Takashi Kato

Nagasaki Institute of Applied Science, Nagasaki, Nagasaki, Japan

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Publications (43)100.49 Total impact

  • Takashi Kato, Tokio Yamabe
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    ABSTRACT: The mechanism of the occurrence of intraatomic diamagnetic currents in the neutral He atoms with microscopic sizes is investigated. It is found that most of all electrons can form electron pairs originating from attractive Coulomb interactions between two electrons with opposite spins occupying the 1s atomic orbital in the neutral He atom at 298 K. Intraatomic diamagnetic currents in the neutral He atoms with microscopic sizes can be explained by such electron pairing. The transition temperature Tc(He),(1s) value at which intraatomic diamagnetic currents can disappear in each He atom is estimated. The Tc(He),(1s) values for the neutral He atoms with microscopic sizes are estimated to be much larger than the superconducting transition temperatures Tc,BCS values for the conventional superconductors with macroscopic sizes. This result can be understood from continuous energy levels of electronic states in conventional superconductivity with macroscopic sizes, and from discrete energy levels of electronic states in the neutral He atoms with microscopic sizes. The energy difference between the occupied and unoccupied orbitals decreases with an increase in material size and thus the second-order perturbation effect becomes more important with an increase in material size. Therefore, the mechanism of the occurrence of intraatomic diamagnetic current in the neutral He atoms suggested in this research would not be true for materials with large sizes. The dependence of electronic properties on temperature in the diamagnetic currents in the neutral He atoms with microscopic sizes is studied and compared with that in the conventional superconductivity with macroscopic sizes.
    The Journal of Physical Chemistry A 10/2007; 111(35):8731-40. · 2.77 Impact Factor
  • Takashi Kato, Tokio Yamabe
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    ABSTRACT: Electron–phonon interactions in the photoinduced excited electronic states are investigated, and compared with those in the monoanionic and monocationic electronic states in acenes. The total electron–phonon coupling constants for the monoanionic (lLUMO), monocationic (lHOMO), and photoinduced excited electronic states (lB1u(HOMO→LUMO)) in acenes are estimated. The lB1u(HOMO→LUMO) values are much larger than the lLUMO and lHOMO values in acenes. The complete phase patterns difference between the highest occupied molecular orbitals (HOMO) and the lowest unoccupied molecular orbitals (LUMO) in acenes, are the main reason why the C–C stretching modes around 1500 cm−1 afford much larger electron–phonon coupling constants in the photoinduced excited electronic states than in the monoanionic and monocationic electronic states in acenes, and the reason why the lB1u(HOMO→LUMO) values are much larger than the lLUMO and lHOMO values in acenes.
    Journal of Molecular Structure. 01/2007; 838:89-93.
  • Takashi Kato, Tokio Yamabe
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    ABSTRACT: The mechanism of the intramolecular diamagnetic ring currents in the (4n+2)π electronic states of neutral acenes with microscopic sizes such as naphthalene (10ac), anthracene (14ac), and tetracene (18ac) is discussed, and compared with that of electrical conductivity in normal metals and conventional superconductors with macroscopic sizes. Diamagnetic intramolecular ring current in the (4n+2)π electronic states of neutral acenes with microscopic sizes can be explained in terms of the electron pairing caused by attractive Coulomb interactions between two electrons with opposite spins occupying the same nondegenerate π molecular orbitals. The critical temperature Tcneutral acenes at which diamagnetic intramolecular ring current states are destroyed for the (4n+2)π electronic states of each neutral acene with microscopic sizes such as 10ac, 14ac, and 18ac are estimated to be much larger than the critical temperature (Tc,BCS) for the conventional superconductors with macroscopic sizes. Energy lowering in the exponential factor in the equation for Tc,BCS, originating from continuous energy levels of electronic states in the conventional superconductors with macroscopic sizes, and the energy lowering factor which is proportional to the Tcneutral acenes values, originating from discrete energy levels of electronic states in acene molecules with small sizes such as 10ac, 14ac, and 18ac, are the main reason that the Tcneutral acenes values for the (4n+2)π electronic states of neutral acenes with microscopic sizes are estimated to be much larger than the Tc,BCS values for the conventional superconductors with macroscopic sizes. In bulk system, electrical conductivity in the (4n+1)π electronic states of the monocation crystal is compared with that in the (4n+2)π electronic states of neutral acene crystals formed by small acene molecules.
