Polyiodides in room-temperature ionic liquids.

Polyiodides, Im-, were formed in room-temperature ionic liquids (RTILs). The RTILs were N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium iodide, [DEME][I], and 1-alkyl-3-methylimidazolium iodide, [Cnmim][I] (n = 1, 2, 3, 4, 6, and 12). In [Cnmim][Im], prepeak and intensity modulation of X-ray diffraction were caused by polyiodides. Above m = 4, polyiodide-mediated local structures were formed, although little alkyl side-chain length, n, dependence was seen in the X-ray diffraction patterns. The viscosity of the mixtures was measured as a function of m to obtain their dynamic properties. The m tendencies of the viscosity and density changed at around m = 4 when fixing n = 4. By 127I-NMR, the local environments of only polyiodides were extracted by changing n, m, and the temperature. Doublet/triplet peak splitting of pure [Cnmim][I] (n = 3, 4, and 6) occurred at low temperature. In [Cnmim][Im] (n = 2 and 4), the effect of polyiodides was clarified from the chemical shifts and peak splitting in the NMR spectra. The experimental results support a Grotthuss-type exchange mechanism of iodide between polyiodides.

SENJU: a new time-of-flight single-crystal neutron diffractometer at J-PARC.

SENJU is a new single-crystal time-of-flight neutron diffractometer installed at BL18 at the Materials and Life Science Experimental Facility of the Japan Accelerator Research Complex (J-PARC). The diffractometer was designed for precise crystal and magnetic structure analyses under multiple extreme sample environments such as low temperature, high pressure and high magnetic field, and for diffraction measurements of small single crystals down to 0.1 mm3 in volume. SENJU comprises three choppers, an elliptical shape straight supermirror guide, a vacuum sample chamber and 37 scintillator area detectors. The moderator-to-sample distance is 34.8 m, and the sample-to-detector distance is 800 mm. The wavelength of incident neutrons is 0.4-4.4 Š(first frame). Because short-wavelength neutrons are available and the large solid angle around the sample position is covered by the area detectors, a large reciprocal space can be simultaneously measured. Furthermore, the vacuum sample chamber and collimator have been designed to produce a very low background level. Thus, the measurement of a small single crystal is possible. As sample environment devices, a newly developed cryostat with a two-axis (ω and φ axes) goniometer and some extreme environment devices, e.g. a vertical-field magnet, high-temperature furnace and high-pressure cell, are available. The structure analysis of a sub-millimetre size (0.1 mm3) single organic crystal, taurine, and a magnetic structure analysis of the antiferromagnetic phase of MnF2 have been performed. These results demonstrate that SENJU can be a powerful tool to promote materials science research.

L-Leucylglycine 0.67-hydrate and [(4S)-2,2-dimethyl-4-(2-methylpropyl)-5-oxoimidazolidin-3-ium-1-yl]acetate.

Crystals of L-leucylglycine (L-Leu-Gly) 0.67-hydrate, C(8)H(16)N(2)O(3)·0.67H(2)O, (I), were obtained from an aqueous solution. There are three symmetrically independent dipeptide zwitterionic molecules in (I) and they are parallel to one another. The hydrogen-bond network composed of carboxylate and amino groups and water molecules extends parallel to the ab plane. Hydrophilic regions composed of main chains and hydrophobic regions composed of the isobutyl groups of the leucyl residues are aligned alternately along the c axis. An imidazolidinone derivative was obtained from L-Leu-Gly and acetone, viz. [(4S)-2,2-dimethyl-4-(2-methylpropyl)-5-oxoimidazolidin-3-ium-1-yl]acetate, C(11)H(20)N(2)O(3), (II), and was crystallized from a methanol-acetone solution of L-Leu-Gly. The unit-cell parameters coincide with those reported previously for L-Leu-Gly dihydrate revealing that the previously reported values should be assigned to the structure of (II). One of the imidazolidine N atoms is protonated and the ring is nearly planar, except for the protonated N atom. Protonated N atoms and deprotonated carboxy groups of neighbouring molecules form hydrogen-bonded chains. The ring carbonyl group is not involved in hydrogen bonding.

Synthesis of the proposed structure of phaeosphaeride A.

The first total synthesis of the proposed structure of phaeosphaeride A has been achieved via six-membered-ring formation by means of an intramolecular vinyl-anion aldol reaction as the key step. This synthesis suggests a revised configurational assignment for phaeosphaeride A.