Dissecting Porosity in Molecular Crystals: Influence of Geometry, Hydrogen Bonding, and [π···π] Stacking on the Solid-State Packing of Fluorinated Aromatics.

Porous molecular crystals are an emerging class of porous materials that is unique in being built from discrete molecules rather than being polymeric in nature. In this study, we examined the effects of molecular structure of the precursors on the formation of porous solid-state structures with a series of 16 rigid aromatics. The majority of these precursors possess pyrazole groups capable of hydrogen bonding, as well as electron-rich aromatics and electron-poor tetrafluorobenzene rings.

Cyclotetrabenzoin: Facile Synthesis of a Shape-Persistent Molecular Square and Its Assembly into Hydrogen-Bonded Nanotubes.

Cyanide-catalyzed benzoin condensation of terephthaldehyde produces a cyclic tetramer, which we propose to name cyclotetrabenzoin. Cyclotetrabenzoin is a square-shaped macrocycle ornamented with four α-hydroxyketone functionalities pointing away from the central cavity, the dimensions of which are 6.9×6.

Benzobisimidazole cruciform fluorophores.

A series of 11 cross-conjugated cruciform fluorophores based on a benzobisimidazole nucleus has been synthesized and characterized. Like in their previously reported benzobisoxazole counterparts, the HOMOs of these new fluorophores are localized along the vertical bisethynylbenzene axes, while their LUMOs remain relatively delocalized across the molecule, except in cruciforms substituted with electron-withdrawing groups along the vertical axis. Benzobisimidazole cruciforms exhibit a pronounced response to deprotonation in their UV/vis absorption and emission spectra, but their response to protonation is significantly attenuated.

Benzobisoxazole cruciforms as fluorescent sensors.

CONSPECTUS: Cross-conjugated molecular cruciforms are intriguing platforms for optoelectronic applications. Their two intersecting π-conjugated arms allow independent modulation of the molecules' HOMO and LUMO levels and guarantee a well-defined optical response to analyte binding. In addition, the rigid cross-conjugated geometries of these molecules allow their organization in two- and three-dimensional space with long-range order, making them convenient precursors for the transition from solution-based to the more practical solid-state- and surface-based devices.

L-shaped benzimidazole fluorophores: synthesis, characterization and optical response to bases, acids and anions.

Nine L-shaped benzimidazole fluorophores have been synthesized, computationally evaluated and spectroscopically characterized. These "half-cruciform" fluorophores respond to bases, acids and anions through changes in fluorescence that vary from moderate to dramatic.