Neutral 4π-electron tetrasilacyclobutadiene contains unusual features of a Möbius-type aromatic ring.

The search for stable compounds containing an antiaromatic cyclic 4π system is a challenge for inventive chemists that can look back on a long history. Here we report the isolation and characterization of the novel 4π-electron tetrasilacyclobutadiene, an analogue of a 4π neutral cyclobutadiene that exhibits surprising features of a Möbius-type aromatic ring. Reduction of RSiCl (R = (Pr)PCH) with KC in the presence of cycloalkyl amino-carbene (cAAC) led to the formation of corresponding silylene 1.

Structure Elucidation of Lithium Compounds Using Li Residual Quadrupolar Couplings.

A new NMR method for the structure elucidation of lithium compounds under solution-like conditions is presented. It is based on the measurement of Li residual quadrupolar couplings (RQCs) in a stretched polystyrene (PS) gel, and comparison to RQCs predicted from crystal or DFT-derived model structures in combination with alignment tensors derived from one-bond H, C residual dipolar couplings (RDCs). The method was applied to five lithium model complexes containing monoanionic, bidentate bis(benzoxazole-2-yl)methanide, bis(benzothiazole-2-yl)methanide and bis(pyridyl)methanide ligands, of which two are first introduced in this work.

Polymer brushes under high load.

Polymer coatings are frequently used to provide repulsive forces between surfaces in solution. After 25 years of design and study, a quantitative model to explain and predict repulsion under strong compression is still lacking. Here, we combine experiments, simulations, and theory to study polymer coatings under high loads and demonstrate a validated model for the repulsive forces, proposing that this universal behavior can be predicted from the polymer solution properties.

Synthesis and aqueous solution properties of polyelectrolyte-grafted silica particles prepared by surface-initiated atom transfer radical polymerization.

A range of polyelectrolyte-grafted silica particles have been prepared by grafting suitable initiators onto near-monodisperse, 304-nm-diameter silica particles using siloxane chemistry, followed by surface-initiated atom transfer radical polymerization (ATRP) of four ionic vinyl monomers, namely sodium 4-styrenesulfonate (SStNa), sodium 4-vinylbenzoate (NaVBA), 2-(dimethylamino)ethyl methacrylate (DAM), and 2-(diethylamino)ethyl methacrylate (DEA) in protic media. The resulting polyelectrolyte-grafted silica particles were characterized using dynamic light scattering (DLS), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), helium pycnometry, and diffuse reflectance infrared Fourier transfer spectroscopy (DRIFTS). The TGA results indicated that the polyelectrolyte contents of the silica particles could be varied from 0.