Photochromism is a term that describes the photoreversible isomerization between two different states or isomers with distinct performances. Among all the photochromic molecule family, diarylethene ...is considered one of the most popular star molecules on account of its fast photoresponsibility, excellent thermal stability, fatigue resistance, high photoreaction quantum yield, and conversion ratio as well as good performances in both solution and solid phases. In the past decades, the development of diarylethene is witnessed in molecule design, solution applications, surface/interface assembly, bulky crystals and polymers, optic‐electronic devices fabrication, and biotechnology. This review mainly focuses on the latest development of diarylethenes in recent five years and commences with the newly designed molecular structures with functional ethene bridges and aryl moieties. The application of diarylethenes in materials science, soft materials, molecular data processing, and biomaterials, is further discussed in prospect. A brief summary is given in the end of the review together with some perspectives.
The development of photochromic diarylethene materials in the past five years is reviewed in this article. This review first focuses on the newly designed diarylethene structures with functional ethene bridges, aryl groups, and visible light photochromism. Then, applications of diarylethene derivatives in broad research areas of materials science are introduced, including soft materials, data processing systems, as well as biomaterials.
Pure organic, heavy‐atom‐free room‐temperature phosphorescence (RTP) materials have attracted much attention and have potential applications in photoelectric and biochemical material fields owing to ...their rich excited state properties. They offer long luminescent lifetime, diversified design, and facile preparation. However, recent achievements of efficient phosphorescence under ambient conditions mainly focus on ordered crystal lattices or embedding into rigid matrices, which require strict growth conditions and have poor reproducibility. Herein, we developed a concise approach to give RTP with a decent quantum yield and ultralong phosphorescence lifetime in the amorphous state by radical binary copolymerization of acrylamide and different phosphors with oxygen‐containing functional groups. The cross‐linked hydrogen‐bonding networks between the polymeric chains immobilize phosphors to suppress non‐radiative transitions and provide a microenvironment to shield quenchers.
He ain't heavy: The radical binary copolymerization of acrylamide and different phosphors with oxygen‐containing functional groups allows efficient room‐temperature phosphorescence with ultralong lifetime in an amorphous polymer. The cross‐linked hydrogen‐bonding networks between the polymeric chains immobilize phosphors and suppress non‐radiative transitions.
Research on pure organic room-temperature phosphorescent (RTP) materials has made great advances but near-infrared (NIR) RTP emitting materials are still rare. Novel amorphous acrylamide copolymers ...containing iodine substituted borondipyrromethene (Bodipy) were prepared to obtain strong absorption in the visible region and moderate RTP in the NIR region with much larger Stokes shift than the fluorescence emission of traditional Bodipy dyes. Expensive metals and crystallization were left out to avoid biotoxicity and strict preparation conditions. Monoiodo and diiodo-Bodipy derivatives were both designed to study the substitution effect of iodine atoms. Photophysical properties, phosphorescence quantum yield and lifetime were characterized. Gels with NIR RTP emission were facilely prepared with the incorporation of ureidopyrimidone (UPy) and
N
,
N
′-methylenebisacrylamide (MBAA). The mechanical properties of the gels were measured using a rheometer and the results showed that the gels displayed fast self-healing ability due to the strong quadruple hydrogen bonding between UPy moieties.
Near-infrared room-temperature phosphorescence was achieved by employing iodine substituted Bodipy into amorphous polymers. The self-healable gels were also obtained with the incorporation of a crosslinker and quadruple hydrogen bond based moieties.
Materials displaying room‐temperature phosphorescence (RTP) have been attracting wide attention in recent years due to their distinctive characteristics including long emissive lifetime and large ...Stokes shift, and their various applications. Most synthesized RTP materials are metal complexes that display enhanced intersystem crossing and crystallization is a common way to restrict nonradiative transition. Amorphous metal‐free RTP materials, which do not rely on expensive and toxic metals and can be prepared in a straightforward fashion, have become an important branch of the field. This Minireview summarizes recent progress in amorphous RTP materials according to the approaches used to immobilize phosphors: host–guest interactions, molecule doping, copolymers, and small‐molecule self‐assembly. Some existing challenges and insightful perspectives are given at the end of the Minireview, which should benefit the future design and development of amorphous metal‐free RTP materials.
All aglow: Amorphous metal‐free materials with room‐temperature phosphorescence display unique photophysical properties and present promising applications. This Minireview summarizes recent progress and gives insightful perspectives in this rapidly developing field, which will be beneficial to the future development of luminescent materials.
Solid‐state materials with efficient room‐temperature phosphorescence (RTP) emissions have found widespread applications in materials science, while liquid or solution‐phase pure organic RTP emission ...systems has been rarely reported, because of the nonradiative decay and quenchers from the liquid medium. Reported here is the first example of visible‐light‐excited pure organic RTP in aqueous solution by using a supramolecular host‐guest assembly strategy. The unique cucurbit8uril‐mediated quaternary stacking structure allows tunable photoluminescence and visible‐light excitation, enabling the fabrication of multicolor hydrogels and cell imaging. The present assembly‐induced emission approach, as a proof of concept, contributes to the construction of novel metal‐free RTP systems with tunable photoluminescence in aqueous solution, providing broad opportunities for further applications in biological imaging, detection, optical sensors, and so forth.
True colors: An assembly‐induced emission strategy was utilized to endow a simple dye molecule with room‐temperature phosphorescence and tunable photoluminescence in aqueous solution. The obtained supramolecular assembly structure has intriguing photophysical properties and enables the fabrication of multicolor hydrogels and cell imaging.
