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排序方式: 共有205条查询结果,搜索用时 31 毫秒
81.
Ramalingam M Jaccob M Swaminathan J Venuvanalingam P Sundaraganesan N 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,71(3):996-1002
The FTIR and FT-Raman spectra of morpholine-4-ylmethylthiourea (MMTU) were recorded in the region of mid-IR (400-4,000 cm(-1)). Initial geometry generated from the standard geometrical parameters was relaxed without any constraint on the potential energy surface at MP2 and DFT levels adopting the standard 6-31++G and 6-311+G basis set. With the help of two specific scaling procedures the computed harmonic frequencies have been compared with the observed vibrational wave numbers of FTIR and FT-Raman spectra and assigned to different normal modes of the molecule. Most of the vibrational modes have wave numbers in the expected range. The appropriate theoretical spectrograms of the IR spectra of MMTU have been also constructed. 相似文献
82.
Withanolides, the secondary metabolite from Withania species is used in Ayurvedic medicine and now proved to have potential use in treating cardiovascular, Alzheimer’s disease, etc. Its production in plants varies between genotypes with very low yield. For improved industrial commercialisation, there is a need to increase its production. Endophytic fungi are symbiotically associated with plants and can synthesise the same bioactive compounds and natural products as their host plant. There are no reports available on withanolide-producing (endophytic) fungi. The present study identified an endophytic fungus (Taleromyces pinophilus) from leaves of Withania somnifera which produces withanolides in the medium. The structure of withanolide was confirmed by 1H NMR, LC-MS analyses and quantified by HPLC analysis. The fungus produces high amount of withanolide when compared to leaf and root of W. somnifera. The fungus can be exploited to produce the withanolide to meet its demand. 相似文献
83.
An WJ Wang WN Ramalingam B Mukherjee S Daubayev B Gangopadhyay S Biswas P 《Langmuir : the ACS journal of surfaces and colloids》2012,28(19):7528-7534
Two novel deposition methods were used to synthesize Pt-TiO(2) composite photoelectrodes: a tilt-target room temperature sputtering method and aerosol-chemical vapor deposition (ACVD). Pt nanoparticles (NPs) were sequentially deposited by the tilt-target room temperature sputtering method onto the as-synthesized nanostructured columnar TiO(2) films by ACVD. By varying the sputtering time of Pt deposition, the size of deposited Pt NPs on the TiO(2) film could be precisely controlled. The as-synthesized composite photoelectrodes with different sizes of Pt NPs were characterized by various methods, such as SEM, EDS, TEM, XRD, and UV-vis. The photocurrent measurements revealed that the modification of the TiO(2) surface with Pt NPs improved the photoelectrochemical properties of electrodes. Performance of the Pt-TiO(2) composite photoelectrodes with sparsely deposited 1.15 nm Pt NPs was compared to the pristine TiO(2) photoelectrode with higher saturated photocurrents (7.92 mA/cm(2) to 9.49 mA/cm(2)), enhanced photoconversion efficiency (16.2% to 21.2%), and increased fill factor (0.66 to 0.70). For larger size Pt NPs of 3.45 nm, the composite photoelectrode produced a lower photocurrent and reduced conversion efficiency compared to the pristine TiO(2) electrode. However, the surface modification by Pt NPs helped the composite electrode maintain higher fill factor values. 相似文献
84.
Organic light‐emitting materials based on iridium(III) complexes bearing phenanthroimidazole ligands
Jayaraman Jayabharathi Ramalingam Sathishkumar Venugopal Thanikachalam 《Journal of Physical Organic Chemistry》2014,27(6):504-511
We present the elegant synthesis and the photophysical and electroluminescent properties of a series of cyclometalated iridium(III) complexes [Ir(PPI)2(pic), PPI: 1,2‐diphenyl‐1H‐phenanthro[9,10‐d]imidazole; pic: picolinic acid]. The Ir(PPI)2(pic) complexes showed characteristic phosphorescence with an emission range of 556–579 nm and a high quantum efficiency with microsecond lifetimes. The strongly allowed phosphorescence in these complexes is the result of significant spin–orbit coupling of the Ir center. All bis(PPI) derivatives exhibit intense triplet metal‐to‐ligand charge transfer (MLCT) photoluminescence in the fluid solutions at room temperature. The impact of different solvents, substituents on the phenanthroimidazole ligands and complex concentrations upon their emissive behavior have been examined and demonstrate that their emission energies can be systematically modified. Weak bands located at longer wavelength have been assigned to the 1MLCT ← S0 and 3MLCT ← S0 transitions of iridium complexes. Application of the 3MLCT excited state of the [Ir(PPI)2(pic)] materials in organic light‐emitting devices are described. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
85.
