Sequential halochromic/mechanochromic luminescence of pyridyl-substituted solid-state emissive dyes: thermally controlled stepwise recovery of the original emission color

A stepwise temperature-controlled emission-color switch has been achieved in a system that combines halochromic and mechanochromic luminescence in series.


Single-crystal X-ray diffraction analyses
X-ray analysis of 1 A single crystal of 1 was obtained from vapor diffusion of hexane into a chloroform/DMF solution of 1 and was mounted on a glass fiber. All measurements were made on a Rigaku XtaLAB P200 diffractometer using multi-layer mirror monochromated Cu-Kα radiation (λ = 1.54184 Å). The data were collected at a temperature of -50 ± 1 °C to a maximum 2θ value of 150.5°. A total of 2786 oscillation images were collected. The crystal-to-detector distance was 40.00 mm. Readout was performed in the 0.172 mm pixel mode.
Of the 25682 reflections that were collected, 4448 were unique (R int = 0.0301); equivalent reflections were merged. Data were collected and processed using CrysAlisPro (Rigaku Oxford Diffraction). 1 The linear absorption coefficient, µ, for Cu-Kα radiation is 14.374 cm -1 . An empirical absorption correction was applied which resulted in transmission factors ranging from 0.654 to 0.826.
The data were corrected for Lorentz and polarization effects.
The structure was solved by direct methods (SIR2011) 2 and expanded using Fourier techniques.

X-ray analysis of 1•2a
A single crystal of 1•2a was obtained from vapor diffusion of hexane into a chloroform solution of a 1:1 molar mixture of 1 and 2a and was mounted on a glass fiber. All measurements were made on a Rigaku XtaLAB P200 diffractometer using graphite monochromated Cu-Kα radiation (λ = 1.54184 Å). The data were collected at a temperature of -50 ± 1 °C to a maximum 2θ value of 152.2°. A total of 3032 oscillation images were collected. The crystal-to-detector distance was 40.00 mm. Readout was performed in the 0.172 mm pixel mode.
Of the 33807 reflections that were collected, 5609 were unique (R int = 0.0471); equivalent reflections were merged. Data were collected and processed using CrysAlisPro (Rigaku Oxford Diffraction). 1 The linear absorption coefficient, µ, for Cu-Kα radiation is 12.956 cm -1 . An empirical absorption correction was applied which resulted in transmission factors ranging from 0.570 to 0.768.
The data were corrected for Lorentz and polarization effects.
The structure was solved by direct methods (SIR2011) 2 and expanded using Fourier techniques.
The non-hydrogen atoms were refined anisotropically. Hydrogen atoms were refined using the riding model. The positions of hydrogen atoms of carboxy groups were localized from the differential Fourier synthesis. All calculations were performed using the CrystalStructure 3 crystallographic software package except for refinement, which was performed using SHELXL Version 2014/7. 4 Crystal data for 1•2a (CCDC 1935320

X-ray analysis of 1•2b
A single crystal of 1•2b was obtained from vapor diffusion of hexane into a chloroform solution of a 1:1 molar mixture of 1 and 2b and was mounted on a glass fiber. All measurements were made on a Rigaku XtaLAB P200 diffractometer using graphite monochromated Cu-Kα radiation (λ = 1.54184 Å). The data were collected at a temperature of -50 ± 1 °C to a maximum 2θ value of 150.4°. A total of 4052 oscillation images were collected. The crystal-to-detector distance was 40.00 mm. Readout was performed in the 0.172 mm pixel mode.
Of the 47704 reflections that were collected, 5951 were unique (R int = 0.0425); equivalent reflections were merged. Data were collected and processed using CrysAlisPro (Rigaku Oxford Diffraction). 1 The linear absorption coefficient, µ, for Cu-Kα radiation is 14.217 cm -1 . An empirical absorption correction was applied which resulted in transmission factors ranging from 0.721 to 0.872.
The data were corrected for Lorentz and polarization effects.
The structure was solved by direct methods (SIR2011) 2 and expanded using Fourier techniques.
The non-hydrogen atoms were refined anisotropically. Hydrogen atoms were refined using the riding model. The positions of hydrogen atoms of carboxy groups were localized from the differential Fourier synthesis. All calculations were performed using the CrystalStructure 3 crystallographic software package except for refinement, which was performed using SHELXL Version 2014/7. 4 Crystal data for 1•2b (CCDC 1935321