    Synthetic Metals - SYNTHET METAL. 01/2007; 157(21):793-806.
  • Takashi Kato, Tokio Yamabe
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    ABSTRACT: Possible electron pairing in pi-conjugated positively charged annulenes such as (CH)(18) (18an) and (CH)(30) (30an) is studied and compared with that in the positively charged acenes. The total electron-phonon coupling constants in the monocations (l(HOMO)) for 18an and 30an are estimated. The E(2g) modes of 1611 and 1201 cm(-1) most strongly couple to the highest occupied molecular orbitals (HOMO) in 18an and 30an, respectively. The l(HOMO) values for annulenes are larger than those for acenes. The phase pattern difference between the HOMO of acenes localized on the edge part of carbon atoms and the delocalized HOMO of annulenes is the main reason for the calculated results. In view of the calculated results of the l(HOMO) values, intramolecular electron mobility (sigma(intra,HOMO)), and the reorganization energies (RE(HOMO)) in the positively charged molecules, the monocations of annulenes cannot easily become good conductors compared with the monocations of acenes, but the condition of the attractive electron-electron interactions is realized more easily in the monocations of annulenes than in the monocations of acenes. The hypothetical intramolecular supercurrent originating from both intramolecular and intermolecular vibrations in the monocations of annulenes and acenes in a case where the distance between two adjacent molecules is too large for the molecular crystal to become normal metallic state, is also discussed.
    The Journal of Physical Chemistry B 10/2006; 110(37):18166-79. · 3.61 Impact Factor
  • Takashi Kato, Tokio Yamabe
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    ABSTRACT: Electron-phonon interactions in the monocation of corannulene are studied by using the hybrid Hartree-Fock (HF)/density-functional-theory (DFT) method in the Gaussian 98 program package. The C-C stretching mode of 1498 cm(-1) most strongly couples to the e1 highest occupied molecular orbitals (HOMO) in corannulene. The total electron-phonon coupling constant for the monocation (l(HOMO)) of corannulene is estimated to be 0.165 eV. The l(HOMO) value for corannulene is much larger than those for coronene and acenes with similar numbers of carbon atoms. The delocalized electronic structures and the intermediate characteristics between the strong sigma-orbital interactions and weak pi-orbital interactions originating from a bowl-shaped C(5v) geometry are the main reason that the l(HOMO) value for corannulene is much larger than those for planar D(6h) symmetric pi-conjugated coronene and D(2h) symmetric pi-conjugated acenes with similar numbers of carbon atoms. The electron transfer in the positively charged corannulene is also discussed. Intramolecular electron mobility (sigma(intra,monocation)) in the positively charged corannulene is estimated to be smaller than those for the positively charged pi-conjugated acenes and coronene. The reorganization energy for the positively charged corannulene (0.060 eV) is estimated to be larger than those for the positively charged acenes and coronene. The strong orbital interactions between two neighboring carbon atoms in the HOMO of corannulene with the bowl-shaped structure are the main reasons for the calculated results. Thus, the larger overlap integral between two neighboring molecules is needed for the positively charged corannulene to become a better conductor than those for positively charged coronene and acenes. The smaller density of states at the Fermi level n(0) values are enough for the conditions of the attractive electron-electron interactions to be realized in the monocation of corannulene than in the monocations of coronene and acenes with similar numbers of carbon atoms. The multimode problem is also treated in order to investigate how consideration of the multimode problem is closely related to the characteristics of the electron-phonon interactions.
