Strikingly different luminescent properties arising from single crystals grown from solution or from the vapor phase in a diketopyrrolopyrrole analogue

摘要

The title compound (DCPP) is an analogue of diketopyrrolopyrrole known as a red pigment on the market. Brilliant orange photoluminescence has been observed in crystals of DCPP grown from solution (crystal I), although no luminescence was recognized in solution. Furthermore, the luminescence is found to be completely quenched above 300℃ ("thermal quenching"). On the other hand, the crystals grown from the vapor phase (crystal II) shows quite weak luminescence. To elucidate the difference in luminescent properties, a series of structure analysis have been carried out on crystals I and II at -180, RT, 150, and 200℃. However, no crystallographic difference is recognized between crystals I and II. Nevertheless, a slight difference is observed in sublimation temperature (crystal I: 306.2℃; crystal II: 309.9℃). The present difference in cohesion is closely correlated to the lattice vibration and determines the "radiativeon-radiateive" fraction of the excited energy between crystals I and II.