Polymorphic Equilibrium Responsive Thermal and Mechanical Stimuli in Light-emitting Crystals of <i>N</i>‑Methylaminonaphthyridine

Crystal polymorphs of 1,8-naphthyridine derivative, being <i>anti</i> and <i>syn</i> conformers, show a reversible transformation from <i>anti</i> to <i>syn</i> by heating and from <i>syn</i> to <i>anti</i> by grinding with the alteration of emittance intensity, and notably, thermal transformation from <i>anti</i> to <i>syn</i> conformer took place in single-crystal-to-single-crystal (SC-to-SC) form, which was confirmed by a single crystal X-ray crystallography

Thermal Single Crystal to Single Crystal Transformation among Crystal Polymorphs in 2‑Dimethylamino-5,7-bis(trifluoromethyl)-1,8-naphthyridine and in a 1‑Quinoline Analogue

2-Dimethylamino-5,7-bis­(trifluoromethyl)-1,8-naphthyridine <b>1</b> was prepared as a new solid-state fluorophore. Recrystallization of <b>1</b> from CH₂Cl₂/<i>n</i>-hexane afforded three crystal polymorphs, <b>G</b>, <b>BM</b>, and <b>BO</b>, with the space group (crystal class) <i>C</i>2/<i>c</i> (monoclinic), <i>P</i>2₁/<i>c</i> (monoclinic), and <i>Pbca</i> (orthorhombic), respectively, at 23 °C. DSC curves for <b>G</b> showed one endothermic peak at 110 °C in the high temperature region and two pairs of endo- and exothermic peaks at ca. 18 and 7 °C in the low temperature region, which were assigned as crystal phase transitions. In the high temperature region, a reversible transformation from <b>G</b> to <b>B</b> (a mixture of <b>BM</b> and <b>BO</b>) by heating at 110 °C and from <b>B</b> to <b>G</b> by grinding was observed with alteration of the emitted color. In the low temperature region, X-ray crystallography suggested that <b>G</b> transformed to <b>G2</b> (10 °C) and <b>G4</b> (−50 °C) with a subtle alteration of molecular arrangements through thermal single crystal to single crystal interconversion. Eventually, <b>1</b> provided five crystal polymorphs, <b>G</b>, <b>G2</b>, <b>G4</b>, <b>BM</b>, and <b>BO</b>, containing eight crystallographically independent molecules. In contrast, the 1-quinoline analogue, <b>2</b>, provided two crystal polymorphs, <b>2α</b> (23 °C) and <b>2β</b> (−123 °C)

Thermal Single Crystal to Single Crystal Transformation among Crystal Polymorphs in 2‑Dimethylamino-5,7-bis(trifluoromethyl)-1,8-naphthyridine and in a 1‑Quinoline Analogue

2-Dimethylamino-5,7-bis­(trifluoromethyl)-1,8-naphthyridine <b>1</b> was prepared as a new solid-state fluorophore. Recrystallization of <b>1</b> from CH₂Cl₂/<i>n</i>-hexane afforded three crystal polymorphs, <b>G</b>, <b>BM</b>, and <b>BO</b>, with the space group (crystal class) <i>C</i>2/<i>c</i> (monoclinic), <i>P</i>2₁/<i>c</i> (monoclinic), and <i>Pbca</i> (orthorhombic), respectively, at 23 °C. DSC curves for <b>G</b> showed one endothermic peak at 110 °C in the high temperature region and two pairs of endo- and exothermic peaks at ca. 18 and 7 °C in the low temperature region, which were assigned as crystal phase transitions. In the high temperature region, a reversible transformation from <b>G</b> to <b>B</b> (a mixture of <b>BM</b> and <b>BO</b>) by heating at 110 °C and from <b>B</b> to <b>G</b> by grinding was observed with alteration of the emitted color. In the low temperature region, X-ray crystallography suggested that <b>G</b> transformed to <b>G2</b> (10 °C) and <b>G4</b> (−50 °C) with a subtle alteration of molecular arrangements through thermal single crystal to single crystal interconversion. Eventually, <b>1</b> provided five crystal polymorphs, <b>G</b>, <b>G2</b>, <b>G4</b>, <b>BM</b>, and <b>BO</b>, containing eight crystallographically independent molecules. In contrast, the 1-quinoline analogue, <b>2</b>, provided two crystal polymorphs, <b>2α</b> (23 °C) and <b>2β</b> (−123 °C)

