Tetsuya Tsunekawa

New organic non-linear optical crystals of benzylidene-aniline derivative

Abstract The benzylidene-aniline derivative with an electron-donating group at the 4-position and an electron-accepting group at the 4′-position has been suggested, by MO calculations, to have a small molecular dipole moment in spite of the large second-order hyperpolarizability, and hence to be a promising molecule in the search for new organic crystals with large second-order optical non-linearity. By modification of the molecule suggested, a series of crystals having high second-harmonic generation (SHG) activities have been discovered; one of them showed a larger powder SHG than 2-methyl-4-nitroaniline (MNA).

Monte Carlo simulations on adsorptions of benzene and xylenes in sodium-Y zeolites

Abstract The structures of benzene and C8 isomers ( o -xylene, m -xylene, p -xylene) in NaY simulated by the canonical Monte Carlo method were in good agreement with the experimental data of the available neutron diffraction analysis. All these sorbed compounds are stacked through the aromatic π-electron interaction on the cation of the SII site in the Sodium-Y. The experimental adsorption order ( m -xylene > o -xylene > p -xylene) of xylene isomers in the faujasite was also in good agreement with the order obtained from calculated heats of adsorption. It was shown that the difference in the interaction between the 4-ring sites and the methyl groups of xylene caused the better adsorption of m -xylene compared to those of the others. From these results, our conclusion is that the adsorption of the C8 isomers in the faujasite can be explained by considering only the interaction between the zeolite framework and the adsorbate approximated as a rigid model. Moreover, this type of simulation proved to be very useful to understand the mechanism of the adsorption of aromatic compounds in zeolites like faujasites.

Ab initio CPHF calculations of first hyperpolarizabilities of nitrogen-containing polyenes with donor-acceptor substituents

Abstract Ab initio CPHF calculations of static hyperpolarizabilities (β) were carried out in order to clarify the effects of nitrogen-atom substitution in π-conjugated chains with donor—acceptor substituents. The β values decrease gradually with the number of nitrogen atoms, and change drastically with the position of nitrogen-atom substitution in the polyenes. The effects of nitrogen-atom substitution are explained by the energy levels and the shapes of the frontier orbitals.

Dihedral rigid molecule in crystal engineering for optimized phase-matchable SHG: DNBB

It is important to control a polarization anisotropy, thus, a molecular alignment in obtaining such a crystal that can exhibit optimized phase-matchable second harmonic generation ( SHG ). Along with this view, we designed a novel dihedral rigid molecule which has two nitroaniline moieties rigidly connected each other through two adjacent sp3 carbons. We synthesized the molecules so designed and examined their crystals in SHG activities and phase-matching characteristics by a convenient powder method with a Nd:YAG laser. It has been found that one of crystals, namely, 3,9-dinitro-5a,6, ha, 12-tetrahydro[1,4]benzoxadino[3 ,2-bJ][1,4]- benzoxadine ( DNBB ) crystal manifests larger phase-matchable SHG than N-(4-nitrophenyl)-L-prolinol ( NPP ) crystal so far known as the typical efficient phase-matchable organic crystal. DNBB crystal has been shown to possess much improved material properties ; high thermal stability, distinguished hardness, insolubility to water, no sublimation, and high registivity to optical damage, for device applications in comparison with the crystals of p-nitroaniline derivatives reported so far.