Tetsuya Taketsugu - Academia.edu (original) (raw)

Papers by Tetsuya Taketsugu

Physical Chemistry Chemical Physics, 2017

Solvent effects on the excited-state double proton transfer (ESDPT) mechanism in 7-azaindole (7AI... more Solvent effects on the excited-state double proton transfer (ESDPT) mechanism in 7-azaindole (7AI) dimer were investigated using the time-dependent density functional theory (TDDFT) method. Excited-state potential energy profiles along the reaction paths in locally excited (LE) state and charge transfer (CT) state were calculated using polarizable continuum model (PCM) to include the solvent effect. A series of non-polar and polar solvents with different dielectric constant were used to examine the polarity effect on the ESDPT mechanism. The present results suggest that in non-polar solvent and polar solvent with a small dielectric constant, ESDPT follows the concerted mechanism, similar to the case in the gas phase. In polar solvent with a relatively large dielectric constant, however, ESDPT is likely to follow the stepwise mechanism via a stable zwitterionic intermediate in the LE state on the adiabatic potential energy surface, although inclusion of zero-point vibrational energy (ZPE) corrections again suggests the concerted mechanism. In the meantime, the stepwise reaction path involving the CT state with neutral intermediates is also examined, and is found to be less competitive than the concerted or stepwise path in the LE state in both non-polar and polar solvents. The present study provides a new insight into the experimental controversy of the ESDPT mechanism of 7AI dimer in a solution.

Physical Chemistry Chemical Physics, 2013

Recently, Kosma et al. 7 observed appreciable dependence of decay profiles on the excitation wave... more Recently, Kosma et al. 7 observed appreciable dependence of decay profiles on the excitation wavelength in the femtosecond time-resolved pump-probe ionization spectroscopy of isolated cytosine, and attributed this remarkable observation to the coexistence of the keto, imino, and enol tautomers. With the excitation wavelengths of 290, 280, 270, and 267 nm, the observed transients were decomposed into three components with lifetimes of τ 1 < 0.25 ps, τ 2 = 1.1 − 2.3 ps, and τ 3 ≥ 19 ps. With the help of quantum chemical calculations of excitation energies by Tomić et al., 22 the transients with excitation at the former two wavelengths were assigned to the keto tautomer, while those at the latter two were assigned to a mixture of the keto and enol or imino tautomers. With an excitation at 260 nm, on the other hand, only two transients were identified with lifetime constants of τ 1 = 0.12 ps and τ 2 = 3.8 ps. The dominant component for this wavelength was determined as the enol form, with a minor contribution of the imino form. The authors also proposed that the long-time constant of τ 3 , varied from 19 to more than 150 ps, corresponds to a long-lived state of the imino form populated by the excited-state tautomerization from the keto form. More recently, Ho et al. 8 further clarified the dependence of decay profiles on the excitation wavelength (260 to 300 nm) in the femtosecond pump-probe photoionization spectra of cytosine, 1-methylcytosine, and 5-fluorocytosine in the gas phase, where these molecules have different population ratio of their tautomers. 8 After detailed analysis, the authors concluded that the long time constant of 3 to 45 ps observed at excitation wavelengths between 260 and 285 nm corresponds to the decay from the enol tautomer and that the subpicosecond time constant for excitation wavelengths between 260 and 300 nm is assigned to the decay from the keto and imino tautomers. For the enol tautomer, they estimated the barrier height for the decay process to be ~0.15 eV from the minimum of structures for imino cytosine. The SA(4)-CASSCF(10,8) electronic energies of the (S 0) min , (S 1) min = (1 nπ*)' min , TS, and MECI structures for enol cytosine.

a^{a}aK. Ishii. T. Hirano. U. Nagashima, B. Weis, and K. Yamashita, Astrophys. J. 410. L43, (1993... more $^{a}$K. Ishii. T. Hirano. U. Nagashima, B. Weis, and K. Yamashita, Astrophys. J. 410. L43, (1993) b^{b}bK. Kawaguchi, E. Kagi. T. Hirano, S. Takano, and S. Saito, Astrophys. J. 406. L39. (1993) c^{c}cL. M. Ziurys. A. J. Apponi. M. Guelin, and J. Cemicharo Astrophys. J. 445, L47, (1995)

