桝 飛雄真

A circular dichroism (CD) spectral study on chiral aromatic chain imides possessing anthracene and naphthalene moieties with bulky N substituents showed that their helical chirality based on folding remained for a reasonably long time without racemization in solution. Racemization due to conformational equilibration occurred very slowly, requiring over 1 week at ambient temperature. Their CD spectra both in solution and in the solid state gave similar CD signals, suggesting retention of helicity observed in the solid state even after dissolving. As an application of this novel chiral folding of aromatic chain imides, a chiral photochromic system was investigated based on the photo [4 + 4] cycloaddition and its thermal cycloreversion of an anthracene-naphthalene system. The foldamer possessing an anthracene moiety in the center connected with two naphthalene moieties below and above it by iminodicarbonyl linkers was prepared for this purpose. Induced CD was observed for the foldamer with (S)-1-(1-naphthyl)ethyl substituents at the imide nitrogen atoms. Chiral photochromic cycles were monitored by CD spectral measurement.

Two novel red pigments, uroleuconaphins A(1) (1) and B-1 (2) were isolated from the aphid Uroleucon nigrotuberculatum (Olive). The structures and the absolute configurations of 1 and 2 were determined by single-crystal X-ray analysis of their derivatives. These structures were constituted as dimeric compounds of two molecules of quinone A (3), which were linked via a dihydrofuran ring system. (c) 2006 Elsevier Ltd. All rights reserved.

N-Phenylbenzohydroxamic acid (3) showed solvent-dependent conformational alteration. Thus, compound 3 exists predominantly in cis form (>98%) in CD2Cl2, whereas the percentage of the cis isomer decreased to 49% in methanol-d(4), and the trans conformer was major (77%) in acetone-d(6). Solvent-dependent alteration of the amide conformation was observed only in the hydroxamic acids, and the ratio of the cis conformer (98% in CD2Cl2) of N-phenylbenzhydrazide (6) was little affected by the solvent. Two unique crystal structures were obtained depending on the recrystallization solvent, and each crystal corresponded in structure to the major conformer in the solvent. These two crystals of 3 were distinguished by IR spectroscopy and DSC analysis. Although the origin of the solvent-dependent conformational switching of 3 is unclear, the results could be applied to design and development of solvent- or external-stimuli-responsive molecular machines.

Fluorescence spectra of aromatic chain imides possessing anthracene and naphthalene moieties were examined both in solution and in the solid state. Depending on the substituents at the imide nitrogen atom, their fluorescence spectra varied in the solid state. However, their spectra in solution were almost identical. In solution, emission corresponding to a naphthalene-anthracene exciplex was observed. In contrast, the imides possessing an intermolecular anthracene-anthracene interaction exhibited red-shifted fluorescence in the solid state. This red-shifted fluorescence could originate in an anthracene excimer or the exciplex formed from a sum of fluorophores. In contrast, compounds without this anthracene-anthracene interaction in the solid state had very similar solution and solid-state fluorescence spectra.

The crystal structures of 1,2-bis(N-benzenesulfonylamino)benzenes with secondary and/or tertiary sulfonamide groups were determined by X-ray crystallographic analysis. Every Ar-sulfonamide group existed in synclinal conformation in the crystals even though it was secondary or tertiary. Each compound showed different types of hydrogen bonds in the crystal structure. 1,2-Bis(N-benzenesulfonylamino)benzene (1) formed two double hydrogen bonds connected to the next molecules, 1-(N-benzenesulfonylamino)-2-(N-benzenesulfonyl-N- methylamino)benzene (2) contained double hydrogen bond involved by both the sulfonamide moieties, 1,2-bis(N-4-toluenesulfonylamino)benzene (3) had both intra- and intermolecular hydrogen bonds, and 1-(N-methyl-N-4-toluenesulfonylamino)-2-(N-4-toluenesulfonylamino)benzene (4) had one double hydrogen bond involved by only one sulfonamide moiety. Sulfonamides 1 and 3 formed infinite arrays of the molecules, and sulfonamides 2 and 4 formed racemic dimer of their conformational enantiomers via the hydrogen bonds. (c) 2006 Elsevier Ltd. All rights reserved.

A triple helicate, a macrocyclic aromatic amide with a helical structure, is complexed with La(III) ion leading to the self-assembly of a helical coordination polymer. Each La(III) atom is coordinated by a pair of oxygen of the tertiary benzenetrianifide moieties from two adjacent ligands, resulting in the formation of chiral infinite coordination networks of alternating La(III) atoms and ligands. Here, we demonstrate that the chirality of a one-dimensional polymeric structure in the crystal was derived from T-shaped aromatic-aromatic (CH-pi) interactions of each molecule twisted in the same direction.

Octahomotetraoxacalix[ 4] arenes bearing long alkyl chains on their lower rim were prepared. Ester 4a existed in a 1,2-alternate conformation in its crystal structure, which was examined by single-crystal X-ray diffraction analysis. To prepare liquid crystalline materials possessing calixarene moieties by self-assembling, carboxylic acid derivatives 5 were synthesized. Among them, 5c, the octadecyloxy derivative, showed smectic liquid crystal phase. Homooxacalixarenes 5 also formed liquid crystal phases with longer layer distances when two equivalent moles of 1,2-ethylenediamine were added as a linker. These phases were investigated with X-ray diffraction, differential scanning calorimetry, and polarized optical microscopy.