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Inspired by the previous machine‐learning study that the number of hydrogen‐bonding acceptor (NHBA) is important index for the hole mobility of organic semiconductors, seven dithienobenzothiazole (DBT) derivatives 1 a–g (NHBA=5) were designed and synthesized by one‐step functionalization from a common precursor. X‐ray single‐crystal structural analyses confirmed that the molecular arrangements of 1b (the diethyl and ethylthienyl derivative) and 1c (the di(n‐propyl) and n‐propylthienyl derivative) in the crystal are classified into brickwork structures with multidirectional intermolecular charge‐transfer integrals, as a result of incorporation of multiple hydrogen‐bond acceptors. The solution‐processed top‐gate bottom‐contact devices of 1b and 1c had hole mobilities of 0.16 and 0.029 cm2 V−1s−1, respectively. [ABSTRACT FROM AUTHOR]

The nudged elastic band (NEB) method is utilized to find reaction paths (RPs) using discretized intermediate structures called "images" between a reactant and a product. In fact, NEB calculations do not always converge because of the bent of RPs. Mathematically, more images are needed for complex curves, and here, we focused on the curvature. In this study, we propose a new method for calculating the curvature of the RPs as well as a method for weighting the spring constant of the NEB with the curvature, which we named the curvature weighted NEB (CW‐NEB) method. In addition, we will propose the CW‐NEB method with the climbing image (CI) method (CW‐CI‐NEB). To show the efficiency of our method, calculations for the ene‐reaction of the CW‐CI‐NEB method were performed and compared with those of the CI‐NEB methods. The CW‐CI‐NEB methods converged in shorter iteration times than the CI‐NEB calculation, which was found by gathering the bent of RPs. [ABSTRACT FROM AUTHOR]

The oxy-Cope rearrangement reaction in the antibody AZ28 is investigated using ab initio molecular orbital calculations and molecular mechanical dynamics simulations. It is shown that the differences in flexibility between the germ line and the mature form and the differences in structure between TSA and the transition state are the origin of the negative correlation in AZ28-catalyzed oxy-Cope rearrangement.

A study of the quantum effects on the proton-transfer reaction in the N2H7 (super +) cluster using the classical ab initio Monte Carlo method and a one dimensional model for the quantum wave packet dynamics on the ab initio MP2/6-31 +G (super *) potential energy surface is presented. The results show that the vibrational frequency for the N-H stretching mode which corresponds to the proton transfer is estimated to be 706.7 cm (super -1) by including proton quantum effects in contrast with 2100.1 cm (super -1) obtained by the conventional ab initio MO method for the C (sub 3v) structure.

The reaction paths of methylenecyclopropane 1 on the potential energy surfaces (PESs) of the lowest triplet (T1) state and the lowest excited singlet (S1) state, as well as that of the ground state (S0), were explored by using the nudged elastic band method at the MRMP2//MCSCF/6‐31++G(d,p) and DFT(B3LYP)/6‐31++G(d,p) levels of theory. After vertical excitation of 1, three transition states on the PES of the lowest triplet state and one transition state on the S1 PES were found along the reaction path to produce a carbene, cyclobutylidene 2. All of these transition states are lower in energy than the S1 state produced by vertical excitation at the S0 energy minimum in 1. Fast transition is predicted to occur from the T1 state or from the S1 state to the S0 state due to strong spin‐orbit coupling or nonadiabatic coupling in the geometrical vicinity of 2. On the MRMP2 S0 PES, the energy barriers of 5.0, 10.3 and 13.5 kcal mol−1 were obtained for C migration reaction (backward reaction), 1,2‐H migration reaction to cyclobutene 3, and 1,3‐H migration reaction to bicyclopropane 4, respectively, started at 2. The introduction of phenyl groups makes the energy barriers smaller due to the π conjugation between the carbene center and phenyl groups. [ABSTRACT FROM AUTHOR]