Physical Chemistry Chemical Physics, 2018

Hydrogen peroxide (H 2 O 2) decomposition mechanisms under the absence and presence of iron ions ... more Hydrogen peroxide (H 2 O 2) decomposition mechanisms under the absence and presence of iron ions in aqueous solution, which contain no OH radical formations, are theoretically determined. Calculating the oxygen-oxygen bond dissociation energies of H 2 O 2 , we confirmed that the OH radical formation requires spin-forbidden transitions. Instead, we tested an H 2 O 2 dimer-based decomposition mechanism and found that this mechanism provides reasonable barrier heights with 52 ∼ 62 kcal/mol, which are close to the experimental activation energy. We next calculated the oxygen-oxygen bond dissociation of H 2 O 2 coordinating to the iron ion hydration complex in order to explore the H 2 O 2 decomposition under the presence of iron ions. Surprisingly, we found that a monovalent iron ion complex provides no reaction barrier to dissociate H 2 O 2 , in contrast to the ferrous (Fe 2+) and ferric (Fe 3+) ion complexes accompanying very high barriers. Following this result, we determined the subsequent oxygen formation mechanism of the monovalent iron ion complex and found that this mechanism needs a hydrogen bond network around H 2 O 2 to proceed at room temperature. We, therefore, conclude that the H 2 O 2 decomposition under the presence of iron ions is driven by the electron transfer to the iron ion hydration complex and proceeds by hydrogen transfers in the hydrogen bond network around H 2 O 2 .

The Journal of Physical Chemistry A, 2021

Isolated nickel-doped aluminum oxide cations (NiO m)(Al 2 O 3) n (AlO) + with m = 1−2 and n = 1−3... more Isolated nickel-doped aluminum oxide cations (NiO m)(Al 2 O 3) n (AlO) + with m = 1−2 and n = 1−3 are investigated by infrared photodissociation (IRPD) spectroscopy in combination with density functional theory and the singlecomponent artificial force-induced reaction method. IRPD spectra of the corresponding He-tagged cations are reported in the 400− 1200 cm −1 spectral range and assigned based on a comparison to calculated harmonic IR spectra of low-energy isomers. Simulated spectra of the lowest energy structures generally match the experimental spectra, but multiple isomers may contribute to the spectra of the m = 2 series. The identified structures of the oxides (m = 1) correspond to inserting a Ni−O moiety into an Al−O bond of the corresponding (Al 2 O 3) 1−3 (AlO) + cluster, yielding either a doubly or triply coordinated Ni 2+ center. The m = 2 clusters prefer similar structures in which the additional O atom either is incorporated into a peroxide unit, leaving the oxidation state of the Ni 2+ atom unchanged, or forms a biradical comprising a terminal oxygen radical anion Al−O •− and a Ni 3+ species. These clusters represent model systems for under-coordinated Ni sites in aluminasupported Ni catalysts and should prove helpful in disentangling the mechanism of selective oxidative dehydrogenation of alkanes by Ni-doped catalysts.

Chemical Communications, 2021

We review the on-the-fly trajectory mapping and Reaction Space Projector methods to analyze dynam... more We review the on-the-fly trajectory mapping and Reaction Space Projector methods to analyze dynamical trajectories based on a reduced-dimensionality subspace.

