• Dinesh

      Articles written in Journal of Chemical Sciences

    • Study of some metallic silicates as ion-exchangers

      Dinesh B Bhushan

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      The extraction of ammine complexes of Cu2+, Cd2+, Ni2+, Co2+ and Zn2+ by synthesised manganese, nickel and zinc silicates has been studied at different pH and ionic concentrations in the external solution. It has been found that the uptake of the metal ion Co2+, Cu2+ and Zn2+ increases with increase in pH of the external solution, attains a maximum and then decreases. However, the uptake for Cd2+ and Ni2+ increases continuously. The qA values of all the silicates increases with the increase in the concentration of the exchanging ion and its order for the investigated metal ions is Ni2+ < Co2+ < Cd2+ < Zn2+ < Cu2+.

    • Gallium nitride nanoparticles for solar-blind detectors

      Dinesh Kabra Kripasindhu Sardar K S Narayan

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      We investigate the properties of GaN semiconducting nanoparticles as a potential candidate for photodetection in the solar-blind region. The photocurrent spectral response is studied spanning the range 1.6-5.5 eV. A significant fraction of the response is in the range 4–5.5 eV. The results are compared to other optical properties and the origins of the features observed in the spectra are speculated upon.

    • A microspectroscopic study of the electronic homogeneity of ordered and disordered Sr2FeMoO6

      Dinesh Topwal U Manju Sugata Ray S Raj D D Sarma S R Krishnakumar M Bertolo S La Rosa G Cautero

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      Disordered Sr2FeMoO6 shows a drastic reduction in saturation magnetization compared to highly ordered samples, moreover magnetization as a function of the temperature for different disordered samples shows qualitatively different behaviours. We investigate the origin of such diversity by performing spatially resolved photoemission spectroscopy on various disordered samples. Our results establish that extensive electronic inhomogeneity, arising most probably from an underlying chemical inhomogeneity in disordered samples, is responsible for the observed magnetic inhomogeneity. It is further pointed out that these inhomogeneities are connected with composition fluctuations of the type Sr2Fe1+xMo1-xO6 with Fe-rich (x > 0) and Mo-rich (x < 0) regions.

    • Synthesis, magnetic and spectral studies on polystyrene-anchored coordination complexes of bi-, tri-, tetra- and hexavalent metal ions with unsymmetrical dibasic tetradentate ONNO donor Schiff base derived from 3-formylsalicylic acid, ethylenediamine and 2-benzoylacetanilide

      Dinesh Kumar Arun Syamal Jaipal Lalit Kumar Sharma

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      Polystyrene-anchored Cu(II), Zn(II), Cd(II), Ni(II), Mn(II), MoO2(II), UO2(II), Fe(III) and Zr(IV), complexes of the unsymmetrical dibasic tetradentate ONNO donor Schiff base derived from the condensation of chloromethylated polystyrene, 3-formylsalicylic acid, ethylenediamine and 2-benzoylacetanilide (PS-LH2) has been synthesized. The polystyrene anchored complexes have the formulae: PS-LM (where M = Cu, Zn, Cd, Ni, MoO2, UO2), PS-LFeCl.DMF, PS-LMn$.2$DMF and PS-LZr(OH)$_2.$DMF. The polystyrene-anchored coordination compounds have been characterized by elemental analysis, IR, reflectance, ESR and magnetic susceptibility measurements. The per cent reaction conversion of polystyrene anchored Schiff base to polystyrene supported coordination compounds lies between 28.98 and 85.9. The coordinated dimethylformamide is completely lost on heating the complexes. The shifts of the ν(C=N)(azomethine) and ν(C-O)(phenolic) stretches have been monitored in order to find out the donor sites of the ligands. The Cu(II) complex is paramagnetic with square planar structure; the Ni(II) complex is diamagnetic with square planar structure; the Zn(II) and Cd(II) complexes are diamagnetic and have tetrahedral structure; the Mn(II) and Fe(III) complexes are paramagnetic and have octahedral structure; the MoO2(II) and UO2(II) complexes are diamagnetic and have octahedral structure and the Zr(IV) complexes are diamagnetic and have pentagonal bipyramidal structure.

    • Generation of serine/threonine check points in HN(C)N spectra

      Dinesh Kumar Jeetender Chugh Ramakrishna V Hosur

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      We describe here a simple modification of the HN(C)N experiment for the generation of serine/threonine check points in the three-dimensional experiment. The various `triplet of residue’ specific peak patterns in the spectra are documented for ease of analysis and sequential backbone resonance assignment. The performance of this experiment, referred to as HN(C)N-ST, is demonstrated using two proteins, one properly folded and the other completely denatured. It is noteworthy that, even in the denatured protein, where spectral dispersions are rather poor, about 90% of the sequential connectivities through the chain could be established from this single experiment. This would have great implications for structural genomics efforts.

