Design of High-Contrast Mechanochromic Materials Based on Aggregation-Induced Emissive Pyran Derivatives Guided by Polymorph Predictions

Abstract

High contrast mechanochromic materials are prominent candidates for sensor, security and memory applications; however, the development of materials with a large luminescence change (Δλ em >100 nm) under external stimuli is challenging. Considering that polymorphic molecules usually exhibit reversible mechanochromism, polymorph prediction is adopted for the first time to guide the design of high-contrast mechanochromic materials in this study. We designed and synthesized a series of donor-π-acceptor pyran derivatives bearing different electron donors and acceptors as model systems. The polymorph prediction indicated that 4-dicyanomethylene-2,6-distyryl-4H-pyran and 4H-pyran-4-one derivatives had the potential to crystallize in both monomer and π-dimer aggregates, while barbituric acid-based compound tended to pack tightly in all aggregated states. The experimental results agreed well with the prediction that the derivatives potentially possessing both monomer and π-dimer aggregate structures exhibit excellent mechanochromic behavior, whereas the fluorescence difference for the barbituric acid-based compounds is minimal. Moreover, a compound with an excellent fluorescence difference of three colors during reversible mechanochromism was chosen as the candidate for an optical recording material and security ink. This work proposes an effective

A temperature-dependent tricoloured mechanochromic fluorescence material with polymorphic structures

“…As for the fluorescence bands at 527 and 600 nm, they were ascribed to the monomer and p cluster emissions of nano-particles, which would emit red-shifted fluorescence compared to the monomers in dilute solutions. 41,57,58 The fluorescence properties of its single crystals also match this hypothesis. Similar AIE behaviour was found for MBAV-I (Fig.…”

“…Recently, we successfully screened out a series of highcontrast mechanochromic molecules by predicting potential polymorphs. 40,41 Due to the fact that sufficient crystal structures have not been obtained to match the predicted ones, the reliability of this strategy needs to be proved. Our previous studies demonstrated that a D-p-A molecule has a higher potential to emit polymorphism-dependent fluorescence.…”

Structure–activity strategies for mechanically responsive fluorescent materials: a molecular perspective

“…Therefore, current focus is limited to local modification of existing organic fluorophores. 10 The strategy commonly employed for this involves the introduction of long alkyl chains, 11 or different substituents to fluorophores, as well as altering donor-receptor interactions [12][13][14] or substituent positions. Substituents can adapt the response of solid fluorescent molecules to stimuli and influence the fluorescence quantum yield, [15][16][17] whereas introducing long alkyl chains can play an important role in regulating the photoelectric properties of fluorescent molecules.…”

Polymorphous meso-Dicyanovinyl-Substituted Tetraphenylethylene Derivative Showing Distinguishing Two-Color Emission and Ultrahigh-Contrast Mechano-Responsive Luminescence Behavior

“…A TPE-dioxaborine fluorophore reported by Yang et al with four polymorphs and one amorphous solid state exhibited four emission colors ranging from green to red . Xiao and Yi et al also designed high-contrast MRL materials by polymorph prediction. , …”

“…23 Xiao and Yi et al also designed high-contrast MRL materials by polymorph prediction. 24,25 As the most concerned aggregation-induced emission (AIE) group, TPE has always been favored by researchers because of its unique advantages, and many TPE derivatives were found to be polymorphous. The blue fluorescence of TPE could be easily regulated by introducing strong electron-donating and electronaccepting groups.…”