(Z)-1,2-Di(1-pyrenyl)disilene: Synthesis, Structure, and Intramolecular Charge-Transfer Emission.

(Z)-1,2-Di(1-pyrenyl)disilene containing bulky 1,1,3,3,5,5,7,7-octaethyl-s-hydrindacen-4-yl (Eind) groups has been obtained as purple crystals by the reductive coupling reaction of the corresponding dibromosilane with lithium naphthalenide. An X-ray crystallographic analysis revealed an Eind- and pyrenyl-meshed molecular gear around the disilene core adopting the Z configuration, in which the two pyrenyl groups intramolecularly interact through the π-π stacking with a distance of 3.635 Å between the centers of the two pyrene rings. The disilene π-system exhibits a π(Si-Si) → π*(pyrene) intramolecular charge-transfer (ICT) fluorescence at room temperature, whose wavelengths depend on the solvent polarity. The photophysical properties are theoretically supported by computational studies including excited-state calculations.

Air-stable, room-temperature emissive disilenes with π-extended aromatic groups.

π-Conjugated disilenes with 2-naphthyl or 2-fluorenyl groups on the silicon atoms have been synthesized as air-stable emissive red solids using the bulky 1,1,3,3,5,5,7,7-octaethyl-s-hydrindacen-4-yl (Eind) groups. The strong π-π* absorptions and distinct emission at room temperature, both in solution and in the solid state, have been observed due to the substantial contribution of the 3p(π)*(Si-Si)-2p(π)*(carbon π-electron system) conjugation.

Vapochromic and mechanochromic tetrahedral gold(I) complexes based on the 1,2-bis(diphenylphosphino)benzene ligand.

Tetrahedral gold(I) complexes containing the diphosphane ligand (dppb=1,2-bis(diphenylphosphino)benzene), [Au(dppb)(2)]X [X=Cl (1), Br (2), I (3), NO(3) (4), BF(4) (5), PF(6) (6), B(C(6)H(4)F-4)(4) (7)], and the ethanol and methanol adducts of complex 4, 8, and 9, were prepared to analyze their unique photophysical properties. These complexes are classified into two categories on the basis of their crystal structures. In Category I, the complexes (1-5) have relatively-small counter anions and two dppb ligands are symmetrically coordinated to the central Au(I) atom, and display an intense blue phosphorescence. Alternatively, the complexes (6-9) in Category II have large counter anions and two dppb ligands asymmetrically coordinated to Au(I) atom, and display a yellow or yellow orange phosphorescence. The difference in the phosphorescence color of the complexes between the Category I and II is ascribed to the change in the structure of the cationic moiety in the complex. According to DFT calculations, the symmetry reduction caused by the large counter anion of the complex in Category II gives the destabilization of HOMO (σ*) levels, leading to the red-shift of the emission peak. We have demonstrated that the symmetry reductions are responsible for the phosphorescence color alteration caused by external stimuli (volatile organic compounds and mechanical grinding).

Isolated monomeric and dimeric mixed diorganocuprates based on the size-controllable bulky "rind" ligands.

Isolable mixed diorganocopper(I) complexes have been synthesized and structurally characterized by introducing a variety of bulky "Rind" groups based on a fused-ring octa-R-substituted s-hydrindacene skeleton. Treatment of RindLi with CuBr produced organobromocuprate dimers [Cu(Rind)/CuBr](2) or monomers Li[Cu(Rind)Br], depending on the steric bulkiness of the Rind ligands. Subsequent substitution of the bromine atoms in these complexes by lithium trimethylsilylacetylide gave dimeric and monomeric aryl(alkynyl)copper(I) complexes A and B, respectively. Complex B is the first isolable mixed diorganocuprate monomer formulated as LiCuRR' and was found to selectively undergo oxidative cross-coupling of two different organic groups on copper.

Field-induced carrier delocalization in the strain-induced mott insulating state of an organic superconductor.

We report the influence of the field effect on the dc resistance and Hall coefficient in the strain-induced Mott insulating state of an organic superconductor kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Br. Conductivity obeys the formula for an activated transport sigma(square)=sigma(0)exp(-W/k(B)T), where sigma(0) is a constant and W depends on the gate voltage. The gate-voltage dependence of the Hall coefficient shows that, unlike in conventional field-effect transistors, the effective mobility of dense hole carriers ( approximately 1.6x10(14) cm(-2)) is enhanced by a positive gate voltage. This implies that carrier doping involves delocalization of intrinsic carriers that were initially localized due to electron correlation.