Photocontrolled Intramolecular Charge/Energy Transfer and Fluorescence Switching of Tetraphenylethene‐Dithienylethene‐Perylenemonoimide Triad with Donor–Bridge–Acceptor Structure

Photochromic 1,2‐dithienylethene (DTE) derivatives with a high thermal stability and fatigue resistance are appealing for optical switching of fluorescence. Here, we introduce a donor–photochromic bridge–acceptor tetraphenylethene‐dithienylethene‐perylenemonoimide (TPE‐DTE‐PMI) triad, in which TPE acts as the electron donor, PMI as the electron acceptor, and DTE as the photochromic bridge. In this system, the localized and intramolecular charge transfer emission of TPE‐DTE‐PMI with various Stokes shifts have been observed due to the photoinduced intramolecular charge transfer in different solvents. Upon UV irradiation, the fluorescence quenching resulting from photochromic fluorescence resonance energy transfer in TPE‐DTE‐PMI has been demonstrated in solution and in solid films. The fluorescence on/off switching ratio in polymethylacrylate film exceeds 100, a value much higher than in polymethylmethacrylate film, thus indicating that the fluorescence switching is dependent on matrices.     

Photochromic fluorescence switching from diarylethenes and its applications

The review describes the photochromic and fluorescent characteristics of various diarylethene (DAET) derivatives, and presents recent research into their applications. This comprises a discussion of the optical characteristics of some DAET-based molecules exhibiting red, green, or blue (RGB) colors or fluorescence. Molecular calculations of the optical properties of DAET interpret intriguing experimental observations and predict photochemical or photophysical properties. In particular, stabilization of HOMO in the BTFOn (n = 1, 2, 3, 4) increases the energy difference between the HOMO and the LUMO, which leads to the blue-shift of absorption and emission bands as the number of oxygen attached to sulfur (n) increases. Various devices and application studies have been designed as photon-mode systems based on photochemical control of the fluorescence energy. The photochromic DAET materials have shown promise as optical data storage, switching devices, and biological applications such as the development of biomaterial sensors, analysis of biological dynamics, and live cell imaging.     

萘并吡喃光致变色荧光开关研究进展

萘并吡喃及其衍生物是经典的光致变色材料,具有很低的背景颜色、优良的光致变色抗疲劳性、易于调控的变色动力学、开环体具有宽的吸收等优点,受到了研究者的重视。本文综述了近几年来作者课题组利用萘并吡喃构建光致变色荧光开关的研究进展,通过将荧光基团和萘并吡喃以掺杂模式、共聚物和有机小分子等形式构建光致变色荧光开关,研究了它们在溶液和薄膜中的荧光开关性能,初步探讨了萘并吡喃荧光开关在非破坏性读出和荧光成像等方面的应用潜能。     

Readily accessible rhodamine B-based photoresponsive material

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Photochromic switching of excited-state intramolecular proton-transfer (ESIPT) fluorescence: a unique route to high-contrast memory switching and nondestructive readout

Aiming at the high-contrast photochromic switching of fluorescence emission and its perfect nondestructive readout, a polymer film highly loaded with a specific photochromic compound, 1,2-bis(2'-methyl-5'-phenyl-3'-thienyl)perfluorocyclopentene (BP-BTE), and an excited-state intramolecular proton-transfer (ESIPT)-active compound, 2,5-bis(5'-tert-butyl-benzooxazol-2'-yl)hydroquinone (DHBO), was employed in this work. The special class of photochrome, BP-BTE, has negligible absorbance at 415 nm both in the open form and in the 365 nm photostationary state (PSS), and the ESIPT fluorophore, DHBO, emits large Stokes' shifted (175 nm; lambda(max)(abs) = 415 nm, lambda(max)(em) = 590 nm) and enhanced fluorescence (Phi(F)(powder) = 10%, Phi(F)(soln) = 2%). Bistability, high-contrast switching (on/off fluorescence switching ratio >290), nondestructive readout (over 125000 shots), and erasability were all together accomplished in this novel recording medium.     

