Search results for: Keiji Morokuma

Items from 1 to 20 out of 220 results

article

Non‐adiabatic dynamic of atmospheric unimolecular photochemical reactions of 4,4‐difluoro‐crotonaldehyde using TD‐DFT and TSH approaches

Pedro J. Castro, Satoshi Maeda, Keiji Morokuma

International Journal of Quantum Chemistry > 121 > 14 > n/a - n/a

Photochemical reactions of small molecules occur upon irradiation by ultraviolet or visible light, and they are a very important chemical processes in the Earth's atmosphere because they impact our quality of life and health. Small‐unsaturated carbonyl compounds play an important role in the chemistry of the polluted troposphere. The fluorinated aldehydes are very reactive under the sunlight driving...

article

Bridged Stilbenes: AIEgens Designed via a Simple Strategy to Control the Non‐radiative Decay Pathway

Riki Iwai, Satoshi Suzuki, Shunsuke Sasaki, Amir Sharidan Sairi, more

Angewandte Chemie International Edition > 59 > 26 > 10566 - 10573

To broaden the application of aggregation‐induced emission (AIE) luminogens (AIEgens), the design of novel small‐molecular dyes that exhibit high fluorescence quantum yield (Φ_fl) in the solid state is required. Considering that the mechanism of AIE can be rationalized based on steric avoidance of non‐radiative decay pathways, a series of bridged stilbenes was designed, and their non‐radiative decay...

article

Bridged Stilbenes: AIEgens Designed via a Simple Strategy to Control the Non‐radiative Decay Pathway

Riki Iwai, Satoshi Suzuki, Shunsuke Sasaki, Amir Sharidan Sairi, more

Angewandte Chemie > 132 > 26 > 10653 - 10660

article

Synthesis, Structure and Reactivities of Pentacoordinated Phosphorus–Boron Bonded Compounds

Nathan J. O'Brien, Naokazu Kano, Nizam Havare, Ryohei Uematsu, more

European Journal of Inorganic Chemistry > 2020 > 20 > 1995 - 2003

The isolation and reactivities of two pentacoordinated phosphorus–tetracoordinated boron bonded compounds were explored. A highly Lewis acidic boron reagent and electron‐withdrawing ligand system were required to form the pentacoordinated phosphorus state of the P–B bond. The first compound, a phosphoranyl‐trihydroborate, gave a THF stabilised phosphoranyl‐borane intermediate upon a single hydride...

article

Foreword

Keiji Morokuma

Journal of Computational Chemistry > 40 > 1 > 11 - 13

article

Multistructural microiteration technique for geometry optimization and reaction path calculation in large systems

Kimichi Suzuki, Keiji Morokuma, Satoshi Maeda

Journal of Computational Chemistry > 38 > 26 > 2213 - 2221

We propose a multistructural microiteration (MSM) method for geometry optimization and reaction path calculation in large systems. MSM is a simple extension of the geometrical microiteration technique. In conventional microiteration, the structure of the non‐reaction‐center (surrounding) part is optimized by fixing atoms in the reaction‐center part before displacements of the reaction‐center atoms...

article

Trihydroborates and Dihydroboranes Bearing a Pentacoordinated Phosphorus Atom: Double Ring Expansion To Balance the Coordination States

Naokazu Kano, Nathan J. O'Brien, Ryohei Uematsu, Romain Ramozzi, more

Angewandte Chemie > 129 > 21 > 5976 - 5979

The first trihydroborate bearing a pentacoordinated phosphorus atom was synthesized as a new P−B bonded compound. Hydride abstraction of the trihydroborate gave an intermediary dihydroborane, which showed hydroboration reactivity and was trapped with pyridine whilst maintaining the P−B bond. The dihydroborane underwent a rearrangement, which involved a double ring expansion to compensate for the unbalanced...

article

Trihydroborates and Dihydroboranes Bearing a Pentacoordinated Phosphorus Atom: Double Ring Expansion To Balance the Coordination States

Naokazu Kano, Nathan J. O'Brien, Ryohei Uematsu, Romain Ramozzi, more

Angewandte Chemie International Edition > 56 > 21 > 5882 - 5885

article

Quantum mechanical simulation reveals the role of cold helium atoms and the coexistence of bottom-up and top-down formation mechanisms of buckminsterfullerene from carbon vapor

Hu-Jun Qian, Ying Wang, Keiji Morokuma

Carbon > 2017 > 114 > C > 635-641

After the discovery of the highly symmetric Buckminsterfullerene (BF), a major goal of the fullerene community has been to understand its formation mechanism. In the various mechanisms proposed in literature, BF forms by either a bottom-up only or a top-down only process. Here we present a comprehensive quantum mechanical molecular dynamics simulation study, that reports for the first time the observations...

