Tatsuya Imase

Stability of Superoxide Ion in Imidazolium Cation-Based Room-Temperature Ionic Liquids

The stability of superoxide ion (O(2)(*-)) generated chemically by dissolving KO(2) in dried dimethyl sulfoxide solutions containing imidazolium cation [e.g., 1-ethyl-3-methylimidazolium (EMI(+)) and 1-n-butyl-2,3-dimethylimidazolium (BMMI(+))] based ionic liquids (ILs) was investigated with UV-visible spectroscopic, NMR, and voltammetric techniques and an ab initio molecular orbital calculation. UV-visible spectroscopic and cyclic voltammetric measurements reveal that the O(2)(*-) species reacts with BMMI(+) and EMI(+) cations of ILs to form hydrogen peroxide. The pseudo first order rate constant for the reaction of BMMI(+) and O(2)(*-) species was found to be about 2.5 x 10(-3) s(-1). With a molecular orbital calculation, the O(2)(*-) species is understood to attack the 2-position (C-2) of the imidazolium ring (i.e., BMMI(+)) to form an ion pair complex in which one oxygen atom is bounded to C-2 and the other to the hydrogen atom of -CH(3) group attached to C-2. Eventually, the ion pair complex of BMMI(+) cation and O(2)(*-) species undergoes a ring opening reaction as evidenced with (1)H NMR measurement.

Conformational analysis of 1,3-benzenediol dibenzoate as a model of banana-shaped molecules forming chiral smectic phases

Abstract Banana-shaped molecules, e.g. 1,3-phenylene bis[4-(4-n-alkoxyphenyliminomethyl)benzoates] and 1,3-phenylene bis[4-(4-n-alkylphenyliminomethyl)benzoates], form ferroelectric and chiral smectic phases without a chiral carbon. 13C NMR measurement suggested that 1,3-benzenediol dibenzoate (BD) moiety assumes asymmetrically twisted conformation which may be ascribed to the chirality of the phases. In this study, conformational analysis was carried out for BD by using the density functional theory (DFT) calculation. The results indicated that the asymmetrical twist conformation of the BD moiety is most stable.

Electrocatalytic Reduction of Oxygen in a Novel Catalytic System with Cobalt Phthalocyanines and Manganese Oxide

This article concerns the efficient dioxygen (O 2 ) reduction by a novel catalytic system that is comprised of two catalysts: one for the electroreduction of O 2 through the two-electron process and the other for the subsequent chemical decomposition of hydrogen peroxide generated. Here we represent the combined catalytic system of cobalt phthalocyanines and manganese oxide (MnOOH). Each catalyst performs well independently, leading to the totally four-electron reduction of O 2 in alkaline media. This was confirmed from almost twofold increases of the cathodic current in cyclic voltammograms and the steady-state current in rotating ring disk electrode voltammograms, the collection efficiency and the number of electrons calculated from the Koutecky-Levich plot. As a consequence, it is concluded that this combined catalytic system works efficiently for the O 2 reduction.

Internal rotation of ester linkage in phenyl benzoate and hydroxybenzoic acid dimer as models of aromatic polyesters using density functional theory

The internal rotation of the ester linkage was reinvestigated more quantitatively by using the density functional theory (DFT) in order to understand the characteristic stiffness and extendedness of polymer chain found in aromatic polesters. Phenyl benzoate (PB) and p-hydroxybenzoic acid (HBA) dimer (HB) were selected as models of aromatic polyesters. The relaxed potential energy surface (PES) scan was arried out along the internal rotation of three bond (denoted as R, S, and T, respectively) of the aromatic esters by using the hybrid DFT (B3LYP) with 6-31G* basis set. The rotation of S bond, which mainly determines the linearity of the molecule, leads to the trans- and cis-conformers of PB. Since the cis-conformer of PB is 7.69 kcal.mol -1 higher than the trans-conformer, the cis-conformer has little population at standard condition. HB doest not have the cis-conformer. In addition, the chain persistence length of 364 A is obtained by the rotation matrix formalism using the structural parameters of HB. These agree with the experimental understanding that poly(p-hydroxybenzoic acid) is the class of stiff and extended polymer.