    The Journal of Physical Chemistry A 04/2006; 110(8):2785-95. · 2.77 Impact Factor
  • Takashi Kato, Tokio Yamabe
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    ABSTRACT: Electron-phonon interactions in the monocations of trans-polyacetylenes such as C2H4 (2tpa), C4H6 (2tpa), C6H8 (6tpa), and C8H10 (8tpa) are studied. The C-C stretching Ag modes around 1700 cm(-1) afford the largest electron-phonon coupling constants in the monocations of polyacetylenes. However, the C-C bending Ag modes around 1200 cm(-1) afford much smaller electron-phonon coupling constants than the C-C stretching Ag modes around 1700 cm(-1) in the monocations of polyacetylenes. The total electron-phonon coupling constants for the monocations (l HOMO) are estimated to be 0.357, 0.285, 0.281, and 0.279 eV for 2tpa, 4tpa, 6tpa, and 8tpa, respectively. The l HOMO values for polyacetylenes with C 2h geometry hardly change with an increase in molecular size while those for polyacenes with D 2h geometry significantly decrease with an increase in molecular size. The l HOMO values for polyacetylenes are larger than those for polyacenes. The calculated results are rationalized in terms of the phase patterns of the molecular orbitals in detail. The electron transfer in the positively charged polyacetylenes is also discussed. Intramolecular electron mobility (sigma(intra,monocation)) in the positively charged polyacetylenes is estimated to be smaller than those for the positively charged polyacenes. The reorganization energies for the positively charged polyacetylenes are estimated to be larger than those for the positively charged polyacenes. Thus, the larger overlap integrals between two neighboring molecules are needed for the positively charged polyacetylenes to become good conductor than those for positively charged polyacenes. On the other hand, the conditions under which the electron-electron interactions are attractive are more easily realized in the monocations of polyacetylenes than in the monocations of polyacenes. The quality as conducting materials would not significantly depend on the molecular size in the positively charged polyacetylenes, compared with that in the positively charged polyacenes. Multimode problem is also treated in order to investigate how consideration of multimode problem is closely related to the characteristics of the electron-phonon interactions.
    The Journal of Chemical Physics 03/2006; 124(8):084705. · 3.12 Impact Factor
  • Takashi Kato, Tokio Yamabe
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    ABSTRACT: Electron–phonon interactions in the monocations of triphenylene and coronene are discussed. The total electron–phonon coupling constants for the monocations (lHOMO) of triphenylene and coronene are estimated to be 0.138 and 0.110eV, respectively. The lHOMO values for benzene and tetracene were estimated to be 0.244 and 0.107eV, respectively. Therefore, the molecular structures as well as the molecular sizes are closely related to the strengths of the electron–phonon interactions. The reason for the calculated results is discussed in detail in terms of the phase patterns of the highest occupied molecular orbitals (HOMO). The condition under which two electron pairing and the Bose–Einstein condensation are realized is also discussed.
    Chemical Physics 01/2006; 325(2):437-444. · 1.96 Impact Factor
  • Takashi Kato, Tokio Yamabe
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    ABSTRACT: The vibronic interactions and single charge transfer through chloroacenes such as C6Cl6 (1cl), C10Cl8 (2cl), C14Cl10 (3cl), and C18Cl12 (4cl), and iodoacenes such as C6I6 (1i), C10I8 (2i), and C14I10 (3i) are discussed. The reorganization energies between the neutral molecules and the corresponding monoanions are estimated to be 0.344, 0.078, 0.060, and 0.047eV for 1cl, 2cl, 3cl, and 4cl, respectively, and thus the reorganization energies decrease with an increase in molecular size in chloroacenes. This result implies that the smaller the molecular size of chloroacenes is, the larger overlap integral between the lowest unoccupied molecular orbitals (LUMO) of two neighboring molecules is needed for the molecule to become good conductor. On the other hand, the reorganization energies are estimated to be 0.138, 0.139, and 0.135 eV for 1i, 2i, and 3i, respectively. Therefore, the reorganization energies hardly change with an increase in molecular size in negatively charged iodoacenes. The C–C stretching modes around 1200–1600cm−1 play an essential role in the vibronic interactions in the monoanions of chloroacenes, while the low frequency modes as well as the high frequency modes play an essential role in the vibronic interactions in the monoanions of iodoacenes. By comparing these calculated results for chloroacenes and iodoacenes with those for acenes and fluoroacenes, we investigate how the halogen substitutions are closely related to the characteristics of these physical values.