The potential energy surfaces of low-lying states in rhenium tetrahydride (ReH4) were explored by using the multiconfiguration self-consistent field (MCSCF) method together with the SBKJC effective core potentials and the associated basis sets augmented by a set of f functions on rhenium atom and by a set of p functions on hydrogen atoms, followed by spin-orbit coupling (SOC) calculations to incorporate nonscalar relativistic effects. The most stable structure of ReH4 was found to have a D2d symmetry and its ground state is 4A2. It is found that this is lower in energy than the dissociation limit, ReH2+H2, after dynamic correlation effects are taken into account by using second-order multireference Mo\ller-Plesset perturbation (MRMP2) calculations. This reasonably agrees with previous results reported by Andrews et al. [J. Phys. Chem. 107, 4081 (2003)]. The present investigation further revealed that the dissociation reaction of ReH4 cannot occur without electronic transition from the lowest quartet state to the lowest sextet state. This spin-forbidden transition can easily occur because of large SOC effects among low-lying states in such heavy metal-containing compounds. The minimum-energy crossing (MEX) point between the lowest quartet and sextet states is proved to be energetically and geometrically close to the transition state for the dissociation reaction on the potential energy surface of the lowest spin-mixed state. The MEX point (C2 symmetry) was estimated to be 9184 cm-1 (26.3 kcal/mol) higher than the 4A2 state in D2d symmetry at the MRMP2 level of theory. After inclusion of SOC effects, an energy maximum on the lowest spin-mixed state appears near the MEX point and is recognized as the transition state for the dissociation reaction to ReH2+H2. The energy barrier for the dissociation, evaluated to be MEX in the adiabatic picture, was calculated to be 5643 cm-1 (16.1 kcal/mol) on the lowest spin-mixed state when SOC effects were estimated at the MCSCF level of theory. [ABSTRACT FROM AUTHOR]

This is the second paper in a series of investigations on spin-orbit coupling (SOC) effects in dihydrides of third-row transition elements. The dissociation path of rhenium dihydride was explored using the multiconfiguration self-consistent-field method followed by diagonalization of SOC matrices, in which the Stevens–Basch–Krauss–Jasien–Cundari (SBKJC) basis sets were employed after adding one set of polarization functions for each atom. The most stable rhenium dihydride has a linear structure and its ground state is 6Σg+. Both C2v and Cs dissociation paths into a Re atom and a hydrogen molecule (Re(6S)+H2(1Σg+)) were explored on the potential energy curves of low-lying states. A relatively high energy barrier was obtained along the C2v path and two conical intersections were found at the H–Re–H angles of 29.8° and 96.1° along the C2v path. Since it was revealed that the geometrical deformation to Cs symmetry at the H–Re–H angle of 29.8° does not provide explicit lowering of the energy barrier for the dissociation, even after considering nonadiabatic couplings (NACs) in the neighborhood of the conical intersections, it can be concluded that the most feasible path is hopping from the lowest 6A1 state to the lowest 6B2 state at the H–Re–H angle of 96.1° followed by hopping from the lowest 6B2 state back to the lowest 6A1 state at the H–Re–H angle of 29.8°, where the latter crossing point is the highest in energy along this path. Thus, when the molecular system can reach the areas of these crossing points, the molecular system hops from one of the states to another owing to NAC or SOC effects; especially, SOC effects become important at the crossing point with C2v symmetry. [ABSTRACT FROM AUTHOR]

The molecular dynamics simulation study is employed to study the stabilities, as well as reactivities of the NADH-cytochrome b5 reductase (b5R). The transfer of electrons and hydride ions between the enzymes, FAD and NADH is also studied.

A study is conducted to investigate the spin-orbit coupling (SOC) effects in the radiative processes from the electronically excited states of bis-[2-(2-thienyl)-pyridine] platinum (Pt[(thpy).sub.2] and palladium (Pd[(thypy).sub.2]. Results reveal that the low-lying excited singlets and triplets are strongly mixed with each other by SOC in (Pt[(thpy).sub.2]

The quantum effects of the proton motion on single proton-transfer reactions in small ammonia-hydrogen chloride cluster NH3:HCl:(H2O)n are investigated by using an ab initio MP2/aug-cc-pVDZ level of theory. The results suggest that three-body interactions play an important role to determine the relative stability in each size of cluster.