Ionic liquid-containing coordination polymer: solvent-free synthesis, incongruent melting, and glass formation.

An ionic-liquid-containing 2D coordination polymer was synthesized via a solvent-free reaction. The material exhibited incongruent melting at 112 °C, forming a solid-liquid mixture; further heating to 240 °C led to complete melting. Upon cooling, the melt transformed into a solid-liquid mixture, from which the coordination polymer was gradually recovered at ambient temperature. Rapid cooling (>200 °C s-1) of the melt resulted in complete vitrification at -28 °C.

Novel ferromagnetic materials of SmCo5 nanoparticles in single-nanometer size: chemical syntheses and characterizations.

We first succeeded in preparing ferromagnetic materials of SmCo(5) nanoparticles in sizes of single nanometers by a chemical route using a polyol process. In order to produce ferromagnetic SmCo(5) nanoparticles with a CaCu(5)-type structure, the chemical preparation was conducted under a molar ratio of 1:1.3 of Sm:Co as compositions of metallic precursors when tetraethylene glycol (TEG), and oleic acid and oleylamine were used as a reductant and protectant, respectively. However, XRD profiles of the products showed the presence of oxides and other by-products besides the CaCu(5)-type structured nanoparticles. The best metallic precursors and protective reagent to prevent oxidization under reaction were SmCl(3) and Co(acac)(3), and 1-adamantanecarboxylic acid (ACA) and poly(N-vinyl-2-pyrrolidone) (PVP), respectively when TEG was used as the reducing reagent. We found that oxides and other by-products were not detected and pure SmCo(5) nanoparticles with the CaCu(5)-type structure were prepared under the chemical condition. The SmCo(5) nanoparticles coated by ACA and PVP were 6.2 nm in diameter and showed a coercivity of 1500 Oe at 300 K.

Synthesis, Photochromic Properties, and Crystal Structures of Salts Containing a Pyridinium-Fused Spiropyran: Positive and Negative Photochromism in the Solution and Solid State.

Salts containing the merocyanine form of a pyridinium-fused spiropyran ([6'-MC]X; X = I and PF6) were prepared, and their crystal structures were determined. In addition, the photochromic properties of the salts were spectroscopically and kinetically investigated. In the solution state, the salts exhibited negative photochromism. Theoretical calculations revealed that the negative photochromism of the salt originates from the drastic stabilization of the merocyanine structure by electron delocalization of the pyridinium ring. Furthermore, the salts containing the merocyanine and spiropyran forms ([6'-MC]I, [6'-MC]PF6, and [6'-SP]PF6) were obtained by recrystallization. The crystals of [6'-SP]PF6 exhibited positive photochromism in the solid state; however, no photochromism was observed in the [6'-MC]X crystals.

Hydro-nium bis-(tri-fluoro-methane-sulfon-yl)amide-18-crown-6 (1/1).

The structure of the title compound, H3O+·C2F6NO4S2 -·C12H24O6 or [H3O+·C12H24O6][N(SO2CF3)2 -], which is an ionic liquid with a melting point of 341-343 K, has been determined at 113 K. The asymmetric unit consists of two crystallographically independent 18-crown-6 mol-ecules, two hydro-nium ions and two bis-(tri-fluoro-methane-sulfon-yl)amide anions; each 18-crown-6 mol-ecule complexes with a hydro-nium ion. In one 18-crown-6 mol-ecule, a part of the ring exhibits conformational disorder over two sets of sites with an occupancy ratio of 0.533 (13):0.467 (13). One hydro-nium ion is complexed with the ordered 18-crown-6 mol-ecule via O-H⋯O hydrogen bonds with H2OH⋯OC distances of 1.90 (6)-2.19 (7) Å, and the other hydro-nium ion with the disordered crown mol-ecule with distances of 1.85 (6)-2.36 (6) Å. The hydro-nium ions are also linked to the anions via O-H⋯F hydrogen bonds. The crystal studied was found to be a racemic twin with a component ratio of 0.55 (13):0.45 (13).

A biferrocenium salt containing paramagnetic tetracyanoquinodimethane hexamers: charge disproportionation via donor-acceptor interactions.

[Dineopentyl-biferrocene]2[Cl1TCNQ]7, which has an unprecedented high donor-acceptor ratio of 2 : 7, contains a linear paramagnetic hexamer of Cl1TCNQ. Both the donor and acceptor molecules exhibit charge disproportionation in the crystal through mutual electrostatic interactions.

Direct synthesis and characterizations of fct-structured FePt nanoparticles using poly(N-vinyl-2-pyrrolidone) as a protecting agent.

FePt alloy in a bulk state is well known as a magnetic material. FePt nanoparticles, which are protected by poly(N-vinyl-2-pyrrolidone) (PVP) and have a face-centered tetragonal (fct) structure at a size of a few nanometers in diameter, have been directly synthesized by a polyol process in high-boiling point tetraethylene glycol used as a reducing reagent for the reduction of Fe(III) acetylacetonate and Pt(II) acetylacetonate. Their magnetic properties (coercivity and saturation magnetization) were dependent on the size and made progress as their diameters increased. The size in diameter was easily controlled by altering the content of PVP, the time for refluxing, and reaction temperature. FePt nanoparticles showed diameter-dependent coercivities at room temperature and they abruptly increased at over 4 nm in diameter. Ferromagnetic FePt nanoparticles with an fct structure were also synthesized at relatively low reaction temperature without refluxing. Likewise, as-synthesized FePt nanoparticles prepared by refluxing at 251 degrees C for 3 h displayed the fct structure and clearly indicated the ferromagnetism at room temperature. Reaction kinetics such as long refluxing time and slow temperature elevation rate were found to be important key factors to synthesize the ferromagnetic FePt nanoparticles although the reaction temperature was very critical as well.