    Chemical Physics 01/2006; 321(1):149-158. · 1.96 Impact Factor
  • Takashi Kato, Tokio Yamabe
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    ABSTRACT: The conditions under which the attractive electron-electron interactions are realized in the monocations of sigma-conjugated cyanodienes such as C(6)N(4)H(4), C(8)N(6)H(4), and C(10)N(8)H(4) and of pi-conjugated acenes are discussed. The total electron-phonon coupling constants for the monocations l(HOMO) of cyanodienes are much larger than those for the monocations of acenes. The strong sigma orbital interactions between two neighboring atoms in the highest occupied molecular orbitals (HOMO) of sigma-conjugated cyanodienes are the main reason for the calculated results. Furthermore, we discuss how the conditions under which the monocation crystals become good conductor are related to the molecular size. Both the l(HOMO) values and the reorganization energies between the neutral molecules and the monocations decrease with an increase in molecular size in cyanodienes. The calculated results for the sigma-conjugated cyanodienes are compared with those for the pi-conjugated acenes in order to investigate how the CH-N substitutions in cyanodienes are closely related to the l(HOMO) values and the reorganization energies. Both the l(HOMO) and the reorganization energies in the positively charged sigma-conjugated cyanodienes are much larger than those in the positively charged pi-conjugated acenes. This means that in order to become good conductors, the positively charged sigma-conjugated cyanodienes need larger overlap integral between two adjacent molecules than the positively charged pi-conjugated acenes. On the other hand, since the l(HOMO) values for cyanodienes are much larger than those for acenes, the condition of attractive electron-electron interactions is more easily to be realized in the monocations of cyanodienes than in the monocations of acenes. It is suggested that the positively charged sigma-conjugated cyanodienes cannot easily become good conductors, but the conditions under which the electron-electron interactions become attractive are realized more easily in the positively charged sigma-conjugated cyanodienes than in the positively charged pi-conjugated acenes.
    The Journal of Chemical Physics 10/2005; 123(9):94701. · 3.12 Impact Factor
  • Takashi Kato, Tokio Yamabe
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    ABSTRACT: The electron-phonon coupling constants [l(B1u(HOMO-->LUMO))] in the photoinduced excited electronic states in fluoroacenes are estimated and compared with those in the monoanions (l(LUMO)) and cations (l(HOMO)). The l(B1u(HOMO-->LUMO)) values are much larger than the l(LUMO) and l(HOMO) values in fluoroacenes. Furthermore, the Coulomb pseudopotential mu* values for the excited electronic states are estimated to be smaller than those for the monoanions and cations. The complete phase patterns difference between the highest occupied molecular orbitals (HOMOs) and the lowest unoccupied molecular orbitals (LUMOs) is the main reason why the electron-phonon coupling constants and the mu* values are larger and smaller, respectively, in the photoinduced excited electronic states than in the monoanions and cations. The possible electron pairing and Bose-Einstein condensation in the excited electronic states of fluoroacenes are discussed. Because of larger electron-phonon coupling constants and smaller mu* values in the excited electronic states than in the charged states, the conditions under which the electron-electron interactions become attractive can be more easily realized, in principle, in the excited electronic states than in the charged states in fluoroacenes. The l(B1u(HOMO-->LUMO)) values hardly change by H-F substitution, even though the l(LUMO) and l(HOMO) values significantly increase by H-F substitution in acenes. Antibonding interactions between carbon and fluorine atoms in the HOMO and LUMO are the main reason why the l(B1u(HOMO-->LUMO)) values hardly change by H-F substitution in acenes.
