Showing papers by "Indian Association for the Cultivation of Science published in 1999"
TL;DR: In this article, a simple, efficient, and general method was developed for the synthesis of α-amino phosphonates through a one-pot reaction of aldehydes and ketones with amines in the presence of indium(III) chloride as a catalyst.
266 citations
TL;DR: The results indicate the smooth performance of the state-specific perturbative formalisms in and around the region of intruders in the PES, indicating their suitability in bypassing intruders.
Abstract: We explore in this paper the efficacy of the Rayleigh-Schrodinger (RS) and the Brillouin-Wigner (BW) perturbative counterparts of our recently developed multireference state-specific coupled-cluster formalism (SS-MRCC) with a complete active space (CAS). It is size-extensive and is designed to avoid intruders. The parent SS-MRCC method uses a sum-of-exponentials type of Ansatz for the wave operator. The redundancy inherent in such a choice is resolved by postulating suitable sufficiency conditions which at the same time ensure size-extensivity and size-consistency. The combining coefficients c μ for φμ's are completely relaxed and are obtained by diagonalizing an effective operator in the model space, one root of which is the target eigenvalue of our interest. By invokation of a suitable partitioning of the Hamiltonian, very convenient perturbative versions of the formalism in both the RS and the BW forms are developed for the second-order energy. The unperturbed Hamiltonian is akin to the Epstein-Nesbet type when at least one of the orbitals is inactive and is the entire active portion of the Hamiltonian when all the orbitals involved are active. Illustrative numerical applications are presented for potential energy surfaces (PES) of a number of model and realistic systems where intruders exist and for molecules in their ground states with pronounced multireference character. Single reference MBPT and effective Hamiltonian-based multireference MBPT second-order results are also presented for comparisons. The results indicate the smooth performance of our state-specific perturbative formalisms in and around the region of intruders in the PES, indicating their suitability in bypassing intruders. In contrast, the effective Hamiltonian-based MBPT methods behave poorly in the regions of intruders.
144 citations
01 Sep 1999
TL;DR: The results of studies on the interaction of binary mixtures of sodium deoxycholate and polyoxyethylene sorbitan monooleate in bulk and at the air/water interface obtained from conductance, surface tension, and fluorescence measurements are described.
Abstract: The results of studies on the interaction of binary mixtures of sodium deoxycholate (NaDC) and polyoxyethylene sorbitan monooleate (Tween 80) in bulk and at the air/water interface obtained from conductance, surface tension, and fluorescence measurements are described. The critical micelle concentration (CMC), thermodynamics of micellization, free energy of interfacial adsorption, minimum average area occupied by the surfactant species at the interface, micellar polarity, and aggregation number of the mixed aggregates have been determined. The mixed micellar composition and the estimation of the interacting forces involved are evaluated on the basis of recent theoretical models. The estimated interaction parameter indicates an overall attractive force in the mixed state, and the proportion of NaDC in the mixed micelle is found to be lower compared to the stoichiometric compositions. The mixed aggregates with higher mole fractions of NaDC show less stability in comparison with those having higher proportions of the nonionic component.
121 citations
TL;DR: In this article, the hydrodynamic diameter, diffusion coefficient, and the polydispersity index of the colloidal dispersions prepared in the absence and presence of gelatin at different ω have been determined by the dynamic light scattering method; the static light scatter method has been employed to estimate the average particle weight of the dispersion.
Abstract: Colloidal dispersions of Cu2[Fe (CN)6] have been prepared in the nanodomain water pools of water/AOT/n-heptane water-in-oil microemulsion at various [water]/[AOT] mole ratios, ω, by reacting CuSO4 with K4[Fe(CN)6]. The UV−visible absorption spectra of the isotropic molecular aggregates of Cu2[Fe(CN)6] surrounded by a layer of amphiphile AOT have been measured. The hydrodynamic diameter, diffusion coefficient, and the polydispersity index of the colloidal dispersions prepared in the absence and presence of gelatin at different ω have been determined by the dynamic light scattering method; the static light scattering method has been employed to estimate the average particle weight of the dispersion. The formation of Cu2[Fe(CN)6] in the dispersion has been established by X-ray diffraction measurements. The size and shape of the colloidal dispersions and the isolated particles have been examined by the transmission electron microscopy and scanning electron microscopy methods. The enthalpies of formation of Cu...
