Faculty Publications
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Item Supramolecular synthons in noncovalent synthesis of a class of gelators derived from simple organic salts: Instant gelation of organic fluids at room temperature via in situ synthesis of the gelators(2009) Das, U.K.; Trivedi, D.R.; Adarsh, N.N.; Dastidar, P.(Chemical Equation Presented) The supramolecular synthon approach has been employed to synthesize noncovalently a series of low molecular mass organic gelators (LMOGs) derived from benzylammonium salts of variously substituted benzoic acids. The majority of the salts (75%) prepared showed interesting gelation properties. Instant gelation of an organic fluid, namely methyl salicylate, was achieved at room temperature by using most of the gelator salts by in situ synthesis of the gelators. Table top rheology and scanning electron microscopy (SEM) were used to characterize the gels. Single crystal X-ray diffraction studies revealed the presence of both 1D and 2D supramolecular synthons. X-ray powder diffraction (XRPD) studies indicated the presence of various crystalline phases in the fibers of the xerogels. By using these data, a structure-property correlation has been attempted and the working hypothesis for designing the gelator has been reinforced. © 2009 American Chemical Society.Item Highly Efficient Regioselective Synthesis of 2-Imino-4-oxothiazolidin-5-ylidene Acetates via a Substitution-Dependent Cyclization Sequence under Catalyst-Free Conditions at Ambient Temperature(American Chemical Society service@acs.org, 2015) Wagh, Y.B.; Kuwar, A.S.; Patil, D.R.; Tayade, Y.A.; Jangale, A.D.; Terdale, S.S.; Trivedi, D.R.; Gallucci, J.; Dalal, D.S.A green and efficient method for the synthesis of newer 2-imino-4-oxothiazolidin-5-ylidene acetate derivatives under catalyst-free conditions by simply stirring symmetrical and unsymmetrical 1,3-diarylthioureas with dialkyl acetylenedicarboxylates in ethanol at room temperature has been developed. Interestingly, the regioselective synthesis affords the 2-imino-4-oxothiazolidin-5-ylidene acetate derivatives: the amine nitrogen bonded to an electron-withdrawing substituent becomes part of the imino component, and the amine nitrogen bonded to an electron-donating substituent becomes the heterocyclic nitrogen. This is the first report wherein the impact of substituents in directing the regiocyclization has been explained and the structure conflict resolved by single-crystal X-ray analysis. © 2015 American Chemical Society.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 A new colorimetric chemosensors for Cu2+ and Cd2+ ions detection: Application in environmental water samples and analytical method validation(Elsevier B.V., 2017) Tekuri, V.; Trivedi, D.R.A new heterocyclic thiophene-2-caboxylic acid hydrazide based chemosensor R1 to R4 were designed, synthesized and characterized by various spectroscopic techniques like FT-IR, UV-Vis, 1H NMR, 13C NMR, Mass and SC-XRD. The chemosensor R3 showed a significant color change from colorless to yellow in the presence of Cu2+ ions and chemosensor R4 showed a significant color change from colorless to yellow in the presence of Cd2+ ions over the other tested cations such as Cr3+, Mn2+, Fe2+, Fe3+, Co2+, Ni2+, Zn2+, Ag2+, Al3+, Pb2+, Hg2+, K+, Ca2+ and Mg2+. The high selective and sensitivity of R3 towards Cu2+ and R4 towards Cd2+ ions was confirmed by UV-Vis spectroscopic study. The R3 showed a red shift in the presence of Cu2+ ions by ??max 67 nm and R4 showed a red shift in the presence of Cd2+ ions by ??max 105 nm in the absorption spectrum. The binding stoichiometric ratio of the complex between R3 - Cu2+ and R4 - Cd2+ ions have been found to be 1:1 using the B-H plot. Under optimized experimental conditions, the R3 and R4 exhibits a dynamic linear absorption response range, from 0 to 50 ?M for Cu2+ ions and 0 to 30 ?M for Cd2+ ions, with the detection limit of 2.8 × 10?6 M for Cu2+ and 2.0 × 10?7 M for Cd2+ ions. The proposed analytical method for the quantitative determination of Cu2+ and Cd2+ ions was validated and successfully applied for the environmental samples with good precision and accuracy. © 2017 Elsevier B.V.Item Structural and physicochemical characterization of pyridine derivative salts of anti-inflammatory drugs(Elsevier B.V., 2017) Nechipadappu, S.K.; Trivedi, D.R.Salts of common anti-inflammatory drugs mefenamic acid (MFA), tolfenamic acid (TFA) and naproxen (NPX) with various pyridine derivatives (4-amino pyridine (4AP), 4-dimethylaminopyridine (DMAP) and 2-amino pyridine (2AP)) were synthesized by crystal engineering approach based on the pKa values of API's and the salt former. All the salts were characterized systematically by various spectroscopic methods including FT-IR and 1H NMR and the crystal structure was determined by single-crystal X-ray diffraction techniques (SCXRD). DMAP salt of NPX and 2AP salts of MFA and TFA were not obtained in the salt screening experiments. All the molecular salts exhibited 1:1 molecular stoichiometry in the asymmetric unit and except NPX-2AP salt, all the molecular salts included a water molecule in the crystal lattice. Physicochemical and structural properties between drug-drug molecular salts of MFA-4AP, TFA-4AP and NPX-4AP have been evaluated and it was found that these molecular salts were found to be stable for a time period of six months at ambient condition and further hydration of molecular salts were not observed even at accelerated humid conditions (?75% RH). It was found that 4AP salts of MFA and TFA and DMAP salts of MFA and TFA are isostructural. © 2017 Elsevier B.V.Item Photophysical and electrochemical properties of organic molecules: Solvatochromic effect and DFT studies(Elsevier B.V., 2018) Mohan, M.; Pangannaya, S.; Satyanarayan, M.N.; Trivedi, D.R.A series of five Schiff base molecules M1, M2, M3, M4 and M5 have been designed and synthesized by aldol condensation reaction. Synthesized molecules have been characterized by standard spectroscopic techniques in order to confirm their structural traits. The solvatochromic behavior of molecules M1 to M5 in solvents of varying polarity were investigated by UV–Vis, fluorescence spectroscopy and supported by TD-DFT calculations. DFT studies performed in the gas phase confirmed the energy stabilized structure of the molecules M1 to M5. Structural characteristics of molecule M2 favored higher fluorescence emission with a quantum yield of 0.35 and a solid-state emission of 512 nm. Fluorescence lifetime measurement of the molecules M1 to M5 exhibited a lifetime of order 2–5 ns. Overall, molecule M2 can find its application in organic light emitting diodes as a non-dopant emitter material. © 2018 Elsevier B.V.Item 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.