吾郷 友宏

We developed and characterized four polyfluorinated bistolane derivatives. These compounds, which possess either two alkoxy substituents or an alkoxy group and a bromine atom in their two molecular terminals, were synthesized from readily available 4-alkoxy-1-ethynylbenzene with a facile three-step procedure. Their thermodynamic and photophysical properties were evaluated in detail, and they were found to display both liquid-crystalline (LC) and photoluminescence properties. Remarkably, the photoluminescence behaviors dramatically changed during the thermal phase transition between the crystal and LC phases. Thus, these polyfluorinated bistolanes may be promising candidates for thermoresponsive luminous molecules.

We herein describe the synthesis of novel pentafluorinated tolane fluorophores, which possess an extended pi-conjugated structure with a large molecular dipole moment along the longitudinal axis. We also report a detailed evaluation of both the photophysical and thermal behaviors of these fluorophores. All molecules displayed photoluminescence (PL) characteristics in both the crystalline state and in dilute solutions. The large longitudinal dipole moment induced solvatochromic PL behavior, which switched sensitively with changes in the solvent polarity. In addition, incorporation of the fluorinated tolane-based solid-state light-emitting moiety into the polymer side chain was found to be responsible for the PL characteristics observed in the solid state. It was also noteworthy that the polymerization protocol led to a significant enhancement in the thermal stability, with the thermal decomposition temperature increased by 90 degrees C. Accordingly, novel solid-state light-emitting materials with high thermal stabilities were successfully developed as promising candidates for use in light-emitting and optoelectronic applications.

Dihydroxylation of 3,3,4,4,5,5-hexafluorocyclopentene by KMnO4 afforded a highly-fluorinated 1,2-cycloalkanediol, 3,3,4,4,5,5-hexafluoro-cis-1,2-cyclopentanediol, as a colorless crystalline solid. The cis-configuration of the two hydroxy groups was elucidated by the X-ray crystallographic analysis on the dibenzoate of the 1,2-diol. Treatment of the 1,2-diol with several diacid chlorides afforded the corresponding oligoesters in good yields.

Phosphanylalumanes bearing hydrogen and halogen substituents (RHP–AlXR, R = organic substituent, X = halogen) are expected to be useful synthetic precursors for P=Al doubly bonded species, phosphaalumenes (RP=AlR), though there have been only limited number of H,X-functionalized phosphanylalumanes. In this communication, synthesis and structure of a Lewis base coordinated phosphanylalumane bearing P–H and Al–Br moieties are reported. Reaction of LiPHMes with BbpAlBr2(OEt2) {Bbp = 2,6-[CH(SiMe3)2]2C6H3} followed by the treatment with a N-heterocyclic carbene (L) afforded the Lewis base coordinated H,Br-functionalized phosphanylalumane, MesP(H)-Al(Br)(L)Bbp (L = N-heterocyclic carbene). Its Al–P bond length is comparable to that observed for the previously reported H,Cl-functionalized phosphanylalumane free from Lewis base-coordination, indicating the negligible contribution of Al=P double-bond character in the phosphanylalumane derivatives.

The reactions of the fused-ring bulky Eind-substituted 1,2-dibromodisilene, (Eind)BrSi=SiBr(Eind) (1a) (Eind = 1,1,3,3,5,5,7,7-octaethyl-s-hydrindacen-4-yl (a)), with N-heterocyclic carbenes (NHCs) (Im-Me4 = 1,3,4,5-tetramethylimidazol-2-ylidene and Im-iPr2Me2 = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) are reported. While the reaction of 1a with the sterically more demanding Im-iPr2Me2 led to the formation of the mono-NHC adduct of arylbromosilylene, (Im-iPr2Me2)→SiBr(Eind) (2a'), a similar reaction using the less bulky Im-Me4 affords the bis-NHC adduct of formal arylsilyliumylidene cation, [(Im-Me4)2→Si(Eind)]+[Br-] (3a). The NHC adducts 2a' and 3a can also be prepared by the dehydrobromination of Eind-substituted dibromohydrosilane, (Eind)SiHBr2 (4a), with NHCs. The NHC-coordinated silicon compounds have been characterized by spectroscopic methods. The molecular structures of bis-NHC adduct, [(Im-iPr2Me2)2→Si(Eind)]+[Br-] (3a'), and 4a have been determined by X-ray crystallography.

