Control of aurophilic interaction: conformations and electronic structures of one-dimensional supramolecular architectures.

Gold(i) chloride complexes with the diarsenic ligands cis-1,4-dihydro-1,4-diarsinines (cis-DHDAs) were synthesized. X-ray diffraction revealed that they formed one-dimensional polymeric structures through aurophilic interactions. Their higher-ordered structures are controlled by the ligand structure; methyl- and t-butyl substituted ligands offered transoid-transoid and transoid-cisoid conformations, respectively. Density functional theory (DFT) calculations indicated that the electronic structure of the aurophilic network was highly dependent on the conformations. This is the first study on the relationship between the chain conformation and 5d-orbital structures of gold complexes.

Modification of TiO2 Nanoparticles with Oleyl Phosphate via Phase Transfer in the Toluene-Water System and Application of Modified Nanoparticles to Cyclo-Olefin-Polymer-Based Organic-Inorganic Hybrid Films Exhibiting High Refractive Indices.

Oleyl-phosphate-modified TiO2 nanoparticles (OP_TiO2) were prepared via phase transfer from an aqueous phase containing dispersed TiO2 nanoparticles to a toluene phase containing oleyl phosphate (OP, a mixture of monoester and diester), and employed for the preparation of OP_TiO2/cyclo-olefin polymer (COP) hybrid films with high-refractive indices. The modification of TiO2 by OP was essentially completed by reaction at room temperature for 8 h, and essentially all the TiO2 nanoparticles in the aqueous phase were transferred to the toluene phase. The infrared and solid-state 13C cross-polarization and magic-angle spinning (CP/MAS) NMR spectrum of OP_TiO2 showed the presence of oleyl groups originating from oleyl phosphate. The solid-state 31P MAS NMR spectrum of OP_TiO2 exhibited new signals at -1.4, 2.1, and 4.8 ppm, indicating the formation of Ti-O-P bonds. CHN and inductively coupled plasma analyses revealed that the major species bound to the TiO2 surface was tridentate CH3(CH2)7CH═CH(CH2)8P(OTi)3. These results clearly indicate that the surfaces of the TiO2 nanoparticles were modified by OP moieties via phase transfer. OP_TiO2/COP hybrid films exhibited excellent optical transparency up to 19.1 vol % TiO2 loading, and the light transmittance of the hybrid films with 19.1 vol % TiO2 loading was 99.8% at 633 nm. The refractive index of these hybrid films rose to 1.83.

Synthesis of Fluorine-Doped Hydrophilic Carbon Nanoparticles from Hexafluorobenzene by Femtosecond Laser Pulses.

We report on the preparation and characterization of fluorine-doped hydrophilic carbon nanoparticles by the exposure of hexafluorobenzene or a water/hexafluorobenzene bilayer solution to femtosecond laser pulses. Uniform atom distributions are achieved not only on the particle surface but also inside the particles. The semi-ionic character of C-F bonds and the non-aggregating feature of the nanoparticles play key roles in the water-dispersible character of fluorine-doped carbon nanoparticles. We suggest the following building-up process of carbon nanoparticles: the fragmentation of hexafluorobenzene initiated by the electrons generated in laser-induced plasma followed by the reconstruction of a carbon framework of nanoparticles.

Preparation of Transparent Bulk TiO2/PMMA Hybrids with Improved Refractive Indices via an in Situ Polymerization Process Using TiO2 Nanoparticles Bearing PMMA Chains Grown by Surface-Initiated Atom Transfer Radical Polymerization.

