Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
9 results
Search Results
Item 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.Item Identification of robust synthon in the molecular salts of 2-aminothiazole with substituted benzoic acids: A case study(Springer India sanjiv.goswami@springer.co.in, 2014) Oruganti, M.; Pallepogu, R.; Trivedi, D.R.Six new salts of an API intermediate 2-aminothiazole with different carboxylic acid coformers were synthesized and characterized by IR (Infrared spectroscopy), 1H-NMR, DSC (Differential scanning calorimetry), XRPD (X-ray powder diffraction) and single crystal XRD. The crystal structure of the salts with benzoic acid, 2,3-, 2,4-, 2,5-, 2,6- dihydroxybenzoic acids and 2,4-dinitrobenzoic acid were determined. The thiazole moiety exhibited solvent (polarity) assisted tautomerism in all reported salts and proton transfer was noticed to the ring N of thiazole due to which two point supramolecular synthon N+-H(thiazole)?O-(acid), N-H(amine)?O-(acid) was observed. The crystal structures were studied with respect to the positional effect of the competing functional groups like hydroxyl (-OH) and nitro (-NO2) as well as their donor and acceptor abilities for hydrogen bonding. The presence of the non-conventional hydrogen bond (C-H?O) has been found to play a critical role in the formation of secondary supramolecular architectures. © 2014 Indian Academy of Sciences.Item The hierarchies of hydrogen bonds in salts/cocrystals of isoniazid and its Schiff base - A case study(Royal Society of Chemistry, 2016) Oruganti, M.; Khade, P.; Das, U.K.; Trivedi, D.R.A series of two salts of isoniazid and two cocrystals of its Schiff base have been synthesised and characterized using FT-IR, 1H-NMR, DSC, XRPD and SCXRD. The crystal structures with 2,5-dihydroxybenzoic acid, 2,6-dihydroxy benzoic acid, 3-aminobenzoic acid and o-phthalic acid have been deduced. In all complexes the involvement of pyridine N (proton transfer/robust synthon) is noticed. The unit cell similarity index was calculated between two cocrystals (N-(propan-2-ylidene)isonicotinohydrazide)·(2,5-dihydroxybenzoic acid) and (3-aminobenozic acid)·(N-(propan-2-ylidene)isonicotinohydrazide). Furthermore, the index was compared with the reported complexes and it was found to be close to zero indicating isostructurality. The correlation between the NPyr-H?O (acid) hydrogen bond distance for the reported cocrystals and their corresponding pKa values has been deduced and validated. © The Royal Society of Chemistry 2016.Item Cocrystals of Ethenzamide: Study of Structural and Physicochemical Properties(American Chemical Society service@acs.org, 2016) Hariprasad, V.M.; Nechipadappu, S.K.; Trivedi, D.R.Pharmaceutical cocrystals of an analgesic drug ethenzamide (ETZ) with various coformers, namely, gallic acid (GA), 2-nitrobenzoic acid (2NB), 3-nitrobenzoic acid (3NB), 2,4-dinitrobenzoic acid (DNB), and 3-toluic acid (3TA) were synthesized by the solvent evaporation method. All the cocrystals were characterized by various analytical techniques, and the crystal structures were determined by the single-crystal X-ray diffraction method (SCXRD). SCXRD analysis revealed that all the synthesized cocrystals were formed through a robust supramolecular acid-amide heterosynthon except the ethenzamide/gallic acid cocrystal, where molecules interacted through O-H···O hydrogen bond involving -OH of gallic acid and oxygen of amide group of the ETZ molecule. The physicochemical properties such as stability, hygroscopicity, and solubility studies of the ETZ-GA cocrystal were evaluated. It was found that the ETZ-GA cocrystal has a higher solubility (2-fold) than that of the pure ETZ drug molecule. Hygroscopic study of the ETZ-GA cocrystal revealed that synthesized cocrystal was non-hygroscopic at ?75% RH conditions. The ETZ-GA cocrystal found to be stable for a time period of four months at ambient temperature. © 2016 American Chemical Society.Item Design and synthesis of a new organic receptor and evaluation of colorimetric anion sensing ability in organo-aqueous medium(Elsevier B.V., 