Browsing by Author "S. Jaiswal"

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Ab initio determination of geometries and vibrational characteristics of building blocks of organic superconductors: 4,5-Ethylenedithio-1,3-dithiole-2-thione, and 4,5-ethylenedithio-1,3-dithiole-2-one
(2010) S. Jaiswal; Deepshikha Singh; R.L. Prasad; R.A. Yadav
RHF and DFT calculations were carried out to study the optimized molecular geometries and vibrational characteristics of the 4,5-ethylenedithio-1,3-dithiole-2-thione (EDT-DTT) and 4,5-ethylenedithio-1,3-dithiole-2-one (EDT-DTO) molecules and their radical cations and anions. It is found that the anionic radical of the EDT-DTO molecule is unstable. Both the neutral molecules and their radical cations have non-planar structures with C2 symmetry while the radical anion of the EDT-DTT molecule has non-planar structure with C1 symmetry. It is found that the most of the vibrational characteristics of the radicals are similar to their corresponding neutral molecules, however, for some of the modes significant changes are noticed. As a result of anionic radicalization of EDT-DTT, the IR intensity and Raman activity increase and Raman band becomes polarized for both the CH2 twisting modes. Drastic enhancements in the Raman activity and reduced IR intensity are noticed for the C{double bond, long}S/O stretching mode in going from neutral molecules to their radical ions consistent with charge separation along this bond. The C{double bond, long}S and C{double bond, long}C stretching wavenumber changes are consistent with corresponding bond length changes in going from neutral to their radical ions. © 2010 Elsevier B.V. All rights reserved.
Ab initio determination of molecular geometries and vibrational frequencies of CX3 COOH (X = H, F, Cl, Br)
(2008) R.A. Yadav; M. Kumar; R. Singh; P. Singh; S. Jaiswal; G. Srivastav; R.L. Prasad
Using Gaussian 03 Revision C.02 version of the quantum chemical program ab initio and DFT computations have been carried out at the rhf/6-31+g*, b3lyp/6-31+g*, b3lyp/6-31++g** and b3lyp/6-311++g** levels to compute optimized geometries, harmonic vibrational frequencies along with intensities in IR and Raman spectra and atomic charges for the acetic (ethanoic) acid and its 1,1,1-tri-halo (fluoro, chloro and bromo) derivatives. The optimized molecular structures for all the four molecules are found to possess Cs point group symmetry. The symmetric stretching mode is found to have lowest magnitude of the three CX3 stretching modes for all the four molecules, whereas the symmetric deformation mode is found to have the lowest magnitude for EA and TFEA and the highest magnitude for TCEA and TBEA. The parallel rocking mode of the CX3 group is found to have lower magnitude than the perpendicular rocking mode for EA and TFEA where reverse is found for TCEA and TBEA. The modes of the COOH group are substituent sensitive except the OH stretching mode. Moreover, the maximum effect is found for the TFEA molecule. The CF3 group is found to have the characteristic frequencies as 235-505, 787, 1150-1190 and 1400 cm-1 which are due to the modes δs(CF3), νs(CF3), νas(CF3) and ν(C-CF3), respectively. © 2008 Elsevier B.V. All rights reserved.
Ab initio studies of molecular structures, conformers and vibrational spectra of heterocyclic organics: I. Nicotinamide and its N-oxide
(2010) M. Kumar; S. Jaiswal; R. Singh; G. Srivastav; P. Singh; T.N. Yadav; R.A. Yadav
FTIR spectra of nicotinamide and its N-oxide have been recorded and analyzed in the range 400-4000 cm-1. The stabilities, optimized molecular geometries, APT charges and vibrational characteristics for the two possible conformers of nicotinamide and its N-oxide have been studied theoretically using restricted Hartree-Fock (RHF) and density functional theory (DFT) methods. The E (trans) conformers of nicotinamide and its N-oxide are found to be more stable and less polar than their respective Z (cis) conformers. Due to addition of an O atom at the N1 site in the NA molecule the magnitudes of atomic charges on all the H atomic sites are found to increase. For all the studied molecules, magnitude of the wagging mode of the NH2 group is found to be higher than its torsion mode, which is in the reverse order as compared to that for the aniline molecule. Most of the vibrational frequencies have nearly the same magnitude for the two conformers of nicotinamide and its N-oxide, however, significant changes are noticed in their IR intensities, Raman activities and depolarization ratios of the Raman bands. The frequency of the ring breathing mode for the NA molecule is found to decrease by 100 cm-1 in going to the NANO molecule for both the conformers. The IR intensity for the scissoring mode of the CON(H2) group is found to decrease significantly for the NA-II conformer as compared to that for the NA-I conformer. © 2009 Elsevier B.V. All rights reserved.
