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Masanori Tachikawa - One of the best experts on this subject based on the ideXlab platform.
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a path integral molecular dynamics study on intermolecular hydrogen bond of acetic acid arsenic acid Anion and acetic acid phosphoric acid Anion Clusters
Journal of Computational Chemistry, 2019Co-Authors: Yukio Kawashima, Keisuke Sawada, Takahito Nakajima, Masanori TachikawaAbstract:We apply ab initio path integral molecular dynamics simulation employing ωB97XD as the quantum chemical calculation method to acetic acid-arsenic acid Anion and acetic acid-phosphoric acid Anion Clusters to investigate the difference of the hydrogen bond structure and its fluctuation such as proton transfer. We found that the nuclear quantum effect enhanced the fluctuation of the hydrogen bond structure and proton transfer, which shows treatment of the nuclear quantum effect was essential to investigate these systems. The hydrogen bond in acetic acid-arsenic acid Anion Cluster showed characters related to low-barrier hydrogen bonds, while acetic acid-phosphoric acid Anion Cluster did not. We found non-negligible distinction between these two systems, which could not be found in conventional calculations. We suggest that the difference in amount of atomic charge of the atoms consisting the hydrogen bond is the origin of the difference between acetic acid-arsenic acid and acetic acid-phosphoric acid Anion Cluster. © 2018 Wiley Periodicals, Inc.
Daniel M Neumark - One of the best experts on this subject based on the ideXlab platform.
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Anion spectroscopy of uracil thymine and the amino oxo and amino hydroxy tautomers of cytosine and their water Clusters
Chemical Physics, 1998Co-Authors: J Schiedt, R Weinkauf, Daniel M Neumark, E W SchlagAbstract:Abstract In this work we investigate different forms of electron binding in the mass-selected and cooled nucleobases uracil, thymine and cytosine and their water Clusters. In photodetachment–photoelectron spectra of the pyrimidine nucleobases, sharp structures were found at 86±8 meV (uracil), 62±8 meV (thymine) and 85±8 meV (cytosine), which are due to photodetachment of dipole-bound states. The photodetachment angle dependence of these states shows mostly p-wave detachment, which confirms the predicted predominant s-character of the electronic wave function of dipole-bound states. This anisotropy of electron emission and their sharp photodetachment structures can be taken for dipole-bound state recognition. Water attachment to the nucleobases results in positive valence-bound electron affinity, s-wave detachment and broad spectra, implying that the electron now is trapped inside the π * LUMO of the nucleobases, stabilized by the water dipole. The solvent shifts in dependence on water aggregation are linear and allow by extrapolation an estimation of the monomer electron affinities. All three pyrimidine nucleobases are estimated to have a very similar valence-bound electron affinity in the range of 0–200 meV. In nucleobase·(H 2 O) n Clusters, due to the large total dipole moment, dipole-bound states also exist. Resonant excitation of these dipole-bound states with a photon of 1064 nm wavelength causes dissociation of the Anion Cluster, leading to monomer Anions in their dipole-bound state. These monomer Anions can be photodetached by a second IR photon. Whereas, for uracil and thymine, one dipole-bound state is detected, for cytosine we find two dipole-bound states (85±8, 230±8 meV) which are attributed to the dipole-bound states of the simultaneously present amino-hydroxy and amino-oxo cytosine tautomers. We also give a possible explanation why the formation of the dipole-bound state of the amino-oxo tautomer at 230 meV is improbable in the supersonic expansion.