Highly regio- and stereoselective transformation of commercially available 4-bromo-3,3,4,4-tetrafluoro-1-butene into multisubstituted alkenes having a tetrafluoroethylene fragment through Heck reactions and/or Suzuki-Miyaura cross coupling reactions was established. Thus, the obtained alkenes underwent a smooth reductive coupling reaction with aldehydes under the influence of MeLi/LiBr-free, affording structurally unprecedented fluorinated materials.

We synthesised a series of dissymmetric bistolane derivatives and evaluated their liquid-crystalline (LC) and photoluminescence properties in detail. In measuring LC behaviours, rational structural design based on the dissymmetric molecular structure and electron-density distribution facilitated the production of the LC phase with a wide temperature range (up to 97 °C). In addition, dissymmetric bistolane derivatives were shown to strongly emit blue-photoluminescence in dilute solution and in crystalline states. It was found that dissymmetric bistolanes possess emissive features in even the LC phase and photoluminescence behaviours such as emission intensity and colour were sensitively switched depending on the molecular aggregate structure caused by applying a thermal stimulus.

An iron-bromoalumanyl complex with a tri-coordinated aluminum was synthesized. Its CO-stretching frequencies are shifted to lower-frequency region compared to those of the related boryl and gallyl complexes. Theoretical investigations suggested the importance of the Br-Al mesomeric effect on the stability of the alumanyl complex.

Phosphasilenes, P=Si doubly bonded compounds, have received considerable attention due to their unique physical and chemical properties. We report on the synthesis and structure of a chlorophosphasilene coordinated by an N-heterocyclic carbene (NHC), which has the potential of functionalization at the Si-Cl moiety. Treatment of a silylphosphine, ArPH-SiCl2RSi (Ar = bulky aryl group, R-Si = Si(SiMe3)(3)) with two equivalents of Im-Me-4 (1,3,4,5-tetramethylimidazol-2-ylidene) afforded the corresponding NHC-coordinated phosphasilene, ArP= SiClRSi(Im-Me-4) as a stable compound. Bonding properties of the P=Si bond coordinated to an NHC will be discussed on the basis of theoretical calculations.

Activation of dihydrogen by masked dialumenes (Al=Al doubly bonded species) is reported. Reactions of barrelene-type dialumanes, which have the reactivity as masked equivalents of 1,2-diaryldialumenes ArAl=AlAr, with H-2 afforded dihydroalumanes ArAlH2 at room temperature (Ar: bulky aryl groups). These dihydroalumanes form hydrogen-bridged dimers [ArHAl(-H)](2) in the crystalline state, while a monomer-dimer equilibrium was suggested in solution. The 1,2-diaryldialumenes generated from the barrelene-type dialumanes are the putative active species in the cleavage of H-2.

Stable alumole and gallole derivatives have been synthesized, and their reactivity was investigated. Mes(*)-substituted alumole and gallole have tri-coordinated heavier group 13 element moieties even in the presence of Lewis bases, because of the steric hindrance of the bulky Mes(*) group. Treatment of the Mes(*)-substituted heavier group 13heteroles with Li metal afforded the Li salts of the corresponding heterole dianions. Furthermore, 1-bromo- and 1-chloro-alumole derivatives were synthesized by applying the same synthetic method as used for the synthesis of the Mes(*)-substituted alumole. In the solid state, the 1-haloalumoles exhibit dimeric structures due to the halogen-aluminum coordination interactions. Utilization of the 1-bromoalumole for the synthesis of new cyclic organoaluminum compounds through the reactions with nucleophiles and alkynes are also described.