100 citations
TL;DR: In this article, the authors explore the Rayleigh-Schrodinger and Brillouin-Wigner perturbative counterparts of our recently developed state-specific coupled-cluster formalism with a complete active space.
94 citations
TL;DR: In this article, terminal alkynes reacted with acid chlorides in the presence of cuprous iodide as a catalyst in Et 3 N at room temperature yielding α,β-acetylenic ketones in good to excellent yields.
76 citations
TL;DR: In this article, the authors measured the electrical conductivity of HCl doped conducting polyaniline in the presence as well as in the absence of a magnetic field in the temperature range 1.8 K≤ T ≤ 300 K.
75 citations
TL;DR: In this article, the microhardness of Larginine hydrobromide monohydrate (LAHBr) has been investigated and the work hardening index n for the three planes is greater than 1.6 which indicates that LAHBr is a soft crystal.
Abstract: Vicker's microhardness study of (100), (010) and (001) faces of a non-linear optical crystal, L-arginine hydrobromide monohydrate (LAHBr)have been reported.(100) plane is found to be the weakest plane. It has been observed that the microhardness decreases with increasing load for the three crystal planes. The microhardness behaviour have been explained successfully with the help of the PSR model proposed by Li and Bradt. Work hardening index n for the three planes are found to be greater than 1.6 which indicates that LAHBr is a soft crystal.
74 citations
TL;DR: A dinuclear copper(II) complex, [Cu2(bhsNO2)2(H2O)2] was isolated by reacting Cu(O2CCH3)2·H 2O and 2-hydroxy-5-nitrobenzaldehyde benzoylhydrazone (H2bhs NO2) in methanol as mentioned in this paper.
72 citations
TL;DR: In the solid state, (ImH)[L(1)OV-(&mgr;-O)-VOL(2)] (2) provides an example of a divanadium(IV,V) compound with a syn angular [V(2)O(3)](3+) core structure that exhibits crystallographically imposed mirror symmetry due to static disorder.
Abstract: Reaction of [VIVOL1(Im)] (H2L1 = S-methyl-3-((2-hydroxyphenyl)methyl)dithiocarbazate) with [VVOL(OCH3)] allows isolation of (ImH)[L1OV-(μ-O)-VOL] complexes 2 (H2L = H2L2 = S-methyl-3-((5-bromo-2-hy...
67 citations
TL;DR: The WPVS provides a scale for PV performance measurements that has been established through round-robin calibration of a group of primary monocrystalline Si reference cells and is traceable to Systeme International (SI) units.
Abstract: This paper describes the World Photovoltaic Scale (WPVS) international reference cell calibration program. The WPVS provides a scale for PV performance measurements that has been established through round-robin calibration of a group of primary monocrystalline Si reference cells and is traceable to Systeme International (SI) units. Procedures for recalibration of the reference cell group have been devised, along with procedures for admittance and calibration of new reference cells. A reference cell package has been designed that meets the unique needs of the WPVS. It is hoped that the existing WPVS group will eventually be replaced with cells of the new design that have passed a comprehensive acceptance-test procedure. Copyright © 1999 John Wiley & Sons, Ltd.
TL;DR: The acid-base and redox chemistry of the binuclear complexes has been studied over the pH range 1-12 in acetonitrile-water (3:2) medium and the equilibrium constants of the species involving protonation and deprotonation of the benzimidazole NH protons and the metal oxidation states covering +2 and +3 have been evaluated by spectrophotometric and cyclic voltammetric measurements.