The Journal of Physical Chemistry C, 2021

The mechanism of catalytic oxidation of carbon monoxide and epoxidation of ethylene by molecular ... more The mechanism of catalytic oxidation of carbon monoxide and epoxidation of ethylene by molecular oxygen adsorbed on the carbon-doped hexagonal boron nitride (h-BN) is investigated theoretically. The energy profiles and the dependence of the activation barriers on the distance between the doped carbon atom are analyzed. It is shown that the considered oxidation and epoxidation reactions can occur not only on the B atom sites in the close vicinity to the C dopant but also at relatively large distances from the C dopant. Therefore, CB/h-BN possesses many active sites and it is possible to achieve a wide activation area (~5.0 Å from the doped C) of the catalyst at the small concentration of C. The results of calculations demonstrate that the reaction intermediates along these reaction pathways are slightly destabilized with an increase in the distance from the doped C atom; however, the reaction barriers remain mainly intact. Therefore, C doping of h-BN is a highly promising way for catalytic functionalization of the inert h-BN based materials for oxidation and epoxidation reactions by molecular oxygen.

Journal of Chemical Theory and Computation, 2020

Following our recent work to reduce a dimension of a set of reference structures along the intrin... more Following our recent work to reduce a dimension of a set of reference structures along the intrinsic reaction coordinate (IRC) by a classical multidimensional scaling (CMDS) approach (J. Chem. Theory Comput. 2018, 14, 4263−4270), we propose the method to project on-the-fly trajectories into a reduced-dimension subspace determined by the IRC network, using the out-of-sample extension of CMDS. The method was applied to the SN2 reaction, OH-+ CH3F, in which trajectories show a bifurcating nature around the highly-curved region of the IRC path, and to the structural transformation of Au5 cluster in which the global reaction path network consists of five equilibrium structures and 14 IRCs. It was demonstrated that the present analysis can visualize the dynamics effect by showing a dynamic reaction route on the basis of the static reaction paths.

Surface enhanced Raman scattering (SERS) is presented via a case study of 2,2’-bipyridyl(22BPY) m... more Surface enhanced Raman scattering (SERS) is presented via a case study of 2,2’-bipyridyl(22BPY) molecules adsorbed on pure Au and Ag as well as on Au-Ag alloy nanodiscs. ExperimentalSERS spectra from Au and Ag nanodics show similar peaks, but those from Au-Ag alloyreveal new spectral features. The physical enhancement factors due to surface nano-texture wereconsidered by numerical simulations of light intensity distribution for the nano-textured Au, Ag,and Au-Ag alloy surfaces, but found to cause only minor differences. For the chemical insights ofenhancement, the density functional theory (DFT) calculations were performed using Au20, Ag20,and Au10Ag10 clusters of a pyramidal structure for SERS modeling. Binding of 22BPY to the clusterswas simulated by considering possible arrangements of vertex and planar physical as well aschemical adsorption models. A qualitative match with experimental SERS results for the pure Auand Ag was obtained. DFT models showing spectral shifts of 22BPY S...

Scientific Reports, 2018

We investigate the bottom-up growth of N = 7 armchair graphene nanoribbons (7-AGNRs) from the 10,... more We investigate the bottom-up growth of N = 7 armchair graphene nanoribbons (7-AGNRs) from the 10,10′-dibromo-9,9′-bianthracene (DBBA) molecules on Ag(111) with the focus on the role of the organometallic (OM) intermediates. It is demonstrated that DBBA molecules on Ag(111) are partially debrominated at room temperature and lose all bromine atoms at elevated temperatures. Similar to DBBA on Cu(111), debrominated molecules form OM chains on Ag(111). Nevertheless, in contrast with the Cu(111) substrate, formation of polyanthracene chains from OM intermediates via an Ullmann-type reaction is feasible on Ag(111). Cleavage of C–Ag bonds occurs before the thermal threshold for the surface-catalyzed activation of C–H bonds on Ag(111) is reached, while on Cu(111) activation of C–H bonds occurs in parallel with the cleavage of the stronger C–Cu bonds. Consequently, while OM intermediates obstruct the Ullmann reaction between DBBA molecules on the Cu(111) substrate, they are required for the f...

