Crystal Structures and Packing of 2,4,6-tris(4-Fluorophenoxy)-1,3,5-triazine and 2,4,6-tris(3,4-Dimethylphenoxy)-1,3,5-triazine. New Materials for Octupolar Nonlinear Optics

The crystal structures and packing of 2,4,6-tris(4-fluorophenoxy)-1,3,5-triazine and 2,4,6-tris(3,4-dimethylphenoxy)-1,3,5-triazine are discussed. These structures have been determined as a continuation of a series of octupolar NLO materials we have been investigating. The crystal structures are characterized by C–H...F and C–H... hydrogen bonds, respectively. A characteristic of these triazine structures is the presence of dimeric Piedfort Units (PU) that are extended into more elaborate two-dimensional (2-D) networks. The structure of the fluoro derivative is compared with that of the corresponding unsubstituted and chloro/bromo-substituted derivatives. The structure of the dimethyl triazine is compared with that of the corresponding 4-methyl derivative. The noncentrosymmetric nature of the dimethyl derivative was confirmed by a powder SHG signal at 1.064 m of the order of 0.5 × KDP. Interestingly, the dimethyl derivative studied here is isostructural with the corresponding 4-methyl triazine. This H/Me isostructurality is shown to be an uncommon phenomenon by an analysis with the CSD.     

Generation of 30-50 nm structures using easily fabricated,composite PDMS masks

This communication demonstrates an approach to generate simple nanostructures with critical dimensions down to 30 nm over cm2-sized areas using composite PDMS masks. These masks were patterned with feature sizes down to 100 nm. When used in phase-shifting lithography, these masks generated arrays of structures in photoresist with line widths as small as 30 nm, slots in metal with features down to 40 nm, and wells in epoxy with diameters as small as 100 nm. The wells were used to prepare arrays of uniformly sized nanocrystals of salts.     

Effect of alkyl chain parity on the face-selective crystal growth of a drug polymorph

Carboxy terminated alkanethiol self-assembled monolayers promote the face-selective nucleation of the P-monoclinic polymorph of carbamazepine; the type of face nucleated depends on the parity of the alkyl chain.