Regulating the fluorescent properties of organic small molecules in a controlled and dynamic manner has been a fundamental research goal. Although several strategies have been exploited, realizing ...multi-color molecular emission from a single fluorophore remains challenging. Herein, we demonstrate an emissive system by combining pyrene fluorophore and acylhydrazone units, which can generate multi-color switchable fluorescent emissions at different assembled states. Two kinds of supramolecular tools, amphiphilic self-assembly and γ-cyclodextrin mediated host-guest recognition, are used to manipulate the intermolecular aromatic stacking distances, resulting in the tunable fluorescent emission ranging from blue to yellow, including a pure white-light emission. Moreover, an external chemical signal, amylase, is introduced to control the assembly states of the system on a time scale, generating a distinct dynamic emission system. The dynamic properties of this multi-color fluorescent system can be also enabled in a hydrogel network, exhibiting a promising potential for intelligent fluorescent materials.
Recently, a remarkable advance has been made for metal‐free room‐temperature phosphorescence (RTP) crystals with high phosphorescence quantum yield. However, amorphous, especially heavy‐atom‐free, ...RTP materials still suffer from low quantum yield due to the transition‐forbidden character of phosphorescence and the relatively poor suppression of nonradiative transition in amorphous materials. In this study, a series of single‐benzene structure‐based high intersystem crossing yield phosphor is obtained. After embedding into polyvinyl alcohol matrix, all these phosphor exhibits efficient phosphorescence emission (ФP, up to 44.0%). Besides, photo‐switchable phosphorescence emission can be obtained by doping these molecules into a polymethyl methacrylate (PMMA) matrix. The phosphorescence can be gradually switched on by consuming the residual oxygen in the PMMA matrix under continuous UV light irradiation. Furthermore, the phosphorescence will be spontaneously switched off under ambient conditions. Taking advantage of the photoactivation character, this material has potential in information storage and anti‐counterfeiting.
A series of polyvinyl alcohol thin films with high intersystem crossing yields and phosphorescence quantum yields (up to 44.0%) are prepared from newly synthesized single‐benzene based, heavy‐atom‐free derivatives. Furthermore, an information writing‐erasing‐rewriting film and anti‐counterfeiting label are established by using the poor oxygen barrier properties of polymethyl methacrylate and the photo‐induced oxygen scavenge process.
Despite the great progress in research on molecular carbons containing multiple helicenes around one core, realizing the stereoselectivity of carbons containing multiple helicenes around more cores ...is still a great challenge. Herein, molecular carbon C204 featuring 12‐fold 5helicenes around four cores was successfully constructed by using nine perylene diimide (PDI) units, and exhibits good solubility and stability. Despite 256 possible stereoisomers caused by the 12‐fold 5helicenes, we only obtained one pair of enantiomers with D3 symmetry. There are four possible pairs of enantiomers with D3 symmetry, namely 7A, 7B, 7C and 7D. Theoretical and experimental results verify that the obtained structure belongs to 7C, which has the lowest energy. The enantiomers can also be separated by chiral HPLC. These results suggest that choosing PDIs as building blocks can not only improve the solubility and stability but also realize the stereoselectivity and chirality of molecular carbons.
A molecular carbon imide featuring 12‐fold 5helicenes around four cores has been constructed using perylene diimide units. The structure exhibits high stereoselectivity and chirality, good solubility, and stability. Although there are four possible pairs of enantiomers with D3 symmetry, the results verify that the obtained structure belongs to the one having the lowest energy. The enantiomers can also be separated by HPLC on a chiral stationary phase.
There are limited reports about the transformation of pure organic room‐temperature phosphorescence (RTP) materials with multilevel stimuli‐responsiveness at different RTP emission wavelengths under ...external stimuli. It is difficult to ensure efficient intersystem crossing (ISC) in different states of a single‐component system. This research reports the conversion of the organic single‐component small molecule 1,2‐bis(4‐alkoxyphenyl)ethane‐1,2‐dione (N‐BOX) with multilevel stimuli‐responsiveness between high‐efficiency blue and yellow RTP by grinding or thermal annealing N‐BOX crystals. The RTP emission of N‐BOX in the crystalline state was easy to adjust by external stimuli (grinding or thermal annealing) due to its non‐compact packing, which led to a phase transition and generated unique multilevel stimuli‐responsiveness. In particular, the RTP quantum yield of 7‐BOX with multilevel stimuli‐responsiveness reached 68.4 %, which provides an opportunity for regulation of smart optical materials based on pure organic RTP.
A single‐component organic small molecule with a high phosphorescence quantum yield (68.4 %) and multilevel stimuli‐responsiveness (mechanical and thermal stimuli‐responsiveness) has been synthesized. The multilevel stimuli‐responsiveness is based on a phase transition of the N‐BOX from a crystalline state to an amorphous state. The phase transition regulates the reversible change of N‐BOX between high‐efficiency blue and yellow room‐temperature phosphorescence.
Supramolecular polymers that can heal themselves automatically usually exhibit weakness in mechanical toughness and stretchability. Here we exploit a toughening strategy for a dynamic dry ...supramolecular network by introducing ionic cluster‐enhanced iron‐carboxylate complexes. The resulting dry supramolecular network simultaneous exhibits tough mechanical strength, high stretchability, self‐healing ability, and processability at room temperature. The excellent performance of these distinct supramolecular polymers is attributed to the hierarchical existence of four types of dynamic combinations in the high‐density dry network, including dynamic covalent disulfide bonds, noncovalent H‐bonds, iron‐carboxylate complexes and ionic clustering interactions. The extremely facile preparation method of this self‐healing polymer offers prospects for high‐performance low‐cost material among others for coatings and wearable devices.
High‐density iron‐carboxylate ionic clusters can remarkably toughen a dry supramolecular network by forming high‐affinity secondary ionic clusters. The toughened network exhibits high mechanical strength, high stretchability, efficient self‐healing ability, and processability at room temperature.
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