Reversible mechanochromism in dipyridylamine-substituted unsymmetrical benzothiadiazoles

Abstract

We report the design and synthesis of push-pull benzothiadiazoles (BTDs) of type D 1 -p-A-p-D 2 and D 1 -p-A-D 2 . These BTDs show strong charge transfer interaction. BTD 3 shows reversible mechanochromism with color contrast between yellow (crystalline state) and orange (amorphous state). Photophysical and computational studies reveal that the planar orientation of the pyridyl and BTD unit in 2 results in no change in solid state emission whereas non-planar orientation of the dipyridylamine and BTD unit in 3 results in efficient mechanochromism.Scheme 1 Synthesis of BTDs 2 and 3. Reaction conditions: (i) PdCl 2 (PPh 3 ) 2 , CuI, THF-TEA (1 : 1), 60 C, 24 h; (ii) CuSO 4 , K 2 CO 3 , 1,2-dichlorobenzene, 180 C, 48 h.

Reversible fluorescence switching and topochemical conversion in an organic AEE material: polymorphism, defection and nanofabrication mediated fluorescence tuning

“…2c, S7). [38][39][40][41][42][43][44][45] PXRD studies also confirm the amorphous phase for grounded DPAMBM powder (Fig. 2d, S8).…”

“…In both crystals, the phenyl groups of triphenyl amine 80 adopted different orientation (Fig. [38][39][40][41][42] Interestingly, heating/solvent 40 exposure of strongly grounded DPAMBM-1 powder further blue shifted the fluorescence that matches with DPAMBM-2 (λ max = 545 nm, Fig. The acceptor malononitrile (A) and donor aminophenyl (D) adopted nearly a linear conformation (dihedral angle = 1.0°) and the other two phenyl groups are nearly eclipsed with each other in DPAMBM-2 (Fig.…”

“…[30][31][32][33] External stimuli such as heat, mechanical force and solvent exposure often changes the molecular conformation or phase of the materials (crystalline to amorphous) and switches the fluorescence. [38][39][40][41][42][43][44][45] For example, conformationally twisted cyanostilbene based AEE materials showed dramatic fluorescence switching with external force. [38][39][40][41][42][43][44][45] For example, conformationally twisted cyanostilbene based AEE materials showed dramatic fluorescence switching with external force.…”

Multi-functional bis(alkynyl)gold(iii) N⁁C complexes with distinct mechanochromic luminescence and electroluminescence properties

“… 17 This, together with the fact that 1–4 show no mechanochromic behavior, suggests that the bathochromic shift in both the absorption and emission spectra in the ground phase is probably due to the reduction of the interplanar angle between the donor and acceptor units, resulting in better π-conjugation and a more planarized conformation in these metastable amorphous states. 13f , 18 Differential scanning calorimetry (DSC) studies on 8 further reveal that the pristine samples display no peaks until the decomposition temperature has been reached (Fig. S6 † ), while an additional exothermic peak at ca.…”

Effect of the cyano group on solid state photophysical behavior of tetraphenylethene substituted benzothiadiazoles

“…11 Herein we have designed and synthesized TPE substituted unsymmetrical D-A benzothiadiazoles (BTDs) 3a, and 3b and studied their photophysical and mechanochromic properties. 11 Herein we have designed and synthesized TPE substituted unsymmetrical D-A benzothiadiazoles (BTDs) 3a, and 3b and studied their photophysical and mechanochromic properties.…”