further transformed from orange to blood red in receptor R1 and pale yellow to dark yellow in receptor R2. This result was due to the formation of initial hydrogen bonds followed by the deprotonation of receptors at higher concentrations of F- ions. © the Partner Organisations 2014.
Colorimetric receptors for naked eye detection of inorganic fluoride ion in aqueous media using ICT mechanism
(Royal Society of Chemistry, 2012) Kigga, M.; Nityananda Shetty, A.N.; Trivedi, D.R.
A new series of receptors were designed and synthesized based on benzohydrazide for the colorimetric detection of fluoride ion. The receptors L1 and L2 are highly selective towards fluoride ion over other anions. These receptors are able to detect inorganic fluoride such as NaF in aqueous solutions. The presence of two carbonyl groups in the receptor molecule makes the -NH proton highly acidic and hence these receptors are capable of competing with water molecules to bind fluoride ion. The receptors L1 and L2 showed a significant colour change from colourless to yellow in aqueous solutions of NaF with a ??max of 149 nm and 147 nm respectively. The mechanism involved in the colour change was deprotonation, formation of imidic acid intermediate followed by stabilization of complex through Intramolecular Charge Transfer (ICT). This was further confirmed by 1H NMR titrations where the formation of imidic acid was observed. The receptor L1 proved itself to be potentially useful for real-life applications by detecting fluoride ion quantitatively in sea water and commercially available mouth wash. © 2012 The Royal Society of Chemistry.
Dual colorimetric receptor with logic gate operations: Anion induced solvatochromism
(Royal Society of Chemistry, 2014) Kigga, M.; Swathi, N.; Manjunatha, J.R.; Das, U.K.; Nityananda Shetty, A.N.; Trivedi, D.R.
A receptor R1 was designed and synthesised for colorimetric detection of F- ions as well as Cu2+ ions via intramolecular charge transfer mechanism. Upon addition of F- ions in dry DMSO, the color of the receptor R1 changed from pale yellow to blue. The receptor showed a unique property of solvatochromism by displaying different coloration with different solvents only in the presence of F- ions, which were applied to determine the percentage composition of binary solvent mixtures. The receptor R1 was able to detect Cu2+ ions colorimetrically where it exhibited a color change from pale yellow to orange-red. In addition, the receptor was subjected to molecular logic gate applications, wherein it showed 'ON-OFF' switching operations. © 2014 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
"Naked-eye" detection of inorganic fluoride ion in aqueous media using base labile proton: A different approach
(2014) Kigga, M.; Trivedi, D.R.
Two new receptors R1 and R2 were designed and synthesized based on 1-naphthohydrazide Schiff's bases for the colorimetric detection of fluoride ion. The receptor R1 was selective toward fluoride ion over other anions in organic media. The presence of carbonyl group in 1-naphthohydrazide makes -NH proton acidic and therefore it could deprotonate with addition of basic anion such as fluoride. However, the acidic -NH proton easily gets solvated even with the trace amount of water. Alternatively, the receptor R2, encompasses highly base labile, hydroxyl (-OH) functionality which detects basic fluoride ions via deprotonation mechanism not only in organic solutions but also in aqueous media. The mechanism involved in the color change of receptor R1 is deprotonation of acidic -NH followed by stabilization of complex through intramolecular charge transfer (ICT) transition which was evidenced by the formation of HF2 peak in 1H NMR titration. The color change of receptor R2 involves initial hydrogen bond formation of F- ion with -NH group and deprotonation at higher concentration of F- ions which leads to intramolecular charge transfer transition in organic media. On the other hand, in aqueous solution of receptor R2, addition of the basic fluoride ion leads to the deprotonation of base labile hydroxyl (-OH) proton, which is responsible for colorimetric detection. 2014 Elsevier B.V.
"Naked-eye" detection of inorganic fluoride ion in aqueous media using base labile proton: A different approach
(2014) Kigga, M.; Trivedi, D.R.
Two new receptors R1 and R2 were designed and synthesized based on 1-naphthohydrazide Schiff's bases for the colorimetric detection of fluoride ion. The receptor R1 was selective toward fluoride ion over other anions in organic media. The presence of carbonyl group in 1-naphthohydrazide makes -NH proton acidic and therefore it could deprotonate with addition of basic anion such as fluoride. However, the acidic -NH proton easily gets solvated even with the trace amount of water. Alternatively, the receptor R2, encompasses highly base labile, hydroxyl (-OH) functionality which detects basic fluoride ions via deprotonation mechanism not only in organic solutions but also in aqueous media. The mechanism involved in the color change of receptor R1 is deprotonation of acidic -NH followed by stabilization of complex through intramolecular charge transfer (ICT) transition which was evidenced by the formation of HF2 peak in 1H NMR titration. The color change of receptor R2 involves initial hydrogen bond formation of F- ion with -NH group and deprotonation at higher concentration of F- ions which leads to intramolecular charge transfer transition in organic media. On the other hand, in aqueous solution of receptor R2, addition of the basic fluoride ion leads to the deprotonation of base labile hydroxyl (-OH) proton, which is responsible for colorimetric detection. © 2014 Elsevier B.V.
Receptor with an active methylene group as binding site for extraction of inorganic fluoride ions from seawater
(Wiley-VCH Verlag info@wiley-vch.de, 2014) Kigga, M.; Trivedi, D.R.
Two new receptors R1 and R2 based on triphenylphosphonium salts with an active methylene group as binding site have been designed and synthesised for the detection of F- ions. The detection limit of these receptors in organic media was found to be 0.2 ppm. Upon adding F- ions, a ??max of 188 nm and 256 nm was observed for receptors R1 and R2, respectively. The detection process followed deprotonation of the methylene proton, which has been confirmed by 1H NMR titration. The receptors were evaluated for real-life applicability by extracting F- ions from aqueous media and seawater into organic media. Receptor R2 was able to extract F- ions from seawater with 99 % efficiency. The level of F- ions present in seawater has been quantified and found to be 1.4 ppm, which is comparable to the reported literature value. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.