Hideko Koshima

Mechanical Motion of Azobenzene Crystals upon Photoirradiation

Photomechanical bending of trans-4-(dimethylamino)azobenzene microcrystals was observed. Upon UV irradiation, the (001) face of the platelike microcrystals bent quickly in the direction opposite the light source, reaching the maximum deflection after 0.5 s. The microcrystal returned to its initial flat shape 30 s after the illumination was stopped. This mechanical motion was reversible over repeated cycles of UV irradiation. The bending effect was attributed to a gradient in the extent of UV-induced trans-cis photoisomerization as a function of light penetration, causing the expansion of the irradiated crystal surface along the b axis to result in a bent macrostructure.

Adsorption of metal ions on activated carbon from aqueous solutions at pH 1–13

Adsorption of microgram amounts of 20 metal species on activated carbon powder from aqueous solutions of pH 1-13 was investigated. The species examined were Cs(I), Y(III), Ce(III), Ti(IV), Zr(IV), Cr(III), Cr(VI), Mn(II), Fe(III), Co(II), Ni(II), Ru(III), Cu(II), Ag(I), Zn(II), Cd(II), Al(III), Pb(II), Sb(III) and Bi(III).

Collection of mercury from artificial sea-water with activated carbon☆

Nanogram amounts of mercury(II) and methylmercury in artificial sea-water containing mineral acids as preserving reagents were shown to be collected quantitatively with activated carbon. Mercury concentrated on activated carbon was determined directly by combustion, trapping on gold and electrothermal atomic-absorption spectrophotometry. The activated carbon was purified by heating at 350 degrees for 2 hr. Sulphuric acid and hydrochloric acid were purified by treatment with activated carbon. Interference from iodide was eliminated by using a carbonate buffer wash before the atomic-absorption measurement. Less than 4 ng of mercury in 200-300 ml of artificial sea-water, whether acidified or not (with sulphuric, hydrochloric or nitric acid), was satisfactorily collected with 100 mg of activated carbon. Mercury was also collected quantitatively after oxidative treatment of artificial sea-water.

Preparation, structure and discrimination of a chiral bimolecular crystal by the self-assembly of 3-indolepropionic acid and phenanthridine

Although 3-indolepropionic acid and phenanthridine are achiral molecules, a chiral bimolecular crystal is spontaneously formed; torsional conformation of the propionic acid group plays an important role in the helix formation through hydrogen bonding chain within the crystal lattice.

Preparation and photoreaction of organogels based on benzophenone

Abstract In this paper, first photoreactive low-molecular weight organogels are described. Benzophenone derivatives functionalised with two long alkylamides 1a–c were designed and synthesized as photoreactive gelator molecules. The compounds formed organogels in several hydrogen donor solvents, e.g. 2-propanol and 1,3,5-triisopropylbenzene. Microstructures of the gels by scanning electron microscopy (SEM) revealed a 3D fibrous network and spherical aggregation. Compound 4 based on isopropylbenzene having an octadecylamide, which was designed as a photochemical hydrogen donor molecule, occurred gelation in a variety of organic solvents. In the case of a 1:1 mixture of 1c and 4 in several solvents, each component independently caused gelation to give a simple mixture of different gels. Irradiation of the gel of 1a in 2-propanol decomposed gradually the gel into solution to give pinacol as a main product. Similarly, photoreaction of the 1:1 two-component gel of 1c and 4 in benzene afforded corresponding pinacol.

Extraction of iron(III), gold(III), gallium(III), thallium(III), antimony(V) and antimony(III) from hydrochloric acid solution with crown ethers

Chloroform solutions of dicyclohexyl-18-crown-6 (DC18C6), dibenzo-18-crown-6 (DB18C6) and 18-crown-6 (18C6) efficiently extracted iron(III), gold(III), gallium(III), thallium(III) and antimony(V) from solution in hydrochloric acid. Extraction with 15-crown-5 (15C5) and 12-crown-4 (12C4) was poor. Antimony(III) in the presence of titanium(III) chloride was efficiently extracted only with DC18C6. When tervalent iron, gold, gallium and thallium were extracted from acidic lithium chloride solution, even 15C5 and 12C4 gave good extractabilities. The molar ratio of crown ether to the metal ions, except antimony(III), in the extracted species is probably 1 : 1, and the metals are probably extracted as chloro complexes, e.g., HFeCl4 and LiFeCl4. Iron and gallium in aluminium-base alloys were determined after their separation by DC18C6 extraction.

Ionic chiral handle-induced asymmetric synthesis in a solid state Norrish type II photoreaction

Abstract Irradiation of crystals of salts formed between 4-(2,4,6-triisopropylbenzoyl)benzoic acid ( 1a ) and various optically active amines is shown to lead to optically active Norrish type II photoproducts in low to moderate enantiomeric excesses, a process in which the ammonium ion has acted as an “ionic chiral handle.” X-ray crystallography reveals that the salts crystallize with two independent, mirror image-related molecules of the benzophenone moiety in the asymmetric unit, and this is suggested to be the source of the low ee s observed.

CHIRAL CRYSTALLINE SALTS FROM ACHIRAL BIPHENYLCARBOXYLIC ACIDS AND TRYPTAMINE

Abstract Chiral crystals of quaternary ammonium salts 5 – 7 were prepared by crystallization of achiral biphenylcarboxylic acids 1 – 3 and achiral tryptamine 4 . Molecular chirality is defined by chiral conformations of the biphenyl group and crystal chirality by a helical arrangement of the molecules in the lattice. The enantiomorphous crystals were easily discriminated by measuring their solid state (powder) CD spectra.

A multistep photoreaction of aromatic aldehydes with heteroaromatics in the solid state

Abstract Mixed crystals, prepared by resolidification of the melt of a mixture of 5-formyl-1,3-dimethyluracil (1a) and antipyrine (7) crystals (molar ratio, 1:2.5), and irradiated with a high-pressure mercury lamp under nitrogen, gave a photocondensation product 8a, as in the previously reported solid state photoreaction between 1a and indole. Similarly, irradiation of mixed crystals of substituted benzaldehydes and indole gave the corresponding photocondensation product 3. A mechanism involving an oxetane intermediate 4 was proposed for the formation of 3. The nature of the starting mixed crystals was examined by powder X-ray diffractometry.

Solid-State Photoreaction in Two-Component Molecular Crystals of Thienylacetic Acids and Aza Aromatic Compounds

Abstract A series of two-component molecular crystals of 2-thienylacetic acid (1) or bis(2-thienyl)acetic acid (2) with aza aromatic compounds such as acridine (a) and phenanthridine (b) were prepared by crystallization from the solutions of both components. Irradiation of the crystals caused photodecarboxylation and radical intermediates which give decarboxylated and condensation products. The relationship between the crystal structures and the reaction paths are discussed.