2017) Pangannaya, S.; Tarafder, K.; Trivedi, D.R.A new organic receptor has been designed and synthesized by the combination of aromatic dialdehyde with nitro-substituted aminophenol resulting in a Schiff base compound. The receptor exhibited a colorimetric response for F? and AcO? ion with a distinct color change from pale yellow to red and pink respectively in dry DMSO solvent and yellow to pale greenish yellow in DMSO:H2O (9:1, v/v). UV–Vis titration studies displayed a significant shift in absorption maxima in comparison with the free receptor. The shift could be attributed to the hydrogen bonding interactions between the active anions and the hydroxyl functionality aided by the electron withdrawing nitro substituent on the receptor. 1H NMR titration and density functionality studies have been performed to understand the nature of interaction of receptor and anions. The lower detection limit of 1.12 ppm was obtained in organic media for F? ion confirming the real time application of the receptor. © 2016Item Salt/Cocrystal of Anti-Fibrinolytic Hemostatic Drug Tranexamic acid: Structural, DFT, and Stability Study of Salt/Cocrystal with GRAS Molecules(American Chemical Society service@acs.org, 2019) Nechipadappu, S.K.; Reddy, I.R.; Tarafder, K.; Trivedi, D.R.Tranexamic acid (TXA) is an important and essential medicine needed in a health system and is approved by the US FDA for the treatment of excessive blood loss from trauma, postpartum bleeding, surgery, tooth removal, nosebleeds, and heavy menstruation. One of the notable disadvantages of the TXA drug is that has low absorption (â35-40%) in the gastrointestinal tract, possibly due to its amphoteric nature. In the present work, nine molecular salts and two cocrystals of the TXA molecule have been synthesized by a simple water-mediated solvent evaporation method. The coformers/counterions used were salicylic acid (SAL), 3-hydroxybenzoic acid (3HBA), 2,4-dihydroxybenzoic acid (2,4HBA), 2,5-dihydroxybenzoic acid (2,5HBA), 2,6-dihydroxybenzoic acid (2,6HBA), gallic acid (GAA), oxalic acid (TXA), tartaric acid (TTA), fumaric acid (FUM), succinic acid (SUA), and crotonic acid (CRA). The synthesized salts/cocrystals were characterized by various spectroscopic, thermal, and XRD techniques. The crystal structures of all of the molecular adducts were determined by SC-XRD techniques. In the synthesized salts, charge-assisted acid···amine heterosynthons and O-H···O hydrogen bonds between the acid group of TXA and the coformer are favored, and the salts TXA-FUM and TXA-SUA were found to be isostructural on the basis of the isostructural parameters Ï€ and Î? . In the cocrystal, molecules interacted through the acid group of the coformer with the carboxyl group of the TXA molecule. Further, these salts/cocrystals were found to be stable for a period of 6 months under ambient conditions (â25-30 °C, â60-65% RH). Furthermore, density functional theory (DFT) calculations were carried out to better understand the geometric structure of the molecules presented in our study. The interaction energies of the molecular salts and cocrystals were calculated, and they supported the reported structure of the crystalline adducts. The cocrystal formation in the case of TXA-GAA and TXA-CRA has been confirmed by a DFT calculation study, as the salt formation in these cases resulted in a higher interaction energy in comparison to the cocrystal. Consequently, these molecular salts offer promise for the development of new drug products of TXA, and a few salts, namely TXA-SAL and TXA-2,5HBA, offer the possibility of development of combination drugs. © 2018 American Chemical Society.Item Design and synthesis of malonohydrazide based colorimetric receptors for discrimination of maleate over fumarate and detection of F?, AcO? and AsO2 ? ions(Elsevier B.V., 2020) Singh, A.; Mohan, M.; Trivedi, D.R.In this study, we have designed and synthesized two new organic receptors R1 and R2 based on malonohydrazide for the recognition of biologically important anions. The receptor R1 capable of colorimetric discrimination of maleate over fumarate ion, exhibit significant