    The Journal of Chemical Physics 08/2005; 123(2):24301. · 3.12 Impact Factor
  • Takashi Kato, Tokio Yamabe
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    ABSTRACT: Electron-phonon interactions in the monoanions of polyacetylenes such as C2H4 (2tpa), C4H6 (4tpa), C6H8 (6tpa), and C8H10 (8tpa) are studied and compared with those in the monoanions of polyacenes. The C-C stretching A(g) modes around 1500 cm(-1) the most strongly couple to the lowest unoccupied molecular orbitals (LUMO) in polyacetylenes. The estimated total electron-phonon coupling constants for the monoanions (l(LUMO)) are 0.579, 0.555, 0.463, and 0.401 eV for 2tpa, 4tpa, 6tpa, and 8tpa, respectively. The l(LUMO) values for polyacetylenes are much larger than those for polyacenes. Furthermore, the l(LUMO) value for polyacetylene with C(2h) geometry is estimated to be 0.254 eV, and is larger than that (0.024 eV) for polyacene with D(2h) geometry. The phase patterns difference between the LUMO of polyacenes localized on the edge part of carbon atoms, and the delocalized LUMO of polyacetylenes is the main reason for the calculated results. The single charge transfer through the molecule in polyacetylenes are also discussed. The reorganization energies between the neutral molecule and the corresponding monoanion are estimated to be 0.164, 0.144, 0.125, and 0.113 eV for 2tpa, 4tpa, 6tpa, and 8tpa, respectively. Such reorganization energy decreases with an increase in molecular size. The conditions under which the attractive electron-electron interactions are realized in the monoanions of polyacetylenes and polyacenes are discussed. In terms of the electron-phonon interactions and the reorganization energies, the relationships between the normal and possible superconducting states are briefly discussed. We find that the monoanions with smaller molecular size cannot easily become good conductors, however, the conditions under which the interactions between two electrons are attractive are more easily realized in the monoanions with smaller molecular size than in the monoanions with larger molecular size.
    The Journal of Physical Chemistry B 07/2005; 109(21):10620-30. · 3.61 Impact Factor
  • Takashi Kato, Tokio Yamabe
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    ABSTRACT: Electron-phonon interactions in the photoinduced excited electronic states in molecular systems such as phenanthrene-edge-type hydrocarbons are discussed and compared with those in the monoanions and cations. The complete phase patterns difference between the highest occupied molecular orbitals (HOMO) and the lowest unoccupied molecular orbitals (LUMO) (the atomic orbitals between two neighboring carbon atoms combined in phase (out of phase) in the HOMO are combined out of phase (in phase) in the LUMO) are the main reason that the C-C stretching modes around 1500 cm(-1) afford much larger electron-phonon coupling constants in the excited electronic states than in the charged electronic states. The frequencies of the vibrational modes that play an essential role in the electron-phonon interactions for the excited electronic states are similar to those for the monoanions and cations in phenanthrene-edge-type hydrocarbons. Possible electron pairing and Bose-Einstein condensation in the photoinduced excited electronic states as well as those in the monoanions and cations in molecular systems such as phenanthrene-edge-type hydrocarbons are also discussed.
