Erzwungene Planarität: eine Strategie für stabile, borhaltige π-konjugierte Materialien

Methylene Bridging Effect on the Structures, Lewis Acidities and Optical Properties of Semi-planar Triarylboranes

Three synthetic methods towards semi-planar triarylboranes with two aryl rings connected by a methylene bridge have been developed. The fine-tuning of their stereoelectronic properties and Lewis acidities was achieved by introducing fluorine, methyl, methoxy, n-butyl and phenyl groups either at their exocyclic or bridged aryl rings. X-ray diffraction analysis and quantum-chemical calculations provided quantitative information on the structural distortion experienced by the near planar hydro-boraanthracene skeleton during the association with Lewis bases such as NH₃ and F^- . Though the methylene bridge between the ortho-positions of two aryl rings of triarylboranes decreased the Gibbs free energies of complexation with small Lewis bases by less than 5 kJ mol^-1 relative to the classical Lewis acid BAr₃ , the steric shielding of the CH₂ bridge is sufficient to avoid the formation of Lewis adducts with larger Lewis bases such as triarylphosphines. A newly synthesized spirocyclic amino-borane with a long intramolecular B-N bond that could be dissociated under thermal process, UV-irradiation, or acidic conditions might be a potential candidate in Lewis pairs catalysis.

Regioselective Functionalization of Stable BN-Modified Luminescent Tetraphenes for High-Resolution Fingerprint Imaging

A series of novel BN tetraphene derivatives have been prepared successfully for the first time via a post-functionalization strategy. The optical and electronic properties of these derivatives could be tuned systematically by the incorporation of different substituents on the main skeleton. The functionalized BN-containing luminogens have been explored for the detection of latent fingerprints (LFPs) on different substrates, including glass, aluminum foil, plastic, and ironware. This strategy provides great versatility in LFP imaging and good potential in elucidating the chemical information within LFPs, making the strategy valuable in forensic investigations.

Highly electron-deficient and air-stable conjugated thienylboranes

Introduced herein is a series of conjugated thienylboranes, which are inert to air and moisture, and even resist acids and strong bases. X-ray analyses reveal a coplanar arrangement of the thiophene rings, an arrangement which facilitates p-π conjugation through the boron atoms despite the presence of highly bulky 2,4,6-tri-tert-butylphenyl (Mes*) or 2,4,6-tris(trifluoromethyl)phenyl ((F)Mes) groups. Short B⋅⋅⋅F contacts, which lead to a pseudotrigonal bipyramidal geometry in the (F)Mes species, have been further studied by DFT and AIM analysis. In contrast to the Mes* groups, the highly electron-withdrawing (F) Mes groups do not diminish the Lewis acidity of boron toward F(-) anions. These compounds can be lithiated or iodinated under electrophilic conditions without decomposition, thus offering a promising route to larger conjugated structures with electron-acceptor character.