Thermal Single Crystal to Single Crystal Transformation among Crystal Polymorphs in 2‑Dimethylamino-5,7-bis(trifluoromethyl)-1,8-naphthyridine and in a 1‑Quinoline Analogue

2-Dimethylamino-5,7-bis­(trifluoromethyl)-1,8-naphthyridine <b>1</b> was prepared as a new solid-state fluorophore. Recrystallization of <b>1</b> from CH₂Cl₂/<i>n</i>-hexane afforded three crystal polymorphs, <b>G</b>, <b>BM</b>, and <b>BO</b>, with the space group (crystal class) <i>C</i>2/<i>c</i> (monoclinic), <i>P</i>2₁/<i>c</i> (monoclinic), and <i>Pbca</i> (orthorhombic), respectively, at 23 °C. DSC curves for <b>G</b> showed one endothermic peak at 110 °C in the high temperature region and two pairs of endo- and exothermic peaks at ca. 18 and 7 °C in the low temperature region, which were assigned as crystal phase transitions. In the high temperature region, a reversible transformation from <b>G</b> to <b>B</b> (a mixture of <b>BM</b> and <b>BO</b>) by heating at 110 °C and from <b>B</b> to <b>G</b> by grinding was observed with alteration of the emitted color. In the low temperature region, X-ray crystallography suggested that <b>G</b> transformed to <b>G2</b> (10 °C) and <b>G4</b> (−50 °C) with a subtle alteration of molecular arrangements through thermal single crystal to single crystal interconversion. Eventually, <b>1</b> provided five crystal polymorphs, <b>G</b>, <b>G2</b>, <b>G4</b>, <b>BM</b>, and <b>BO</b>, containing eight crystallographically independent molecules. In contrast, the 1-quinoline analogue, <b>2</b>, provided two crystal polymorphs, <b>2α</b> (23 °C) and <b>2β</b> (−123 °C)

Thermal Single Crystal to Single Crystal Transformation among Crystal Polymorphs in 2‑Dimethylamino-5,7-bis(trifluoromethyl)-1,8-naphthyridine and in a 1‑Quinoline Analogue

2-Dimethylamino-5,7-bis­(trifluoromethyl)-1,8-naphthyridine <b>1</b> was prepared as a new solid-state fluorophore. Recrystallization of <b>1</b> from CH₂Cl₂/<i>n</i>-hexane afforded three crystal polymorphs, <b>G</b>, <b>BM</b>, and <b>BO</b>, with the space group (crystal class) <i>C</i>2/<i>c</i> (monoclinic), <i>P</i>2₁/<i>c</i> (monoclinic), and <i>Pbca</i> (orthorhombic), respectively, at 23 °C. DSC curves for <b>G</b> showed one endothermic peak at 110 °C in the high temperature region and two pairs of endo- and exothermic peaks at ca. 18 and 7 °C in the low temperature region, which were assigned as crystal phase transitions. In the high temperature region, a reversible transformation from <b>G</b> to <b>B</b> (a mixture of <b>BM</b> and <b>BO</b>) by heating at 110 °C and from <b>B</b> to <b>G</b> by grinding was observed with alteration of the emitted color. In the low temperature region, X-ray crystallography suggested that <b>G</b> transformed to <b>G2</b> (10 °C) and <b>G4</b> (−50 °C) with a subtle alteration of molecular arrangements through thermal single crystal to single crystal interconversion. Eventually, <b>1</b> provided five crystal polymorphs, <b>G</b>, <b>G2</b>, <b>G4</b>, <b>BM</b>, and <b>BO</b>, containing eight crystallographically independent molecules. In contrast, the 1-quinoline analogue, <b>2</b>, provided two crystal polymorphs, <b>2α</b> (23 °C) and <b>2β</b> (−123 °C)

Thermal Single Crystal to Single Crystal Transformation among Crystal Polymorphs in 2‑Dimethylamino-5,7-bis(trifluoromethyl)-1,8-naphthyridine and in a 1‑Quinoline Analogue

