Luminescence properties of carborane-containing distyrylaromatic systems

A set of distyrylbenzene, distyrylbiphenyl and distyrylanthracene end-substituted with carborane clusters is introduced herein. All these compounds have been prepared from the corresponding styrene-containing carborane derivatives via Heck coupling reaction. High regioselectivity has been achieved yielding exclusively E isomers. All compounds have been fully characterized and the crystal structure of the distyrylbiphenyl end-substituted with Methyl-o-carborane was analyzed by X-ray diffraction. The absorption properties of compounds were elucidated by TD-DFT calculations, highlighting the importance of the aromatic core and π-conjugation. It is worth noting that the luminescence properties of these systems depend on the aromatic core; in solution, benzene and biphenyl derivatives showed higher fluorescence emission than the anthracene ones and the presence of the carborane clusters does not induce any major change in fluorescence as compared to the pristine non-carborane containing partners. Nevertheless, all compounds exhibited low fluorescence quantum yields in aggregation state, which gives clear evidence of considerable intermolecular interactions between aggregates that could be the reason of the fluorescence quenching.