color change from pale yellow to wine red due to intermolecular hydrogen bond between the R1 and maleate ion, supported by 1HNMR titration, where the peak at ?12.0 ppm attributed to the NH proton experiences a downfield shift upon binding with maleate ion. Receptor R1, equipped with two electron-withdrawing [sbnd]NO2 moieties as the chromogenic signaling unit enhance the hydrogen bonding tendency and acidity, and thus when comparing with receptor R2, R1 displayed substantial higher redshift (??max) of 148 nm, 143 nm, and 140 nm towards F?, AcO?, and maleate anion in the DMSO. In addition, the synthesized receptors R1 and R2 are able to detect F?, AcO?, and AsO2 ? ions as their sodium salts in an aqueous solution with visual color change. Receptor R1 exhibit electrochemical response towards F? and AcO? ions. The receptors R1 and R2 are successfully applied for quantitative detection of F? ion in the toothpaste solution in an aqueous medium. Additionally, R1 and R2 exhibit fluorescence enhancement towards F? and AcO? ions in the DMSO. As well, R1 and R2 demonstrate to be potentially useful colorimetric chemosensor for sensing maleate ion using the test strip. The theoretical calculation based on TD-DFT corroborates well with the experimental results of the receptors R1 and R2 with fluoride, acetate and maleate. © 2019 Elsevier B.V.Item Colorimetric chemosensors for the selective detection of arsenite over arsenate anions in aqueous medium: Application in environmental water samples and DFT studies(Elsevier B.V., 2023) K, K.; Nityananda Shetty, A.N.; Trivedi, D.R.Novel organic receptors N3R1- N3R3 were developed for the selective colorimetric recognition of arsenite ions in the organo-aqueous media. In the 50% aq. acetonitrile media and 70% aq. DMSO media, receptors N3R2 and N3R3 showed specific sensitivity and selectivity towards arsenite anions over arsenate anions. Receptor N3R1 showed discriminating recognition of arsenite in the 40% aq. DMSO medium. All three receptors formed a 1:1 complex with arsenite and stable for a pH range of 6–12. The receptors N3R2 and N3R3 achieved a detection limit of 0.008 ppm (8 ppb) and 0.0246 ppm, respectively, for arsenite. Initial hydrogen bonding on binding with the arsenite followed by the deprotonation mechanism was well supported by the UV–Vis titration, 1H- NMR titration, electrochemical studies, and the DFT studies. Colorimetric test strips were fabricated using N3R1- N3R3 for the on-site detection of arsenite anion. The receptors are also employed for sensing arsenite ions in various environmental water samples with high accuracy. © 2023 Elsevier B.V.Item Heterocyclic-based optical responsive chemosensors for the detection of arsenite and phosphate in semi-aqueous medium: Application in logic gate operations, RGB tool, and DFT studies(Elsevier B.V., 2025) Hebbar, S.D.; Trivedi, D.R.Highly selective and sensitive organic chemosensors S2R1-S2R3 were synthesized using thienyl-substituted pyridine derivative and characterized by various spectroscopic techniques. The effect of substituents on selectivity is observed in the chemosensors S2R1 through S2R3, with the rate of reactivity toward ions following the trend as -NO2 > -CN > –OCH3 group. The chemosensor S2R1 exhibited selectivity towards arsenite and phosphate, achieving a Limit of Detection (LOD) of 0.2672 ppm and 0.5042 ppm, respectively, in 30% aq. (CH3)2SO solution. It was also observed that S2R2 was selective for PO43? ions in 100% (CH3)2SO solution with an LOD of 0.521 ppm. The spectral redshifts observed in the organo-aqueous media potentializes the sensor to be colorimetrically active. The probe S2R1 showed the lowest LOD and high binding constant with AsO2? and PO43? ions. Other characterization techniques, such as electrochemical studies, 1H NMR titration, UV–visible titration, and DFT experiments, demonstrated the sensing mechanism of arsenite and phosphate ions with the chemosensors through an intermolecular hydrogen bonding and intermolecular charge transfer (ICT) process followed by its practical applicability for real world-sensing. © 2024 Elsevier B.V.