Photo-controllable room-temperature phosphorescence of organic photochromic polymers based on hexaarylbiimidazole

Pure organic room-temperature phosphorescent(RTP) materials have been attracting widespread attention due to the unique properties and broad applications. However, RTP materials with the adjustable photochromic property are still a challenge.Based on this, two polymers containing hexaarylbiimidazole are strategically designed with dual emission of both fluorescence and phosphorescence. Furthermore, both polymers show sensitive photochromic responses from faint yellow to brown upon exposure to ultraviolet light. This study can enrich pure organic luminescent systems and provide new ideas for functional RTP materials.     

Synthesis and characterization of photoswitchable fluorescent SiO2 nanoparticles

Switchable fluorescent silica nanoparticles have been prepared by covalently incorporating a fluorophore and a photochromic compound inside the particle core. The fluorescence can be switched reversibly between an on‐ and off‐state via energy transfer. The particles were synthesized using different amounts of the photoswitchable compound (spiropyran) and the fluorophore (rhodamine B) in a size distribution between 98 and 140 nm and were characterized in terms of size, switching properties, and fluorescence efficiency by TEM, and UV\Vis and fluorescence spectroscopy.     

Diarylethene doped biocompatible polymer dots for fluorescence switching

The photochromic molecule diarylethene works as a "toggle switch" for biocompatible fluorescence polymer dots and enables fluorescence switching in biological samples.     

Photoregulated fluorescence switching in axially coordinated tin(IV) porphyrinic dithienylethene

Photochromic fluorophore Sn(TTP)(DTE)2 , in which two phenolic derivatives of 1,2-dithienylethene are axially coordinated to (5,10,15,20-tetratolylporphyrinato)tin(IV) in trans position, has been synthesized and fully characterized by various spectroscopic methods. We have also investigated the photoregulated fluorescence switching behavior of Sn(TTP)(DTE)2 . The fluorescence of the porphyrin macrocycle in Sn(TTP)(DTE) 2 greatly depends on the state of the 1,2-dithienyletene photochromic switch. In the open state (Sn(TTP)(o-DTE)2), the porphyrin exhibits high fluorescence intensity at 609 and 664 nm when excited at 410 nm. When the photocyclization reaction was carried out by irradiating Sn(TTP)(o-DTE)2 with the UV light (approximately 365 nm), the fluorescence intensity of the porphyrin macrocycle decreased. Back irradiation with visible light at wavelengths greater than 500 nm regenerated Sn(TTP)(o-DTE)2 and almost restored the original fluorescence spectrum. The fluorescence intensity of the porphyrin fluorophore is efficiently regulated by photochromic switching between Sn(TTP)(o-DTE)2 and Sn(TTP)(c-DTE)2 in several cycles, clearly demonstrating that the Sn(TTP)(DTE)2 can act as a system for reversible data processing using fluorescence as the detection method.     

Diheteroarylethenes as thermally stable photoswitchable acceptors in photochromic fluorescence resonance energy transfer (pcFRET)

We have employed diheteroarylethenes as acceptors for photochromic FRET (pcFRET), a technique introduced for the quantitative determination of fluorescence resonance energy transfer (FRET). In pcFRET, the fluorescent emission of the donor is modulated by cyclical transformations of a photochromic acceptor. Light induces a reversible change in the structure and, concomitantly, in the absorption properties of the acceptor. Only the closed forms of the selected diheteroarylethenes 2a and 2b have an absorption band overlapping the emission band of the donor, 1. The corresponding variation in the overlap integral (and thus critical transfer distance R(o)) between the two states provides the means for reversibly switching the process of FRET on and off, allowing direct and repeated evaluation of the relative changes in the donor fluorescence quantum yield. The diheteroarylethenes demonstrate excellent stability in aqueous media, an absence of thermal back reactions, and negligible fatigue. The equilibration of these systems after exposure to near-UV or visible light follows simple monoexponential kinetics. We developed a general conceptual scheme for such coupled photochromic-FRET reactions, allowing quantitative interpretations of the photostationary and kinetic data, from which the quantum yields for the cyclization and cycloreversion reactions of the photochromic acceptor were calculated.     

