Probing local structure of glass with orientation-dependent luminescence.

The local ordering of particles is considered an important process in glass transition. Ordering is usually observed in simulation and micrometer-sized colloid. However, clear information on local ordering at the molecular level is difficult to obtain experimentally. In this study, we prepared an easily glass-forming fluorophore with a color change owing to the intermolecular arrangement in the liquid, glass, and crystal states. The bathochromic shifts of the photoluminescence spectra indicated a change in the intermolecular orientation upon immediate cooling of the melt. The recovery of the spectra by successive heating indicated that rotation contributed to the change in the intermolecular orientation. The orientation in the glass was distinct from that during crystal growth, which was observed as a slow bathochromic shift by maintaining the temperature between the melting points of the blue- and green-luminescent crystals obtained from dichloromethane/ethanol and dichloromethane/hexane, respectively. Our results demonstrate that the anisotropic interaction between glass-forming luminophores is useful for uncovering molecular-level events in the glassy state.

Copper-Catalyzed Single C-H Amination of 8-Aminoquinoline-Directed Ferrocenes.

An unprecedented copper-catalyzed C-H monoamination of ferrocenes directed by an 8-aminoquinoline amide directing group is described. This reaction proceeds in the presence of a catalytic amount of copper catalyst with both cyclic and acyclic amines to afford the various aminoferrocenes. The C-H amination of ortho-substituted ferroceneamides was also achieved, enabling rapid access to multisubstituted ferrocenes that are useful for developing new functional molecules.

Intra- and intermolecular interaction of anthracene moieties in 7,8-disilabicyclo[3.3.0]octadienyl-bridged bisanthracenes.

Ruthenium-catalyzed dimerization of 9-anthrylarylsilanes afforded air-stable V-shaped bisanthracenes bridged by a 7,8-disilabicyclo[3.3.0]octadiene moiety. The intra- and intermolecular proximity of the anthracene moieties were determined by single-crystal X-ray analysis. Absorption and emission maxima of the disilabicyclo[3.3.0]octadienyl-bridged bisanthracenes in the solution state were observed at longer wavelengths than those of 9-anthryldimethylsilane and bis(9-anthryl)dimethylsilane. The V-shaped bisacenes in the solid state showed excimer emissions with moderate quantum yields.

Twisted Polycyclic Aromatic Systems Prepared by Annulation of Bis(arylethynyl)arenes with Biphenylboronic Acids.

Twisted polycyclic aromatic hydrocarbons (PAHs) were prepared by the successive rhodium-catalyzed annulation and dehydrogenative cyclization of bis(arylethynyl)arenes with di-tert-butylbiphenyl-2-ylboronic acid. The molecular structures of the PAHs were determined by single-crystal XRD analysis. The PAHs showed up to four fjord regions, and the twisting angle was 46.7°. The nonplanarity (NP) and harmonic oscillator model of aromaticity (HOMA) were calculated by using the structural data obtained from XRD analysis. The PAHs derived from dialkynyl naphthalenes showed low planarity and HOMA of the central ring. The optical properties of the PAHs were investigated by UV/Vis absorption and fluorescence spectroscopy analyses. The absorption and emission maxima of the PAHs with a larger planar region appeared at a longer wavelength. DFT calculations support that the absorption band at λ≈450 nm can be mainly attributed to the HOMO-LUMO transition.

Copper- and Silver-Catalyzed Diastereo- and Enantioselective Conjugate Addition Reaction of 1-Pyrroline Esters to Nitroalkenes: Diastereoselectivity Switch by Chiral Metal Complexes.

syn-Diastereoselective conjugate addition of 1-pyrroline esters to nitroalkenes in good yields with an excellent enantioselectivity by using CuOAc/Me-FcPHOX catalyst in the presence of pyridine. In contrast, AgOAc/tBu-ThioClickFerrophos catalyzed the anti diastereoselective conjugate addition with a high enantioselectivity without additional base. Thus, the preparation of chiral 1-pyrroline derivatives bearing diverse stereochemistry could be achieved. The diastereoselective reduction of the imine group in the conjugate adduct could afford the 2,5-cis-proline ester derivative.

Synthesis of Silaphenalenes by Ruthenium-Catalyzed Annulation between 1-Naphthylsilanes and Internal Alkynes through C-H Bond Cleavage.