    The Journal of Physical Chemistry A 07/2005; 109(21):4804-15. · 2.77 Impact Factor
  • Takashi Kato, Tokio Yamabe
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    ABSTRACT: Total electron–phonon coupling constants for the monocations (lHOMO) of B,N-substituted acene-series such as B3N3H6, B5N5H8, and B7N7H10 are estimated. The estimated lHOMO values of 0.357, 0.209, and 0.182 eV for B3N3H6, B5N5H8, and B7N7H10, respectively, are larger than those of 0.244, 0.173, and 0.130 eV for benzene, naphthalene, and anthracene, respectively. Furthermore, the lHOMO value for B,N-substituted polyacene (0.096 eV) is estimated to be larger than that for polyacene (0.036 eV). Stronger orbital interactions between B and N atoms in the highest occupied molecular orbitals (HOMO) in B,N-substituted acene-series than those between two neighboring carbon atoms in the HOMO in acene-series as a consequence of electronegativity perturbation on acene-series, are the main reason why the lHOMO values for B,N-substituted acene-series are larger than those for acene-series.
    Chemical Physics 01/2005; 315:97-108. · 1.96 Impact Factor
  • Takashi Kato, Tokio Yamabe
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    ABSTRACT: Electron–phonon interactions in charged chlorocubane ((CCl)8) are studied. The estimated total electron–phonon coupling constants for the monoanion (lLUMO) and cation (lHOMO) of chlorocubane are 1.018 and 0.276 eV, respectively. The lLUMO value for chlorocubane is larger than that for fluorocubane ((CF)8). The higher electron density on chlorine atoms in the LUMO in (CCl)8 than that on fluorine atoms in (CF)8, and the large displacements of chlorine and fluorine atoms in (CCl)8 and (CF)8, respectively, are the main reason for the calculational results. The lHOMO value for (CCl)8 is much smaller than that for (CF)8. Weaker orbital interactions between carbon and chlorine atoms in the HOMO in (CCl)8 than those between carbon and fluorine atoms in the HOMO in (CF)8, is the main reason for the calculational results. The single charge transfer through (CF)8 and (CCl)8 is also discussed.
    Chemical Physics 01/2005; 314:219-229. · 1.96 Impact Factor
  • Takashi Kato, Tokio Yamabe
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    ABSTRACT: The effects of H–D and H–F substitution on the electron–phonon interactions in the monocations of B, N-substituted acenes are studied. The B–N stretching modes around 1400cm−1 afford large electron–phonon coupling constants in the monocations of B3N3F6 (1f) and B5N5F8 (2f). The total electron–phonon coupling constants for the monocations (lHOMO) are 0.479 and 0.402eV in 1f and 2f, respectively. The lHOMO values become much larger by H–F substitution than by H–D substitution in the monocations of B, N-substituted acenes. The reason for the calculational results are discussed in detail in view of the phase patterns of the frontier orbitals and the vibronic active modes. The effects of H–D and H–F substitution on the charge transfer in the positively charged B, N-substituted acenes are also discussed.
    Chemical Physics 01/2005; 315(1):109-120. · 1.96 Impact Factor
  • Takashi Kato, Tokio Yamabe
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    ABSTRACT: Vibronic interactions and Jahn–Teller effects in the monocations of triphenylene and coronene are discussed. The E′ mode of 1634cm−1 and the E2g mode of 1668cm−1 afford large electron–phonon coupling constants in the monocations of triphenylene and coronene, respectively. The single charge transfer through the molecules in these positively charged species are discussed. The reorganization energies for elementary charge transfer are estimated to be 0.045 and 0.028eV for triphenylene and coronene, respectively. The optimized structures of the monocations are discussed in terms of the frontier orbitals and the vibrational modes.