The Journal of Physical Chemistry C, 2018

Quadrupole mass spectra S2. Experimental spectra compared to computed spectra for all the isomers... more Quadrupole mass spectra S2. Experimental spectra compared to computed spectra for all the isomers S3. Additional possible isomers, spin densities and NBO charges S4. Isomer energies S5. Cartesian atomic coordinates of all calculated isomers

Physical Chemistry Chemical Physics, 2017

The mechanism of dissociative D2 adsorption on Ti2O4− is studied using infrared photodissociation... more The mechanism of dissociative D2 adsorption on Ti2O4− is studied using infrared photodissociation spectroscopy in combination with density functional theory calculations.

Physical Chemistry Chemical Physics, 2017

Solvent effects on the excited-state double proton transfer (ESDPT) mechanism in the 7-azaindole ... more Solvent effects on the excited-state double proton transfer (ESDPT) mechanism in the 7-azaindole (7AI) dimer were investigated using the time-dependent density functional theory (TDDFT) method.

The Chemical Record, 2016

In this account, a technical overview of the artificial force induced reaction (AFIR) method is p... more In this account, a technical overview of the artificial force induced reaction (AFIR) method is presented. The AFIR method is one of automated reaction path search methods developed by the authors, and has been applied extensively to a variety of chemical reactions such as organocatalysis, organometallic catalysis, and photoreactions. There are two modes in the AFIR method, i.e., multi-component mode (MC-AFIR) and single-component mode (SC-AFIR). The former has been applied to bimolecular and multicomponent reactions and the latter to unimolecular isomerization and dissociation reactions. Five numerical examples are presented for Aldol reaction, Claisen rearrangement, Co-catalyzed hydroformylation, a fullerene structure search, and a non-radiative decay path search in an electronically excited naphthalene molecule. Finally, possible applications of the AFIR method are discussed.

Chemical record (New York, N.Y.), Oct 29, 2016

In this Personal Account, we review the work of our group in the area of environmental and energy... more In this Personal Account, we review the work of our group in the area of environmental and energy-related nanocatalysis over the past seven years. We focus on understanding the fundamental mechanisms that control the properties of atomic clusters and nanoparticles - a form of matter that is intermediate between atoms and their bulk counterpart. The emphasis is on the theoretical design of effective catalysts based on cheap and abundant elements. The main idea that stands behind our work is that even catalytically inactive or completely inert materials can be functionalized at the nanoscale via the size, structure, morphology, and support effects. Such an approach opens up new ways to design catalytically active systems based on materials never before considered as catalysts. In particular, we demonstrate that hexagonal boron nitride (h-BN), which has been traditionally considered an inert material, can be functionalized and become active for a number of catalytic reactions involving...

a^{a}aK. Ishii. T. Hirano. U. Nagashima, B. Weis, and K. Yamashita, Astrophys. J. 410. L43, (1993... more $^{a}$K. Ishii. T. Hirano. U. Nagashima, B. Weis, and K. Yamashita, Astrophys. J. 410. L43, (1993) b^{b}bK. Kawaguchi, E. Kagi. T. Hirano, S. Takano, and S. Saito, Astrophys. J. 406. L39. (1993) c^{c}cL. M. Ziurys. A. J. Apponi. M. Guelin, and J. Cemicharo Astrophys. J. 445, L47, (1995)

Author Institution: Department of Chemistry Faculty of Science, Ochanomizu University; Department... more Author Institution: Department of Chemistry Faculty of Science, Ochanomizu University; Department of Chemistry Faculty of Science, National Institute for Advanced Interdisciplinary Research

Theoretica Chimica Acta, 1995

The Journal of Physical Chemistry, 1996

This paper illustrates the utility of combining high-quality electronic structure calculations, m... more This paper illustrates the utility of combining high-quality electronic structure calculations, methods for determining reaction paths, and direct dynamics methods for studying ab initiotrajectories on the fly to develop an understanding of complex chemical reactions. The combined methods are applied to the pseudorotation in SiH5-, competing dissociation paths for N2O2, the dissociation of FN3 into NF + N2, and the potential energy surfaces for AlH2. These DRP results may be thought of as samples of what dynamical processes can be encountered on each potential energy surface.

