Halogenated imidazo[1,5-a]pyridines: chemical structure and optical properties of a promising luminescent scaffold

Abstract A series of halogenated imidazo[1,5- a ]pyridines was prepared and their structural and optical properties investigated. The products were characterized by spectroscopic techniques and their optical properties discussed in relation to their chemical structure. We were able to triplicate the luminescence quantum yields (φ) in solution for three different imidazo[1,5- a ]pyridine derivatives, depending on the halogen nature of the substituent on the imidazo[1,5- a ]pyridine moiety. The effect of the halogen and of the geometrical and chemical characteristics of the molecular skeleton on the crystal packing was studied in the solid state by single crystal X-ray diffraction. At the same time, the possible presence of halogen bonds was evaluated through solid-state NMR analysis.