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991.
Venkatesan V Sundararajan K Sankaran K Viswanathan KS 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2002,58(3):467-478
Conformations of dimethoxymethane (DMM) were studied using matrix isolation infrared spectroscopy. DMM was trapped in an argon matrix using an effusive source at 298, 388 and 430 K. Experiments were also done using a supersonic jet source to look for conformational cooling in the expansion process. As a result of these experiments, spectrally resolved infrared features of the ground and first higher energy conformer of DMM have been recorded, for the first time. The experimental studies were supported by ab initio computations performed at HF and B3LYP levels, using a 6-31++G** basis set. Computationally, four minima were identified corresponding to conformers with GG, TG, G+G- and TT structures. The computed frequencies at the B3LYP level were found to compare well with the experimental matrix isolation frequencies, leading to a definitive assignment of the infrared features of DMM, for the GG and TG conformers. At the B3LYP/6-31++G** level, the energy difference between the GG and TG conformers was computed to be 2.30 kcal mol(-1). The barrier for conformation interconversion, TG-->GG level was calculated to be 0.95 kcal mol(-1). This value is consistent with the experimental observation that the spectral features due to the TG conformer disappeared in the matrix on annealing. 相似文献
992.
A quinolone quinone methide (; R=Me), prepared from 1,3-dimethyl-4- hydroxy-2-quinolone () and DDQ, reacted readily with -methylflindersine () to give a single cyclo-addition product (). 相似文献
993.
Synthesis of piperazine-aniline copolymer has been studied by using various acids. The copolymer was characterized by spectral and physical techniques such as UV-Visible, FT-IR, fluorescence, viscosity, density and SEM studies. Conductivity of the copolymer was tested with various counter ions. The copolymer was found to have significant conductivity in the region of semiconductors. Morphological study reveals that the neutral copolymer forms into spongy and porous structure. Conductivity, density and viscosity are very much influenced by the nature of counter ions. 相似文献
994.
P. Giridhar K. A. Venkatesan T. G. Srinivasan P. R. Vasudeva Rao 《Journal of Radioanalytical and Nuclear Chemistry》2005,265(1):31-38
Summary A systematic study on the extraction of U(VI) from nitric acid medium by tri-n-butylphosphate (TBP) dissolved in a non-traditional diluent namely 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6) ionic liquid (IL) is reported. The results are compared with those obtained using TBP/n-dodecane (DD). The distribution ratio for the extraction of U(VI) from nitric acid by 1.1M TBP/bmimPF6 increases with increasing nitric acid concentration. The U(VI) distribution ratios are comparable in the nitric acid concentration range of 0.01M to 4M, to the ratios measured using 1.1M TBP/DD. In contrast to the extraction behavior of TBP/DD, the D values continued to increase with the increase in the concentration of nitric acid above 4.0M. The stoichiometry of uranyl solvate extracted by 1.1M TBP/IL is similar to that of TBP/DD system, wherein two molecules of TBP are associated with one molecule of uranyl nitrate in the organic phase. Ionic liquid alone also extracts uranium from nitric acid, albeit to a small extent. The exothermic enthalpy accompanying the extraction of U(VI) in TBP/bmimPF6 decreases with increasing nitric acid and with TBP concentrations. 相似文献
995.
Kheradmandan S Venkatesan K Blacque O Schmalle HW Berke H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(19):4872-4885
The dinuclear mixed-valent complex [(MeC5H4)(dmpe)MnC(2)Mn(dmpe)(C5H4Me)](+)[(eta2-MeC5H4)3Mn](-)[1](+)[2]- (dmpe=1,2-bis(dimethylphosphanyl)ethane) was prepared by the reaction of [Mn(MeC5H4)2] with dmpe and Me(3)SnC[triple chemical bond]CSnMe3. The reactions of [1](+)[2]- with K[PF6] and Na[BPh4] yielded the corresponding anion metathesis products [(MeC5H4)(dmpe)MnC2Mn(dmpe)(C5H4Me)][PF6] ([1][PF6]) and [(MeC5H4)(dmpe)MnC2Mn(dmpe)(C5H4Me)][BPh4] ([1][BPh4]). These mixed-valent species can be reduced to the neutral form by reaction with Na/Hg. The obtained complex [(MeC5H4)(dmpe)MnC2Mn(dmpe)(C5H4Me)] (1) displays a triplet/singlet spin equilibrium in solution and in the solid state, which was additionally studied by DFT calculations. The diamagnetic dicationic species [(MeC5H4)(dmpe)MnC2Mn(dmpe)(C5H4Me)][PF6]2 ([1][PF6]2) was obtained by oxidizing the mixed-valent complex [1][PF6] with one equivalent of [Fe(C5H5)2][PF6]. Both redox processes are fully reversible. The dinuclear compounds were characterized by NMR, IR, UV-visible, and Raman spectroscopy, cyclic voltammetry, and magnetic susceptibility measurements. X-ray diffraction studies were performed on [1][2], [1][PF6], [1][BPh4], and [1][PF6]2. 相似文献
996.