Abstract: A number of mixed-ligand mononuclear and binuclear ruthenium(II) complexes of composition [(bpy)2Ru(H3pzbzim)](ClO4)2·2H2O (1), [(phen)2Ru(H3pzbzim)](ClO4)2·3H2O (2), [(bpy)2Ru(H2pzbzim)Ru(bpy)2](ClO4)3·5H2O (3), [(phen)2Ru(H2pzbzim)Ru(phen)2](ClO4)3·4H2O (4), [(bpy)2Ru(H2pzbzim)Ru(phen)2](ClO4)3·4H2O (5), [(bpy)2Ru(pzbzim)Ru(bpy)2](ClO4)·3H2O (6), and [(phen)2Ru(pzbzim)Ru(phen)2](ClO4)·2H2O (7), where H3pzbzim = pyrazole-3,5-bis(benzimidazole), bpy = 2,2‘-bipyridine, and phen = 1,10-phenanthroline, have been prepared and characterized. Complexes 3−5 isolated as mixtures of diastereoisomers have been separated by fractional recrystallization. In the cases of 3 and 4, the meso (ΛΔ) and racemate (rac) (ΛΛ, ΔΔ) forms, and for 5, two enantiomeric pairs [(ΛΔ, ΔΛ) and (ΛΛ, ΔΔ)] have been obtained. These, as well as the meso and rac diastereoisomers of 6, have been characterized by 1H and 13C NMR spectroscopy. The crystal structure of the meso (ΛΔ) form of 3 (C57H53N14Cl3O17Ru2) has been determined, which crysta...
TL;DR: In this article, the ionic conductivity and relaxation in the lithium tellurite glasses with varying Li 2 O content have been investigated in the frequency range 10 Hz to 2 MHz and in the temperature range from 373 K to just below the glass transition temperature.
Abstract: The ionic conductivity and relaxation in the lithium tellurite glasses with varying Li 2 O content have been investigated in the frequency range 10 Hz to 2 MHz and in the temperature range from 373 K to just below the glass transition temperature. The composition dependences of the dc conductivity and the activation energy of these glasses have been compared with those of other glasses formed with traditional network formers such as B 2 O 3 , P 2 O 5 , and SiO 2 containing the same Li + ions as modifiers and explained in terms of composition dependent network structure of these glasses. The frequency-dependent electrical data have been analyzed in the framework of the conductivity and modulus formalisms. Both these formalisms have provided for qualitative similarities in the compositional variation of the relaxation times, interaction between the cations, and the dc conductivity. The finite frequency window has been suggested as the reason for the difference between the numerical values of the stretched exponent β obtained from the odulus formalism and the values of (1-n) obtained from the conductivity formalism.
TL;DR: The optical absorption in these films could be explained by the combined effects of phonon and inhomogeneity broadening along with optical loss due to light scattering at the nanocrystallites.
TL;DR: In this article, photophysical processes of merocyanine 540 (MC540) were studied using picosecond time-resolved emission spectroscopy, and the nonradiative rate of MC540 was shown to increase from 0.32 × 109 s-1 in dioxane to 8.73 × 109 S-1, i.e., nearly 27 times.
Abstract: Photophysical processes of merocyanine 540 (MC540) are studied using picosecond time-resolved emission spectroscopy. The nonradiative rate of MC540 increases from 0.32 × 109 s-1 in dioxane to 8.73 × 109 s-1 in water, i.e., nearly 27 times. This is attributed to the decrease in the barrier of photoisomerization with increase in polarity and the consequent increase in the rate of photoisomerization for MC540. The polarity-dependent isomerization is also shown to be the cause for the observed increase in emission intensity and lifetime of MC540 in aerosol-OT microemulsions and aqueous bovine serum albumin solutions.
TL;DR: In this article, the effects of the concentrations of the stabilizer, the initiator, the monomer, and the solvent composition on particle size have been explained on the basis of particle phase polymerization.
