Unsupported thiolate-capped palladium nanoparticle catalysts are found to be highly substrate-selective for alkene hydrogenation and isomerization. Steric and poisoning effects from thiolate ligands on the nanoparticle surface control reactivity and selectivity by influencing alkene adsorption and directing either di-σ or mono-σ bond formation. The presence of overlapping p orbitals and α proto...

[reaction: see text] We report for the first time that stoichiometric and even catalytic quantities of weak acids in aqueous solution can very efficiently catalyze amide isomerization in a carefully designed system in which a proton donor is situated so that intramolecular hydrogen bonding to the amide nitrogen is highly favored. Our results provide the first experimental verification that hydr...

Reaction of a zinc/zirconium heterobimetallic complex with 1,5-cyclooctadiene (1,5-COD) results in slow isomerization to 1,3-cyclooctadiene (1,3-COD), along with the formation of a new complex that includes a cyclooctyne ligand bridging two metal centers. While analogous magnesium/zirconium and aluminum/zirconium heterobimetallic complexes are competent for the catalytic isomerization of 1,5-CO...

Activation of the visual pigment rhodopsin is caused by 11-cis to -trans isomerization of its retinal chromophore. High-resolution solid-state NMR measurements on both rhodopsin and the metarhodopsin II intermediate show how retinal isomerization disrupts helix interactions that lock the receptor off in the dark. We made 2D dipolar-assisted rotational resonance NMR measurements between (13)C-la...

PAPER Hermann A. Wegner et al. Symmetry as a new element to control molecular switches a The isomerization properties of an azocarbazole macrocycle in solution were investigated utilizing NMR spectroscopy with in situ irradiation in combination with DFT calculations. It was demonstrated that the position of azo units in a rigid macrocyclic system influences the photoisomerization pathway even i...

Molecular dynamics simulations and quantum chemistry calculations have been combined to describe the dark adaptation in bacteriorhodopsin (bR). The process involves the reversible thermally activated transformation of retinal from an all-trans to a 13-cis,15-syn configuration. The potential surface governing the thermal isomerization of retinal around two (13-14, 15-N) double bonds has been det...

The photo-isomerization of o-acetylbenzaldehyde (oABA) in acetonitrile was studied by femto- and nanosecond transient absorption spectroscopy. Spectroscopic signatures are assigned with the aid of TD-DFT, TD-CAM-DFT and DFT-MRCI computations. The isomerization yields a lactone, 3-methylphthalide (3MP), with a quantum yield of 0.3 (30%). As evidenced by femtosecond stimulated Raman spectroscopy ...

The isomerization properties of an azocarbazole macrocycle in solution were investigated utilizing NMR spectroscopy with in situ irradiation in combination with DFT calculations. It was demonstrated that the position of azo units in a rigid macrocyclic system influences the photoisomerization pathway even if the initial all-E isomer is highly symmetric. Furthermore, the effect of ring strain on...

Generally, rotational isomerization about the carbon-carbon single bond in simple ethane derivatives in room-temperature solution under thermal equilibrium conditions has been too fast to measure. We achieved this goal using two-dimensional infrared vibrational echo spectroscopy to observe isomerization between the gauche and trans conformations of an ethane derivative, 1-fluoro-2-isocyanato-et...

We report the characterization and photochemistry of a simple ruthenium coordination complex containing only picolinate (pic) and dmso, which exhibits a large isomerization quantum yield (Phi(SS-->OO) = 0.50) in various solvents. The picolinate ligands of [Ru(pic)(2)(dmso)(2)] are in a cis arrangement so that the carboxylate oxygen of one pic ligand (O1) is trans to the pyridine of the second p...