10.1021/cg5001842.s005 Satoru Karasawa Satoru Karasawa Ryusuke Hagihara Ryusuke Hagihara Yuichiro Abe Yuichiro Abe Naomi Harada Naomi Harada Jun-ichi Todo Jun-ichi Todo Noboru Koga Noboru Koga Crystal Structures, Thermal Properties, and Emission Behaviors of <i>N</i>,<i>N</i>‑R-Phenyl-7-amino-2,4-trifluoromethylquinoline Derivatives: Supercooled Liquid-to-Crystal Transformation Induced by Mechanical Stimuli American Chemical Society 2014 HT HH glass states HTC phase transition Thermal Properties SCL state crystal states type emittance changes 90 K SP emission properties Emission Behaviors crystal Structures 2014-05-07 00:00:00 Dataset https://acs.figshare.com/articles/dataset/Crystal_Structures_Thermal_Properties_and_Emission_Behaviors_of_i_N_i_i_N_i_R_Phenyl_7_amino_2_4_trifluoromethylquinoline_Derivatives_Supercooled_Liquid_to_Crystal_Transformation_Induced_by_Mechanical_Stimuli/2299234 <i>N</i>,<i>N</i>-R-Phenyl-7-amino-2,4-trifluoromethylquinoline derivatives (R = Me (<b>1</b>), Et (<b>2</b>), isopropyl (<b>3</b>), and Ph (<b>4</b>)) were prepared as a new type of fluorophore responsive to external stimuli. <b>1</b>, <b>2</b>, <b>3</b>, and <b>4</b> were obtained as single crystals including three crystal polymorphs (<b>1α</b>, <b>1β</b>, and <b>1γ</b>) of <b>1</b> and two (<b>2α</b> and <b>2β</b>) of <b>2</b>. In <b>4</b>, a phase transition from <b>4</b><sub><b>173</b></sub> and <b>4</b><sub><b>90</b></sub> between 173 and 90 K was observed. The solid-state emission showed a red shift by 30–58 nm compared with the emission in <i>n</i>-hexane, and their emission properties depended on the molecular arrangements. The modes of molecular arrangements for <b>1α</b>, <b>1β</b>, and <b>1γ</b> were a slipped parallel (SP), head-to-tail γ-type herringbone (HT-γ-HB), and head-to-head γ-type herringbone (HH-γ-HB); those for <b>2α</b> and <b>2β</b> were HT-γ-HB and head-to-tail dimer (HT-dimer), and that for <b>3</b> was head-to-tail columnar (HTC). <b>4</b><sub><b>173</b></sub> and <b>4</b><sub><b>90</b></sub> were similar HT-γ-HB. The crystal-to-crystal transformations from <b>1γ</b> to <b>1β</b> and from <b>2β</b> to <b>2α</b> 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 <b>1</b>, “writing” and “erasing” of a letter with scratching and heating, respectively, were demonstrated.