Hexadecanethiol (n-C16), 2,2-dimethylhexadecane-1-thiol (DMC16), and the multidentate thiol-based ligands 2-tetradecylpropane-1,3-dithiol (C16C2), 2-methyl-2-tetradecylpropane-1,3-dithiol (C16C3), and 1,1,1-tris(mercaptomethyl)pentadecane (t-C16) were evaluated for their ability to stabilize large gold nanoparticles (>15 nm) in organic solution. Citrate-stabilized gold nanoparticles (20-50 nm) treated with the ligands were extracted from aqueous solution and dispersed into toluene. The degree of aggregation of the gold nanoparticles was monitored visually and further confirmed by UV-vis spectroscopy and dynamic light scattering (DLS). The bidentate ligands (C16C2 and C16C3) and particularly the tridentate ligand (t-C16) showed enhanced abilities to inhibit the aggregation of large gold nanoparticles in organic solution. For gold nanoparticles modified with these multidentate ligands, bound thiolate (S2p3/2 binding energy of 162 eV) was the predominant sulfur species (>85%) as evaluated by X-ray photoelectron spectroscopy (XPS). Although an entropy-based resistance to ordering of the loosely packed surfactant layers was initially considered to be a plausible mechanism for the enhanced stabilization afforded by the multidentate ligands, when taken as a whole, the data presented here support a model in which the enhanced stabilization arises largely (if not solely) from the multidentate chelate effect.

Molecular-based dye-sensitized photoelectrochemical cells (DSPECs) have traditionally targeted solar-driven water splitting for the conversion of solar energy into fuels in aqueous media. This work reports the use of a DSPEC-type photoanode specifically designed to carry out chemoselective oxidation of benzylic alcohol moieties in lignin model compounds and real lignin in organic media. The TiO 2 -based photoanode incorporates a surface-bound Ru(II)-based photocatalyst and solutiondissolved hydrogen atom transfer (HAT) co-catalyst to perform solar-driven photocatalytic oxidation of the lignin substrates. Under aerobic conditions with simulated solar illumination, conversion efficiencies in excess of 90% are observed for the formation of the oxidized ketone product from model compounds. The DSPEC half-cell exhibited impressive long-term durability, sustaining photocatalytic oxidation of the lignin model compound over a net illumination period of 80 h. This photoelectrochemical heterogeneous catalytic process provides a unique foundation to perform selective C−O bond cleavage for real lignin conversion technologies.

Three new push–pull molecules having either pyridyl or N,N-dimethylanilino groups as electron-donor moieties and the p-iodo-tetrafluorophenyl ring as an electron-acceptor group have been synthesized and their single crystal X-ray structures are reported. Halogen bonding drives the self-assembly of these molecules in the solid state giving rise to head-to-tail halogen-bonded infinite polar chains which crystallize in an antiparallel arrangement. The three new nonlinear optical (NLO)-phores synthesized show high hyperpolarizabilities at the molecular level in solution. Rationalization of the obtained NLO measurements is supported by molecular modeling calculations.