Aluminum phosphide poisoning: Effect of correction of severe metabolic acidosis on patient outcome
(Medknow Publications and Media Pvt. Ltd, 2009) S. Jaiswal; R.K. Verma; N. Tewari
Forty patients of aluminum phosphide poisoning who were admitted to the ICU of Sir Sunder Lal Hospital, Banaras Hindu University, were studied. Restlessness, excessive thirst, shock, arrhythmias, tachypnoea, and severe metabolic acidosis were the common clinical findings. Only repeated and full correction with intravenous sodium bicarbonate was able to cope up with the severity and rapidity of acidosis. There was no significant change in blood pressure, pulse rate, and respiratory rate after full correction but gradually pulse and systolic blood pressure settled after ionotropic support in the survivors. There was significant improvement from 30.36% in the case when only half correction was done, as has been the common practice, to 57.5%, when full correction of metabolic acidosis was done.
Chemical modification of poly (vinyl chloride) sheet with thiourea for cell study
(2013) Monika; R.R. Mishra; S. Jaiswal; G. Kapusetti; N. Misra
Plasticized poly (vinyl chloride) has been used as biomaterial to make medical equipment. An appropriate reaction situation by temperature at 60-85°C for the surface modification of PVC sheet with sodium thiourea has been investigated. Although, the use of a phase-transfer catalyst (Tetra butyl ammonium hydrogen sulphate-TBHAS) makes it feasible for the nucleophilic substitution reaction to take place, the morphology of the film is changed by the reaction, leading to a loss in both surface smoothness and transparency of the film. According to this study, the reaction with sodium thiourea occurs consistently through the sheets, and modified surface have antibacterial capacity. © 2013 AIP Publishing LLC.
DFT study of molecular geometries and vibrational characteristics of uracil and its thio-derivatives and their radical cations
(2010) R. Singh; S. Jaiswal; M. Kumar; P. Singh; G. Srivastav; R.A. Yadav
DFT calculations at the B3LYP/6-311++G** level have been carried out to study the vibrational characteristics of the neutral molecules, anionic and cationic radicals of uracil, 2-thiouracil and 4-thiouracil. In the U molecule, C{double bond, long}C bond loses its double bond character and magnitude of the C{double bond, long}C stretching frequency decreases significantly as a result of radicalization. Frequency for the in-plane deformation mode of C{double bond, long}O increases when a sulfur atom is substituted for the oxygen atom at the site C2 in the uracil molecule but decreases when a sulfur atom is substituted for the oxygen atom at the site C4. The magnitude of both the N-H stretching frequencies decreases in all the radical cations as compared to their neutral molecules. Radicalization leads to significant changes in the magnitudes and intensities corresponding to some of the normal modes for all the three cases. Removal of an electron leads to decrease in the electronic charge mainly from the sulfur atom in the case of 2-TU and 4-TU, whereas it is distributed over the sites N1, C5, O8 and O10 in case of the U molecule. © 2009 Elsevier B.V. All rights reserved.
Energetics and structural insights of molecular conductors using density functional theory methods: 1,3-dithiole-2-thione, 1,3-dithiole-2-one, 1,3-dioxole-2-one, and 1,3-dioxole-2-thione
(2009) R.L. Prasad; A. Kushwaha; Rajendra Prasad; S. Jaiswal; R.A. Yadav
Computations were carried out employing the restricted HartreeFock (RHF) and density functional theory (DFT) methods to investigate the geometries and energies for the 1,3-dithiole-2-thione (DTT), 1,3-dithiole-2-one (DTO), 1,3-dioxole-2-thione (DOT), and 1,3-dioxole-2-one (DOO) molecules and their radical cations. The geometrical parameters of all the four molecules suggest a finite extent of extended conjugation across the molecules. The radical cations of the DTT and DOT molecules exhibit increased extent of conjugation compared to their neutral analogues. However, on going from the neutral DOO and DTO molecules to their radical cations, the extent of conjugation across the ions decreases and two unsaturated sites become isolated from each other. Requirement of the relaxation energy for the formation of radical cation is much lower for the DTT and DOT molecules compared to that for the DOO and DTO molecules. Smaller relaxation energy requirement favors minimal resistance to charge transport along the molecular stacking. Therefore, it is speculated that the DTT and DOT molecules are better molecular conductors as compared to the DOO and DTO molecules. © 2009 World Scientific Publishing Company.
