Direct Simulation of Excited-State Intramolecular Proton Transfer and Vibrational Coherence of 10-Hydroxybenzo[h]quinoline in Solution

We investigate an ultrafast excited-state intramolecular proton transfer (ESIPT) reaction and the subsequent coherent vibrational motion of 10-hydroxybenzo[h]quinoline in cyclohexane by the electronically embedded multiconfiguration Shepard interpolation method, which enables us to generate the potential energy surface of the reaction effectively and thus carry out a direct excited-state dynamics simulation with low computational costs. The calculated time scale of the ESIPT and the frequencies and lifetimes of coherent motions are in good agreement with the experimental results. The present study reveals that the coherent motions are caused by not only the proton transfer itself but also the backbone displacement induced by the ESIPT. We also discuss the effects of the solvent on the dynamics of the coherent vibrational modes

Quantitative Evaluation of Site Energies and Their Fluctuations of Pigments in the Fenna–Matthews–Olson Complex with an Efficient Method for Generating a Potential Energy Surface

We develop an efficient method to generate an accurate semiglobal potential energy surface of a molecule in condensed phases with low computational cost. We apply the method to the calculation of the site energies and their fluctuations of bacteriochlorophyll (BChl) <i>a</i> pigments in the Fenna–Matthews–Olson (FMO) complex using the density functional properly describing the ground and excited states of BChl <i>a</i> in solutions in our previous work (<i>J. Phys. Chem. B</i> <b>2014</b>, <i>118</i>, 10906–10918). The errors of the potential energies calculated from the present and QM/MM methods are small: ∼1 kcal/mol for both the ground and excited states. The calculated site energies are in good agreement with the experimentally fitted results. The calculated spectral density also agrees with the experimentally available data. The spectral densities of BChl 2 and BChl 5 are much larger than those of the other five sites. The present method is expected to provide new insights into the efficient excitation energy transfer in light-harvesting antennas

Cinchona-Based Primary Amine Catalyzed a Proximal Functionalization of Dienamines: Asymmetric α‑Fluorination of α‑Branched Enals

Fluorination of dienamines generated by α-branched enals and 6′-hydroxy-9-amino-9-deoxy-<i>epi</i>-quinidine (30 mol %) with NSFI show excellent α-regioselectivity to construct allylic fluorides containing a highly stereocontrolled quaternary fluorinated carbon (<i>E</i>/<i>Z</i> ≥ 20/1 and up to 93% enantiometric excess (<i>ee</i>)). By DFT calculation, the quinuclidine moiety of the catalyst was shown to function as a coordinating group to promote a reaction at the proximal α-position, and the nonclassical CH hydrogen bond plays an important role in the high enantioselectivity

Theoretical Study on Excited States of Bacteriochlorophyll <i>a</i> in Solutions with Density Functional Assessment

The excited-state properties of bacteriochlorophyll (BChl) <i>a</i> in triethylamine, 1-propanol, and methanol are investigated with the time-dependent density functional theory by using the quantum mechanical and molecular mechanical reweighting free energy self-consistant field method. It is found that no prevalent density functionals can reproduce the experimental excited-state properties, i.e., the absorption and reorganization energies, of BChl <i>a</i> in the solutions. The parameter μ in the range-separated hybrid functional is therefore optimized to reproduce the differences of the absorption energies in the solutions. We examine the origin of the differences of the absorption energies in the solutions and find that sensitive balance between contributions of structural changes and solute–solvent interactions determines the differences. The accurate description of the excitation with the density functional with the adjusted parameter is therefore essential to the understanding of the excited-state properties of BChl <i>a</i> in proteins and also the mechanism of the photosynthetic systems

Spin-Blocking Effect in CO and H₂ Binding Reactions to Molybdenocene and Tungstenocene: A Theoretical Study on the Reaction Mechanism via the Minimum Energy Intersystem Crossing Point

Potential energy profiles and electronic structural interpretation of the CO and H₂ binding reactions to molybdenocene and tungstenocene complexes [MCp₂] (M = Mo and W, Cp = cycropentadienyl) were studied using density functional theory calculations and ab initio multiconfigurational electronic structure calculations. Experimentally observed slow H₂ binding was reasonably explained in terms of the spin-blocking effect. Electronic structural analysis at the minimum-energy intersystem crossing point (MEISCP) revealed that the singly occupied molecular orbital’s π-bonding/σ-antibonding character in the M-CO/H₂ moiety determines the energy levels of the MEISCP. Analysis of the reaction coordinate showed that the singlet-triplet gap significantly depends on the Cp-M-Cp angle. Therefore, not only the metal–ligand distance but also the Cp-M-Cp angle is an important reaction coordinate to reach the MEISCP, the transition state of H₂ binding. The role of spin–orbit coupling is also discussed

Theoretical and Experimental Studies on Vibrational Energy Relaxation of the CO Stretching Mode of Acetone in Alcohol Solutions

The vibrational energy relaxations (VERs) of the CO stretching mode of acetone and its complexes with alcohols are investigated by sub-picosecond pump–probe spectroscopy and molecular dynamics simulation. The time constants of the vibrational energy relaxation of the free acetone and that of the 1:1 complex are 4.4 and 2.3 ps for methanol solvent and 5.2 and 1.8 ps for 1-proponal solvent, respectively. The VER rate is accelerated a few times by formation of the hydrogen bond. This acceleration of the vibrational energy relaxation is successfully reproduced by the Landau–Teller method calculated from the molecular dynamics simulation. Molecular dynamics simulations reveal that the VER time of acetone with the hydrogen bond is largely affected by the solute polarization induced by solvent molecules

Scheme of sagittal CT images of the lumbosacral spine.

<p>Lines with arrows represent measurements of vertebral body diameters (VBD) and dural sac diameters (DSD).</p

CT images of 46-year-old female with Loeys-Dietz syndrome.

<p>Sagittal image of the normal dura (A). Coronal image of right lateral meningocele (arrow) (B). Axial image at S1 shows asymmetric dilatation of the dura (arrow) (C). In this case, visual inspection could detect dural ectasia, but quantitative evaluation could not.</p

Patient characteristics and prevalence of DE determined with qualitative and quantitative methods.

<p>LDS, Loeys-Dietz syndrome; MFS, Marfan syndrome; DSR, dural sac ratio; DE, dural ectasia; NS, not significant; a, difference between LDS and MFS; b, difference between LDS and control; c, difference between MFS and control.</p><p>Difference*, In this column, p values are shown. Differences were not tested for each level from L1 to S1.</p

Mean DSR values.

<p>DSR, dural sac ratio; LDS, Loeys-Dietz syndrome; MFS, Marfan syndrome; DE, dural ectasia; NS, not significant; a, difference between LDS and MFS; b, difference between LDS and control; c, difference between MFS and control.</p><p>CI*, this column shows the confidence interval for significant differences.</p