Reversible mechanofluorochromism of aniline-terminated phenylene ethynylenes

Sharber, Seth A.; Shih, Kuo‐Chih; Mann, Arielle; Frausto, Fanny; Haas, T. E.; Nieh, Mu‐Ping; Thomas, Samuel W.

doi:10.1039/c8sc00980e

Cited by 39 publications

(37 citation statements)

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“…Moreover, emission spectra of these regioisomers shift in opposite directions upon application of force . Similar to other twisted PEs we reported, fluorescence of 2 , 4 , 6‐OMe thin films (Figure ) shifts bathochromically from 454 to 486 nm upon applying shear force manually with a spatula. This shift reverses with thermal annealing, and is consistent over multiple cycles (Figures S4–S6, Supporting Information).…”

Section: Figuresupporting

confidence: 83%

“…Moreover,emission spectra of these regioisomers shift in opposite directions upon application of force. [27] Similar to other twisted PEs we reported, [18,20] evolveso ver time at room temperature:i nitial grinding of a film of 2,4,6-OMe yields brightg reen fluorescence with a % 1.7 increasei nt otal emission intensity and 36 nm shift, which we attribute to shear-induced planarizationa nd/or aggregation of these twisted molecules. [28] Over the course of minutes, this emission dimsa nd shifts to 467 nm, after which point additional heatingb elow the meltingp oint fully restores the original emission.…”

mentioning

confidence: 96%

“…Consistent with our previous work on anilines ubstituted PEs, [20] 2,4,6-NMe2 shifts from green (Em. l max = 565 nm) to orange emission (Em.…”

mentioning

confidence: 99%

“…[16,17] Our previous work has shown that cofacialfluoroarene-arene (ArF-ArH) interactions of perfluorinated side chains can dictate the conformations and assemblies of phenylene-ethynylenes( PEs), and therefore determine their solid-state opticalp roperties. [18][19][20] Although examples exist for which regiochemistry of arene fluorination alters crystalp acking with modest effects on material properties, [21][22][23][24] slightd ifferences in fluorine regiochemistry of non-conjugated side chains would not generally be expected to impact the opticalp roperties of conjugated materials. Here, we describe surprisingly different opticala nd mechanofluorochromic (MFC) properties of solid PEs that depend on slight positional differences of Ha nd Fa toms (2,4,6v s. 2,3,6-trifluoro) on pendant arenes not conjugated to the PE moiety.…”

mentioning

confidence: 99%

“…The molecules described here are variations on our previous work regarding non-covalentc ontrolo fo ptical properties of solid PEs:e lectron-poort rifluorobenzyl ester side chains can participate in cofacial ArF-ArH interactions with terminal areneso ft he PE. [18][19][20] These interactions cause the terminal PE arenest ot wist relative to the centralt erephthalate, preventing the typicallyo bservedb athochromic shifts of PEs when comparings olid to solution [25] by inhibiting both intramolecular and intermolecular electronic coupling. The favorability of the ArF-ArH interaction, and whether it is observed, depends on Hammett-types ubstituent effects in the terminal arenes.…”

mentioning

confidence: 99%

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Small Changes With Big Consequences: Swapping Two Atoms In Side Chains Changes Phenylene‐Ethynylene Packing And Fluorescence

Sharber

Thomas

2018

Chemistry A European J

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Engineering the properties of conjugated materials in the solid state is an unsolved, ongoing challenge important to fundamental understanding of how non‐covalent interactions dictate packing and key properties, as well as the development of technologies based in organic optoelectronics. The most common design paradigm of such materials divide them into a “main chain” with extended conjugation, the chemical structure of which determines optoelectronic properties, and “side chains” not conjugated to the backbone, which provide solubility when they are long alkyl chains. This paper describes comparisons between phenylene‐ethynylene molecules in which slight changes to the structure of “side chains”—swapping hydrogen and fluorine atomic position on an aromatic ring—results in unexpectedly large changes in the solid‐state optical properties. In a pair of anisyl‐terminated three‐ring phenylene‐ethynylenes, switching the side chain arenes of benzyl esters from 2,4,6‐trifluoro to 2,3,6‐trifluoro results in a shift in fluorescence emission spectra of over 100 nm, as well as the opposite direction of force‐induced shifting of emission. Through a combination X‐ray crystal structures, electronic structure calculations, and comparisons with other derivatives, we describe how the 2,4,6‐trifluorinated side chains yield cofacial fluoroarene‐arene stacking interactions that twist the PE backbone out of conjugation, while the 2,3,6‐trifluoro side chains do not stack, instead yielding more coplanar PE backbones that form intermolecular aggregates. Overall, this work demonstrates how slight modifications to parts of conjugated materials normally considered ancillary to optoelectronic properties can determine their solid‐state properties, epitomizing the challenge of rational design but at the same time offering opportunities for materials discovery and improved understanding of non‐covalent interactions.