Manganese(II) catalyzed synthesis of bis(N-cyclohexylthiourea) derived from thiosemicarbazide: Structural characterization, fluorescence, cyclic voltammetry, Hirshfeld surface analysis and DFT calculation
(Elsevier B.V., 2021) S. Jaiswal; M.K. Gond; M.K. Bharty; B. Maiti; S. Krishnamoorthi; R.J. Butcher
A new compound bis(N-cyclohexylthiourea) (H2chth) has been synthesized and characterized with the aid of elemental analyses, IR, NMR and single crystal X-ray diffraction data. Compound H2chth crystallizes in triclinic system with space group P-1. During the course of reaction, the cyclohexyl isothiocynate moiety of the substituted thiosemicarbazide undergoes tautomerization and rearrangement into the corresponding carbothioamide moiety in the presence of manganese(II) acetate. The interaction of H2chth with different metal ions in methanol solution is studied and it shows interesting red shifts with Mn2+, Co2+, Ni2+, Cu2+, Zn2+ and Cd2+ ions which suggests that compound H2chth may be a useful probe for sensing of these metal ions. Cyclic voltammetric studies of H2chth and its interaction with different metal ions exhibit complete irreversible redox behavior. Compound H2chth exhibits emission at 27322 cm−1 upon excitation at 37037 cm−1. The emission spectra of different metal ions with H2chth exhibit less intense emissions as compared to the free H2chth. The structure of compound H2chth is stabilized via intermolecular N-H···S and C-H···S hydrogen bonding. The geometry of the compound H2chth has been optimized using the B3LYP density functional theory method and the results are compared with the X-ray diffraction data. The calculated geometrical parameters corroborate with the experimental data. Frontier molecular orbital analysis suggests that compound H2chth is soft and highly reactive. Hirshfeld surface map and 2D finger print plot were used to explore the intermolecular interactions of H2chth. © 2021 Elsevier B.V.
Occurrence of kornerupine-bearing granulite from Kunjan locality, Salem district, Tamil Nadu, India
(Indian Academy of Sciences, 2021) D. Prakash; C.K. Singh; R.S. Kumar; R. Yadav; S.K. Rai; M.K. Yadav; Pradip K. Singh; S. Jaiswal
Kornerupine, although a rare mineral, has been reported from several locations around the world in various types of aluminomagnesian Proterozoic rocks subjected to amphibolite and granulite facies metamorphism. Here we report the occurrence of kornerupine in qua-rtzo-feldspathic gneisses near Kunjan town located in the southwestern part of Salem district, Tamil Nadu, India. These kornerupine granulites show well-preserved retrogression texture, involving hydration reactions which helped develop the various mineral assemblages. The common stable assemblage in these granulites is orthopyroxene-cordierite-kornerupme-biotite-spinel-K-feldspar-plagioclase. The P-T conditions of these granulites have been derived using the winTWQ program, which gives results of ~800°C and ~6 kbar for kornerupine-bearing assemblage. The high P-T assemblage reported from this area bears a significant relationship with the metamorphic history and exhumation of the Salem-Namakkal block. © 2021. All Rights Reserved.
On the occurrence of Eragrostis trichodes (Poaceae: Chloridoideae) in India
(Indian Association for Angiosperm Taxonomy, 2024) S. Tiwari; D. Prasad; S. Jaiswal; P. Agnihotri
The present paper re-affirms the occurrence of Eragrostis trichodes (Nutt.) Alph.Wood in Indian grass flora based on the collection from Meghalaya state, India. A brief description, taxonomic notes, photoplates along with the distribution map have been provided for easy identification of the species. © 2024 Indian Association for Angiosperm Taxonomy. All rights reserved.
Planktic foraminiferal responses to orbital scale oceanographic changes off the western Iberian margin over the last 900kyr: Results from IODP site U1391
(Elsevier B.V., 2015) A.D. Singh; K. Verma; S. Jaiswal; M. Alonso-Garcia; B. Li; F. Abrantes
This paper presents planktic foraminiferal assemblage records of the last 900 kyr from the SW Iberian margin (IODP Site U1391). The faunal records show the history of surface oceanographic changes on glacial/interglacial scales before and after the Mid-Brunhes Event (MBE), a period when a major shift in the climate pattern was recorded in other regions. Temporal variations in relative abundances of characteristic species/groups are used to infer changes in the latitudinal position of the polar/Arctic water (% Neogloboquadrina pachyderma sinistral and Turborotalita quinqueloba), influence of the transitional subpolar water mass (% N. pachyderma dextral), and subtropical water (% tropical/subtropical species/group). Past changes in the upwelling intensity and productivity pattern associated with seasonal trade wind strength are inferred from the abundance variations of Globigerina bulloides and G. bulloides+. Globigerinita glutinata, respectively. Faunal data reveal the influence of cold water masses (polar/subpolar) at the examined site was more pronounced during glacial stages except for marine isotope stage (MIS) 14 and 16. The magnitude of the polar/subpolar water mass invading the study area was at maximum before the MBE during MIS 18, 20 and 22, resulting in a situation like the present day Arctic Front. Interglacial periods prior to the MBE were also relatively colder than those of the post-MBE. Our faunal based inferences are in agreement with the ice-rafted debris (IRD) concentration and N. pachyderma sinistral records of the subpolar North Atlantic sites. Based on faunal proxies, we recorded major and rapid changes in upwelling intensity and related productivity during glacial Terminations. Both the upwelling intensity and productivity significantly increased after the MBE, particularly during the interglacials MIS 7, 9 and 11. Our productivity record parallels the EPICA CH4 record suggesting teleconnections between trade winds induced productivity and the tropical climate through oceanic-atmospheric processes. © 2015 Elsevier B.V.
