Modulating Photo‐ and Electroluminescence in a Stimuli‐Responsive π‐Conjugated Donor–Acceptor Molecular System

• Published in: Angewandte Chemie International Edition Vol. 57; no. 37; pp. 11982 - 11986
• Main Authors: Isayama, Kohei, Aizawa, Naoya, Kim, Jun Yun, Yasuda, Takuma
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 10.09.2018; Wiley Subscription Services, Inc
• Edition: International ed. in English
• Subjects: Chemistry; Chemistry, Multidisciplinary; Color; Diodes; donor–acceptor systems; Electroluminescence; Emissions; Emitters; External stimuli; Fluorescence; Organic chemistry; Organic light emitting diodes; Organic materials; phase transitions; Photoluminescence; Photons; Physical Sciences; Quantum chemistry; Science & Technology; Security; Solid phases; Stimuli; stimuli-responsive fluorescence; X-ray diffraction; SOLID-STATE LUMINESCENCE; phase transitions; organic light-emitting diodes; HIGHLY EFFICIENT; stimuli-responsive fluorescence; TETRAPHENYLETHENE; donor-acceptor systems; FLUORESCENCE; MECHANOCHROMIC LUMINESCENCE; COLOR CHANGES; PHOTOLUMINESCENT; EMISSION; DERIVATIVES; MECHANOFLUOROCHROMIC MATERIALS
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201806863

Functional organic materials that display reversible changes in fluorescence in response to external stimuli are of immense interest owing to their potential applications in sensors, probes, and security links. While earlier studies mainly focused on changes in photoluminescence (PL) color in response to external stimuli, stimuli‐responsive electroluminescence (EL) has not yet been explored for color‐tunable emitters in organic light‐emitting diodes (OLEDs). Here a stimuli‐responsive fluorophoric molecular system is reported that is capable of switching its emission color between green and orange in the solid state upon grinding, heating, and exposure to chemical vapor. A mechanistic study combining X‐ray diffraction analysis and quantum chemical calculations reveals that the tunable green/orange emissions originate from the fluorophore's alternating excited‐state conformers formed in the crystalline and amorphous phases. By taking advantage of this stimuli‐responsive fluorescence behavior, two‐color emissive OLEDs were produced using the same fluorophore in different solid phases. “ON” in two colors: A newly developed π‐conjugated donor–acceptor fluorophore can switch the color of its solid‐state emission between green and orange in response to external stimuli such as mechanical force, heat, and solvent fuming. Two‐color emissive organic light‐emitting diodes were produced based on this stimuli‐responsive single fluorophore.