Ruthenium-catalyzed annulation of 1-naphthylsilanes with internal alkynes afforded silaphenalenes through cleavage of the C-H bond at the 8-position of the naphthalene. [RuH2 (CO){P(p-FC6 H4 )3 }3 ] efficiently catalyzed the reaction. The use of 1-naphthyldiphenylsilane as a substrate resulted in a better yield of the annulation product compared to the use of silanes with alkyl groups on the silicon atom. Internal alkynes with both aryl and alkyl groups were tolerated in this reaction.

Synthesis of π-Conjugated Polymers Containing Benzodipyrrole Moieties in the Main Chain through Cleavage of C-H Bonds in 1,4-Bis(acetylamino)benzene.

Rhodium-catalyzed copolymerization between 1,4-bis(acetylamino)benzene and diynes through C-H bond cleavage afforded π-conjugated polymers containing benzodipyrrole moieties. The polymers with substituted benzene units exhibited nearly the same absorption peaks and HOMO levels. Fluorenone and benzothiadiazole moieties can be also introduced as electron-acceptor units to the main chain by polymerization in tert-amyl alcohol and tetrahydropyran as mixed solvent, leading to absorption at longer wavelength.

Palladium/clickferrophos-catalyzed asymmetric domino allylstannylation-heck reaction of o-formylaryl triflate.

Asymmetric domino allylstannylation-Heck reaction of o-formylaryl triflates was successively catalyzed by Pd/ClickFerrophos to give the 3-methylene-indan-1-ols in good yields with good to excellent enantioselectivities. The benefit of the reaction is that the starting o-formylaryl triflates are prepared from easily accessible salicylaldehyde derivatives, and the variation of the product, chiral 3-methylene-indan-1-ols, can be expanded. The reaction with 4-substituted substrates gave the corresponding 3-methylene-indan-1-ols in good yields with high enantioselectivities, whereas the reaction with 5- and 6-substituted substrates occasionally afforded the corresponding Stille coupling product in significant amounts along with the desired 3-methylene-indan-1-ols.

Silver/ThioClickFerrophos complex as an effective catalyst for asymmetric conjugate addition of glycine imino ester to unsaturated malonates and α-enones.

The AgOAc/ThioClickFerrophos complex effectively catalyzed the conjugate addition of glycine imino esters to arylidene and alkylidene malonates, furnishing the corresponding adducts in good yields with high enantioselectivities, in the presence or absence of an external base. The complex also catalyzed conjugate addition to α-enones in the presence of 1,4-diazabicyclo[2.2.2]octane with high enantioselectivity, with formation of a small amount of cycloadducts.

Synthesis of dibenzo[b,f]silepins with a benzoquinolyl ligand.

A benzo[h]quinolyl ligand provided pentacoordinate character for silicon in dibenzo[b,f]silepins. Substituents on the silicon center determined both conformations of the dibenzosilepin and luminescence properties in relation to charge transfer.

Synthesis of benzo[h]quinoline-based neutral pentacoordinate organosilicon complexes.

Reactions of 10-benzo[h]quinolyllithium with a series of organosilanes led to the formation of neutral pentacoordinate complexes. The diethynyl-substituted complex was able to be converted to di(arylethynyl)-substituted ones by the Sonogashira-Hagihara coupling reaction. Electronegative substituents shortened N-Si distances and enhanced fluorescence intensity from the complexes.

Synthesis of π-conjugated polymers containing aminoquinoline-borafluorene complexes in the main-chain.

The regulation of electron transfer between a conjugated polymer and ligands orthogonally connected to the main-chain is reported. Poly(arylene-ethynylene)s containing aminoquinoline-borafluorene complexes in the main-chain are synthesized in good yields by a Sonogashira-Hagihara coupling. Single crystal X-ray analysis of a model compound has elucidated the complex's structure in which the aminoquinolate moiety and the borafluorene ring are connected directly and orthogonally. Moreover, the optical properties of the polymers are characterized by UV-vis absorption and photoluminescence spectra. Perfluorinated alkyl chain-containing polymers show strong emission, while hydrocarbon chain-containing ones exhibit only a slight emission. DFT calculation suggests that an electron transfer from the excited main-chain to the aminoquinolate ligand is suppressed because of the lowered LUMO level by introducing the electron withdrawing groups, resulting in the significant emission.