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排序方式: 共有138条查询结果,搜索用时 16 毫秒
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Sharma A Reva I Fausto R Hesse S Xue Z Suhm MA Nayak SK Sathishkumar R Pal R Row TN 《Journal of the American Chemical Society》2011,133(50):20194-20207
Aggregation in hydroxyacetone (HA) is studied using low-temperature FTIR, supersonic jet expansion, and X-ray crystallographic (in situ cryocrystallization) techniques. Along with quantum chemical methods (MP2 and DFT), the experiments unravel the conformational preferences of HA upon aggregation to dimers and oligomers. The O-H···O═C intramolecular hydrogen bond present in the gas-phase monomer partially opens upon aggregation in supersonic expansions, giving rise to intermolecular cooperatively enhanced O-H···O-H hydrogen bonds in competition with isolated O-H···O═C hydrogen bonds. On the other hand, low-temperature IR studies on the neat solid and X-ray crystallographic data reveal that HA undergoes profound conformational changes upon crystallization, with the HOCC dihedral angle changing from ~0° in the gas phase to ~180° in the crystalline phase, hence giving rise to a completely new conformation. These conclusions are supported by theoretical calculations performed on the geometry derived from the crystalline phase. 相似文献
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Madhusmita Behera Subramanian Raju Ganapathy Panneerselvam Mythili Rangachari Saroja Saibaba 《Journal of Physics and Chemistry of Solids》2014
The enthalpy increment for a series of Ti–xTa (x=5, 10, 15, 20 mass%) alloys, having α(hcp)+β(bcc) two phase microstructure has been measured using inverse drop calorimetry in the temperature range 463–1257 K. The studies clearly revealed the occurrence of α→β diffusional phase transformation. Both the α→β transformation onset temperatures and the measured transformation enthalpy Δ0Htrα→β exhibit progressively lower values with increasing Ta content. It is found that the measured enthalpy in the transformation region is constituted of two principal contributions namely, (i) the enthalpy due to untransformed α and coexisting β phases and (ii) the transformation enthalpy due to α→β phase change. Since the fractional extent of α→β transformation varies continuously with temperature, the measured enthalpy variation in the transformation domain has been modeled using Kolmogorov–Johnson–Mehl–Avrami formalism for the diffusional transformation kinetics. The thermodynamic quantities for all the alloys have been derived. 相似文献
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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
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Kaliyamoorthy Panneerselvam Tian‐Huey Lu Ta‐Yung Chi Shu‐Fang Tung Chung‐Sun Chung 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(3):301-302
The crystal structure of the title complex, [Cu(C12H28N4)(H2O)2]Cl2·2H2O, has been determined. The CuII atom is octahedrally coordinated by the four N atoms of the tetradentate macrocyclic ligand in equatorial positions and by the O atoms of two water molecules in axial positions. The crystal structure is stabilized by a three‐dimensional network of hydrogen bonds. 相似文献
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Kaliyamoorthy Panneerselvam Tian‐Huey Lu Ta‐Yung Chi Shu‐Fang Tung Chung‐Sun Chung 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(6):659-660
In the title compound, [Co(C18H37N4O3)](ClO4)Cl·H2O, the CoIII ion has a distorted octahedral geometry, with four N atoms and two O atoms constituting the coordination sphere. The crystal structure is stabilized by a three‐dimensional network of hydrogen bonds. 相似文献