Abstract: Dispersion polymerization of acrylamide in tert-butyl alcohol (TBA)-water media (TBA ⩾ 50 vol %) using poly(vinyl methyl ether) (PVME) as the stabilizer and 2,2′-azobisisobutyronitrile (AIBN) as the initiator at 50°C has been studied. The conversion-time curve shows autoacceleration taking place from the very early stage of the reaction (measured from 4% conversion level). Molecular weight increases with conversion indicating that the gel effect is operative. This suggests that a major part (if not the whole) of the polymerization occurs in the particle phase. The effects of the concentrations of the stabilizer, the initiator, the monomer, and the solvent composition on particle size have been explained on the basis of particle phase polymerization. The feeding of the particles by the monomer presumably occurs through the solvent channels of the swollen particles. The swelling data of polyacrylamide films in various TBA-water mixtures are given. The similarity and differences between the AIBN and ammonium persulfate (APS) initiated systems (published earlier by us) have been discussed. In general, particles are more polydisperse and bigger in the former case than in the latter. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 493–499, 1999
TL;DR: The photophysical process of the laser dye 4-(dicyanomethylene)-2-methyl-6-(p -dimethylaminostyryl)-4H-pyran (DCM) is studied in aerosol-OT microemulsions in n -heptane using picosecond spectroscopy as discussed by the authors.
TL;DR: In this article, the structure and other physical properties of (100-x)MgO-V 2 O 5 glasses of different compositions are reported in different studies like X-ray diffractograms and oxygen molar volume.
Abstract: Structure and other physical properties of (100-x)MgO-xV 2 O 5 glasses of different compositions are reported in this paper. Different studies like X-ray diffractograms and oxygen molar volume show that homogeneous glasses are obtained in the composition domain x=60-90 mol%. It has been observed that the network structure for all glass compositions is built up of VO 4 polyhedra. The glass transition temperatures are observed to decrease with an increase in V 2 O 5 content in the compositions. An increase in the concentration of the reduced V 4+ ions with an increase in V 2 O 5 content is observed from the magnetic susceptibility studies.
TL;DR: The palladium-catalysed reactions of 2-iodobenzamides 1−5 with trimethylsilyl acetylene 6 led to 2-(2-trimethyl silyl)ethynyl benzamides 7−11 in excellent yields.
TL;DR: In this paper, the authors exemplified two novel aromatic ring amination reactions via metal mediation and provided a rationale with respect to site selection for the above amination reaction, based on relative labil...
TL;DR: In this article, it was found that FeCl 3 added to propionic acid reduces the tangential etch rate of (1 − 0 − 0) and (0 − 0 - 1) surfaces.
TL;DR: In this article, the reduction potentials of the coordinated ligand L1 have been used for the transformation of anionic tridentate N,N,N donor L2 to a pyridyl imide fragment.
TL;DR: In this paper, the Anderson-Stuart model was employed to explain the dc activation energy of tellurite glasses and the variation of the stretched exponential parameter with composition was explained in terms of cation-cation distance correlation.
Abstract: The electrical conductivity and conductivity relaxation of $x{\mathrm{Na}}_{2}\mathrm{O}\ensuremath{-}(100\ensuremath{-}x){\mathrm{TeO}}_{2}$ glasses have been investigated in the frequency range of 10 Hz--2 MHz and in the temperature range of 373--533 K and compared with the results of silicate and borate glasses. The Anderson-Stuart model was employed to explain the dc activation energy. The relaxation behavior of these glasses was analyzed in the light of the modulus formalism. The variation of the stretched exponential parameter with composition was explained in terms of cation-cation distance correlation. Furthermore, the structural model of tellurite glasses was employed to explain the composition dependence of the conductivity relaxation time.
TL;DR: In this article, the selective deprotection of t-butyldimethylsilyl ethers has been achieved under mild conditions using an aqueous solution of zinc tetrafluoroborate.
TL;DR: Agarose gel electrophoresis of DNA isolated from lymphocytes cultured under different conditions has shown that this lectin could induce apoptosis in activated T-lymphocytes, as also confirmed by flow cytometric studies.
TL;DR: In this paper, photoinduced electron transfer from N, N -dimethylaniline (DMA) to oxazine 1 (OX-1) is studied in micelles.
TL;DR: In this article, the reaction of KReO4 with L [2-(arylazo)-1-methylimidazole, with aryl=Ph (L1), C6H4Me-p(L2) or C6h4Cl-p (L3) in concentrated HCl afforded [ReVL(O)Cl3] 1.