Transparent TiO2/PMMA hybrids with a thickness of 5 mm and improved refractive indices were prepared by in situ polymerization of methyl methacrylate (MMA) in the presence of TiO2 nanoparticles bearing poly(methyl methacrylate) (PMMA) chains grown using surface-initiated atom transfer radical polymerization (SI-ATRP), and the effect of the chain length of modified PMMA on the dispersibility of modified TiO2 nanoparticles in the bulk hybrids was investigated. The surfaces of TiO2 nanoparticles were modified with both m-(chloromethyl)phenylmethanoyloxymethylphosphonic acid bearing a terminal ATRP initiator and isodecyl phosphate with a high affinity for common organic solvents, leading to sufficient dispersibility of the surface-modified particles in toluene. Subsequently, SI-ATRP of MMA was achieved from the modified surfaces of the TiO2 nanoparticles without aggregation of the nanoparticles in toluene. The molecular weights of the PMMA chains cleaved from the modified TiO2 nanoparticles increased with increases in the prolonging of the polymerization period, and these exhibited a narrow distribution, indicating chain growth controlled by SI-ATRP. The nanoparticles bearing PMMA chains were well-dispersed in MMA regardless of the polymerization period. Bulk PMMA hybrids containing modified TiO2 nanoparticles with a thickness of 5 mm were prepared by in situ polymerization of the MMA dispersion. The transparency of the hybrids depended significantly on the chain length of the modified PMMA on the nanoparticles, because the modified PMMA of low molecular weight induced aggregation of the TiO2 nanoparticles during the in situ polymerization process. The refractive indices of the bulk hybrids could be controlled by adjusting the TiO2 content and could be increased up to 1.566 for 6.3 vol % TiO2 content (1.492 for pristine PMMA).

Photoinduced Bending of Self-Assembled Azobenzene-Siloxane Hybrid.

A novel azobenzene-siloxane hybrid material displaying photoinduced macroscopic motions has been prepared by one-step organosilane self-assembly. Two types of alkoxysilane precursors with either pendant or bridging azobenzene groups were synthesized via thiol-ene click reactions. Hybrid films with well-ordered lamellar structures were obtained by hydrolysis and polycondensation of these precursors. The film with solely pendant azobenzene groups showed reversible and rapid d-spacing variation upon UV-vis irradiation, which was induced by the trans-cis isomerization of azobenzene moieties. The flexible, free-standing film obtained by co-condensation of two types of precursors showed reversible bending-unbending motions upon UV-vis irradiation. The partial cross-linking between the siloxane layers by bridging azobenzene groups was crucial for photoinduced distortion of the film. This film possesses high elastic modulus, good thermal stability, and shows large amplitude of photoinduced bending-unbending over a wide temperature range. This is the first report on photoinduced macroscopic motions of azobenzene-containing siloxane-based materials. These materials possess great potential for applications in smart devices and energy conversion systems.

Practical Synthesis and Properties of 2,5-Diarylarsoles.

2,5-Diarylarsoles were easily synthesized from nonvolatile arsenic precursors. Diiodoarsine was generated in situ and reacted with titanacyclopentadienes to give 2,5-diarylarsoles. The structures and optical properties were studied in comparison with those of 2,5-diarylphosphole. It was found that the arsoles were much more stable in the air than the phosphole. Single crystal X-ray diffraction revealed the arsenic atoms adopted a trigonal pyramidal structure, reflecting on the s-character of the lone pair. The obtained 2,5-diarylarsoles and 2,5-diarylphosphole showed intense emission in solutions and solid state. In addition, the optical properties were controlled by transition-metal coordination.

Color Tuning of the Aggregation-Induced Emission of Maleimide Dyes by Molecular Design and Morphology Control.

Aggregation-induced emission (AIE)-active maleimide dyes, namely, 2-p-toluidino-N-p-tolylmaleimide, 3-phenyl-2-toluidino-N-p-tolylmaleimide, 2-p-thiocresyl-3-p-toluidino-N-p-tolylmaleimide, and 2,3-dithiocresyl-N-arylmaleimides, were synthesized by facile synthetic procedures. The dyes show intense emission in the solid state, and emission colors were controlled from green (λmax =527 nm) to orange (λmax =609 nm) by varying the substituents at the 2- and 3-positions of the maleimide and the packing structures in the solid state. 2,3-Disubstituted maleimide dyes effectively underwent redshifts of their emission wavelength. Furthermore, some of the dyes exhibited mechanochromism and polymorphism, and their emission properties were dramatically dependent on the morphology of the solid samples. The mechanisms of the emission behaviors were investigated by X-ray diffraction. The substituent of the nitrogen atom of the maleimide ring affected the intermolecular interactions and short contacts, which were observed by single crystal X-ray crystallography, to result in completely different emission properties.

As-stereogenic C2-symmetric organoarsines: synthesis and enantioselective self-assembly into a dinuclear triple-stranded helicate with copper iodide.

As-stereogenic C2-symmetric 2,5-diaryl-cis-1,4-dihydro-1,4-diarsinines (2,5-diaryl-cis-DHDAs) were synthesized without volatile precursors. A racemic mixture of the ligands enantioselectively self-assembled into a dinuclear triple-stranded helicate with copper iodide in quantitative yield. In the helicate, two metals were bridged via three enantiomerically pure ligands.

