Dynamic Polymorph Formation during Evaporative Crystallization from Solution: The Key Role of Liquid-Like Clusters as "Crucible" at Ambient Temperature

作者：Oka Narumi; Ito Fuyuki^*; Haketa Yohei; Maeda Hiromitsu; Miyano Tetsuya; Tohnai Norimitsu; Ito Syoji; Miyasaka Hiroshi; Ozeki Sumio

来源：Chemistry - A European Journal, 2018, 24(17): 4343-4349.

DOI：10.1002/chem.201705356

• evaporative crystallization
• fluorescence changes
• liquid-like cluster
• polymorphs
• two-step nucleation model

Understanding the polymorph phenomenon for organic crystals is essential for the development of organic solid materials. Here, the fluorescence study of the evaporative crystallization of 1,3-dipyrrol-2-yl-1,3-propanedione boron difluoride complex (1), which has three polymorphs showing different emission profiles, is reported. The droplet of 1 in 1,2-dichloroethane showed blue emission just after dropping. Solids with bluish-green emission were observed. As time elapsed, a solid with red or orange emission was observed around the droplet. Time evolution of the fluorescence spectra, observed for the first time, implied that the molten state of 1 was observed by emission of an intermediate, even at ambient temperature. These findings suggested that the liquid-like cluster incidentally forms an ordered array as the crystallites nucleate. The liquid-like cluster can be considered as the crucible in the nucleation of polymorphs.

• 出版日期2018-3-20