    • Crystallization of organically templated phosphomolybdate cluster-based solids from aqueous solution

      Minakshi Asnani Dinesh Kumar T Duraisamy Arunachalam Ramanan

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      The paper reports the synthesis and structural characterization of several organic-inorganic solids involving phosphomolybdate clusters. The Strandberg-type {P2Mo$^{\text{VI}}_5$O23} and the lower-valent {P4Mo$^V_6$O31} cluster based solids were isolated in the presence of $en$ (ethylenediamine) by controlling pH of the reaction medium. The lower-valent cluster invariably requires the presence of a suitable metal cation for further stabilization. A detailed investigation of the system was carried out where three different weak acids viz. oxalic acid, succinic acid and glycine were used in the entire pH range (1-12). Our results establish that the organic amine ($en$) is alone capable of reducing the molybdenum core in the absence of an organic acid at a suitable pH. Hence, pH of the reaction medium combined with suitable temperature favours the formation of lower-valent phosphomolybdate cluster. Higher pH favours the precipitation of a new sodium hydrogen phosphate.

    • Antileishmanial polyphenols from Corymbia maculata

      Jasmeen Sidana Dinesh Neeradi Alka Choudhary Sushma Singh William J Foley Inder Pal Singh

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      An activity-guided fractionation was used to identify the antileishmanial compounds of Corymbia maculata. The hexane, ethyl acetate and methanol extracts were active in in vitro antileishmanial assay. Twelve polyphenols including 8-demethyl eucalyptin (1), eucalyptin (2), myrciaphenone A (3), myrciaphenone B (4), quercetin-3-𝑂-𝛽-D-xylopyranoside (5), myricetin-3-𝑂-𝛼-L-rhamnopyranoside (6), quercetin-3-𝑂-𝛽-D-galactopyranoside (7), quercetin-3-𝑂-𝛽-D-glucopyranoside (8), quercetin-3-𝑂-𝛼-L-rhamnopyranoside (9), syringic acid (10), gallic acid-3-methyl ether (11), gallic acid-4-methyl ether (12) and gallic acid (13) were isolated from the active extracts. All the tested compounds except 8-demethyleucalyptin and myrciaphenone B showed strong to moderate (6.9-24.5 𝜇M) antileishmanial activity against Leishmania donovani promastigotes. An HPLC-PDA method has been developed to detect/quantify 29 compounds in the extracts of C. maculata leaves. This validated method allows simultaneous quantitation of seven flavonoids, fourteen phloroglucinols and eight other polyphenols and can be applied for qualitative as well as quantitative determination of phytoconstituents in Eucalyptus matrices.

    • Resolution of the Identity and Cholesky Representation of EOM-MP2 Approximation: Implementation, Accuracy and Efficiency


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      We present a Resolution of Identity and Cholesky Decomposition Based Implementation of EOMMP2 approximation. The RI and CD based EOM-MP2 shows significant speed-up and less storage requirement than the conventional canonical version and can be applied to very large systems. The newalgorithm used for this implementation eliminates the most storage requiring four-index quantities resulting in the decrease of storage requirement, reduction in I/O penalties and improved parallel performance, at the expense of more floating point operations. Therefore, the speed-up compared to conventional EOM-MP2 method is more prominent in case of EA, EE and SF case where the storage bottleneck is significant than the EOM-IP-MP2 method, where thestorage requirement is significantly less. However, the RI/CD based EOM-IP-MP2 can be coupled with frozen natural orbitals to gain further speed-up.

    • Lowest order perturbative approximation to vibrational coupled cluster method in bosonic representation


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      We propose a perturbative approximation to the vibrational coupled cluster method in bosonic representation to reduce the cost of calculating the cluster matrix elements by considering only the first order of S and r for the construction of the effective Hamiltonian ese-SHeSes. With the systematic analysis of theresults of two molecules, H2O and 1,1-difluoroethylene, we find that the accuracy of the transition energies with such low order approximation is comparable to the fully converged VCCM

    • An equation of motion approach for the vibrational transition energies in the effective harmonic oscillator formalism: the Random phase approximation


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      A theory for calculating vibrational energy levels and infrared intensities is developed in the equation of motion framework at the random phase approximation level. The vibrational Hamiltonian is expanded in the harmonic oscillator ladder operators making a Hamiltonian a bosonic Hamiltonian. Theexcitation operator is expanded to include at most two creations and two annihilation operators making it equivalent to the random phase approximation. The method is applied for the calculation of vibrational spectral properties of two molecules. The results are found to be satisfactory, making this approach a viable option for large molecular systems.