Barrelene-type dialumanes bearing bulky aryl substituents were synthesized, and their reactivity as synthetic equivalents of the corresponding dialumenes was elucidated. Reaction of the barrelene-type dialumanes with [Pt(PCy3)(2)] afforded platinum complexes of the corresponding alumylene (ArAl:). Structures of the newly obtained cyclic compounds containing an Al-Al bond and the platinum complexes were determined.

Lewis-base-free diphosphinoalumane and 1-hydro-2-chlorophosphinoalumane derivatives bearing a bulky aryl substituent were synthesized by the reaction of the corresponding lithium phosphide and dichloroalumane. Structures of these phosphinoalumane derivatives were determined by spectro-scopic and X-ray crystallographic analyses. Because of the efficient steric protection by the bulky aryl substituent, the aluminum centers in these phosphinoalumane derivatives have tricoordinate geometry. Reactions of the phosphinoalumane derivatives with organolithium reagents and bases were investigated.

Treatment of a stable dialumane derivative with an excess of t-butyl isocyanide resulted in the homocoupling of the isocyanide to form a diaminoalkyne skeleton. A one-to-one insertion product of the isocyanide with the dialumane should be the intermediate for the generation of the diaminoalkyne derivative.

Treatment of 1-bromo-2,3,4,5-tetraethylalumole (1) with 3-hexyne afforded the corresponding product 1-bromo-1-alumacyclonona-2,4,6,8-tetraene (2), accompanied by the formation of hexaethylbenzene. In the crystalline state, 2 forms a Br-bridged dimer with a pseudo C-2-symmetric and twisted AlC8 nine-membered ring. Deuterium-labeling experiments and DFT calculations on the reaction of 1 with 3-hexyne suggested that 1-bromo-1-alumacyclohepta-2,4,6-triene, which is formed by the insertion of one molecule of 1-hexyne into the AlC bond of alumole 1, is the key intermediate for the generation of 2 as well as hexaethylbenzene.

A 1,2-digermabenzene bearing bulky substituents on its two germanium atoms was successfully synthesized and isolated as a stable, crystalline compound via the reaction of a digermyne precursor with 2 equiv of acetylene. Even though its molecular structure, which was revealed by X-ray crystallographic analysis, showed a trans-bent geometry for the Ge-Ge moiety, theoretical calculations Suggested substantial levels of aromaticity.

A stable Lewis base-free gallole bearing a bulky Mes* group (=2,4,6-(t-Bu)(3)C6H2) was synthesized by the treatment of Mes*GaCl2 with a 3,6-dilithio-3,5-octadiene derivative. Reduction of the gallole with lithium metal afforded the corresponding gallole dianion species as a lithium salt. Structures of the gallole and the lithium salt of the gallole dianion have been elucidated by using X-ray crystallographic analysis, NMR spectroscopies, and density functional theory calculations. Copyright (c) 2014 John Wiley & Sons, Ltd.

Reaction of the stable digermyne BbtGe GeBbt (Bbt = 2,6-[CH(SiMe3)(2)](2)-4-[C(SiMe3)(3)]-C6H2) with ethylene initially afforded the corresponding 1,2-digermacyclobutene. Depending on the reaction conditions applied, further reaction of this 1,2-digermacyclobutene with ethylene furnished two different reaction products: a 1,4-digermabicyclo[2.2.0]hexane or a bis(germiranyl)ethane. Combined experimental and theoretical results suggested that the 1,4-digermabicyclo[2.2.0]hexane and the bis(germiranyl)ethane are the thermodynamic and kinetic reaction products, respectively. A reaction mechanism in agreement with these results was proposed.

Reaction of an isolable 1-bromoalumole with LiN(SiMe3)(2) in toluene afforded a lithium 1,1-diaminodialumoluide, while in THF the corresponding 1-aminoalumole-THF complex was obtained. These amino-substituted alumole derivatives are characterized by X-ray crystallographic analysis and NMR spectroscopy. The lithium 1,1-diaminoalumoluide and the 1-aminoalumole-THF complex were converted to each other by ligand exchange reactions.

