Crystal Structures, Thermal Properties, and Emission Behaviors of N,N-R-Phenyl-7-amino-2,4-trifluoromethylquinoline Derivatives: Supercooled Liquid-to-Crystal Transformation Induced by M

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• 作者：Satoru Karasawa ; Ryusuke Hagihara ; Yuichiro Abe ; Naomi Harada ; Jun-ichi Todo ; Noboru Koga
• 刊名：Crystal Growth & Design
• 出版年：2014
• 出版时间：May 7, 2014
• 年：2014
• 卷：14
• 期：5
• 页码：2468-2478
• 全文大小：494K
• 年卷期：v.14,no.5(May 7, 2014)
• ISSN：1528-7505

文摘

N,N-R-Phenyl-7-amino-2,4-trifluoromethylquinoline derivatives (R = Me (1), Et (2), isopropyl (3), and Ph (4)) were prepared as a new type of fluorophore responsive to external stimuli. 1, 2, 3, and 4 were obtained as single crystals including three crystal polymorphs (1伪, 1尾, and 1纬) of 1 and two (2伪 and 2尾) of 2. In 4, a phase transition from 4₁₇₃ and 4₉₀ between 173 and 90 K was observed. The solid-state emission showed a red shift by 30鈥?8 nm compared with the emission in n-hexane, and their emission properties depended on the molecular arrangements. The modes of molecular arrangements for 1伪, 1尾, and 1纬 were a slipped parallel (SP), head-to-tail 纬-type herringbone (HT-纬-HB), and head-to-head 纬-type herringbone (HH-纬-HB); those for 2伪 and 2尾 were HT-纬-HB and head-to-tail dimer (HT-dimer), and that for 3 was head-to-tail columnar (HTC). 4₁₇₃ and 4₉₀ were similar HT-纬-HB. The crystal-to-crystal transformations from 1纬 to 1尾 and from 2尾 to 2伪 were observed by heating and grinding the crystal, respectively, with emittance changes. After melting, on cooling, all crystals formed supercooled liquid (SCL) and then glass states. In the SCL state, molecules were amorphous and were quickly crystallized by a mechanical stimulus such as scratching. By taking advantage of the difference of emitting intensity between the SCL and the crystal states for 1, 鈥渨riting鈥?and 鈥渆rasing鈥?of a letter with scratching and heating, respectively, were demonstrated.