2-Dimethylamino-5,7-bis­(trifluoromethyl)-1,8-naphthyridine <b>1</b> was prepared as a new solid-state fluorophore. Recrystallization of <b>1</b> from CH₂Cl₂/<i>n</i>-hexane afforded three crystal polymorphs, <b>G</b>, <b>BM</b>, and <b>BO</b>, with the space group (crystal class) <i>C</i>2/<i>c</i> (monoclinic), <i>P</i>2₁/<i>c</i> (monoclinic), and <i>Pbca</i> (orthorhombic), respectively, at 23 °C. DSC curves for <b>G</b> showed one endothermic peak at 110 °C in the high temperature region and two pairs of endo- and exothermic peaks at ca. 18 and 7 °C in the low temperature region, which were assigned as crystal phase transitions. In the high temperature region, a reversible transformation from <b>G</b> to <b>B</b> (a mixture of <b>BM</b> and <b>BO</b>) by heating at 110 °C and from <b>B</b> to <b>G</b> by grinding was observed with alteration of the emitted color. In the low temperature region, X-ray crystallography suggested that <b>G</b> transformed to <b>G2</b> (10 °C) and <b>G4</b> (−50 °C) with a subtle alteration of molecular arrangements through thermal single crystal to single crystal interconversion. Eventually, <b>1</b> provided five crystal polymorphs, <b>G</b>, <b>G2</b>, <b>G4</b>, <b>BM</b>, and <b>BO</b>, containing eight crystallographically independent molecules. In contrast, the 1-quinoline analogue, <b>2</b>, provided two crystal polymorphs, <b>2α</b> (23 °C) and <b>2β</b> (−123 °C)

One‑, Two‑, and Three-Dimensional Heterospin Complexes Consisting of 4‑(<i>N</i>-<i>tert</i>-Butyloxylamino)pyridine (4NOpy), Dicyanamide Ion (DCA), and 3d Metal Ions: Crystal Structures and Magnetic Properties of [M^II(4NOpy)_<i>x</i>(DCA)_<i>y</i>(CH₃CN)_<i>z</i>]_<i>n</i> (M = Mn, Co, Ni, Cu, Zn)

Solutions of 3d metal ion salts, M­(NO₃)₂, 4-(<i>N</i>-<i>tert</i>-butyloxylamino)­pyridine (<b>4NOpy</b>), and dicyanamide (DCA) in CH₃CN were mixed to afford single crystals of the polymeric complexes [M^II(<b>4NOpy</b>)_<i>x</i>(DCA)_<i>y</i>(CH₃CN)_{<i><b>z</b></i>}]_<i>n</i> (M^II = Mn (<b>1</b>), Co (<b>2</b>), Ni (<b>3</b>), Cu (<b>4a</b> and <b>4b</b>), Zn (<b>5</b>)). X-ray crystallography revealed that the crystal structures are a three-dimensional (3-D) network for <b>1</b>, 2-D networks for <b>2</b>, <b>3</b>, <b>4a</b>, and <b>5</b>, and a 1-D chain for <b>4b</b>. Crystals of <b>2</b>, <b>3</b>, <b>4a</b>, and <b>5</b> contained CH₃CN molecules as crystal solvents, which were readily desorbed in the ambient atmosphere. After desorption of the CH₃CN molecules, the crystal structures of <b>2</b> and <b>3</b> were confirmed to be slightly shrunk without destruction of the crystal lattice. Crystals of <b>2</b>, <b>3</b>, <b>4a</b>, and <b>5</b> after desorption of crystal solvents were used for investigations of the magnetic properties. Complex <b>1</b> showed antiferromagnetic interactions to form a ferrimagnetic chain and exhibited the magnetic behavior of a 2-D (or 3-D) spin-canted antiferromagnet with <i>T</i>_N = 12 K. Complex <b>2</b> containing anisotropic Co^II ions also showed the behavior of a 1-D (or 2-D) spin-canted antiferromagnet with <i>T</i>_N = 6 K. In <b>3</b>, <b>4a</b>, and <b>4b</b>, the aminoxyl of <b>4NOpy</b> ferromagnetically interacted with the metal ion with coupling constants of <i>J</i>_M–NO/<i>k</i>_B = 45, 45, and 43 K, respectively. In <b>5</b>, the magnetic couplings between the aminoxyls in <b>4NOpy</b> through the diamagnetic Zn^II ion were weakly antiferromagntic (<i>J</i>_NO–NO = −1.2 K). DCA might be a weak antiferromagnetic connector for the metal chains

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