Kiichi Amimoto

Crystalline photochromism of N-salicylidene-2,6-dialkylanilines: advantage of 2,6-dialkyl substituents of aniline for preparation of photochromic Schiff base crystals

N-(3,5-Dihalosalicylidene)-2,6-dialkylaniline derivatives were prepared and their structure and photochromic properties were investigated. From the X-ray crystallography, it was revealed that steric repulsion between the azomethine hydrogen atom and the alkyl groups at the 2,6-positions of the aniline ring lead to non-planar molecular structure, which was effective for the crystals to exhibit photochromism. The relationship between photochromicity and crystal packing of N-(3,5-dichlorosalicylidene)-2,6-dialkylanilines series was also discussed. The 2,6-dialkylaniline method was suggested to be applicable to the preparation of photochromic Schiff bases with various substituents in the salicylidene rings.

Photochromism of polymorphic 4,4′-methylenebis(N-salicylidene-2,6-diisopropylaniline) crystals

4,4[prime or minute]-Methylenebis(N-salicylidene-2,6-dialkylaniline) derivatives were prepared and their structures were determined by (1)H NMR, IR, DSC and X-ray crystallographic analyses. The 2,6-diisopropylaniline derivative yielded definite polymorphic crystals: the space groups of the crystals were C2/c and P2(1)/n, respectively. It was found that both polymorphs were similarly photochromic but the thermal stability of the photochrome was different due to the variance of the shape of molecule and cavity in each crystal.

The Proton Cryptate of Hexaethylenetetramine

The next higher homologue of hexamethylenetetramine was synthesized as the proton cryptate H+ @1⋅Br- (shown schematically), and its X-ray structure determined. The proton trapped by the lone pairs accumulated at the center of the T-symmetric tetraaza cage could not be exchanged or removed, even after heating for three days in 3 M NaOD.

Photochromism of Guest N-Salicylideneaniline in the Rooms of Host Bile Acid Derivatives

Abstract Definite clathrate crystals of deoxycholic acid and its amide and alcohol derivatives as host molecules with N-salicylideneaniline as a guest molecule were prepared to investigate their photochromic properties. The photocoloration study was done by irradiating the crystal powder with 365 nm light; the thermal fading reaction of the photocolored species was followed by reflectance spectrophotometry at 303 K. From the sharp difference in the first-order rate constants of the thermal bleaching of the photochromes, it was found that the thermal unimolecular motion of photo-colored species was strongly influenced by the neighboring environments in the crystal state.

Deuterium isotope effect on the solid-state thermal isomerization of photo-coloured cis-keto species of N-salicylideneaniline

Deuterium isotope kinetic effect in the solid state was observed by using thermal fading reaction of photo-coloured species derived from N-salicylideneaniline deuterohydroxyl derivative; thus, the existence of a cis-keto form in the photo-coloured Schiff base crystals was suggested experimentally along with 6-methyl-substitution effect on the stability of the photoproduct.

DAS PROTON-CRYPTAT VON HEXAETHYLENTETRAMIN

Das nachsthohere Homologe des Hexamethylentetramins wurde als das Proton-Cryptat H+@1⋅Br− (schematisch gezeigt) hergestellt, und dessen Kristallstruktur wurde ermittelt. Das Proton, das durch die im Zentrum des T-symmetrischen Tetraazakafigs befindlichen freien Elektronenpaare festgehalten wird, konnte sogar durch dreitagiges Erhitzen in 3 M NaOD nicht ausgetauscht oder entfernt werden.

A polymorph of 2,4-dinitro­phenyl­hydrazine

The crystal structure of a previously unreported polymorph (form II) of 2,4-dinitrophenylhydrazine (DNPH), C6H6N4O4, was determined at 90 K. The first polymorph (form I) is described in the monoclinic space group P21/c [Okabe et al. (1993 ▶). Acta Cryst. C49, 1678–1680; Wardell et al. (2006 ▶). Acta Cryst. C62, o318–320], whereas form II is in the monoclinic space group Cc. The molecular structures in forms I and II are closely similar, with the nitro groups at the 2- and 4-positions being almost coplanar with the benzene ring [dihedral angles of 3.54 (1) and 3.38 (1)°, respectively in II]. However, their packing arrangements are completely different. Form I exhibits a herringbone packing motif, whereas form II displays a coplanar chain structure. Each chain in form II is connected to adjacent chains by the intermolecular interaction between hydrazine NH2 and 2-nitro groups, forming a sheet normal to (101). The sheet is stabilized by N—H⋯π interactions.

(S)-Alanine–(S)-2-phen­oxy­propionic acid (1/1)

In the title co-crystal, C3H7NO2·C9H10O3, the (S)-alanine molecule exists in the zwitterionic form stabilized by two pairs of N+—H⋯O− hydrogen bonds and an electrostatic interaction between the ammonium center and the carboxylate anion, forming a sheet along the ab plane. The carboxyl group of the (S)-2-phenoxypropionic acid molecule is connected to the top and bottom of the sheet via N+—H⋯O=C and O—H⋯O− [R 2 2(7) graph set] hydrogen bonds, giving an (S,S)-homochiral layer, in which both methyl groups of (S)-alanine and the phenyl rings of (S)-2-phenoxypropionic acid are oriented in the same direction along the b axis.

「水」を素材とした理科の学習文脈（化学領域） : 化学事象や自然事象における水の役割

本研究の一部は，平成25～27年度科学研究費補助金基盤研究C（課題番号：25350203，研究代表者：網本貴一）および平成25～28年度科学研究費補助金基盤研究A（課題番号：25242015，研究代表者：古賀信吉）の助成を受けて行ったものである。

1,4-Bis(1,1-dimethyl­prop­yl)-2,5-dimeth­oxy­benzene

The title compound, C18H30O2, was prepared by Friedel–Crafts alkylation of 1,4-dimethoxybenzene with 2-methyl-2-butanol. The complete molecule is generated by the application of a crystallographic centre of inversion. The two methoxy groups are oriented in the same plane of the aromatic ring [C—C—O—C torsion angle = 9.14 (16)°]. While one methyl group of the tert-pentyl substituent is coplanar with the benzene ring [C—C—C—C = 0.45 (15)°] and lies towards the less-hindered H atom, the other methyl and ethyl groups are directed to either side of the benzene ring [C—C—C—C torsion angles = 118.78 (12) and 59.11 (14)°, respectively]. In the crystal, the hydrophobic molecules pack to form a brick-wall-like architecture.