Photochromic Properties of New Dithienylethene Copolymer

Photochromic molecular switches can be important memory media for optical information processing and storage as long as their thermal stability and photo-fatigue resistance met certain criteria. Among many photochromic materials, heterocyclic diarylethenes have displayed desirable optical switching characteristics. Specifically, bisthienylethene (BTE)-based photochromic switches have demonstrated high sensitivity and rapid response as well as thermal- and photostability^[1,2]. It has been shown that various BTEs can undergo ca.l0^[4] cycles before significant evidence of fatigue^[3]. It is important that molecules with otherwise improved switching characteristics retain this level of fatigue resistance. For example, the improved characteristics include that the absorption of close form of photochromic materials should be shifted to shorter wavelength region due that semiconductor laser shift to short wavelength are developing trend for high density information storage. Also, fatigue may be different in the solid state than in solution. In general, precedent photochromic polymers consisted of photochromic molecules either dispersed in a matrix or covalent grafted onto the polymer main chain.     

光控二芳烯化学传感器及其研究进展

有机光致变色材料由于在光学记忆及分子开关器件等领域具有潜在的应用价值而备受关注。在众多有机光致变色系统中,二芳烯类光致变色化合物具有热稳定性好、耐疲劳、响应速度快和灵敏度高等优点,在光电材料和生物医学领域具有广阔的应用前景。近年来,围绕二芳烯构建可调控光化学传感器已成为功能材料领域的一大研究热点。本文主要介绍以二芳烯作为光调控单元合成具有多重调控功能的化学传感器的研究进展,并展望了该领域的应用前景和研究方向。     

An all-photonic molecule-based D flip-flop

The photochromic fluorescence switching of a fulgimide derivative was used to implement the first molecule-based D (delay) flip-flop device, which works based on the principles of sequential logic. The device operates exclusively with photonic signals and can be conveniently switched in repeated cycles.     

Giant Amplification of Photoswitching by a Few Photons in Fluorescent Photochromic Organic Nanoparticles

Controlling or switching the optical signal from a large collection of molecules with the minimum of photons represents an extremely attractive concept. Promising fundamental and practical applications may be derived from such a photon‐saving principle. With this aim in mind, we have prepared fluorescent photochromic organic nanoparticles (NPs), showing bright red emission, complete ON–OFF contrast with full reversibility, and excellent fatigue resistance. Most interestingly, upon successive UV and visible light irradiation, the NPs exhibit a complete fluorescence quenching and recovery at very low photochromic conversion levels (<5 %), leading to the fluorescence photoswitching of 420±20 molecules for only one converted photochromic molecule. This “giant amplification of fluorescence photoswitching” originates from efficient intermolecular energy‐transfer processes within the NPs.     

Single boryl isomerization in silyl-bridged photochromic diboryl dyes

Silyl-bridged dimers of a ppy-BMes(2) (ppy = 2-phenylpyridine, Mes = mesityl) photochrome were found to undergo photochromic switching involving a single boryl unit only. A through-space intramolecular energy transfer was found to be responsible for the single-chromophore isomerization phenomenon and fluorescence quenching. Steric congestion in the diboryl molecules was found to have an impact on photoisomerization quantum efficiency.     

Dithienylethene metallodendrimers with high photochromic efficiency

It has been challenging to achieve multi-photochromic systems without affecting the individual photoswitching properties of the constituent units. Herein, we present the design and synthesis of a new family of platinum-acetylide dendrimers containing up to twenty-one photochromic dithienylethene(DTE)units that exhibit both high photochromic efficiency and individual switching properties. Upon irradiation with ultraviolet(UV) and visible(vis) light, the resultant metallodendrimers display high co...     

Unsymmetrical photochromic bithienylethene-bridge tetraphenylethene molecular switches: Synthesis,aggregation-induced emission and information storage

Aggregation-induced emission(AIE) active photochromic molecules have attracted growing attention for their versatile applications.Here we designed and synthesized five newly unsymmetrical photochromic diarylethene(DAE) dyads(BTE1-5) by connecting tetraphenylethene(TPE) and aromatic substituent via bithienylethene(BTE) bridge.The chemical structures of those compounds were identified by ^1H NMR,¹³C NMR and HRMS.The absorption and emission of these dyads were investigated by UV-vis and fluore scence spectroscopy,respectively.The results showed that all those compounds exhibited typically AIE or aggregation-induced emission enhancement(AIEE) characteristic.Particularly,when an aggregationcaused quenching(ACQ) fluorophore(triphenylamine) was grafted to the molecule,connecting with TPE via BTE-bridge,the ACQ phenomenon was dissipated and converted to an AIE luminophore,and those compounds exhibited photochromism upon irradiation with alternative UV and visible light.The solution or solid of those compounds showed distinctly fluorescence switching "ON" or "OFF" observation upon irradiation with alternative UV and visible light.It is interesting that BTE1 could be applied in recording and rewritable information storage,and the cyclization quantum yields could be affected by substituent significantly.     

