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The absorption of carbon monoxide on small, neutral, anionic and cationic silver clusters [Ag.sub.n] (n = 1-7) is studied by using density functional theory (DFT) method. The results suggest that CO adsorbed on small silver clusters preferred the on-top site and adsorption on the most stable bare silver clusters did not always result in the lowest energy complexes.

The elaboration of a fusion protein containing fluorescence donor and acceptor are demonstrated. The experiments made illustrates energy transfers between the incorporated probes, as well as the feasibility of monitoring the separation of the donor and acceptor in real time by the decrease in fluorescence energy transfer.

Mesoporous carbon CMK-3 was synthesized via a hard template method. The structures of the pores were characterized by N2 adsorption at 77K, XRD, and TEM examinations. The BET surface area and total pore volume were 1115 m2/g and 1.11 cm3/g, respectively. Adsorption isotherms of carbon dioxide on the CMK-3 in the presence of water were collected. At 275 K and 3.6 MPa, the CO2 sorption capacity was 42 mmol/g with a water to dry carbon weight ratio (Rw) of 2.35. This is 2.26 times as high as that for the dry CMK-3 sample and 23% higher than the highest CO2 sorption previously obtained on activated carbon with preadsorbed water. The enthalpy change obtained from the sorption isotherms was -55.6 kJ/mol, which is lower than the enthalpy for the formation of CO2 hydrate in pure water. [ABSTRACT FROM AUTHOR]

An organocatalytic arylation of 3-indolylmethanols has been established via chemo- and regiospecific C6-functionalization of 2,3-disubstituted indoles, leading to the production of bisindolyloxindoles containing an all-carbon quaternary stereocenter in high yields (up to 99% yield). This reaction not only represents the first catalytic arylation of 3-indolylmethanols using 2,3-disubstituted indoles as aromatic nucleophiles but also serves as a good example of direct catalytic C6-functionalization of indoles, which have been scarcely investigated. Besides, this approach also provides an efficient method to access a biologically important 3,3'-disubstituted oxindole framework and a 3',6-linked bisindole skeleton. Furthermore, the investigation of the activation mode suggested that the dual activation of an ion pair and H-bond between the substrates and the catalyst cooperatively contributed to the success of the reaction. [ABSTRACT FROM AUTHOR]

Compounds with carbon–boron bonds are versatile intermediates for building more complex molecules via the elaboration of the carbon–boron bonds into other carbon–element bonds. The synthesis of carbon–boron bonds by catalytic dehydrogenative borylation of carbon–hydrogen bonds with dialkoxyboranes (RO)2BH is particularly attractive. It has been demonstrated for a variety of carbon–hydrogen bond types but not for the C(sp)–H bonds of terminal alkynes, for which hydroboration of the triple bond is a competing process. We report a new iridium catalyst that is strictly chemoselective for C–H borylation of terminal alkynes. The key to the success of this catalyst appears to be the new ancillary SiNN pincer ligand that combines amido, quinoline, and silyl donors and gives rise to structurally unusual Ir complexes. A variety of terminal alkynes (RC≣C–H) can be converted to their alkynylboronates (RC≣C–Bpin, where pin = pinacolate) in high yield and purity within minutes at ambient temperature. [ABSTRACT FROM AUTHOR]

Ab initio classical molecular dynamics calculations have been used to simulate the dissociation of H2NCH2+ in a strong laser field. The frequencies of the continuous oscillating electric field were chosen to be ω = 0.02, 0.06, and 0.18 au (2280, 760, and 253 nm, respectively). The field had a maximum strength of 0.03 au (3.2 X 1013 W cm-2) and was aligned with the CN bond. Trajectories were started with 100 kcal/mol of vibrational energy above zero point and were integrated for up to 600 fs at the B3LYP/6-311G(d,p) level of theory. A total of 200 trajectories were calculated for each of the three different frequencies and without a field. Two dissociation channels are observed: HNCH+ + H+ and H2NC+ + H+. About one-half to two-thirds of the H+ dissociations occurred directly, while the remaining indirect dissociations occurred at a slower rate with extensive migration of H+ between C and N. The laser field increased the initial dissociation rate by a factor of ca. 1.4 and decreased the half-life by a factor of ca. 0.75. The effects were similar at each of the three frequencies. The HNCH+ to H2NC+ branching ratio decreased from 10.6:1 in the absence of the field to an average of 8.4:1 in the laser field. The changes in the rates and branching ratios can be attributed to the laser field lowering the reaction barriers as a result of a difference in polarizability of the reactant and transition states. [ABSTRACT FROM AUTHOR]

