Anthracene-Arrangement-Dependent Emissions of Crystals of 9-Anthrylpyrazole Derivatives

We have designed and synthesized a series of 9-anthrylpyrazole derivatives 1,4-bis(3-(9-anthryl)-1-pyrazolylmethyl)benzene (1), 1-(3-(9-anthryl)-1-pyrazolylmethyl)-4-(5-(9-anthryl)-1-pyrazolylmethyl)benzene (2), 1,4-bis(3-(9-anthryl)-1-pyrazolyl)benzene (3), and 1-(3-(9-anthryl)-1-pyrazolyl)-4-(5-(9-anthryl)-1-pyrazolyl)benzene (4). All compounds formed two types of crystals that exhibited anthracene-arrangement-dependent emission colors. For instance, crystal 1a with strong π-overlap between anthracene moieties exhibited an emission maximum at 515 nm, while 1b with no such interchromophore interactions displayed an emission band at 424 nm. The fluorescence quantum yield (Φ_F) measurements showed that the blue-emitting crystals have high quantum yields (Φ_F = 0.46 for 1b, 0.90 for 2a, 0.91 for 2b, 0.77 for 3b, and 0.51 for 4a), suggesting their potential as blue emitters in optoelectronics.