Asymmetric charge separation and recombination in symmetrically functionalized σ-π hybrid oligosilanes.

The flexibility of σ-conjugated silanes presents new opportunities for manipulating charge generation, transport, and non-linear optical properties of materials. Recently we synthesized a series of acceptor-donor-acceptor (ADA) compounds in which a methylated oligosilane core (D) is flanked by electron-deficient cyanovinyl-substituted arenes (A). Based on a detailed characterization of the photophysics of ADA and donor-acceptor (DA) architectures using both steady state and ultrafast spectroscopic measurements we illustrate that asymmetric charge separation occurs directly following light absorption.

Synthesis of a Fragment of Crystalline Silicon: Poly(Cyclosilane).

We report a strategic synthesis of poly(cyclosilane), a well-defined polymer inspired by crystalline silicon. The synthetic strategy relies on the design of a functionalized cyclohexasilane monomer for transition-metal-promoted dehydrocoupling polymerization. Our approach takes advantage of the dual function of the phenylsilyl group, which serves a crucial role both in the synthesis of a novel α,ω-oligosilanyl dianion and as a latent electrophile.

Photoinduced Charge Separation in Molecular Silicon.

Interest in molecular silicon semiconductors arises from the properties shared with bulk silicon like earth abundance and the unique architectures accessible from a structure distinctly different than rigid π-conjugated organic semiconductors. We report ultrafast spectroscopic evidence for direct, photoinduced charge separation in molecular silicon semiconductors that supports the viability of molecular silicon as donor materials in optoelectronic devices. The materials in this study are σ-π hybrids, in which electron-deficient aromatic acceptors flank a σ-conjugated silicon chain.

Mechano-isomerization of azobenzene.

We show that ultrasound-induced mechanical force isomerizes an azobenzene centered within a poly(methyl acrylate) polymer from cis to trans configuration without cleaving the azo bond. The isomerization rate was not altered by the polarity of the solvent indicating that the isomerization occurs through a non-polar, inversion transition state.

Apical functionalization of chiral heterohelicenes.

We describe a synthetic protocol to selectively functionalize chiral bridged triarylamines at the apical position using regioselective copper-catalyzed amination reaction. This protocol allows the coupling of diphenylamines with a sterically hindered but electronically activated aryl-Br bond in the presence of a sterically unhindered but electronically unactivated aryl-Br bond. The unactivated aryl-Br bond was utilized further to synthesize a chiral heterohelicene homodimer using Stille coupling.

Proton conduction in discotic mesogens.

In this communication, we show that liquid crystalline phases lower the activation energy barrier for proton transport. The liquid crystalline phases were obtained using a triphenylene core with alkyl chains bearing a triazole moiety at their termini.