Structural and vibrational studies of molecular conductors using quantum mechanical methods: 1,3-Dithiole-2-thione, 1,3-dithiole-2-one, 1,3-dioxole-2-one and 1,3-dioxole-2-thione
(2009) S. Jaiswal; A. Kushwaha; R. Prasad; R.L. Prasad; R.A. Yadav
Computations were carried out by employing the RHF and density functional theory (DFT) methods to investigate the geometries, atomic charges, harmonic vibrational frequencies for the 1,3-dithiole-2-thione (DTT), 1,3-dithiole-2-one (DTO), 1,3-dioxole-2-thione (DOT) and 1,3-dioxole-2-one (DOO) molecules and their radical cations. The geometrical parameters and atomic charges on various atomic sites of the DTT and DOT molecules and their radical cations suggest extended conjugation in these systems. Contrary to this, for the DOO+ and DTO+ ions there is no evidence in favour of such conjugation, however, the neutral molecules exhibit some conjugation. Harmonic forced field and vibrational mode calculations provided convincing theoretical evidence for the reassignment of some fundamental vibrational modes for all the four molecules. In going from the neutral species to the charged ions for all the four cases the C{double bond, long}C stretching frequency is found to decrease drastically. The C{double bond, long}S stretching frequency reduces drastically for the DTT and DOT molecules as compared to their radical cations whereas the C{double bond, long}O stretching frequency is found to increase in going from the neutral molecule to its radical cation for the DOO and DTO molecules. The ring stretching mode with a1 symmetry and C{double bond, long}C and C{double bond, long}O/S stretching modes in these molecules appear to help in conversion of neutral molecule into respective radical cation and neighbouring radical cation into respective neutral molecule. Thus, there appears the feasibility of stretching vibrational mode coupling with electron transfer. © 2009 Elsevier B.V. All rights reserved.
Synthesis, structural characterization, DFT, fluorescence, and redox behaviour of 4-[5-(2-picolylsulfanyl)-1,3,4-oxadiazole-2-yl]-pyridine
(Elsevier B.V., 2022) S. Chandra; M.K. Gond; S. Jaiswal; M.K. Bharty; B. Maiti; D. Kushwaha; R.J. Butcher
The effective experimental content of this paper reports the synthesis of new 1,3,4-oxadiazole derivative 4-[5-(2-picolylsulfanyl)-1,3,4-oxadiazole-2-yl]-pyridine (pop) which was carried out in a cyclization reaction containing potassium N′-(pyridine-4-carbonyl)-hydrazinecarbodithioate in the presence of 2-picolyl chloride. The synthesized compound pop has been characterized by elemental analyses, UV–vis., Infrared, NMR, and X-ray diffraction data which crystallizes in a triclinic system having space group P-1. The dihedral angle formed between the pyridine ring and oxadiazole ring indicates that all the rings present in the compound are planar with each other. An electrochemical study shows that compound pop exhibits a reversible redox process assignable to a one-electron transfer reaction. The intermolecular C–H···N hydrogen bonding and π···π interactions provide stability to the structure of compound pop. The fingerprint plots associated with Hirshfeld surface analysis clearly shows that there are two types of weak interactions N···H–C and S···C through red spots. Fluorescence spectra of Co2+, Cr2+, Cu2+, Cd2+, Hg2+, and Zn2+ ions with pop exhibit better fluorescence whereas Mn2+ and Ni2+ ions are less fluorescent as compared to the free pop. To get a better understanding of Frontier molecular orbitals and intramolecular charge transfer property, theoretical calculations, such as density functional theory (DFT), were performed which indicates that compound pop is soft and highly reactive. © 2021