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Anion photoelectron spectroscopy of iodine carbon dioxide Clusters
Journal of Chemical Physics, 1992Co-Authors: Don W Arnold, Stephen E Bradforth, Eun Ha Kim, Daniel M NeumarkAbstract:Anion photoelectron spectroscopy has proved to be a powerful method for the study of molecular Clusters because it combines mass-selectivity and reasonable spectral resolution. Anion photoelectron spectra have been reported for elemental and molecular Clusters of the type Ai, in which the additional electron is delocalized over the entire Anion Cluster,‘-6 and for mixed Clusters of the type X(M),, in which a distinct Xchromophore interacts with a “solvating” species, M.‘,s The X(M) ,, photoelectron spectra obtained thus far have exhibited the same vibrational and electronic features seen in the bare Xspectrum, although these features are typically shifted and broadened in the Cluster Anion spectra due to the X-/M interaction. In this Communication, we present photoelectron spectra of the Anion Clusters I(CO,) ,,, n = l-l 3, that are qualitatively different from the Ispectrum in that they show pronounced progressions in vibrational modes of the solvating CO1 molecules. These arise from perturbations to the solvent molecules by the Icore. While Markovich et al. 8(a) have obtained photoelectron spectra for I(CO,),, n = l-7, they did not observe any vibrational structure due to the lower resolution in their experiment. Our results represent a new level of detail in the study of “solute-solvent” interactions in Clusters. The experimental apparatus, described in detail elsewhere,’ employs a pulsed molecular beam (2% HI/C!Oz) propagating at a right angle to a 1 keV electron beam to generate vibrationally and rotationally relaxed Anion Clusters of the form I(COz) n. The Anions are injected into a Wiley-McLaren type time-of-flight mass spectrometer; a typical mass spectrum is shown in Fig. 1. Anion Clusters of the desired mass are photodetached with a properly timed light pulse from a Nd:YAG laser. The fourth (266 nm; 4.66 eV) and fifth (213 nm; 5.82 eV) harmonics of the Nd:YAG were used for these experiments. Energy analysis of the photoelectrons is performed by time-of-flight over a one meter field-free flight tube using microchannel plate detection. The instrumental resolution of the apparatus is 11 meV at 0.65 eV and varies as a function of ( eKE)3’2 (eKE = electron kinetic energy). Photoelectron spectra of I-, I(C02), and I( C02) 2 taken at hv=4.66 eV are presented in Fig. 2. Figure 3 shows the photoelectron spectra of I-(C02)n, n= 1-13, taken with hv=5.82 eV. The 5.82 eV spectra of I(CO,) and I(C02)2, compared with the 4.66 eV spectra, demonstrate the dependence of the instrumental resolution on the eKE. The Ispectrum consists of two peaks corresponding to the 2P3/2 ground state and the 2P1i2 excited state of the iodine atom; the spin-orbit splitting is 0.943 eV. The I( C02), spectra, in contrast, consist of two groups of peaks. The two bands in each spectrum, separated by approximately the I atom spin-orbit splitting, represent transitions to different electronic states of the neutral Cluster which, to first order, can be labeled I(2P3,2) * (CO,), and I( 2P1,2) * ( C02),. The peaks in the I( 2P312) * ( COa), band, when they can be resolved at all, are noticeably broader than those in the I( *PI,,) * ( C02) n band at lower eKE. This is partly, but not totally (see below), due to the poorer resolution of the band at higher eKE. The intensities of peaks at very low eKE ( ~0.3 eV) are reduced due to the cutoff function of the electron detector.’ The Cluster Anion spectra show two important trends relative to the bare Ispectrum. First, the spectral peaks are located at progressively lower eKE’s as the number of CO2 molecules is increased. This “solvent shift,” seen in other X-(M), photoelectron spectra,“’ arises from the stronger attraction of CO2 to Ithan to an I atom. The Cluster size dependence of the solvent shift is shown in Fig. 4. The more novel characteristic of these spectra is the vibrational progression in each of the bands. The average progression spacing” in the I(CO,), spectra, 665 *90 cm-’ (82 meV), is essentially identical to the CO, bending
Yukio Kawashima - One of the best experts on this subject based on the ideXlab platform.
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a path integral molecular dynamics study on intermolecular hydrogen bond of acetic acid arsenic acid Anion and acetic acid phosphoric acid Anion Clusters
Journal of Computational Chemistry, 2019Co-Authors: Yukio Kawashima, Keisuke Sawada, Takahito Nakajima, Masanori TachikawaAbstract:We apply ab initio path integral molecular dynamics simulation employing ωB97XD as the quantum chemical calculation method to acetic acid-arsenic acid Anion and acetic acid-phosphoric acid Anion Clusters to investigate the difference of the hydrogen bond structure and its fluctuation such as proton transfer. We found that the nuclear quantum effect enhanced the fluctuation of the hydrogen bond structure and proton transfer, which shows treatment of the nuclear quantum effect was essential to investigate these systems. The hydrogen bond in acetic acid-arsenic acid Anion Cluster showed characters related to low-barrier hydrogen bonds, while acetic acid-phosphoric acid Anion Cluster did not. We found non-negligible distinction between these two systems, which could not be found in conventional calculations. We suggest that the difference in amount of atomic charge of the atoms consisting the hydrogen bond is the origin of the difference between acetic acid-arsenic acid and acetic acid-phosphoric acid Anion Cluster. © 2018 Wiley Periodicals, Inc.
Don W Arnold - One of the best experts on this subject based on the ideXlab platform.