    Chemical Physics Letters 01/2005; 403(1):113-118. · 2.15 Impact Factor
  • Takashi Kato, Tokio Yamabe
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    ABSTRACT: The single charge transfer through cyanodienes is discussed. The reorganization energies between the neutral molecules and the corresponding monoanions for cyanodienes are larger than those for acenes with D2h geometry. This result implies that the negatively charged cyanodienes would not be better conductors with slow electron transfer than the negatively charged acenes if we assume that the overlap of the lowest unoccupied molecular orbitals (LUMO) between cyanodienes is not significantly different from that between two neighboring acenes. The structures of the monoanions of cyanodienes are optimized under D2h geometry, and the vibronic interaction effects in the monoanions of cyanodienes are discussed. The vibration effect on the charge-transfer problem is also discussed. The C−C and C−N stretching Ag modes around 1000−1500 cm-1 are the main modes converting the neutral structures to the monoanions in cyanodienes. This can be confirmed from the calculational results that the C−C and C−N stretching Ag modes around 1000−1500 cm-1 strongly couple to the LUMO in cyanodienes. The total electron−phonon coupling constants (lLUMO) for the monoanions of cyanodienes are estimated to be larger than those for the monoanions of acenes. The orbital patterns difference between the LUMO localized on carbon atoms located at the edge part of the carbon framework in acenes and the delocalized LUMO in cyanodienes due to electronegativity perturbation is the main reason that the lLUMO values for polycyanodienes are much larger than those for polyacenes. The relationships between the electron transfer and the electron−phonon interactions are discussed. The plot of the reorganization energies against the lLUMO values is found to be nearly linear. In view of the results, the relationships between the normal and possible superconducting states are briefly discussed.
    The Journal of Physical Chemistry A 11/2004; 108(51). · 2.77 Impact Factor
  • Takashi Kato, Tokio Yamabe
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    ABSTRACT: The single charge transfer through acenes, partially H-F substituted acenes, and fluoroacenes is discussed. The reorganization energies between the neutral molecules and the corresponding monoanions for partially H-F substituted acenes lie between those for acenes and fluoroacenes. The delocalization of the lowest unoccupied molecular orbitals (LUMO) by substituting hydrogen atoms by fluorine atoms with the highest electronegativity in every element is the main reason why the reorganization energy between the neutral molecule and the monoanion for partially H-F substituted acenes lies between those for acenes and fluoroacenes. This result implies that the negatively charged partially H-F substituted acenes would be better conductors with rapid electron transfer than the negatively charged fluoroacenes if we assume that the overlap of the LUMO between partially H-F substituted acenes is not significantly different from that between two neighboring fluoroacenes. The structures of the monoanions of acenes, fluoroacenes, and partially H-F substituted acenes are optimized under D2h geometry, and the Jahn-Teller effects in the monoanions of benzene and fluorobenzene are discussed. The vibration effect onto the charge transfer problem is also discussed. The C-C stretching modes around 1500 cm(-1) are the main modes converting the neutral molecules to the monoanions in acenes, fluoroacenes, and partially H-F substituted acenes. It can be confirmed from the calculational results that the C-C stretching modes around 1500 cm(-1) the most strongly couple to the LUMO in these molecules. The main reason why the total electron-phonon coupling constants (lLUMO) for the monoanions of acenes in which four outer hydrogen atoms are substituted by fluorine atoms are larger than those for the monoanions of acenes in which several inner hydrogen atoms are substituted by fluorine atoms is suggested. The relationships between the electron transfer and the electron-phonon interactions are discussed. The plot of the reorganization energies against the lLUMO values is found to be nearly linear. In view of these results, the relationships between the normal and superconducting states are briefly discussed.