article

Computational S_N2‐Type Mechanism for the Difluoromethylation of Lithium Enolate with Fluoroform through Bimetallic C−F Bond Dual Activation

Kazuya Honda, Travis V. Harris, Miho Hatanaka, Keiji Morokuma, more

Chemistry – A European Journal > 22 > 26 > 8796 - 8800

The reaction mechanism for difluoromethylation of lithium enolates with fluoroform was analyzed computationally (DFT calculations with the artificial force induced reaction (AFIR) method and solvation model based on density (SMD) solvation model (THF)), showing an S_N2‐type carbon–carbon bond formation; the “bimetallic” lithium enolate and lithium trifluoromethyl carbenoid exert the C−F bond “dual”...

article

Trimeric cluster of lithium amidoborane—the smallest unit for the modeling of hydrogen release mechanism

Anna V. Pomogaeva, Keiji Morokuma, Alexey Y. Timoshkin

Journal of Computational Chemistry > 37 > 14 > 1259 - 1264

A detailed first‐principle DFT M06/6‐311++G(d.p) study of dehydrogenation mechanism of trimeric cluster of lithium amidoborane is presented. The first step of the reaction is association of two LiNH₂BH₃ molecules in the cluster. The dominant feature of the subsequent reaction pathway is activation of H atom of BH₃ group by three Li atoms with formation of unique Li₃H moiety. This Li₃H moiety is destroyed...

chapter

Transition Metal Catalyzed σ-Bond Activation and Formation Reactions

Djamaladdin G. Musaev, Keiji Morokuma

Topics in Organometallic Chemistry > Theoretical Aspects of Transition Metal Catalysis > 1-30

The factors controlling the transition metal catalyzed σ-bond (including H-H, C-H and C-C) activation and formation, the fundamental steps of many chemical transformations, were analyzed. It was demonstrated that in the mono-nuclear transition metal systems the (1) availability of the lower lying s¹d^n–1 and s⁰dⁿ states of the transition metal atoms, and (2) nature of the ligands facilitating the reduction...

chapter

The Oniom Method and its Applications to Enzymatic Reactions

Marcus Lundberg, And Keiji Morokuma

Challenges and Advances in Computational Chemistry and Physics > Multi-scale Quantum Models for Biocatalysis > Overview of Methodologies > 21-55

ONIOM is a flexible hybrid scheme that can combine the most suitable computational methods for a given system without previous parameterization. The reason for its flexibility is that all calculations are performed on complete molecular systems, and the total energy is obtained from an extrapolation scheme. Most commonly used is the combination of a quantum mechanics and a molecular mechanics method...

article

Automatized Parameterization of the Density‐functional Tight‐binding Method. II. Two‐center Integrals

Henryk A. Witek, Chien‐Pin Chou, Grzegorz Mazur, Yoshifumi Nishimura, more

Journal of the Chinese Chemical Society > 63 > 1 > 57 - 68

We present an efficient numerical integration scheme (TWOCENT) to be used in the context of automatized parameterization of the density‐functional tight‐binding (DFTB) method. The accuracy of the integration process is assessed and its range of applicability is discussed. The functionality of the developed code is tested by reproducing the electronic portion of the existing mio parameter sets and...

article

Rh^III‐Catalyzed C(sp³)H Bond Activation by an External Base Metalation/Deprotonation Mechanism: A Theoretical Study

Julong Jiang, Romain Ramozzi, Keiji Morokuma

Chemistry – A European Journal > 21 > 31 > 11158 - 11164

The C(sp³)H bond activation of 8‐methylquinoline followed by alkyne insertion catalyzed by a Rh^III complex has been studied by using density functional theory (DFT) calculations. Contrary to common belief, the CH bond activation of methylquinoline does not occur by the traditional intramolecular concerted metalation/deprotonation (CMD) mechanism but by an external base CMD mechanism. The use of...

article

Intrinsic reaction coordinate: Calculation, bifurcation, and automated search

Satoshi Maeda, Yu Harabuchi, Yuriko Ono, Tetsuya Taketsugu, more

International Journal of Quantum Chemistry > 115 > 5 > 258 - 269

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

Quantum chemical simulations reveal acetylene-based growth mechanisms in the chemical vapor deposition synthesis of carbon nanotubes

