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101.
The reaction of [Cp*MoCl(4)] with an excess of LiBH(4), followed by thermolysis with tellurium powder in toluene, afforded a tricapped cubane cluster, [(Cp*Mo)(4)B(4)H(4)(μ(4)-BH)(3)] (1), which represents an unprecedented metal-rich metallaborane cluster with a cubane core containing 58 cluster valence electrons (cve) and three metal-metal bonds. 相似文献
102.
Hratchian HP Krukau AV Parandekar PV Frisch MJ Raghavachari K 《The Journal of chemical physics》2011,135(1):014105
Accurate calculations of large systems remain a challenge in electronic structure theory. Hybrid energy techniques are a promising family of methods for treating such systems. Expanding on previous developments, we present a QM:QM electronic embedding model whereby the high-level region is polarized by the electron density of the low-level region within an ONIOM framework. A direct Coulomb embedding model as well a more computationally efficient model involving a density fitting expansion are considered. We also develop a generalized theory for the first derivatives of these classes of QM:QM electronic embedding schemes, which requires solution of a single set of self-consistent field response equations. Two initial test cases are presented and discussed. 相似文献
103.
The structural and dynamical correlations, and the equation of state of crystalline I(2)O(4), I(2)O(5), and I(2)O(6) are investigated by first-principles calculations based on the density functional theory (DFT). The lattice dynamics results reveal distinctive features in the phonon density of states among the three crystals. The frequencies of the stretch modes in I(2)O(4) and I(2)O(5) are clearly separated from those of the other (e.g., bending) modes by a gap, with all stretch modes above the gap. In contrast, the gap in I(2)O(6) separates the highest-frequency stretch modes with other stretch modes, and there is no gap between the stretch and the other modes in I(2)O(6). The motion of iodine atoms is involved in all vibrational modes in I(2)O(5), but only in low-frequency lattice modes in I(2)O(6). In I(2)O(4), iodine atoms are involved in modes with frequency below 700 cm(-1). Van der Waals correction within our DFT calculations is found to reduce the overestimation of the equilibrium volume, with its effect on structure similar to the pressure effect. Namely, both effects significantly decrease the inter-molecular distances, while slightly increasing the bond lengths within the molecules. This causes the frequencies of some vibrational modes to decrease with pressure, resulting in negative "modes Gru?neisen parameters" for those modes. Thermodynamic properties, derived from the equation of state, of crystalline I(2)O(4), I(2)O(5), and I(2)O(6) are discussed within the quasi-harmonic approximation. 相似文献
104.
Kumar KS Kumar PM Kumar KA Sreenivasulu M Jafar AA Rambabu D Krishna GR Reddy CM Kapavarapu R Shivakumar K Priya KK Parsa KV Pal M 《Chemical communications (Cambridge, England)》2011,47(17):5010-5012
Concurrent construction of five and six membered fused N-heretocyclic ring was achieved via a conceptually new three-component reaction affording 6,6a-dihydroisoindolo[2,1-a]quinazoline-5,11-diones as novel inhibitors of TNF-αin vitro. This represents one of the few examples of direct TNF-α inhibition by small molecules. 相似文献
105.
106.
Loumaigne M Vasanthakumar P Richard A Débarre A 《Physical chemistry chemical physics : PCCP》2011,13(24):11597-11605
The Brownian rotation of a nearly spherical gold particle capped with ligands can be observed in the correlation profile of the intensity of the two-photon excited luminescence. Here we report on a multi-parameter study of the luminescence properties, including spectral and polarization analysis of the signal at the single particle level. First, the data confirm the role of the radiative de-excitation of the surface plasmons in the luminescence process. Secondly, the results obtained at low power indicate that the capped particle in water can be approximatively described as a spherical rotor acting in the far-field as a point-like absorption and emission dipole of fixed directions. In addition, we show that the dynamics of the ligands, induced by the heat transfer from the particle to its environment, can be partly controlled by the choice of excitation wavelength. 相似文献
107.
Thakur TS Kirchner MT Bläser D Boese R Desiraju GR 《Physical chemistry chemical physics : PCCP》2011,13(31):14076-14091
Structural and electronic properties of C-H···O contacts in compounds containing a formyl group are investigated from the perspective of both hydrogen bonding and dipole-dipole interactions, in a systematic and graded approach. The effects of α-substitution and self-association on the nature of the formyl H-atom are studied with the NBO and AIM methodologies. The relative dipole-dipole contributions in formyl C-H···O interactions are obtained for aldehyde dimers. The stabilities and energies of aldehyde clusters (dimer through octamer) have been examined computationally. Such studies have an implication in crystallization mechanisms. Experimental X-ray crystal structures of formaldehyde, acrolein and N-methylformamide have been determined in order to ascertain the role of C-H···O interactions in the crystal packing of formyl compounds. 相似文献
108.
Herbal products are believed to be safe as they are naturally occurring, however, this is a misconception. Currently, there are many herbal products which are not manufactured under the Good Manufacturing Practice (GMP) guidelines and hence the quality of the product is not controlled. Quality can be assessed by evaluation of data on levels of either active constituent(s) or chemical markers indicative of origin of plant material. Assessment of published data on levels of quality of herbal medicinal products revealed that only a percentage of the total number of products investigated were found to contain the levels of markers as stated on the label, and others had widely varying levels of constituents. Thus few products complied with acceptable quality control standards. Herbal products are increasingly self-prescribed for the treatment of minor ailments. Patients relying on herbal products for therapeutic effects may expose themselves to either low doses of active constituents causing insufficient effects or alternatively take higher levels than expected, with the increased risk of toxicity or adverse effects, or be affected by the inadvertent inclusion of unexpected components with associated potential health risks. 相似文献
109.
Johra Khan Prashanta Kumar Deb Somi Priya Karla Damin Medina Rajlakshmi Devi Sanjay G. Walode Mithun Rudrapal 《Molecules (Basel, Switzerland)》2021,26(13)
Flavonoids comprise a large group of structurally diverse polyphenolic compounds of plant origin and are abundantly found in human diet such as fruits, vegetables, grains, tea, dairy products, red wine, etc. Major classes of flavonoids include flavonols, flavones, flavanones, flavanols, anthocyanidins, isoflavones, and chalcones. Owing to their potential health benefits and medicinal significance, flavonoids are now considered as an indispensable component in a variety of medicinal, pharmaceutical, nutraceutical, and cosmetic preparations. Moreover, flavonoids play a significant role in preventing cardiovascular diseases (CVDs), which could be mainly due to their antioxidant, antiatherogenic, and antithrombotic effects. Epidemiological and in vitro/in vivo evidence of antioxidant effects supports the cardioprotective function of dietary flavonoids. Further, the inhibition of LDL oxidation and platelet aggregation following regular consumption of food containing flavonoids and moderate consumption of red wine might protect against atherosclerosis and thrombosis. One study suggests that daily intake of 100 mg of flavonoids through the diet may reduce the risk of developing morbidity and mortality due to coronary heart disease (CHD) by approximately 10%. This review summarizes dietary flavonoids with their sources and potential health implications in CVDs including various redox-active cardioprotective (molecular) mechanisms with antioxidant effects. Pharmacokinetic (oral bioavailability, drug metabolism), toxicological, and therapeutic aspects of dietary flavonoids are also addressed herein with future directions for the discovery and development of useful drug candidates/therapeutic molecules. 相似文献
110.