Abstract: The reaction of KReO4 with L [2-(arylazo)-1-methylimidazole, with aryl = Ph (L1), C6H4Me-p(L2) or C6H4Cl-p(L3)] in concentrated HCl afforded [ReVL(O)Cl3] 1. Aromatic amines and PPh3 smoothly converted 1 into [ReVL(NR)Cl3] 2 and [ReIIIL(OPPh3)Cl3] 3 respectively. Treatment of 3 with PPh3 yielded [ReIIIL(PPh3)Cl3] 4. Complexes of type 3 and 4 display large paramagnetic shifts of 1H NMR lines which spread over ≈60 ppm. Structure determination of [ReL1(O)Cl3] 1a, [ReL2(NC6H4Me-p)Cl3] 2a, [ReL3(OPPh3)Cl3] 3c and [ReL3(PPh3)Cl3] 4c has revealed meridional geometry for all except 4c which is facial. In the latter Re–azo and Re–PPh3 back bonding is maximized. The metal atom is displaced away from the equatorial plane by ≈0.3 A towards the oxo ligand in 1a and the imido ligand in 2a. The imidazole nitrogen is co-ordinated trans to oxo, imido, Ph3PO and chloride ligands in 1a, 2a, 3c and 4c, respectively. The azo NN distance is lengthened by ≥0.05 A as a result of direct (3c, 4c) or indirect (1a, 2a) Re–azo back bonding. Azo reduction potential values are consistent with the low-lying nature of the azo(π*) orbital. The metal reduction potentials follow the trends: ReVI–ReV, 1 > 2 (imido better donor than oxo); ReIV–ReIII, 4 > 3 (stabilization of t2 by ReIII–PPh3 back bonding).
TL;DR: In this article, Pentadentate N4S ligands based on methyl 2-aminocyclopent-1-ene-1dithiocarboxylate with flexible pyrazolyl arms (Me2pzCH2)2NC2H3RNHC5H6CSSCH3 (R = H, Hmmecd and R = CH3, Hmmpcd) undergo a nickel(II)-induced alcoholysis reaction through the activation of a saturated C−N bond linkage.
Abstract: Pentadentate N4S ligands based on methyl 2-aminocyclopent-1-ene-1-dithiocarboxylate with flexible pyrazolyl arms (Me2pzCH2)2NC2H3RNHC5H6CSSCH3 (R = H, Hmmecd and R = CH3, Hmmpcd) undergo a nickel(II)-induced alcoholysis reaction through the activation of a saturated C−N bond linkage. The products obtained are square-planar complexes 1−4 containing a modified ligand structure possessing an N3S donor set and a pendant arm that holds the alkoxy group provided by the solvent. [Ni(N3S)-CH2OMe]ClO4 1 crystallizes in the triclinic space group P1 with a = 10.4886(5) A, b = 10.706(1) A, c = 11.487(1) A, α = 108.784(4)°, β = 108.887(6)°, γ = 95.139(6)°, V = 1128.0(4) A3, and Z = 2; while [Ni(N3S)‘-CH2 OPrn]ClO4 4 has the monoclinic space group P21/n with a = 8.875(2) A, b = 18.629(2) A, c = 15.399(2) A, β = 91.37(2)°, V = 2545(1) A3, and Z = 4 per unit cell. Complexes 1−4 with acyclic ligand environments have interesting electrochemical behavior in acetonitrile, involving a reversible Ni(II)/Ni(I) reduction, E1/2 ...
TL;DR: In this article, Raman excitation profiles of several normal vibrations of 2- and 4-benzylpyridine were measured and analyzed, and possible structures and other interesting properties of the two molecules in the excited electronic states were discussed.
Abstract: Raman excitation profiles of several normal vibrations of 2- and 4-benzylpyridine were measured and analyzed. On the basis of the results, possible structures and other interesting properties of the two molecules in the excited electronic states are discussed. Normal mode characteristics are also described. It seems likely that a singlet state, lying in the vacuum ultraviolet region with respect to the ground state, plays a significant role in the scattering phenomena. Copyright © 1999 John Wiley & Sons, Ltd.
TL;DR: In this article, a photoresponsive system was synthesized and recognition by the cavity of the cis-isomer of 1 of dicarboxylic acids of various chain lengths has been studied on irradiation at 310 nm.