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Ochi N.,Kyoto University | Nakao Y.,Kyoto University | Sato H.,Kyoto University | Sakaki S.,Kyoto University | Sakaki S.,Fukui Institute for Fundamental Chemistry
Journal of Physical Chemistry A | Year: 2010

The {2 + 2} cycloaddition of alkyne across the Ti=N bond of [(H 3SiO)2Ti(=NSiH3)] 1 was theoretically investigated. Though1 this cycloaddition is symmetry forbidden in a formal sense by the Woodward-Hoffmann rule, the cycloaddition of 2-butyne (MeC≡CMe) easily occurs with moderate activation barrier (7.6 kcal/ mol) and considerably large exothermicity (41.0 kcal/mol), where the CCSD(T)-calculated energies are presented hereafter. The moderate activation barrier is interpreted in terms of the considerably polarized Ti=N bond; Because the dπ-pπ bonding orbital largely consists of the pπ orbital of the N and moderately of the dπ orbital of the Ti, the π*orbital of 2-butyne interacts with the dπ-pπ bonding orbital so as to form a bonding overlap with the pπ orbital of the N, into which the π orbital of 2-butyne mixes in an antibonding way with the pπ orbital of N. As a result, the C≡C bond of 2-butyne is polarized in the transition state and the symmetry forbidden character becomes very weak, which is the reason of the moderate activation barrier. The {2 + 2} cycloaddition of 1-methoxy-1-propyne (MeCα≡ CβOMe) occurs with smaller activation barrier (3.2 kcal/mol) than that of 2-butyne, when the Cα and Cβ approach the Ti and N, respectively. The higher reactivity of this alkyne is interpreted in terms of its polarized C≡C bond. In the reverse regioselective {2 + 2} cycloaddition in which the Cα and Cβ approach the N and Ti, respectively, the activation barrier becomes larger. From these results, it is concluded that the regioselective {2 + 2} cycloaddition can be performed by introducing such π-electron donating group as methoxy on one C atom of alkyne. The major product contains the Ti-Cα and N-Cβ bonds, where the methoxy group is introduced on the cβ The ratio of the major to minor products is theoretically estimated to be very large.© 2010 American Chemical Society. Source

Maegawa T.,Kyoto Institute of Technology | Irie Y.,Kyoto Institute of Technology | Imoto H.,Kyoto Institute of Technology | Fueno H.,Kyoto University | And 2 more authors.
Polymer Chemistry | Year: 2015

The selective introduction of functional groups at the para-position in mono-functionalized T8-caged silsesquioxanes would enable us to design new organic inorganic hybrid polymers. Here, a para-substituted bisvinylhexaisobutyl-T8 caged monomer was successfully synthesized via a selective corner-opening reaction of the vinylheptaisobutyl-T8 cage followed by a subsequent corner-capping reaction. © The Royal Society of Chemistry 2015. Source

Wang W.-W.,Xian Jiaotong UniversityXian710049 China | Nagase S.,Fukui Institute for Fundamental Chemistry
Journal of Computational Chemistry | Year: 2016

The open edge reconstruction of half-saturated (6,0) zigzag carbon nanotube (CNT) was introduced by density functional calculations. The multistep rearrangement was demonstrated as a regioselective process to generate a defective edge with alternating pentagons and heptagons. Not only the thermal stability was found to be enhanced significantly after reconstruction but also the total spin of CNT was proved to be reduced gradually from high-spin septet to close-shell singlet, revealing the critical role of deformed edge on the geometrical and magnetic properties of open-ended CNTs. Kinetically, the initial transformation was confirmed as the rate-determining step with relatively the largest reaction barrier and the following steps can take place spontaneously. © 2016 Wiley Periodicals, Inc. Source

Morokuma K.,Fukui Institute for Fundamental Chemistry
International Journal of Quantum Chemistry | Year: 2014

The intrinsic reaction coordinate (IRC) approach has been used extensively in quantum chemical analysis and prediction of the mechanism of chemical reactions. The IRC gives a unique connection from a given transition structure to local minima of the reactant and product sides. This allows for easy understanding of complicated multistep mechanisms as a set of simple elementary reaction steps. In this article, three topics concerning the IRC approach are discussed. In the first topic, the first ab initio study of the IRC and a recent development of an IRC calculation algorithm for enzyme reactions are introduced. In the second topic, cases are presented in which dynamical trajectories bifurcate and corresponding IRC connections can be inaccurate. In the third topic, a recent development of an automated reaction path search method and its application to systematic construction of IRC networks are described. Finally, combining these three topics, future perspectives are discussed. © 2014 Wiley Periodicals, Inc. Source

Akagi K.,Kyoto University | Akagi K.,Fukui Institute for Fundamental Chemistry
Kobunshi | Year: 2015

The π-conjugated polymers bearing jt-electrons delocalized over the main chains are extensively investigated from viewpoints of fundamental and applied sciences because of their unique optoelectronic properties and functions. Nowadays it is further required for the conjugated polymers, as next-generation plastic electronics materials, to have newly designed polymer structures, novel functions and high performance in optoelectronic functions. Herein, we discuss helical rc-conjugated polymers with super-hierarchically controlled structures, by focusing on (i) optically active polymers with white colored circularly polarized luminescence (CPL) and intensity amplification of CPL via liquid crystalinity, (ii) external stimulus-responsive π-conjugated polymers and reversible switching in CPL, and (iii) interchain helically stacked assemblies consisting of cationic achiral π-conjugated polymers and anionic chiral molecules and the formation of spherulites based on the polymer assemblies. Source

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