Physical Chemistry Chemical Physics, 2017

Solvent effects on the excited-state double proton transfer (ESDPT) mechanism in 7-azaindole (7AI... more Solvent effects on the excited-state double proton transfer (ESDPT) mechanism in 7-azaindole (7AI) dimer were investigated using the time-dependent density functional theory (TDDFT) method. Excited-state potential energy profiles along the reaction paths in locally excited (LE) state and charge transfer (CT) state were calculated using polarizable continuum model (PCM) to include the solvent effect. A series of non-polar and polar solvents with different dielectric constant were used to examine the polarity effect on the ESDPT mechanism. The present results suggest that in non-polar solvent and polar solvent with a small dielectric constant, ESDPT follows the concerted mechanism, similar to the case in the gas phase. In polar solvent with a relatively large dielectric constant, however, ESDPT is likely to follow the stepwise mechanism via a stable zwitterionic intermediate in the LE state on the adiabatic potential energy surface, although inclusion of zero-point vibrational energy (ZPE) corrections again suggests the concerted mechanism. In the meantime, the stepwise reaction path involving the CT state with neutral intermediates is also examined, and is found to be less competitive than the concerted or stepwise path in the LE state in both non-polar and polar solvents. The present study provides a new insight into the experimental controversy of the ESDPT mechanism of 7AI dimer in a solution.

Physical Chemistry Chemical Physics, 2013

Recently, Kosma et al. 7 observed appreciable dependence of decay profiles on the excitation wave... more Recently, Kosma et al. 7 observed appreciable dependence of decay profiles on the excitation wavelength in the femtosecond time-resolved pump-probe ionization spectroscopy of isolated cytosine, and attributed this remarkable observation to the coexistence of the keto, imino, and enol tautomers. With the excitation wavelengths of 290, 280, 270, and 267 nm, the observed transients were decomposed into three components with lifetimes of τ 1 < 0.25 ps, τ 2 = 1.1 − 2.3 ps, and τ 3 ≥ 19 ps. With the help of quantum chemical calculations of excitation energies by Tomić et al., 22 the transients with excitation at the former two wavelengths were assigned to the keto tautomer, while those at the latter two were assigned to a mixture of the keto and enol or imino tautomers. With an excitation at 260 nm, on the other hand, only two transients were identified with lifetime constants of τ 1 = 0.12 ps and τ 2 = 3.8 ps. The dominant component for this wavelength was determined as the enol form, with a minor contribution of the imino form. The authors also proposed that the long-time constant of τ 3 , varied from 19 to more than 150 ps, corresponds to a long-lived state of the imino form populated by the excited-state tautomerization from the keto form. More recently, Ho et al. 8 further clarified the dependence of decay profiles on the excitation wavelength (260 to 300 nm) in the femtosecond pump-probe photoionization spectra of cytosine, 1-methylcytosine, and 5-fluorocytosine in the gas phase, where these molecules have different population ratio of their tautomers. 8 After detailed analysis, the authors concluded that the long time constant of 3 to 45 ps observed at excitation wavelengths between 260 and 285 nm corresponds to the decay from the enol tautomer and that the subpicosecond time constant for excitation wavelengths between 260 and 300 nm is assigned to the decay from the keto and imino tautomers. For the enol tautomer, they estimated the barrier height for the decay process to be ~0.15 eV from the minimum of structures for imino cytosine. The SA(4)-CASSCF(10,8) electronic energies of the (S 0) min , (S 1) min = (1 nπ*)' min , TS, and MECI structures for enol cytosine.

a^{a}aK. Ishii. T. Hirano. U. Nagashima, B. Weis, and K. Yamashita, Astrophys. J. 410. L43, (1993... more $^{a}$K. Ishii. T. Hirano. U. Nagashima, B. Weis, and K. Yamashita, Astrophys. J. 410. L43, (1993) b^{b}bK. Kawaguchi, E. Kagi. T. Hirano, S. Takano, and S. Saito, Astrophys. J. 406. L39. (1993) c^{c}cL. M. Ziurys. A. J. Apponi. M. Guelin, and J. Cemicharo Astrophys. J. 445, L47, (1995)