Synthesis of dithienogermole-containing oligo- and polysilsesquioxanes as luminescent materials.

Dithienogermole (DTG)-containing oligo- and polysilsesquioxanes were prepared by hydrolysis/condensation of DTGs bearing one () or two trialkoxysilyl group(s) (). The reaction of gave a cage-type octasilsesquioxane with eight DTG groups at the edges () as a viscous oil, whereas the reaction of yielded a network polymer () as a self-standing film. showed a photoluminescence (PL) quantum yield (Φ) of 56% in THF. This value was as high as that of (Φ = 58%), in spite of the accumulation of DTG units in the molecule, as characteristics of the POSS structure. The PL of in THF was suppressed by contact with nitrobenzene, showing the potential of for sensing nitroaromatic explosives. Polymer exhibited a relatively low Φ of 2% as a film, but Φ was improved to 38% by copolymerization with trimethoxymethylsilane. was also copolymerized with a trimethoxysilyl-substituted carbazole derivative () to provide polysilsesquioxanes with DTG and carbazole units, which showed efficient photo-energy transfer from carbazole to DTG in the films. Similar copolymerization of with in the presence of poly(9-vinylcarbazole) provided a composite material with hole-transporting electroluminescence properties, applicable in multi-layered organic light emitting diodes.

Selective Synthesis of cis-trans-cis Cyclic Tetrasiloxanes and the Formation of Their Two-Dimensional Layered Aggregates.

In this study, a single cyclic tetrasiloxane containing propylammonium trifluoromethanesulfonate and methyl side-chain groups (Am-CyTS) was selectively prepared by the hydrolytic condensation of 3-aminopropyldiethoxymethylsilane using aqueous superacid trifluoromethanesulfonic acid. The (1)H NMR spectrum of Am-CyTS in D2O exhibited a single signal assigned to a methyl group, and the (29)Si NMR spectrum of Am-CyTS in DMSO-d6 also exhibited only one signal. In the matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) and the electrospray ionization mass spectrometry (ESI MS) analyses, the peaks corresponding to the masses of the cyclic tetrasiloxane were observed. These results indicate that Am-CyTS is a single cyclic tetrasiloxane without isomers. In addition, the result of a single-crystal X-ray structural analysis of its tert-butoxycarbonyl (Boc)-protected compound (Boc-CyTS) indicated the formation of a cis-trans-cis cyclic tetrasiloxane forming two-dimensional layered aggregates. Moreover, it was found that two-dimensional layered aggregates could be formed by drop-casting an aqueous solution of Am-CyTS and chloroform solution of Boc-CyTS onto glass substrates, as shown by powder X-ray diffraction measurements.

Preparation and electric property of polysilsesquioxane thin films incorporating carbazole groups.

New silsesquioxane incorporating a carbazole groups (PCTSQ) has been synthesized by a click thiol-ene reaction and a subsequent sol-gel reaction. To evaluate the electric property of this hybrid, diode devices have been fabricated by using PCTSQ thin film by spin-coating onto n-type ZnO film prepared by the electrodeposition method. The thin film hybrid devices showed good electric characteristics and high rectification ratio, as well as worked as a rectifier.

Polymorph control of luminescence properties in molecular crystals of a platinum and organoarsenic complex and formation of stable one-dimensional nanochannel.

The mononuclear diiodoplatinum(II) complex (trans-PtI2(cis-DHDAMe)2), where cis-DHDAMe = cis-1,4-dihydro-1,4-dimethyl-2,3,5,6-tetrakis(methoxycarbonyl)-1,4-diarsinine, forms three different crystalline polymorphs that can be either concomitantly or separately obtained on varying the recrystallization conditions. Cubic red crystals (α-phase) and red-orange needles (ß-phase) exhibit solid-state red emissions at room temperature. Cubic red crystals of the γ-phase show no solid-state emission at room temperature. All crystalline structures were confirmed by X-ray crystallography. Room-temperature strongly luminescent crystals (α-phase) (λem = 657 nm, Φ = 0.52) have a triclinic P1 (No. 2) structure and no voids in the crystal structure. Red-orange needle-shaped crystals of the ß-phase exhibit moderate red luminescence (λem = 695 nm, Φ = 0.09) at room temperature and have a trigonal, R3 (No. 148), structure. In the needlelike crystals of the ß-phase, stable hexagonal arrays of nanoporous channels, 5.0 Å in diameter, are formed. Room-temperature nonluminescent crystals (γ-phase) have an orthorhombic, Pbca (No. 61), structure with a void volume that is 4.9% of the total crystal volume. After heating the α-phase crystals at 150 °C for 2 min, a powder XRD pattern different from the original crystal is obtained, and its solid-state emission at room temperature decreased. After heating the ß-phase crystals at 150 °C for 2 min, the emission wavelength and the quantum yield of the solid-state emission at room temperature and the powder XRD pattern are the same as those of the α-phase after heating at 150 °C. A crystal-to-crystal transition triggered by the thermal stimulus produces a different stable polymorph of the mononuclear diiodoplatinum(II) complex. The one-dimensional nanoporous crystals encapsulated iodine without distorting the crystal packing.