Reaction of a dialumene-benzene adduct bearing bulky aryl substituents with diphenylacetylene was found to give a novel 5,6-dialuminabicyclo[2.1.1]hex-2-ene derivative in addition to the 3,4-dialuminacyclobutene derivative, the formal [2+2] cycloadduct of an intermediary dialumene with diphenylacetylene. The molecular structure of the newly obtained 5,6-dialuminabicyclo[2.1.1]hex-2-ene has been elucidated by X-ray crystallographic analysis.

Reactions of stable 1,2-dibromodisilenes ((E)-Ar(Br) Si=Si(Br)Ar) with N-heterocyclic carbenes (NHC) afforded NHC-arylbromosilylene adducts or bromide salts of the corresponding bis-NHC adducts of the formal arylsilyliumylidene cations ([ArSi:](+)). In some cases, an NHC was able to replace a bromide anion in the coordination sphere of the arylbromosilylene-NHC adduct.

Terminal arylalumylene complexes of platinum [Ar-Al-Pt(PCy3)(2)] (Ar=2,6-[CH(SiMe3)(2)](2)C6H3 (Bbp) or 2,6-[CH(SiMe3)(2)](2)-4-(tBu)C6H2 (Tbb)) have been synthesized either by the reaction of a dialumene-benzene adduct with [Pt(PCy3)(2)], or by the reduction of 1,2-dibromodialumanes Ar(Br)Al-Al(Br)Ar in the presence of [Pt(PCy3)(2)]. X-Ray crystallographic analysis reveals that the AlPt bond lengths of these arylalumylene complexes are shorter than the previously reported shortest AlPt distance. DFT calculations suggest that the AlPt bonds in the arylalumylene complexes have a significantly high electrostatic character.

A stable 1-bromoalumole has been synthesized by the reaction of a 1,4-dilithio-1,3-butadiene derivative with AlBr3. The 1-bromoalumole was found to exist as a dimeric structure in the crystalline state. Reaction of the 1-bromoalumole with Mes*Li afforded the corresponding Mes*-substituted alumole (Mes* = 2,4,6-(t-Bu)(3)C6H2), demonstrating the potential of the 1-bromoalumole for the functionalization of alumoles.

Papers on sensing of anions by main group element compounds, which were published in the last decade, are reviewed. Most of them concern fluoride sensing utilizing functionalized triarylboranes. Introduction of an electron-withdrawing group such as a cationic group, chelate formation, and formation of hydrogen bonding are very useful to improve the complexation ability of sensors with anion. Color change of absorption and emission, on-off of fluorescence and phosphorescence, and change of redox potential are mainly used as a signal for anion sensing. Sensing of adenosine diphosphate and adenosine triphosphate, which are very important anions in life science, is also presented. © 2013 Elsevier Ltd. All rights reserved.

Kinetically stabilized 1,2-dihydrodisilenes were successfully synthesized and isolated by the introduction of sterically protecting bulky aryl groups. These 1,2-dihydrodisilenes exhibit distinct Si=Si double-bond character in both solution and the solid state. The Si-H bonds in these 1,2-dihydrodisilenes exhibit higher s character than those of typical σ 4, λ 4-hydrosilanes. Moderate heating of these 1,2-dihydrodisilenes in solution resulted in their isomerization to the corresponding trihydrodisilanes, with an intramolecular hydrogen migration as the rate-determining step. © 2012 American Chemical Society.