Physical Chemistry Chemical Physics, 2018

Hydrogen peroxide (H 2 O 2) decomposition mechanisms under the absence and presence of iron ions ... more Hydrogen peroxide (H 2 O 2) decomposition mechanisms under the absence and presence of iron ions in aqueous solution, which contain no OH radical formations, are theoretically determined. Calculating the oxygen-oxygen bond dissociation energies of H 2 O 2 , we confirmed that the OH radical formation requires spin-forbidden transitions. Instead, we tested an H 2 O 2 dimer-based decomposition mechanism and found that this mechanism provides reasonable barrier heights with 52 ∼ 62 kcal/mol, which are close to the experimental activation energy. We next calculated the oxygen-oxygen bond dissociation of H 2 O 2 coordinating to the iron ion hydration complex in order to explore the H 2 O 2 decomposition under the presence of iron ions. Surprisingly, we found that a monovalent iron ion complex provides no reaction barrier to dissociate H 2 O 2 , in contrast to the ferrous (Fe 2+) and ferric (Fe 3+) ion complexes accompanying very high barriers. Following this result, we determined the subsequent oxygen formation mechanism of the monovalent iron ion complex and found that this mechanism needs a hydrogen bond network around H 2 O 2 to proceed at room temperature. We, therefore, conclude that the H 2 O 2 decomposition under the presence of iron ions is driven by the electron transfer to the iron ion hydration complex and proceeds by hydrogen transfers in the hydrogen bond network around H 2 O 2 .

The Journal of Physical Chemistry A, 2021

Isolated nickel-doped aluminum oxide cations (NiO m)(Al 2 O 3) n (AlO) + with m = 1−2 and n = 1−3... more Isolated nickel-doped aluminum oxide cations (NiO m)(Al 2 O 3) n (AlO) + with m = 1−2 and n = 1−3 are investigated by infrared photodissociation (IRPD) spectroscopy in combination with density functional theory and the singlecomponent artificial force-induced reaction method. IRPD spectra of the corresponding He-tagged cations are reported in the 400− 1200 cm −1 spectral range and assigned based on a comparison to calculated harmonic IR spectra of low-energy isomers. Simulated spectra of the lowest energy structures generally match the experimental spectra, but multiple isomers may contribute to the spectra of the m = 2 series. The identified structures of the oxides (m = 1) correspond to inserting a Ni−O moiety into an Al−O bond of the corresponding (Al 2 O 3) 1−3 (AlO) + cluster, yielding either a doubly or triply coordinated Ni 2+ center. The m = 2 clusters prefer similar structures in which the additional O atom either is incorporated into a peroxide unit, leaving the oxidation state of the Ni 2+ atom unchanged, or forms a biradical comprising a terminal oxygen radical anion Al−O •− and a Ni 3+ species. These clusters represent model systems for under-coordinated Ni sites in aluminasupported Ni catalysts and should prove helpful in disentangling the mechanism of selective oxidative dehydrogenation of alkanes by Ni-doped catalysts.

Chemical Communications, 2021

We review the on-the-fly trajectory mapping and Reaction Space Projector methods to analyze dynam... more We review the on-the-fly trajectory mapping and Reaction Space Projector methods to analyze dynamical trajectories based on a reduced-dimensionality subspace.