Velavan K Venkatesan R Sambasiva Rao P 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,62(1-3):153-156
The electron paramagnetic resonance spectroscopic investigation of VO(II)-doped zinc ammonium trihydrogen bis(orthophosphate) monohydrate single crystal has been carried out at 300K. The single crystal, rotated along the three orthogonally crystallographic axes, have yielded spin Hamiltonian parameters g and A as: g(xx)=1.978, g(yy)=1.974, g(zz)=1.925 and A(xx)=7.4, A(yy)=7.8, A(zz)=19.4 mT. These spin Hamiltonian parameters reflect a slight deviation from axially symmetry to rhombic, which is elucidated by the interstitial occupation of the vanadyl ion. The isofrequency plots and EPR spectra at few orientations have been simulated using the calculated spin Hamiltonian parameters. The Fermi contact parameter (kappa) and dipolar interaction parameter (P) have been calculated as 0.857 and -128 x 10(-4)cm(-1), respectively. The percentage of metaloxygen bond has been identified as 20%. 相似文献
997.
Our preliminary results are reported in the investigation of the tyrosine phosphorylation cascade triggered by the stimulation of the insulin receptor in the adipocyte cell line 3T3-L1 using a mini two-dimensional gel electrophoresis approach. The minigel format, 8 x 10 cm, was found sufficiently resolving and reproducible to study complex biological samples while considerably increasing throughput and lowering costs compared to larger gel formats. Consequently, we used the minigel format to rapidly screen a large number of samples, of which only the most relevant were then analyzed by optimized, preparative two-dimensional gels. The accurate localization and relative quantification of tyrosine-phosphorylated proteins was performed using a nonradioactive triple labeling method. After transfer onto polyvinylidene difluoride (PVDF) membranes, proteins were stained with Sypro Ruby to verify the separation quality and to localize the general region of interest for immunostaining. The membranes were subsequently blocked with polyvinylpyrrolidone-40 and probed with the relevant antibodies for visualization of the phosphorylated proteins by chemiluminescence. Finally, membranes were stained with colloidal gold to obtain a pattern reminiscent of the silver staining of a polyacrylamide gel. We believe that the presented strategy can be generalized for any gel application in which a protein has to be detected and identified based on its immunoreactivity. 相似文献
998.
Brian T. Sterenberg Ravindranath Ramachandran Richard J. Puddephatt 《Journal of Cluster Science》2001,12(1):49-59
The tetranuclear platinum cluster complexes [Pt4(-CO)3(-dppm)3(PPh3)]2+ and [Pt4(-H)(-CO)2(-dppm)3(PPh3)]+ have been prepared by cluster expansion. They have butterfly structures and are fluxional. 相似文献
999.
Ramachandran PV Madhi S Bland-Berry L Ram Reddy MV O'Donnell MJ 《Journal of the American Chemical Society》2005,127(39):13450-13451
A new, general, and practical procedure for the asymmetric synthesis of 4-alkylidenyl glutamic acid derivatives via a catalytic enantioselective tandem conjugate addition-elimination on allylic acetates under chiral phase-transfer conditions is reported. A variety of structural types of allylic acetates have been reacted with the benzophenone imine of glycine tert-butyl ester to give the products in good to excellent yields and enantioselectivities (63-92% yield, 80-97% ee, 8 cases). 相似文献
1000.
A study has been made of the structural and thermal phase behavior of the mixed system αFe2O3xLi2O with a view toward investigating the changes occurring in the properties of different compositions due to substitution of diamagnetic Li+ for Fe3+ at B sites in the inverse spinel lattice. This also indicates whether the addition of Li2O, over and above that (x = 0.2) required for the formation of the spinel LiFe5O8, enters the substitutional or interstitial sites. Characterization by X-ray powder diffraction, initial magnetic susceptibility, magnetic hysteresis, Mössbauer spectroscopy, and differential thermal analysis clearly indicates that Li+ does not enter the spinel lattice, but forms a biphasic system LiFe5O8 and LiFeO2, which are not miscible. 相似文献