Diarylethene Unit Research Articles

Rational Design of Photocontrolled Rectifier Switches in Single-Molecule Junctions Based on Diarylethene.

The construction of multifunctional, single-molecule nanocircuits to achieve the miniaturization of active electronic devices is a challenging goal in molecular electronics. In this paper, we present an effective strategy for enhancing the multifunctionality and switching performance of diarylethene-based molecular devices, which exhibit photoswitchable rectification properties. Through a molecular engineering design, we systematically investigate a series of electron donor/acceptor-substituted diarylethene molecules to modulate the electronic properties and investigate the transport behaviors of the molecular junctions using the non-equilibrium Green's function combined with the density functional theory. Our results demonstrate that the asymmetric configuration, substituted by both the donor and acceptor on the diarylethene molecule, exhibits the highest switching ratio and rectification ratio. Importantly, this rectification function can be switched on/off through the photoisomerization of the diarylethene unit. These modulations in the transport properties of these molecular junctions with different substituents were obtained with molecule-projected self-consistent Hamiltonian and bias-dependent transmission spectra. Furthermore, the current-voltage characteristics of these molecular junctions can be explained by the molecular energy level structure, showing the significance of energy level regulation. These findings have practical implications for constructing high-performance, multifunctional molecular-integrated circuits.

A turn-on mode fluorescent diarylethene having an azacrown ether receptor: Metal-ion-gated enhancement of the photoreactivity and fluorescence

We report the metal-ion-gated enhancement of the photoreaction and fluorescence of a newly synthesized photoswitchable fluorescent diarylethene derivative having an azacrown ether receptor. In the absence of metal ions, the diarylethene molecule underwent the photoisomerization and turn-on mode switching of fluorescence, but the photoreactivity and fluorescing ability were suppressed by intramolecular photoinduced electron transfer (PET) from the azacrown ether moiety to the diarylethene unit. Upon binding of a metal ion to the azacrown ether, the PET process was blocked, and the photoreactivity and fluorescence were significantly enhanced. Such photoswitchable fluorescent molecules that change their photoresponsive properties upon recognizing metal ions have the potential to function as metal-ion chemosensors and molecular probes in metal-ion-sensitive super-resolution fluorescence microscopy.

Substrate-Bound Diarylethene-Based Anisotropic Metal-Organic Framework Films as Photoactuators with a Directed Response.

Molecular machines and responsive materials open a plethora of new opportunities in nanotechnology. We present an oriented crystalline array of diarylethene (DAE)-based photoactuators, arranged in a way to yield an anisotropic response. The DAE units are assembled, together with a secondary linker, into a monolithic surface-mounted metal-organic framework (SURMOF) film. By Infrared (IR) and UV/Vis spectroscopy as well as by synchrotron X-ray diffraction, we show that the light-induced extension changes of the molecular DAE linkers multiply to yield mesoscopic and anisotropic length changes. Due to the special architecture and substrate-bonding of the SURMOF, these length changes are transferred to the macroscopic scale, leading to the bending of a cantilever and performing work. This research shows the potential of assembling light-powered molecules into SURMOFs to yield photoactuators with a directed response, presenting a path to advanced actuators.

All-Visible (>500 nm)-Light-Induced Diarylethene Photochromism Based on Multiplicity Conversion via Intramolecular Energy Transfer.

Photoswitching molecules that reversibly switch upon visible-light irradiation are some of the most attractive targets for biological and imaging applications. In this study, we found a diarylethene (DAE) derivative having a covalently attached perylenebisimide (PBI) unit (DAE-PBI dyad) underwent an unexpected cyclization reaction upon irradiation with green (500-550 nm) light, where the DAE unit has no absorbance. The photoreactivity was enhanced in solvents containing heavy atoms and in the presence of oxygen. As inferred from the solvent dependence and the calculated excited-state energies of DAE and PBI units, it was suggested that the probable mechanism for this unique visible-light-induced cyclization reaction is multiplicity conversion based on intramolecular energy transfer from the excited singlet state of the PBI unit to the triplet state of DAE units (i.e., DAE-1[PBI]* → 3[DAE]*-PBI). Such a unique photoreaction mechanism with the assistance of oxygen will pave the way for new molecular design for the development of visible-light switching molecules.

Future‐Oriented Advanced Diarylethene Photoswitches: From Molecular Design to Spontaneous Assembly Systems

Diarylethene (DAE) photoswitch is a new and promising family of photochromic molecules and has shown superior performance as a smart trigger in stimulus-responsive materials. During the past few decades, the DAE family has achieved a leap from simple molecules to functional molecules and developed toward validity as a universal switching building block. In recent years, the introduction of DAE into an assembly system has been an attractive strategy that enables the photochromic behavior of the building blocks to be manifested at the level of the entire system, beyond the DAE unit itself. This assembly-based strategy will bring many unexpected results that promote the design and manufacture of a new generation of advanced materials. Here, recent advances in the design and fabrication of diarylethene as a trigger in materials science, chemistry, and biomedicine are reviewed.

Unprecedented ON/OFF Ratios in Photoactive Diarylethene-Bisthienylbenzene Molecular Junctions.

Photoactive molecular junctions, based on 4 nm thick diarylethene (DAE) and 5 nm thick bisthienylbenzene (BTB) layers, were fabricated by electrochemical deposition. Total thickness was around 9 nm, that is, above the direct tunneling limit and in the hopping regime. The DAE units were switched between their open and closed forms. The DAE/BTB bilayer structure exhibits new electronic functions combining photoswitching and photorectification. The open form of DAE/BTB shows low conductance and asymmetric I-V curves while the closed form shows symmetric I-V curves and high conductance. More importantly, unprecedented ON/OFF current ratios of over 10 000 at 1 V were reproducibly measured.