The Journal of Physical Chemistry C, 2021

The mechanism of catalytic oxidation of carbon monoxide and epoxidation of ethylene by molecular ... more The mechanism of catalytic oxidation of carbon monoxide and epoxidation of ethylene by molecular oxygen adsorbed on the carbon-doped hexagonal boron nitride (h-BN) is investigated theoretically. The energy profiles and the dependence of the activation barriers on the distance between the doped carbon atom are analyzed. It is shown that the considered oxidation and epoxidation reactions can occur not only on the B atom sites in the close vicinity to the C dopant but also at relatively large distances from the C dopant. Therefore, CB/h-BN possesses many active sites and it is possible to achieve a wide activation area (~5.0 Å from the doped C) of the catalyst at the small concentration of C. The results of calculations demonstrate that the reaction intermediates along these reaction pathways are slightly destabilized with an increase in the distance from the doped C atom; however, the reaction barriers remain mainly intact. Therefore, C doping of h-BN is a highly promising way for catalytic functionalization of the inert h-BN based materials for oxidation and epoxidation reactions by molecular oxygen.

Journal of Chemical Theory and Computation, 2020

Following our recent work to reduce a dimension of a set of reference structures along the intrin... more Following our recent work to reduce a dimension of a set of reference structures along the intrinsic reaction coordinate (IRC) by a classical multidimensional scaling (CMDS) approach (J. Chem. Theory Comput. 2018, 14, 4263−4270), we propose the method to project on-the-fly trajectories into a reduced-dimension subspace determined by the IRC network, using the out-of-sample extension of CMDS. The method was applied to the SN2 reaction, OH-+ CH3F, in which trajectories show a bifurcating nature around the highly-curved region of the IRC path, and to the structural transformation of Au5 cluster in which the global reaction path network consists of five equilibrium structures and 14 IRCs. It was demonstrated that the present analysis can visualize the dynamics effect by showing a dynamic reaction route on the basis of the static reaction paths.

Surface enhanced Raman scattering (SERS) is presented via a case study of 2,2’-bipyridyl(22BPY) m... more Surface enhanced Raman scattering (SERS) is presented via a case study of 2,2’-bipyridyl(22BPY) molecules adsorbed on pure Au and Ag as well as on Au-Ag alloy nanodiscs. ExperimentalSERS spectra from Au and Ag nanodics show similar peaks, but those from Au-Ag alloyreveal new spectral features. The physical enhancement factors due to surface nano-texture wereconsidered by numerical simulations of light intensity distribution for the nano-textured Au, Ag,and Au-Ag alloy surfaces, but found to cause only minor differences. For the chemical insights ofenhancement, the density functional theory (DFT) calculations were performed using Au20, Ag20,and Au10Ag10 clusters of a pyramidal structure for SERS modeling. Binding of 22BPY to the clusterswas simulated by considering possible arrangements of vertex and planar physical as well aschemical adsorption models. A qualitative match with experimental SERS results for the pure Auand Ag was obtained. DFT models showing spectral shifts of 22BPY S...

Scientific Reports, 2018

We investigate the bottom-up growth of N = 7 armchair graphene nanoribbons (7-AGNRs) from the 10,... more We investigate the bottom-up growth of N = 7 armchair graphene nanoribbons (7-AGNRs) from the 10,10′-dibromo-9,9′-bianthracene (DBBA) molecules on Ag(111) with the focus on the role of the organometallic (OM) intermediates. It is demonstrated that DBBA molecules on Ag(111) are partially debrominated at room temperature and lose all bromine atoms at elevated temperatures. Similar to DBBA on Cu(111), debrominated molecules form OM chains on Ag(111). Nevertheless, in contrast with the Cu(111) substrate, formation of polyanthracene chains from OM intermediates via an Ullmann-type reaction is feasible on Ag(111). Cleavage of C–Ag bonds occurs before the thermal threshold for the surface-catalyzed activation of C–H bonds on Ag(111) is reached, while on Cu(111) activation of C–H bonds occurs in parallel with the cleavage of the stronger C–Cu bonds. Consequently, while OM intermediates obstruct the Ullmann reaction between DBBA molecules on the Cu(111) substrate, they are required for the f...

