Carbonyl vibrational wave packet circulation in Mn2(CO)10 driven by ultrashort polarized laser pulses

The excitation of the degenerate E(1) carbonyl stretching vibrations in dimanganese decacarbonyl is shown to trigger wave packet circulation in the subspace of these two modes. On the time scale of about 5 ps, intramolecular anharmonic couplings do not cause appreciable disturbance, even under conditions where the two E(1) modes are excited by up to about two vibrational quanta each. The compactness of the circulating wave packet is shown to depend strongly on the excitation conditions, such as pulse duration and field strength. Numerical results for the solution of the seven-dimensional vibrational Schro?dinger equation are obtained for a density functional theory based potential energy surface and using the multi-configuration time-dependent Hartree method.     

Vibrationally quantum-state-specific dynamics of the reactions of CN radicals with organic molecules in solution

The dynamics of reactions of CN radicals with cyclohexane, d(12)-cyclohexane, and tetramethylsilane have been studied in solutions of chloroform, dichloromethane, and the deuterated variants of these solvents using ultraviolet photolysis of ICN to initiate a reaction. The H(D)-atom abstraction reactions produce HCN (DCN) that is probed in absorption with sub-picosecond time resolution using ～500 cm(-1) bandwidth infrared (IR) pulses in the spectral regions corresponding to C-H (or C-D) and C≡N stretching mode fundamental and hot bands. Equivalent IR spectra were obtained for the reactions of CN radicals with the pure solvents. In all cases, the reaction products are formed at early times with a strong propensity for vibrational excitation of the C-H (or C-D) stretching (v(3)) and H-C-N (D-C-N) bending (v(2)) modes, and for DCN products there is also evidence of vibrational excitation of the v(1) mode, which involves stretching of the C≡N bond. The vibrationally excited products relax to the ground vibrational level of HCN (DCN) with time constants of ～130-270 ps (depending on molecule and solvent), and the majority of the HCN (DCN) in this ground level is formed by vibrational relaxation, instead of directly from the chemical reaction. The time-dependence of reactive production of HCN (DCN) and vibrational relaxation is analysed using a vibrationally quantum-state specific kinetic model. The experimental outcomes are indicative of dynamics of exothermic reactions over an energy surface with an early transition state. Although the presence of the chlorinated solvent may reduce the extent of vibrational excitation of the nascent products, the early-time chemical reaction dynamics in these liquid solvents are deduced to be very similar to those for isolated collisions in the gas phase. The transient IR spectra show additional spectroscopic absorption features centered at 2037 cm(-1) and 2065 cm(-1) (in CHCl(3)) that are assigned, respectively, to CN-solvent complexes and recombination of I atoms with CN radicals to form INC molecules. These products build up rapidly, with respective time constants of 8-26 and 11-22 ps. A further, slower rise in the INC absorption signal (with time constant >500 ps) is attributed to diffusive recombination after escape from the initial solvent cage and accounts for more than 2/3 of the observed INC.     

Trialkylphosphine-stabilized copper(I) phenylchalcogenolate complexes--crystal structures and copper-chalcogenolate bonding

A series of trialkylphosphine-stabilized copper(I) phenylchalcogenolate complexes [(R(3)P)(m)(CuEPh)(n)] (R = Me, Et, (i)Pr, (t)Bu; E = S, Se, Te) has been prepared and structurally characterized by X-ray diffraction. Structures were found to be mono-, di-, tri-, tetra-, hexa-, hepta-, or decanuclear, depending mainly on size and amount of phosphine ligand. Several structural details were observed, including unusually long Cu-E bonds or secondary Cu-E connections, μ(4)-bridging, and planar bridging chalcogenolate ligands. Relatively rigid Cu-E-C angles were found to be of significant influence on the flexible molecular structures, especially for bridging chalcogenolate ligands, since in these cases a correlation results between the Cu-E-Cu angles and the inclination of the E-C bonds to their Cu-E-Cu planes. We further address some of these phenomena by means of density functional computations.     

Pd-catalyzed asymmetric conjugate addition of arylboronic acids to 2-nitroacrylates: a facile route to β-homophenylglycines

Asymmetric conjugate addition of arylboronic acids to 2-nitroacrylamide in the presence of cationic palladium–Chiraphos complex proceeds with high yield and enantioselectivity (73–89% ee) using as low as 0.05–0.25 mol % of the catalyst. The adducts can be smoothly transformed into the corresponding β²-homophenylglycines in two simple steps.     

Specific CLK inhibitors from a novel chemotype for regulation of alternative splicing

There is a growing recognition of the importance of protein kinases in the control of alternative splicing. To define the underlying regulatory mechanisms, highly selective inhibitors are needed. Here, we report the discovery and characterization of the dichloroindolyl enaminonitrile KH-CB19, a potent and highly specific inhibitor of the CDC2-like kinase isoforms 1 and 4 (CLK1/CLK4). Cocrystal structures of KH-CB19 with CLK1 and CLK3 revealed a non-ATP mimetic binding mode, conformational changes in helix αC and the phosphate binding loop and halogen bonding to the kinase hinge region. KH-CB19 effectively suppressed phosphorylation of SR (serine/arginine) proteins in cells, consistent with its expected mechanism of action. Chemical inhibition of CLK1/CLK4 generated a unique pattern of splicing factor dephosphorylation and had at low nM concentration a profound effect on splicing of the two tissue factor isoforms flTF (full-length TF) and asHTF (alternatively spliced human TF).