X-ray analysis of 1•2c
A single crystal of 1•2c was obtained from vapor diffusion of hexane into a chloroform solution of a 1:1 molar mixture of 1 and 2c and was mounted on a glass fiber. All measurements were made on a Rigaku XtaLAB P200 diffractometer using graphite monochromated Cu-Kα radiation (λ = 1.54184 Å). The data were collected at a temperature of -50 ± 1 °C to a maximum 2θ value of 150.6°. A total of 2916 oscillation images were collected. The crystal-to-detector distance was 40.00 mm. Readout was performed in the 0.172 mm pixel mode.
Of the 34401 reflections that were collected, 5741 were unique (R int = 0.0333); equivalent reflections were merged. Data were collected and processed using CrysAlisPro (Rigaku Oxford Diffraction). 1 The linear absorption coefficient, µ, for Cu-Kα radiation is 13.041 cm -1 . An empirical absorption correction was applied which resulted in transmission factors ranging from 0.696 to 0.795.
The data were corrected for Lorentz and polarization effects.
The structure was solved by direct methods (SIR2011) 2 and expanded using Fourier techniques.
The non-hydrogen atoms were refined anisotropically. Hydrogen atoms were refined using the riding model. The positions of hydrogen atoms of carboxy groups were localized from the differential

X-ray analysis of 1•2d
A single crystal of 1•2d was obtained from vapor diffusion of hexane into a chloroform solution of a 1:1 molar mixture of 1 and 2d and was mounted on a glass fiber. All measurements were made on a Rigaku XtaLAB P200 diffractometer using graphite monochromated Cu-Kα radiation (λ = 1.54184 Å). The data were collected at a temperature of -50 ± 1 °C to a maximum 2θ value of 152.0°. A total of 3226 oscillation images were collected. The crystal-to-detector distance was 40.00 mm. Readout was performed in the 0.172 mm pixel mode.
Of the 36448 reflections that were collected, 5700 were unique (R int = 0.0452); equivalent reflections were merged. Data were collected and processed using CrysAlisPro (Rigaku Oxford Diffraction). 1 The linear absorption coefficient, µ, for Cu-Kα radiation is 13.822 cm -1 . An empirical absorption correction was applied which resulted in transmission factors ranging from 0.284 to 0.643.
The data were corrected for Lorentz and polarization effects.
The structure was solved by direct methods (SIR2011) 2 and expanded using Fourier techniques.
The non-hydrogen atoms were refined anisotropically. Hydrogen atoms were refined using the riding model. The positions of hydrogen atoms of carboxy groups were localized from the differential Fourier synthesis. All calculations were performed using the CrystalStructure 3 crystallographic software package except for refinement, which was performed using SHELXL Version 2014/7. 4 Crystal data for 1•2d (CCDC 1935323 1 and 1•2a-d.

Theoretical calculations
Based on the single-crystal X-ray diffraction structures, absorption wavelengths of 1 in 1•2a-d and discrete hydrogen-bond-forming complexes 1•2a-d were calculated by time-dependent density functional theory (TD-DFT) at the CAM-B3LYP/6-31G(d) level of theory (Table S1).

Differential scanning calorimetry (DSC) analyses
In the DSC thermograms of 1•2b-d, endothermic peaks that correspond to the vaporization of 2bd (T v ) and the melting points of 1 (T m ) were observed for crystalline samples, and cold crystallization transition peaks (T c ) followed by T v and T m were observed for ground samples (Fig. S17-S19).   S20). No diffraction peak attributed to 4 was observed by PXRD analyses of 4/2b-d, although trace diffraction peaks of crystalline 2b-d were detected probably due to the higher crystallinity of 2b-d than 2a (Fig. S21-S23).