Digital photoswitching of fluorescence based on the photochromism of diarylethene derivatives at a single-molecule level

Photochromic reactions of diarylethene derivatives were detected at a single-molecule level by using a fluorescence technique. Fluorescent photoswitching molecules in which photochromic diarylethene and fluorescent bis(phenylethynyl)anthracene units are linked through an adamantyl spacer were synthesized, and switching of fluorescence upon irradiation with UV and visible light was followed in solution as well as on polymer films at the single-molecule level. Although in solution the fluorescence intensity gradually changed upon irradiation with UV and visible light, digital on/off switching between two discrete states was observed at the single-molecule level. The "on"- and "off"-times were dependent on the power of UV and visible light. When the power of UV and visible light was increased, the average on- and off-times became short in proportion to the reciprocal power of the light. The response-times were found to show distribution. The distribution of the on- and off-times is considered to reflect the difference in the micro-environment as well as conformation of the molecules.     

The Unusual Photochromic and Hydrochromic Switching Behavior of Cellulose-Embedded 1,8-Naphthalimide-Viologen Derivatives in the Solid-State

Stimuli-responsive chromic materials such as photochromics, hydrochromics, thermochromics, and electrochromics have a long history of capturing the attention of scientists due to their potential industrial applications and novelty in popular culture. However, hybrid chromic materials that combine two or more stimuli-triggered color changing properties are not so well known. Herein, we report a design strategy that has led to a series of emissive 1,8-naphthalimide-viologen dyads which exhibit unusual dual photochromic and hydrochromic switching behavior in the solid-state when embedded in a cellulose matrix. This behavior manifests as reversible solid state fluorescence hydrochromism upon changes in atmospheric relative humidity (RH), and reversible solid state photochromism upon generation of a cellulose-stabilized viologen radical cation. In this design strategy, the bipyridinium unit serves as both a water-sensitive receptor for the hydrochromic fluorophore-receptor system, and a photochromic group, capable of eliciting its own visible colorimetric response, generating a fluorescence quenching radical cation with prolonged exposure to ultraviolet (UV) light. These dyes can be inkjet-printed onto cellulose paper or drop-cast as cellulose powder-based films and can be unidirectionally cycled between three different states which can be characteristically visualized under UV light or visible light. The material's photochromism, hydrochromism, and underlying mechanism of action was investigated using computational analysis, dynamic vapor sorption/desorption isotherms, electron paramagnetic resonance spectroscopy, and variable humidity UV-Vis adsorption and fluorescence spectroscopies.     

Photoswitchable fluorescent dyads incorporating BODIPY and [1,3]oxazine components

We designed and synthesized three compounds incorporating a BODIPY fluorophore and an oxazine photochrome within the same molecular skeleton and differing in the nature of the linker bridging the two functional components. The [1,3]oxazine ring of the photochrome opens in less than 6 ns upon laser excitation in two of the three fluorophore-photochrome dyads. This process generates a 3H-indolium cation with a quantum yield of 0.02-0.05. The photogenerated isomer has a lifetime of 1-3 μs and reverts to the original species with first-order kinetics. Both photochromic systems tolerate hundreds of switching cycles with no sign of degradation. The visible excitation of the dyads is accompanied by the characteristic fluorescence of the BODIPY component. However, the cationic fragment of their photogenerated isomers can accept an electron or energy from the excited fluorophore. As a result, the photoinduced transformation of the photochromic component within each dyad results in the effective quenching of the BODIPY emission. Indeed, the fluorescence of these photoswitchable compounds can be modulated on a microsecond time scale with excellent fatigue resistance under optical control. Thus, our operating principles and choice of functional components can ultimately lead to the development of valuable photoswitchable fluorescent probes for the super-resolution imaging of biological samples.