Single- and double-layered organically modified nanosheets by selective interlayer grafting and exfoliation of layered potassium hexaniobate.

Organically modified niobate nanosheets are promising building blocks for the design of advanced hybrid materials. Nanosheets with controlled thickness and surface composition are important for precise structural design of the nanosheet-based materials. In this work, single-layered and double-layered niobate nanosheets functionalized by phenylphosphonate moieties were selectively prepared by interlayer grafting of A-type and B-type intercalation derivatives of potassium hexaniobate (K4Nb6O17·3H2O) with phenylphosphonic acid (PPA), followed by exfoliation by ultrasonication in acetonitrile. The interlayer grafting of PPA was monitored using X-ray diffraction (XRD), Fourier transform infrared (FTIR), and solid-state NMR spectroscopy, and the thicknesses of the exfoliated nanosheets were measured by atomic force microscopy (AFM). Transparent hybrid films were obtained by incorporating the single- and double-layered nanosheets into an epoxy matrix.

Thermochromism and structural change in polydiacetylenes including carboxy and 4-carboxyphenyl groups as the intermolecular hydrogen bond linkages in the side chain.

We investigated the thermochromic behavior of polydiacetylenes including the carboxy and 4-carboxyphenyl groups as the side-chain substituents adjacent to the conjugated main chain, and then, the thermal stability and the thermochromism reversibility of the polymers were related to changes in the polymer conformations monitored by IR and Raman spectroscopies and powder X-ray diffractions. The polydiacetylenes with no or a phenylene spacer between the main chain and the carboxylic acid moiety were revealed to exhibit a thermal resistance for maintaining reversible thermochromism in a high temperature range, rather than polydiacetylenes with a conventional structure with a flexible alkylene spacer. The molecular stacking structures of the diacetylenes and the corresponding polymers in the crystals were discussed based on the results of an X-ray single-crystal structure analysis as well as the powder X-ray diffraction measurements.

Organic vapor triggered repeatable on-off crystalline-state luminescence switching.

A nonporous crystalline solid consisting of an organoarsenic platinum(II) complex, i.e., a mononuclear diiodoplatinum(II) complex trans-PtI(2)(cis-DHDAtBu)(2) (1) with cis-1,4-dihydro-1,4-dimethyl-2,3,5,6-tetrakis(tert-butoxycarbonyl)-1,4-diarsinine (cis-DHDAtBu), shows on-off solid-state luminescence switching through reversible solvent vapor uptake and escape. The on-off switching of solid-state luminescence was achieved without changing the structure or electronic state of the organoarsenic platinum(II) complex.

Formation of metal nanoparticles on the surface of polymer particles incorporating polysilane by UV irradiation.

Polystyrene particles incorporating poly(methylphenylsilane) (PMPS) were synthesized by miniemulsion polymerization. UV irradiation of the emulsion under air in the presence of metal salts such as HAuCl4.4H2O, AgNO3, and Na2PdCl4 led to the formation of metal nanoparticles on the surface of polymer particles; thus, metal nanoparticle/polymer hybrid particles were obtained. The structures of the hybrid particles were confirmed by the surface plasmon resonance band and transmission electron microscopy images. The formation of metal nanoparticles depended on the functional groups and charge on the surface of the polymer particle. The metal nanoparticles were formed due to the reduction of metal ions, accompanied by the oxidation of PMPS. The interaction between the surface of the polymer particle and the metal ions plays an important role in the formation of the metal nanoparticle.