    • Triethylenetetramine complexes of cobalt(III) having anion binding sites: synthesis, characterisation, crystal structure, anti-bacterial and anti-cancer properties of [Co(trien)(NO2)2]2Cr2O7 and [Co(trien)(NO2)2]SCN


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      Crystals of cobalt(III) salts dinitro(triethylenetetramine)cobalt(III) dichromate [Co(trien)(NO2)2]2Cr2O7 (1) and dinitro(triethylenetetramine)cobalt(III) thiocyanate [Co(trien)(NO2)2]SCN (2) have been synthesized to investigate [Co(trien)(NO2)2]+ cation as a promising host to capture dichromate and thiocyanate anions. The characterization of the newly synthesized compounds was accomplished by elemental analysis and spectroscopic techniques (IR, UV/visible and 1H-NMR) and solubility product measurement. The asymmetric unit of complex 1 has a half dichromate anion and one [Co(trien)(NO2)2]+ cation while that of complex 2 has one thiocyanate anion and one [Co(trien)(NO2)2]+ cation as divulged by X-ray structure determination. The structural investigation exhibited that the crystal lattice was stabilized by second sphere hydrogen bonding interactions such as N–Htrien...O (dichromate), C–Htrien...O (dichromate), N–Htrien...N (thiocyanate) and C–Htrien...N (thiocyanate) interactions resulting in the formation of supramolecular assemblies. The complexes 1 and 2 were further examined for antibacterial activity and the findings unveiled moderate activity against gram-negative bacteria such as Escherichia coli and Pseudomonas aeruginosa species. These complexes were also scrutinized for anti-proliferative activity against malignant PANC-1 cells using MTT cell survival analysis. Complex 1 exhibited remarkable anticancer activity whereas complex 2 has comparatively lesser anticancer potential

      Crystals of cobalt(III) ion [Co(trien)(NO2)2].X (X= ½.Cr2O7 (1)/ SCN (2)) have been synthesized and characterized by various spectroscopic and analytical techniques. Structural study of 1 and 2 were established and divulge formation of supramolecular assemblies through H-bonding. Complex 1 and 2 were further examined for antibacterial and antiproliferative activity. Complex 1 exhibited remarkable anticancer activity whereas complex 2 has comparatively lesser anticancer potential

    • Developing a highly potent anthelmintic: study of catalytic application of L-proline derived aminothiourea in rapid synthesis of biscoumarins and their in vitro anthelmintic essay


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      Due to serious side effects of benzimidazoles such as apoptosis and mitotic arrest, development of alternative anthelmintic drugs with comparable efficacy to target the acetylcholine receptors of parasites is considered very important to control this parasitic disease. Here we have developed an excellent method for synthesis of biscoumarins by employing a mild and efficient proline derived bifunctional thiourea catalyst bearing pyrrolidine and thiourea catalytic sites and tested their anthelmintic activity against helminth parasites Raillietina echinobothrida and Syphacia obvelata. The compounds 2a, 2j, 2k and 2o demonstrated much stronger anthelmintic activity against Raillietina echinobothrida in comparison to the standard drug, Praziquantel. Molecular docking simulations of the optimized compounds with b-tubulin showed excellent binding interactions with several amino acid residues of the active site and the docking scores with b-tubulin were found to be comparable to the in vitro anthelmintic activity.

      A series of biscoumarins were synthesized and they showed excellent anthelmintic properties in comparison to conventional benzimidazoles.

    • Structural and electrical properties of M-doped TiO2 (M = Ni, Cu, Zn) relevant to their application as electrolytes for solid oxide fuel cells


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      Low-cost semiconductors have emerged as potential electrolyte materials for intermediate temperature solid oxide fuel cells (IT-SOFC). The present work describes the synthesis and characterizationof Ti0.95M0.05O2-δ (M = Ni, Cu, Zn) followed by the determination of ionic conductivity using a.c. impedance technique. The formation of the solid solution was confirmed by XRD, Raman, FTIR, DR-UV–Vis, PL, BET,FE-SEM, and EDX. The obtained ionic conductivities (in S cm-1) for TiO2 (1.92 9 10-5), Ti0.95Ni0.05O2-δ(2.78 9 10-5), Ti0.95Zn0.05O2-δ (2.16 9 10-5) at 973 K and for Ti0.95Cu0.05O2-δ (2.39 9 10-3) at 1023 K are comparable to commercially available YSZ operating at high temperature and doped ceria electrolytes. The ionic conductivities were found to increase linearly in the temperature range of 673–1023 K. The lower activation energy of 1.08, 1.41, and 1.17 eV was obtained for TiO2, Ti0.95Ni0.05O2-δ, and Ti0.95Zn0.05O2-δ,respectively. Thus, low-cost Ni, Cu, Zn-doped TiO2 solid solutions may be regarded as plausible electrolyte materials for SOFCs.

      Structural and electrical properties of Ti0.95M0.05O2−δ (M = Ni, Cu, Zn) are reported for their plausible applications as SOFC electrolytes. Lower Ea of 1.08, 1.41, and 1.17 eV are obtained for TiO2, Ni-TiO2 and Zn-TiO2, samples respectively. The Cu-TiO2 showed comparable oxide ion conductivity with other potential electrolyte materials.

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