| 1. |
T Takeuchi, K Yoshizawa, Y Shiota, O Nakamura, H Kageyama, T Yamabe, Orbital interaction and vibrational mode analyses for phase transitions of BaTiO3, JOURNAL OF MATERIALS CHEMISTRY, 10.1039/a607475h, Vol.7, No.6, pp.969-975, 1997.06, The phase transitions of ATiO(3)-type perovskite structures, mainly those of barium titanate (BaTiO3), aro studied theoretically in terms of orbital interactions and vibrational modes. Vibrational analyses for fundamental TiO6 clusters, up to Ti8O36, are performed with a hybrid (Hartree-Fock/density functional) method. Important structural distortions from the high symmetry cubic phase are rationalized by a second-order perturbational treatment of quantum chemistry. The orbital symmetry argument based on group theory indicates that the transition density around frontier molecular orbitals plays an important role in the motions of ions at the transition temperatures. Our orbital interaction and vibrational mode analyses of the phase transitions are consistent with the soft mode theory of Cochran.. |
| 2. |
K Yoshizawa, Y Shiota, T Yamabe, Methane-methanol conversion by MnO+, FeO+, and CoO+: A theoretical study of catalytic selectivity, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 10.1021/ja971723u, Vol.120, No.3, pp.564-572, 1998.01, The entire reaction pathway for the gas-phase methane-methanol conversion by late transition-metal-oxide ions, MnO+, FeO+, and CoO+, is studied using an ab initio hybrid (Hartree-Fock/density-functional) method. For these oxo complexes, the methane-methanol conversion is proposed to proceed via two transition states (TSs) in such a way MO+ + CH4 --> OM+(CH4) --> [TS1] --> HO-M+-CH3 --> [TS3] --> M+(CH3OH) --> M+ + CH3OH, where M is Mn, Fe, and Co. A crossing between high-spin and low-spin potential energy surfaces occurs both at the entrance channel and at the exit channel for FeO+ and CoO+, but it occurs only once near TS2 for MnO+. The activation energy from OMn+(CH4) to HO-Mn+-CH3 via TS1 is calculated to be 9.4 kcal/mol, being much smaller than 22.1 and 30.9 kcal/mol for FeO+ and CoO+, respectively. This agrees with the experimentally reported efficiencies for the reactions. The excellent agreement between theory and experiment indicates that HO-M+-CH3 plays a central role as an intermediate in the reaction between MO+ and methane and that the reaction efficiency is most likely to be determined by the activation energy from OM+(CH4) to HO-M+-CH3 via TS1. We discuss in terms of qualitative orbital interactions why MnO+ (d(4) oxo complex) is most effective for methane C-H bond activation. The activation energy from HO-M+-CH3 to M+(CH3OH) via TS2 is computed to be 24.6, 28.6, and 35.9 kcal/mol for CoO+, FeO+, and MnO+, respectively. This result explains an experimental result that the methanol-branching ratio in the reaction between MO+ and methane is 100% in CoO+, 41% in FeO+, and < 1% in MnO+. We demonstrate that both the barrier heights of TS1 and TS2 would determine general catalytic selectivity for the methane-methanol conversion by the MO+ complexes.. |
| 3. |
K Yoshizawa, T Kamachi, Y Shiota, A theoretical study of the dynamical aspects of alkane hydroxylation by compound I of cytochrome p450, JOURNAL OF INORGANIC BIOCHEMISTRY, Vol.86, No.1, p.488, 2001.08. |
| 4. |
Y Shiota, K Yoshizawa, A theoretical study of the mononuclear non-hem iron complex of phenylalanine hydroxylase (PAH), JOURNAL OF INORGANIC BIOCHEMISTRY, Vol.96, No.1, p.228, 2003.07. |
| 5. |
K. Yoshizawa, Y. Shiota, G. Juhasz, Role of tyrosine residue in methane activation by pMMO, JOURNAL OF BIOLOGICAL INORGANIC CHEMISTRY, Vol.19, p.S216, 2014.03. |
| 6. |
西部貴久, 荻島郁弥, 小谷弘明, 石塚智也, 岡島敏浩, 野澤俊介, 塩田淑仁, 吉澤一成, 小島隆彦, 大環状アニオン性配位子を有する鉄錯体の高酸化状態における電子構造, 錯体化学会討論会講演要旨集, Vol.66th, p.257, 2016.08. |
| 7. |
西部貴久, 荻島郁弥, 小谷弘明, 石塚智也, 岡島敏浩, 野澤俊介, 塩田淑仁, 吉澤一成, 小島隆彦, 酸化還元活性な配位子を有する鉄錯体の高酸化状態における電子構造, 錯体化学会討論会講演要旨集, Vol.67th, p.22, 2017.09. |
| 8. |
塩田淑仁, 堀優太, 小寺政人, 吉澤一成, 銅2核錯体によるC‐H結合活性化に関する理論的研究, 日本化学会春季年会講演予稿集(CD-ROM), Vol.98th, p.ROMBUNNO.1E2‐43, 2018.03. |
| 9. |
塩田 淑仁, 超次元マテリアルの理論設計, セラミクス 55 （2020） 575, 2020.05, 量子化学計算は原子配列を元にそこに存在する電子 のエネルギーを計算し，さらに核配置を最適化するこ とでその物質の構造と電子状態を求める方法である. これらの方法は今までに孤立分子や周期系の固体に適 用され，その有効性が確かめられてきた.計算能力向 上によって大きな系へ適用できるようになり，欠陥や 不純物などを含む不均一な系においてもある程度定量 的な評価が可能となった.その結果，特異な構造を有 する材料の解析も工夫次第でアプローチできるように なりつつある.. |
| 10. |
塩田 淑仁, メタン活性化—電子状態理論からのアプローチ-, 触媒, 2013.06, 金属オキソ種は安定な分子であるメタンを水酸化することが知られている．本稿では単純な気相反応から出発して，触媒，酵素の活性点などすこし複雑なものまでの理論研究を紹介する．メタン活性化には不活性なC−H結合切断とその結果生じるメチルラジカルの制御が不可欠である．. |