Supramolecular extended frameworks based on a rotational molecular clip and having the same "primary structure" can exhibit either an unfolded or a folded framework. This process is driven by intramolecular pi-pi interactions, resulting in the formation of an infinite pi-stacked column within the folded supramolecular framework

A 1,4-azaborine derivative fused by two naphthalene rings, a dinaphthoazaborine was synthesized, and its molecular structure was revealed by X-ray crystallographic analysis. UV vis absorption and fluorescence spectra of the dinaphthoazaborine indicated a decrease in the HOMO-LUMO energy gap compared with that of dibenzoazaborines. Electrochemical measurements elucidated the enhanced electron-accepting characteristics of the dinaphthoazaborine.

pi-Extended silafluorenes and spirobisilafluorenes bearing electron-donating aminostyryl substituents at the 2,7- or 3,6-positions were synthesized by a Horner-Wadsworth-Emmons reaction. The electronic influence of spirocyclic structure and substitution mode of the aminostyryl substituents was investigated by UV/Vis spectroscopy, which indicated the existence of a spiroconjugation effect in the 3,6-substituted spirobisilafluorene. They exhibited moderate to strong fluorescence emission, and the fluorescence properties were compatible with the UV/Vis absorption characteristics, except for the 3,6-substituted spirobisilafluorene, which showed relatively large enhancement of fluorescence quantum yield and Stokes shift. The influence of the spirocyclic structure and substitution mode on the photophysical properties of the silicon compounds was investigated by DFT calculations.

A stepwise synthetic method for a 9,10-dihydro-9,10-diboraanthracene was developed, and the optical and electrochemical properties as well as the molecular structure of the 9,10-dihydro-9,10-diboraanthracene were elucidated. The 9,10-dihydro-9,10-diboraanthracene exhibited high complexation ability against fluoride ion, and the complexation was accompanied by the enhancement of photoluminescence emission, probably due to intramolecular charge transfer between the two boron atoms. © 2010 Elsevier Ltd. All rights reserved.

Novel hetero-pi-conjugated compounds (dibenzochalcogenaborins) with the same molecular framework, bearing a boron atom as an acceptor and chalcogen atoms as a donor, were synthesized, and systematic comparisons among these molecules were performed. X-ray crystallographic analysis of these molecules showed similar structures with high planarity. UV/Vis spectroscopy and theoretical calculations revealed that the absorption maxima and the HOMO-LUMO gap changed by systematically changing the bridging chalcogen atom. Dibenzooxaborin and dibenzothiaborin showed fluorescence emission both in solution and in the solid state with a small Stokes shift, indicating the high rigidity of these compounds. On the other hand, dibenzoselenaborin exhibited a very weak fluorescence as a result of the heavy atom effect.

An azaborine bearing two dimesitylboryl groups on its periphery showed very strong light absorption and moderate photoluminescence emission; the reaction of the title compound with fluoride ion resulted in multi-step fluoride ion complexation on the boron atoms of the dimesitylboryl groups, producing mono- and bisfluoroborates.

New cationic triarylboranes bearing ammonio or phosphonio groups on the periphery were synthesized from a common intermediate, a dibromodibenzoazaborine. These cationic molecules are soluble in highly polar organic solvents as well as water, and they exhibit strong light absorption and photoluminescence emission in water. Complexation of the cationic azaborines with fluoride and cyanide ions in aqueous media proceeded and could be monitored by NMR, UV/Vis, and fluorescence spectroscopy.

A phosphoniafluorene and a spirobiphosphoniafluorene bearing 4-(diethylamino)styryl groups were synthesized. These compounds exhibited bathochromically shifted absorption and emission, compared with their silicon analogues, because of the strong acceptor property of the phosphonium core. They also showed enhanced two-photon absorptions at around 930 nm.

Two cationic triarylboranes based on phosphomoborin frameworks have been investigated. Electron-withdrawing phosphonio groups enhanced the Lewis acidity of these boranes which capture fluoride ion in aqueous media and transport it into organic phase.

The phosphonium borane [p-Mes(2)B(C6H4)PMePh2](+) complexes fluoride in water containing 10% methanol with a binding constant of 1.0(+/- 0.1) x 10(3) M-1 to afford the zwitterion p- Mes(2)FB(C6H4) PMePh2.