S. Ramalingam S. Periandy M. Govindarajan S. Mohan 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2010,75(5):1552-1558
In this work, the experimental and theoretical spectra of nicotinamide (C6H6N2O) are studied. FT-IR and FT-Raman spectra of title molecule in the liquid phase have been recorded in the region 4000–100 cm?1. The structural and spectroscopic data of the molecule in the ground state have been calculated by using Hartree–Fock and density functional method (B3LYP) with the 6-31+G*(d, p) and 6-31++G* (d, p)basis set. The vibrational frequencies have been calculated and scaled values have been compared with the experimental FT-IR and FT-Raman spectra. The observed and calculated frequencies are found in good agreement. The DFT-B3LYP/6-31++G (d, p) calculations have been found are more reliable than the ab initio HF/6-31+G (d, p) calculations for the vibrational study of nicotinamide. The optimized geometric parameters (bond lengths and bond angles) are compared with experimental values of the molecule. The alteration of vibrational bands due to the substitutions in the base molecule is also investigated from their characteristic region of linked spectrum. 相似文献
86.
S. Boobalan 《Journal of Physics and Chemistry of Solids》2010,71(11):1527-1533
In order to understand the structural behaviour of Cu(II) in a variety of ligand environments, single crystal electron paramagnetic resonance studies of Cu(II) doped in hexaaquazincdiaquabis(malonato)zincate [Zn(H2O)6][Zn(mal)2(H2O)2] are carried out at 300 K. Angular variation of copper hyperfine lines in three orthogonal planes shows the presence of single site, with spin Hamiltonian parameters as gxx=2.034, gyy=2.159, gzz=2.388, Axx=3.39 mT, Ayy=4.89 mT and Azz=13.72 mT. The g/A tensor direction cosines are compared with various Zn-O directions in the host lattice, which confirm that Cu(II) enters substitutionally in the lattice. The low value of Azz has been explained by considering admixture of d2x−2y ground state with d2z excited state. EPR powder spectra at 300 and 77 K give identical spin Hamiltonian parameters (g∥=2.367, g⊥=2.088, A∥=11.47 mT, A⊥=2.63 mT). IR, UV-vis and powder XRD data confirm the structure and symmetry of the Cu(II) ion in the host lattice. 相似文献
87.
Mulliken, NPA and ESP derived charge analyses have been carried out along the minimal energy reaction path using the IRC method for 1CHCl and 1CCl2 insertion into C–H bonds of methane and ethane. Transition states (TS) of these reactions have been investigated at HF, MP2, CCSD (for methane only) and DFT levels with 6-31g (d,p) basis set. G3MP2 calculations have significantly improved the energetics. The occurrence of TSs either in the electrophilic or nucleophilic phase has been identified through NBO charge analyses in addition to the net charge flow to the carbene. 相似文献
88.
S. Ramalingam 《合成通讯》2013,43(7):1299-1309
Yttria-zirconia–based Lewis acid efficiently catalyzes the three-component cyclocondensation reaction of aldehyde, β-keto ester, and urea or thiourea in refluxing acetonitrile to produce the corresponding dihydropyrimidones in high yields. 相似文献
89.
90.
Udayakumar V Periandy S Ramalingam S 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,79(5):920-927
The FT-IR and FT-Raman spectra of 1-bromo-4-chlorobenzene (1-Br-4-CB) have been recorded using Bruker IFS 66V spectrometer in the region of 4000-100 cm(-1). Ab-initio-HF (HF/6-311+G (d, p)) and DFT (B3LYP/6-31++G (d, p)/6-311++G (d, p)) calculations have been performed giving energies, optimized structures, harmonic vibrational frequencies, depolarization ratios, IR intensities, Raman activities. The vibrational frequencies are calculated and scaled values are compared with FT-IR and FT-Raman experimental values. Comparison of simulated spectra with the experimental spectra provides important information, the computational method have the ability to describe the vibrational methods. The frequency estimation analysis on HF and DFT is made. The impact of di-substituted halogens on the benzene molecule has also been discussed. 相似文献