Ying Wang, Xingfa Gao, Hu-Jun Qian, Yasuhito Ohta, more

Carbon > 2014 > 72 > C > 22-37

Nonequilibrium quantum chemical molecular dynamics (QM/MDs) simulation of early stages in the nucleation process of carbon nanotubes from acetylene feedstock on an Fe₃₈ cluster was performed based on the density-functional tight-binding (DFTB) potential. Representative chemical reactions were studied by complimentary static DFTB and density functional theory (DFT) calculations. Oligomerization and...

article

The origin of enantioselectivity for intramolecular Friedel–Crafts reaction catalyzed by supramolecular Cu/DNA catalyst complex

Galina P. Petrova, Zhuofeng Ke, Soyoung Park, Hiroshi Sugiyama, more

Chemical Physics Letters > 2014 > 600 > C > 87-95

The present theoretical investigation aims at understanding the origin of enantioselectivity of intramolecular Friedel–Crafts reaction, catalyzed by supramolecular Cu/DNA catalyst. 28 Conformations of the supramolecular L-Cu(II)-R/d(CAAAAATTTTTG)₂ complex were thoroughly modeled to estimate their stability and structural features depending on the metal complex conformation and its intercalation position...

article

Exploring transition state structures for intramolecular pathways by the artificial force induced reaction method

Satoshi Maeda, Tetsuya Taketsugu, Keiji Morokuma

Journal of Computational Chemistry > 35 > 2 > 166 - 173

Finding all required transition state (TS) structures is an important but hard task in theoretical study of complex reaction mechanisms. In the present article, an efficient automated TS search method, artificial force induced reaction (AFIR), was extended to intramolecular reactions. The AFIR method has been developed for intermolecular associative pathways between two or more reactants. Although...

article

Development of Azo‐Based Fluorescent Probes to Detect Different Levels of Hypoxia

Wen Piao, Satoru Tsuda, Yuji Tanaka, Satoshi Maeda, more

Angewandte Chemie > 125 > 49 > 13266 - 13270

Lass es leuchten: Neue Hypoxie‐sensitive Fluoreszenzsonden bestehen aus einer Rhodamin‐Einheit mit einem Azo‐Substituenten in direkter Konjugation zum Fluorophor. Aufgrund sehr schneller Konformationsänderung entlang der NN‐Bindung fluoreszieren die Verbindungen nicht unter Normoxie; unter hypoxischen Bedingungen wird jedoch die Azo‐Einheit reduziert, und ein stark fluoreszierendes Rhodamin‐Derivat...

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INFONA - science communication portal

Search results for: Keiji Morokuma

Non‐adiabatic dynamic of atmospheric unimolecular photochemical reactions of 4,4‐difluoro‐crotonaldehyde using TD‐DFT and TSH approaches

Bridged Stilbenes: AIEgens Designed via a Simple Strategy to Control the Non‐radiative Decay Pathway

Bridged Stilbenes: AIEgens Designed via a Simple Strategy to Control the Non‐radiative Decay Pathway

Synthesis, Structure and Reactivities of Pentacoordinated Phosphorus–Boron Bonded Compounds

Foreword

Multistructural microiteration technique for geometry optimization and reaction path calculation in large systems

Trihydroborates and Dihydroboranes Bearing a Pentacoordinated Phosphorus Atom: Double Ring Expansion To Balance the Coordination States

Trihydroborates and Dihydroboranes Bearing a Pentacoordinated Phosphorus Atom: Double Ring Expansion To Balance the Coordination States

Quantum mechanical simulation reveals the role of cold helium atoms and the coexistence of bottom-up and top-down formation mechanisms of buckminsterfullerene from carbon vapor

Computational S_N2‐Type Mechanism for the Difluoromethylation of Lithium Enolate with Fluoroform through Bimetallic C−F Bond Dual Activation

Trimeric cluster of lithium amidoborane—the smallest unit for the modeling of hydrogen release mechanism

Transition Metal Catalyzed σ-Bond Activation and Formation Reactions

The Oniom Method and its Applications to Enzymatic Reactions

Automatized Parameterization of the Density‐functional Tight‐binding Method. II. Two‐center Integrals

Rh^III‐Catalyzed C(sp³)H Bond Activation by an External Base Metalation/Deprotonation Mechanism: A Theoretical Study

Intrinsic reaction coordinate: Calculation, bifurcation, and automated search

Quantum chemical simulations reveal acetylene-based growth mechanisms in the chemical vapor deposition synthesis of carbon nanotubes

The origin of enantioselectivity for intramolecular Friedel–Crafts reaction catalyzed by supramolecular Cu/DNA catalyst complex

Exploring transition state structures for intramolecular pathways by the artificial force induced reaction method

Development of Azo‐Based Fluorescent Probes to Detect Different Levels of Hypoxia

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