The gas phase reaction of Th숫 H2O to produce HThO H and ThO H2was investigated using density functional theory and coupled cluster methods. RRKM calculations of the branching ratio favor the H atomic elimination channel in disagreement with experiment. Ab initio classical trajectory calculations were carried out to obtain a better model of the molecular dynamics. The molecular dynamics simulations yield a branching ratio of ca. 80% for the H2elimination channel to 20% for the H atomic elimination channel in qualitative agreement with the observed ratio of 65% to 35%. [ABSTRACT FROM AUTHOR]

Complexes of the form An2(C8H8)2 (An = Th, Pa, U, and Np) were investigated using density functional theory with scalar-relativistic effective core potentials. For uranium, a coaxial isomer with D8h symmetry is found to be more stable than a Cs isomer in which the dimetal unit is perpendicular to the C8 ring axis. Similar coaxial structures are predicted for Pa2(C8H8)2 and Np2(C8H8)2, while in Th2(C8H5)2, the C8H8 rings tilt away from the An-An axis. Going from Th2(C8H8)2 to Np2(C8H8)2, the An-An bond length decreases from 2.81 Å to 2.19 Å and the An-An stretching frequency increases from 249 to 354 cm-1. This is a result of electrons populating An-An 5f π- and σ-type bonding orbitals and ϕ nonbonding orbitals, thereby increasing in An-An bond order. U2(C8H8)2 is stable with respect to dissociation into U(C8H8) monomers. Disproportionation of U2(C8H8)2 into uranocene and the U atom is endothermic but is slightly exothermic for uranocene plus ½U2, suggesting that it might be possible to prepare double stuffed uranocene if suitable conditions can be found to avoid disproportionation. [ABSTRACT FROM AUTHOR]

Vacuum ultraviolet photoionization coupled to secondaiy neutral mass spectrometiy (VUV-SNMS) of deposited tryptophan and thymine films are performed at the Chemical Dynamics Beamline. The resulting mass spectra show that while the intensity of the VUV-SNMS signal is lower than the corresponding secondary ion mass spectroscopy (SIMS) signal, the mass spectra are significantly simplified in VUV-SNMS. A detailed examination of tryptophan and thymine neutral molecules sputtered by 25 keV Bi3+ indicates that the ion-sputtered parent molecules have ∼2.5 eV of internal energy. While this internal energy shifts the appearance energy of the photofragment ions for both tryptophan and thymine, it does not change the characteristic photoionizaton efficiency (PIE) curves of thymine versus photon energy. Further analysis of the mass spectral signals indicate that approximately 80 neutral thymine molecules and 400 tryptophan molecules are sputtered per incident Bi3+ ion. The simplified mass spectra and significant characteristic ion contributions to the VIWSNMS spectra indicate the potential power of the technique for organic molecule surface analysis. [ABSTRACT FROM AUTHOR]

The structures and energetics of the reactants, intermediates, transition states, and products for the dissociation of methanimine neutral, monocation, dication, and trication were calculated at the CBS-APNO level of theory. The dissociations of the neutral, monocation, and dication were studied by abinitio direct classical trajectory calculations at the B3LYP/6-311G(d,p) level of theory. A microcanonical ensemble using quasiclassical normal mode sampling was constructed by distributing 200, 150, and 120 kcal/mol of excess energy above the local minima of the neutral, singly, and doubly charged species, respectively. Many of the trajectories dissociate directly to produce H+, H atom, or H2. However, for a fraction of the cases, substantial migration of the hydrogen occurs within the molecule before dissociation. The preferred dissociation product for the neutral and the monocation is hydrogen atom. Elimination of H2was seen in 20% of the trajectories for the neutral and in 5% of the trajectories for the monocation. Dissociations of the dication and trication produced H+rather than H atom. HCNH+was formed in 85−90% of the dissociating trajectories for the monocation and dication. [ABSTRACT FROM AUTHOR]