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communications Anion photoelectron spectroscopy of iodine carbon dioxide Clusters
2003Co-Authors: Don W Arnold, Stephen E Bradforth, Eun Ha Kim, Daniel M NeumarkbAbstract:Anion photoelectron spectroscopy has proved to be a powerful method for the study of molecular Clusters because it combines mass-selectivity and reasonable spectral resolution. Anion photoelectron spectra have been reported for elemental and molecular Clusters of the type Ai, in which the additional electron is delocalized over the entire Anion Cluster,‘-6 and for mixed Clusters of the type X- (M),, in which a distinct X- chromophore interacts with a “solvating” species, M.‘,s The X- (M) ,, photoelectron spectra obtained thus far have exhibited the same vibrational and electronic features seen in the bare X- spectrum, although these features are typically shifted and broadened in the Cluster Anion spectra due to the X-/M interaction. In this Communication, we present photoelectron spectra of the Anion Clusters I- (CO,) ,,, n = l-l 3, that are qualitatively different from the I- spectrum in that they show pronounced progressions in vibrational modes of the solvating CO1 molecules. These arise from perturbations to the solvent molecules by the I- core. While Markovich et al. 8(a) have obtained photoelectron spectra for I- (CO,),, n = l-7, they did not observe any vibrational structure due to the lower resolution in their experiment. Our results represent a new level of detail in the study of “solute-solvent” interactions in Clusters. The experimental apparatus, described in detail elsewhere,’ employs a pulsed molecular beam (2% HI/C!Oz) propagating at a right angle to a 1 keV electron beam to generate vibrationally and rotationally relaxed Anion Clusters of the form I- (COz) n. The Anions are injected into a Wiley-McLaren type time-of-flight mass spectrometer; a typical mass spectrum is shown in Fig. 1. Anion Clusters of the desired mass are photodetached with a properly timed light pulse from a Nd:YAG laser. The fourth (266 nm; 4.66 eV) and fifth (213 nm; 5.82 eV) harmonics of the Nd:YAG were used for these experiments. Energy analysis of the photoelectrons is performed by time-of-flight over a one meter field-free flight tube using microchannel plate detection. The instrumental resolution of the apparatus is 11 meV at 0.65 eV and varies as a function of ( eKE)3’2 (eKE = electron kinetic energy). Photoelectron spectra of I-, I- (C02), and I- ( C02) 2 taken at hv=4.66 eV are presented in Fig. 2. Figure 3 shows the photoelectron spectra of I-(C02)n, n= 1-13, taken with hv=5.82 eV. The 5.82 eV spectra of I- (CO,) and I- (C02)2, compared with the 4.66 eV spectra, demonstrate the dependence of the instrumental resolution on the eKE. The I- spectrum consists of two peaks corresponding to the 2P3/2 ground state and the 2P1i2 excited state of the iodine atom; the spin-orbit splitting is 0.943 eV. The I- ( C02), spectra, in contrast, consist of two groups of peaks. The two bands in each spectrum, separated by approximately the I atom spin-orbit splitting, represent transitions to different electronic states of the neutral Cluster which, to first order, can be labeled I(2P3,2) * (CO,), and I( 2P1,2) * ( C02),. The peaks in the I( 2P312) * ( COa), band, when they can be resolved at all, are noticeably broader than those in the I( *PI,,) * ( C02) n band at lower eKE. This is partly, but not totally (see below), due to the poorer resolution of the band at higher eKE. The intensities of peaks at very low eKE ( ~0.3 eV) are reduced due to the cutoff function of the electron detector.’ The Cluster Anion spectra show two important trends relative to the bare I- spectrum. First, the spectral peaks are located at progressively lower eKE’s as the number of CO2 molecules is increased. This “solvent shift,” seen in other X-(M), photoelectron spectra,“’ arises from the stronger attraction of CO2 to I- than to an I atom. The Cluster size dependence of the solvent shift is shown in Fig. 4. The more novel characteristic of these spectra is the vibrational progression in each of the bands. The average progression spacing” in the I- (CO,), spectra, 665 *90 cm-’ (82 meV), is essentially identical to the CO, bending
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Anion photoelectron spectroscopy of iodine carbon dioxide Clusters
