Syntheses and structures of new luminescent B(III) complexes: BPh2(2-(2-pyridyl)naphtho[b]imidazole) and BF2(2-(2-pyridyl)naphtho[b]imidazole)

A novel chelating ligand, 2-(2-pyridyl)naphtho[b]imidazole (PNI) has been synthesized and structurally characterized. The PNI molecule reacts readily with BPh3 and BF3 to form BPh2(2-(2-pyridyl)naphtho[b]imidazole) (1) and BF2(2-(2-pyridyl)naphtho[b]imidazole) (2), respectively. The structures of PNI and 1 were determined by single crystal X-ray diffraction, while that 2 by spectroscopic methods. The structure of 1 reveals that the boron center is four-coordinated. The electroluminescent device using 1 as the emitting layer shows bright yellow luminescence with a maximum emission peak at 540 nm. Complexes 1 and 2 form a new family of organometallic emitting materials which could be of interest for practical applications.