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Section: Figuresupporting

confidence: 83%

mentioning

confidence: 96%

“…Consistent with our previous work on anilines ubstituted PEs, [20] 2,4,6-NMe2 shifts from green (Em. l max = 565 nm) to orange emission (Em.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Small Changes With Big Consequences: Swapping Two Atoms In Side Chains Changes Phenylene‐Ethynylene Packing And Fluorescence

Sharber

Thomas

2018

Chemistry A European J

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Luminogens Based on Cyano‐Substituted Anthracene Isomers: Different Molecular Packing and Distinct Piezochromic Properties

Gao

et al. 2021

Advanced Optical Materials

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Pure organic materials with piezochromic property have been intensively studied in recent years. Many examples describe response to both mechanical grinding and hydrostatic pressure, but the examples in realizing high color contrast as well as high sensitivity, especially under high external pressure, are very rare which hampers their practical applications as pressure sensors. Herein, two anthracene‐based structural isomers, NDHA‐p and NDHA‐m, are developed applying 9,10‐bis(diphenylmethylene)‐9,10‐dihydroanthracene (DHA) as the basic skeleton and substituted by four cyano groups on para‐ or meta‐positions of the periphery benzene rings, respectively. In high‐pressure experiment, as compared to the NDHA‐m which shows a color contrast of 60 nm and a sensitivity of 7.87 nm·GPa‐1, NDHA‐p exhibits a dramatically larger color contrast of 138 nm and higher sensitivity of 13.20 nm·GPa‐1, whose performance is among the best pure organic piezochromic materials so far. The systematical experimental and theoretical analyses indicate that NDHA‐p possesses a lower crystal density, relatively looser molecular packing mode, and higher degree of electronic communications than NDHA‐m, which are responsible for the excellent piezochromic performance. This design method will open a new avenue for controlling the molecular packing configuration of luminescent materials via structural isomerization, and further extending their applications.

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High‐Efficiency Wideband Excitable Mechanoluminescence from a Yellow MOF Phosphor as White LED and Multicolor Thin Films

Duan

et al. 2021

Advanced Optical Materials

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to achieve the enhanced luminescence efficiency. [2b,c,3] Nowadays, many intelligent synthetic strategies, such as assembling chromophoric ligands into metal-organic frameworks (MOFs), [4] encapsulating emissive guest molecules/ions into porous MOFs, [5] and incorporating emissive metal clusters into MOFs, [6] and so on, have been developed to construct highly luminescent MOFs. [1a-e,7] One of the most potential strategies in this area is mechanically induced luminescence, namely, mechanoluminescence. Mechanically induced luminescent materials can show luminescence enhancement or color change when subject to mechanical stimuli, including compressing, grinding, rubbing and etc. [8] As mechanical energy is ubiquitously available in nature, mechanoluminescence offers potential solutions to challenging problems in fields of optoelectronics, energy and environmental sciences. By virtue of the well-recognized advantages, the mechanoluminescence has been involved in a highly interdisciplinary field. The development of novel mechanoluminescent materials and devices has aroused considerable interest for improving the luminescence performances related to color, brightness, and spectral tunability. Recently, Su and coworkers have reported an intriguing piezochromic LMOF, in which the pressing could significantly increase the luminescence PLQY from 21.7% to 67.7%. [8b] Tan et al. have prepared a novel guest@MOF system (Perylene@ ZIF-8) via employing an optically inactive MOF host (sodalite cage of ZIF-8) to spatially confine a bulky polycyclic fluorophore guest (Perylene). [9] The guest@MOF materials exhibit an interesting switchable emission color change when subject to a reversible mechanical stress or hydrostatic pressure.In the field of lighting technology, a common convenient method for manufacturing white light-emitting diode (WLED) is that the blue-emitting LED chip is used to excite the yellow phosphors. [10] Currently, the yellow phosphors applied in the commercial WLED devices mainly rely on the rare-earthcontaining luminescent materials, such as the cerium-doped yttrium aluminum garnet (YAG:Ce 3+ ). In consideration of sustainable development and environmentally friendly LED technologies, the development of MOF-based yellow phosphors for substituting rare-earth-based WLED is highly demanding. However, the direct synthesis of highly luminescent MOF High-efficiency multifunctional metal-organic framework (MOF) phosphor is highly desired for various practical applications, such as in lighting, anticounterfeiting, sensing, and so on. Herein, a highly yellow-emitting MOF (Zn-TPPA) phosphor is prepared via mechanical grinding for application as white light-emitting diode (LED) and composite films. Under UV or visiblelight excitation, Zn-TPPA exhibits the intense cyan emission (λ em = 497 nm) with a high photoluminescence quantum yield (PLQY). Zn-TPPA undergoes an intriguing reversible mechanochromic luminescence through mechanical stimuli (grinding). Notably, the grinding not only induces emissive color changes...

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Reversible mechanofluorochromism of aniline-terminated phenylene ethynylenes

Abstract: Alkyl chain length tunes the reversion temperature of mechanofluorochromic phenylene-ethynylenes that show reversible force-induced change of fluorescence from green to orange.

Cited by 39 publications

References 104 publications

Small Changes With Big Consequences: Swapping Two Atoms In Side Chains Changes Phenylene‐Ethynylene Packing And Fluorescence

Small Changes With Big Consequences: Swapping Two Atoms In Side Chains Changes Phenylene‐Ethynylene Packing And Fluorescence

Luminogens Based on Cyano‐Substituted Anthracene Isomers: Different Molecular Packing and Distinct Piezochromic Properties

High‐Efficiency Wideband Excitable Mechanoluminescence from a Yellow MOF Phosphor as White LED and Multicolor Thin Films

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