Journal of Chemical Physics, 1992Co-Authors: Don W Arnold, Stephen E Bradforth, Eun Ha Kim, Daniel M NeumarkAbstract:Anion photoelectron spectroscopy has proved to be a powerful method for the study of molecular Clusters because it combines mass-selectivity and reasonable spectral resolution. Anion photoelectron spectra have been reported for elemental and molecular Clusters of the type Ai, in which the additional electron is delocalized over the entire Anion Cluster,‘-6 and for mixed Clusters of the type X(M),, in which a distinct Xchromophore interacts with a “solvating” species, M.‘,s The X(M) ,, photoelectron spectra obtained thus far have exhibited the same vibrational and electronic features seen in the bare Xspectrum, although these features are typically shifted and broadened in the Cluster Anion spectra due to the X-/M interaction. In this Communication, we present photoelectron spectra of the Anion Clusters I(CO,) ,,, n = l-l 3, that are qualitatively different from the Ispectrum in that they show pronounced progressions in vibrational modes of the solvating CO1 molecules. These arise from perturbations to the solvent molecules by the Icore. While Markovich et al. 8(a) have obtained photoelectron spectra for I(CO,),, n = l-7, they did not observe any vibrational structure due to the lower resolution in their experiment. Our results represent a new level of detail in the study of “solute-solvent” interactions in Clusters. The experimental apparatus, described in detail elsewhere,’ employs a pulsed molecular beam (2% HI/C!Oz) propagating at a right angle to a 1 keV electron beam to generate vibrationally and rotationally relaxed Anion Clusters of the form I(COz) n. The Anions are injected into a Wiley-McLaren type time-of-flight mass spectrometer; a typical mass spectrum is shown in Fig. 1. Anion Clusters of the desired mass are photodetached with a properly timed light pulse from a Nd:YAG laser. The fourth (266 nm; 4.66 eV) and fifth (213 nm; 5.82 eV) harmonics of the Nd:YAG were used for these experiments. Energy analysis of the photoelectrons is performed by time-of-flight over a one meter field-free flight tube using microchannel plate detection. The instrumental resolution of the apparatus is 11 meV at 0.65 eV and varies as a function of ( eKE)3’2 (eKE = electron kinetic energy). Photoelectron spectra of I-, I(C02), and I( C02) 2 taken at hv=4.66 eV are presented in Fig. 2. Figure 3 shows the photoelectron spectra of I-(C02)n, n= 1-13, taken with hv=5.82 eV. The 5.82 eV spectra of I(CO,) and I(C02)2, compared with the 4.66 eV spectra, demonstrate the dependence of the instrumental resolution on the eKE. The Ispectrum consists of two peaks corresponding to the 2P3/2 ground state and the 2P1i2 excited state of the iodine atom; the spin-orbit splitting is 0.943 eV. The I( C02), spectra, in contrast, consist of two groups of peaks. The two bands in each spectrum, separated by approximately the I atom spin-orbit splitting, represent transitions to different electronic states of the neutral Cluster which, to first order, can be labeled I(2P3,2) * (CO,), and I( 2P1,2) * ( C02),. The peaks in the I( 2P312) * ( COa), band, when they can be resolved at all, are noticeably broader than those in the I( *PI,,) * ( C02) n band at lower eKE. This is partly, but not totally (see below), due to the poorer resolution of the band at higher eKE. The intensities of peaks at very low eKE ( ~0.3 eV) are reduced due to the cutoff function of the electron detector.’ The Cluster Anion spectra show two important trends relative to the bare Ispectrum. First, the spectral peaks are located at progressively lower eKE’s as the number of CO2 molecules is increased. This “solvent shift,” seen in other X-(M), photoelectron spectra,“’ arises from the stronger attraction of CO2 to Ithan to an I atom. The Cluster size dependence of the solvent shift is shown in Fig. 4. The more novel characteristic of these spectra is the vibrational progression in each of the bands. The average progression spacing” in the I(CO,), spectra, 665 *90 cm-’ (82 meV), is essentially identical to the CO, bending
Fengxing Zhang - One of the best experts on this subject based on the ideXlab platform.
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a novel 3d metal organic framework with silver iodide Anion Cluster ag14i16 2 as node synthesis structure and fluorescence property
ChemInform, 2014Co-Authors: Weixia Zhou, Shiliang Huang, Jiao Niu, Fengxing ZhangAbstract:Colorless block crystals of [Ag14I16(HDABCO)2]·DABCO are synthesized from AgI dissolved in saturated KI solution and DABCO in EtOH (room temperature, 14 d, 51% yield).
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a novel 3d metal organic framework with silver iodide Anion Cluster ag14i16 2 as node synthesis structure and fluorescence property
Inorganic Chemistry Communications, 2014Co-Authors: Weixia Zhou, Shiliang Huang, Jiao Niu, Fengxing ZhangAbstract:Abstract A novel 3D silver iodide metal–organic framework {[Ag14I16(HDABCO)2]·(DABCO)}n (DABCO = 1,4-diazabicyclo[2.2.2]octane) (1) has been synthesized solvothermally. In this compound, a [Ag14I16]2 − Anion Cluster was formed by twelve AgI4 tetrahedra and two AgI3 triangles by sharing their edges, in which its charge is compensated by two mono-protoned HDABCO+. Each [Ag14I16]2 − Cluster connects to six neighboring Clusters by sharing corner I− ions between the AgI4 tetrahedra, resulting in a 3D framework. The compound 1 displays intense fluorescence emission with maximum at 400 nm and 465 nm upon 310 nm excitation at room temperature.