Molecular Modeling of a Polar Rod-Like Aromatic Polyester Forming Nematic Liquid Crystal. Part 2. Molecular Dynamics Simulation for Polar Association of Molecules

Abstract The most stable molecular packing systems of aromatic polyester molecules have been investigated by molecular dynamics (MD) simulations performed for decamer (ten repeating units) of p-hydroxybenzoic acid (HBA) in the nematic phase. The MD simulations were started from eight possible packing structures. Among them, we found the polar ordering structure with the intermolecular ester carbonyl groups aligned in the same direction is energetically most favorable. This is consistent with our previous experimental observation for the second-harmonic generation (SHG) intensity measurement.

Molecular Modeling of a Polar Rod-Like Aromatic Polyester Forming Nematic Liquid Crystal. Part 1. Ab Initio Study of Origin of Strong SHG-Activity

Abstract The aromatic copolyester of 4-hydroxybenzoic acid (HBA) and 6-hydroxy-2-naphtoic acid (HNA) shows strong SHG-activity in the nematic phase as well as the crystalline phase in spite of no absorption in the visible region. Ab initio quantum chemistry calculations of the copolyester have been carried out in order to clarify the origin of this strong SHG-activity. The second-order hyperpolarizability of the HBA dimer is comparable to that of p-nitroaniline and it increases with the degree of polymerization. The large hyperpolarizability of the aromatic polyester is ascribed to the large electronic transition moment.

Polar nematic liquid crystal formed from aromatic polyesters with head-tail character

We describe a distinct polar nematic liquid crystal formed from the polar rod-like aromatic polyester which comprises 4-hydroxybenzoaic acid (HBA) and 6-hydroxy-2naphthoic acid (HNA) in a molar ratio of 73/27. The nemtic liquid crystal is biaxial and the polarity appears along both axes as determined by measurements of the second harmonic generation. The polar structure disappeasrs when the molecular weight in polyester is decreased, showing that the large dipole moment of each chain is responsible for the polar ordering. The strong dipole-dipole interaction between polar rod-like molecules may be ascribed to the origin of the polarility.

Transition state structures of thermal cis-trans isomerization reaction of azobenzenes

Abstract Density functional calculations (B3LYP/6–31G*) have been carried out to investigate the transition state structure for the inversion mechanism in the thermal cis-trans isomerization reaction of azobenzene and 4-amino-4′-nitroazobenzene. Four and eight conformations were optimized in order to find the inversion transition state of azobenzene and 4-amino-4′-nitroazobenzene, respectively. As a result, it is found that azobenzene and 4-amino-4′-nitroazobenzene have only one genuine inversion transition state, respectively. The inversion barrier of 4-amino-4′-nitroazobenzene is smaller than that of azobenzene. The dipole moment of the inversion transition state of 4-amino-4′-nitroazobenzene is extremely large compared to those of the cis and trans structures.

Effects of Conformation of Diastereomer Liquid Crystals on the Preference of Antiferroelectricity

Abstract We have already synthesized a new type of antiferroelectric liquid crystals (AFLCs) with double stereogenic centers, β-methyl-substituted TFMHPOBC(4-(1-trifluoromethyl-hepty-loxycarbonyl)phenyl 4′-octyloxybiphenyl-4-carboxylate) and its analogues, based on α-trifluoromethyl-β-methylcarbinol, and its conformational effects on the antiferroelectricity[1-5]. Now we report another new type of AFLC and ferroelectric liquid crystals (FLC) with double stereogenic centers bearing β-trifluoromethylcarbinol. which can be regarded as a β-trifluoromethyl-substituted MHPOBC(4-(methylheptyloxycarbonyl)phenyl 4′-octyloxybiphenyl-4-carboxylate) analogue, and examined its properties such as the phase transition. From these results and ab initio calculations using Gaussian 94 program, we conclude that their conformations strongly affect their preference of antiferroelectricity and that the bend-like structure is more essential for the appearance of antiferroelectricity, than the extended-like one.