cg5001842_si_005.cif (27.84 kB)
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 Mechanical Stimuli
dataset
posted on 2014-05-07, 00:00 authored by Satoru Karasawa, Ryusuke Hagihara, Yuichiro Abe, Naomi Harada, Jun-ichi Todo, Noboru KogaN,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 (1α, 1β, and 1γ) of 1 and two (2α and 2β) 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 30–58 nm compared with the emission in n-hexane, and their emission properties depended on the
molecular arrangements. The modes of molecular arrangements for 1α, 1β, and 1γ 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 2α and 2β were HT-γ-HB
and head-to-tail dimer (HT-dimer), and that for 3 was
head-to-tail columnar (HTC). 4173 and 490 were similar HT-γ-HB.
The crystal-to-crystal transformations from 1γ to 1β and from 2β to 2α 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, “writing” and “erasing” of
a letter with scratching and heating, respectively, were demonstrated.