    The Journal of Chemical Physics 09/2004; 121(5):2356-66. · 3.12 Impact Factor
  • Takashi Kato, Tokio Yamabe
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    ABSTRACT: Electron-phonon interactions in the monoanions of B, N-substituted acenes such as B(3)N(3)F(6) (1f) and B(5)N(5)F(8) (2f) are studied, and compared with those in the monoanions of B(3)N(3)H(6) (1h) and B(5)N(5)H(8) (2h), and B(3)N(3)D(6) (1d) and B(5)N(5)D(8) (2d). The low frequency modes around 500 cm(-1) as well as the frequency modes higher than 1000 cm(-1) strongly couple to the lowest unoccupied molecular orbitals (LUMO) in 1f and 2f. The total electron-phonon coupling constants (l(LUMO)) are estimated to be 2.710 and 2.054 eV for 1f and 2f, respectively, and those are estimated to be 0.342 and 0.235 eV for 1d and 2d, respectively, while those were estimated to be 0.340 and 0.237 eV for 1h and 2h, respectively. That is, the l(LUMO) value increases much more significantly by H-F substitution than by H-D substitution in B, N-substituted acenes. The larger displacements of B and N atoms in the vibronic active modes in 1f and 2f than those in 1d and 2d due to larger atomic mass of fluorine than that of deuterium, and the phase patterns difference between the LUMO in 1f and 2f, in which the atomic orbitals between N and its neighboring F atoms form strong sigma-antibonding interactions, and that in 1d and 2d, in which the atomic orbitals between two neighboring B and N atoms form weak pi-bonding and pi-antibonding interactions, are the main reason why the l(LUMO) value increases much more significantly by H-F substitution than by H-D substitution. The reorganization energies between the neutral molecules and the corresponding monoanions are estimated to be 0.122, 0.063, 0.733, and 0.830 eV for 1h, 2h, 1f, and 2f, respectively. Therefore, the estimated reorganization energies between the neutral molecules and the corresponding monoanions for 1f and 2f are much larger than those for 1h and 2h.
    The Journal of Chemical Physics 08/2004; 121(1):501-9. · 3.12 Impact Factor
  • Takashi Kato, Tokio Yamabe
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    ABSTRACT: Electron-phonon interactions in the monocations of deutero- and fluoroacenes are studied and compared with those in the monocations of acenes and those in the monoanions of fluoroacenes. Because of the significant phase pattern difference between the highest occupied molecular orbitals (HOMO) and the lowest unoccupied molecular orbitals (LUMO), the frequency modes lower than 500 cm(-1) and the high-frequency modes around 1400 cm(-1) couple more strongly to the LUMO than to the HOMO, while the frequency modes around 500 cm(-1) and the frequency modes around 1600 cm(-1) couple more strongly to the HOMO than to the LUMO in fluoroacenes with D2h geometry. The total electron-phonon coupling constants for the monocations (l(HOMO)) are estimated and compared with those for the monoanions (l(LUMO)) in deutero- and fluoroacenes. The l(HOMO) values are estimated to be 0.418, 0.399, 0.301, 0.255, and 0.222 eV for C6F6 (1f), C10F8 (2f), C14F10 (3f), C18F12 (4f), and C22F14 (5f), respectively. The l(HOMO) values are smaller than the l(LUMO) values in small fluoroacenes. But the l(HOMO) value decreases with an increase in molecular size less rapidly than the l(LUMO) value in fluoroacenes, and the l(HOMO) value of 0.074 eV is much larger than the l(LUMO) value of 0.009 eV in polyfluoroacene. The logarithmically averaged phonon frequencies for the monocations (omega(ln,HOMO)) are estimated to be larger than those for the monoanions (omega(ln,LUMO)) in fluoroacenes. This is because the C-C stretching modes around 1600 cm(-1) couple most strongly to the HOMO, and those around 1400 cm(-1) couple the most strongly to the LUMO in fluoroacenes. The significant phase pattern difference between the HOMO and the LUMO is the main reason for the calculational results. The l(HOMO) values increase much more significantly by H-F substitution than by H-D substitution in acenes. The possible inverse isotope effects in the electron-phonon interactions as a consequence of deuteration in the monocations of nanosized molecules are suggested.
    The Journal of Chemical Physics 05/2004; 120(16):7659-72. · 3.12 Impact Factor

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120 Citations
100.49 Total Impact Points

Institutions

  • 2002–2007
    • Nagasaki Institute of Applied Science
      Nagasaki, Nagasaki, Japan
  • 1998–2005
    • Kyoto University
      • • Department of Material Chemistry
      • • Fukui Institute for Fundamental Chemistry
      • • Department of Molecular Engineering
      Kyoto, Kyoto-fu, Japan
  • 2001
    • Kyushu University
      Hukuoka, Fukuoka, Japan