The Journal of Physical Chemistry C, 2018

Quadrupole mass spectra S2. Experimental spectra compared to computed spectra for all the isomers... more Quadrupole mass spectra S2. Experimental spectra compared to computed spectra for all the isomers S3. Additional possible isomers, spin densities and NBO charges S4. Isomer energies S5. Cartesian atomic coordinates of all calculated isomers

Physical Chemistry Chemical Physics, 2017

The mechanism of dissociative D2 adsorption on Ti2O4− is studied using infrared photodissociation... more The mechanism of dissociative D2 adsorption on Ti2O4− is studied using infrared photodissociation spectroscopy in combination with density functional theory calculations.

Physical Chemistry Chemical Physics, 2017

Solvent effects on the excited-state double proton transfer (ESDPT) mechanism in the 7-azaindole ... more Solvent effects on the excited-state double proton transfer (ESDPT) mechanism in the 7-azaindole (7AI) dimer were investigated using the time-dependent density functional theory (TDDFT) method.

The Chemical Record, 2016

In this account, a technical overview of the artificial force induced reaction (AFIR) method is p... more In this account, a technical overview of the artificial force induced reaction (AFIR) method is presented. The AFIR method is one of automated reaction path search methods developed by the authors, and has been applied extensively to a variety of chemical reactions such as organocatalysis, organometallic catalysis, and photoreactions. There are two modes in the AFIR method, i.e., multi-component mode (MC-AFIR) and single-component mode (SC-AFIR). The former has been applied to bimolecular and multicomponent reactions and the latter to unimolecular isomerization and dissociation reactions. Five numerical examples are presented for Aldol reaction, Claisen rearrangement, Co-catalyzed hydroformylation, a fullerene structure search, and a non-radiative decay path search in an electronically excited naphthalene molecule. Finally, possible applications of the AFIR method are discussed.

Chemical record (New York, N.Y.), Oct 29, 2016

In this Personal Account, we review the work of our group in the area of environmental and energy... more In this Personal Account, we review the work of our group in the area of environmental and energy-related nanocatalysis over the past seven years. We focus on understanding the fundamental mechanisms that control the properties of atomic clusters and nanoparticles - a form of matter that is intermediate between atoms and their bulk counterpart. The emphasis is on the theoretical design of effective catalysts based on cheap and abundant elements. The main idea that stands behind our work is that even catalytically inactive or completely inert materials can be functionalized at the nanoscale via the size, structure, morphology, and support effects. Such an approach opens up new ways to design catalytically active systems based on materials never before considered as catalysts. In particular, we demonstrate that hexagonal boron nitride (h-BN), which has been traditionally considered an inert material, can be functionalized and become active for a number of catalytic reactions involving...

a^{a}aK. Ishii. T. Hirano. U. Nagashima, B. Weis, and K. Yamashita, Astrophys. J. 410. L43, (1993... more $^{a}$K. Ishii. T. Hirano. U. Nagashima, B. Weis, and K. Yamashita, Astrophys. J. 410. L43, (1993) b^{b}bK. Kawaguchi, E. Kagi. T. Hirano, S. Takano, and S. Saito, Astrophys. J. 406. L39. (1993) c^{c}cL. M. Ziurys. A. J. Apponi. M. Guelin, and J. Cemicharo Astrophys. J. 445, L47, (1995)

Author Institution: Department of Chemistry Faculty of Science, Ochanomizu University; Department... more Author Institution: Department of Chemistry Faculty of Science, Ochanomizu University; Department of Chemistry Faculty of Science, National Institute for Advanced Interdisciplinary Research

Theoretica Chimica Acta, 1995

The Journal of Physical Chemistry, 1996

This paper illustrates the utility of combining high-quality electronic structure calculations, m... more This paper illustrates the utility of combining high-quality electronic structure calculations, methods for determining reaction paths, and direct dynamics methods for studying ab initiotrajectories on the fly to develop an understanding of complex chemical reactions. The combined methods are applied to the pseudorotation in SiH5-, competing dissociation paths for N2O2, the dissociation of FN3 into NF + N2, and the potential energy surfaces for AlH2. These DRP results may be thought of as samples of what dynamical processes can be encountered on each potential energy surface.