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

<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>_<b>173</b> and <b>4</b>_<b>90</b> 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>_<b>173</b> and <b>4</b>_<b>90</b> 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

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

<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>_<b>173</b> and <b>4</b>_<b>90</b> 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>_<b>173</b> and <b>4</b>_<b>90</b> 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

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

<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>_<b>173</b> and <b>4</b>_<b>90</b> 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>_<b>173</b> and <b>4</b>_<b>90</b> 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

Magnetic Properties of 1:2 Mixed Cobalt(II) Salicylaldehyde Schiff-Base Complexes with Pyridine Ligands Carrying High-Spin Carbenes (<i>S</i>_car = 2/2, 4/2, 6/2, and 8/2) in Dilute Frozen Solutions: Role of Organic Spin in Heterospin Single-Molecule Magnets

The 1:2 mixtures of Co­(<i>p</i>-tolsal)₂, <i>p</i>-tolsal = <i>N</i>-<i>p</i>-tolylsalicylideniminato, and diazo-pyridine ligands, <b>DXpy</b>; <b>X</b> = <b>1</b>,<b> 2</b>,<b> 3l</b>,<b> 3b</b>, and <b>4</b>, in MTHF solutions were irradiated at cryogenic temperature to form the corresponding 1:2 cobalt–carbene complexes Co­(<i>p</i>-tolsal)₂(<b>CXpy</b>)₂, with <i>S</i>_total = 5/2, 9/2, 13/2, 13/2, and 17/2, respectively. The resulting Co­(<i>p</i>-tolsal)₂(<b>CXpy</b>)₂, <b>X</b> = <b>1</b>,<b> 2</b>,<b> 3l</b>,<b> 3b</b>, and <b>4</b>, showed magnetic behaviors characteristic of heterospin single-molecule magnets with effective activation barriers, <i>U</i>_eff/<i>k</i>_B, of 40, 65, 73, 72, and 74 K, for reorientation of the magnetic moment and temperature-dependent hysteresis loops with a coercive force, <i>H</i>_c, of ∼0, 6.2, 10, 6.5, and 9.0 kOe at 1.9 K, respectively. The relaxation times, τ_Q, due to a quantum tunneling of magnetization (QTM) were estimated to be 1.6 s for Co­(<i>p</i>-tolsal)₂(<b>C1py</b>)₂, ∼2.0 × 10³ s for Co­(<i>p</i>-tolsal)₂(<b>C2py</b>)₂, and >10⁵ s for Co­(<i>p</i>-tolsal)₂(<b>CXpy</b>)₂; <b>X</b> = <b>3b</b>,<b> 3l</b>, and <b>4</b>. In heterospin complexes, organic spins, carbenes interacted with the cobalt ion to suppress the QTM pathway, and the τ_Q value increased with increasing the <i>S</i>_total values