Photoresponsive supramolecular coordination polyelectrolyte as smart anticounterfeiting inks

While photoluminescence printing is a widely applied anticounterfeiting technique, there are still challenges in developing new generation anticounterfeiting materials with high security. Here we report the construction of a photoresponsive supramolecular coordination polyelectrolyte (SCP) through hierarchical self-assembly of lanthanide ion, bis-ligand and diarylethene unit, driven by metal-ligand coordination and ionic interaction. Owing to the conformation-dependent photochromic fluorescence resonance energy transfer between the lanthanide donor and diarylethene acceptor, the ring-closure/ring-opening isomerization of the diarylethene unit leads to a photoreversible luminescence on/off switch in the SCP. The SCP is then utilized as security ink to print various patterns, through which photoreversible multiple information patterns with visible/invisible transformations are realized by simply alternating the irradiation with UV and visible light. This work demonstrates the possibility of developing a new class of smart anticounterfeiting materials, which could be operated in a noninvasive manner with a higher level of security.

Tunable Photomechanics in Diarylethene-Driven Liquid Crystal Network Actuators.

The response of soft actuators made of stimuli-responsive materials can be phenomenologically described by a stimulus-deformation curve, depicting the controllability and sensitivity of the actuator system. Manipulating such stimulus-deformation curve allows fabricating soft microrobots with reconfigurable actuation behavior, which is not easily achievable using conventional materials. Here, we report a light-driven actuator based on a liquid crystal polymer network containing diarylethene (DAE) photoswitches as cross-links, in which the stimulus-deformation curve under visible-light illumination is tuned with UV light. The tuning is brought about by the reversible electrocyclization of the DAE units. Because of the excellent thermal stability of the visible-absorbing closed-form DAEs, the absorbance of the actuator can be optically fixed to a desired value, which in turn dictates the efficiency of photothermally induced deformation. We employ the controllability in devising a logical AND gate with macroscopic output, i.e., an actuator that bends negligibly under UV or visible light irradiation, but with profound shape change when addressed to both simultaneously. The results provide design tools for reconfigurable microrobotics and polymer-based logic gating.

A new multi-functional fluorescent mercuric ion sensor based on diarylethene with triazole-linked rhodamine B unit

A novel photochromic diarylethene fluorescence sensor 1o bearing a triazole-linked rhodamine B unit was designed and synthesized. Results showed that 1o had multi-responsive photoswitchable characteristics under the stimulation of light, proton, and specific metal ions. It also showed highly selectivity and sensitivity to recognize Hg2+ over other interfering heavy and transition metal ions through the spirolactam ring-opening reaction, which could be detected with “naked-eyes”. Upon the treatment with Hg2+, the fluorescence intensity of 1o at 606 nm was enhanced by 88-fold with notable fluorescence color changing from dark to pink. And its detection limit to Hg2+ was as low as 0.13 μM. Significant fluorescence quenching was observed upon the irradiation with 297 nm light due to FRET between rhodamine B moiety and diarylethene unit. Moreover, an INHIBIT logic gate was established with UV light and proton as the dual data inputs, and the fluorescence intensity at 605 nm as the data output.

Light‐Controllable Ionic Conductivity in a Polymeric Ionic Liquid

AbstractPolymeric ionic liquids (PILs) have attracted considerable attention as electrolytes with high stability and mechanical durability. Light‐responsive materials are enabling for a variety of future technologies owing to their remote and noninvasive manipulation, spatiotemporal control, and low environmental impact. To address this potential, responsive PIL materials based on diarylethene units were designed to undergo light‐mediated conductivity changes. Key to this modulation is tuning of the cationic character of the imidazolium bridging unit upon photoswitching. Irradiation of these materials with UV light triggers a circa 70 % drop in conductivity in the solid state that can be recovered upon subsequent irradiation with visible light. This light‐responsive ionic conductivity enables spatiotemporal and reversible patterning of PIL films using light. This modulation of ionic conductivity allows for the development of light‐controlled electrical circuits and wearable photodetectors.

Light-Controllable Ionic Conductivity in a Polymeric Ionic Liquid.

Polymeric ionic liquids (PILs) have attracted considerable attention as electrolytes with high stability and mechanical durability. Light-responsive materials are enabling for a variety of future technologies owing to their remote and noninvasive manipulation, spatiotemporal control, and low environmental impact. To address this potential, responsive PIL materials based on diarylethene units were designed to undergo light-mediated conductivity changes. Key to this modulation is tuning of the cationic character of the imidazolium bridging unit upon photoswitching. Irradiation of these materials with UV light triggers a circa 70 % drop in conductivity in the solid state that can be recovered upon subsequent irradiation with visible light. This light-responsive ionic conductivity enables spatiotemporal and reversible patterning of PIL films using light. This modulation of ionic conductivity allows for the development of light-controlled electrical circuits and wearable photodetectors.

Luminescent probe based on photochromic cyclometalated iridium(III) complex for high selectivity detection of thiophenol

A novel cyclometalated iridium(III) complex 1oo including two photochromic diarylethene (DTE) units and 2,4-dinitrobenzenesulfonyl (DNBS) group was designed and synthesized as a probe for thiophenol. Due to the intramolecular charge transfer (ICT) mechanism, probe 1oo displayed almost non-fluorescence. After nucleophilic elimination reaction occurred triggered by thiophenol a fluorescence complex 2oo was generated, the ICT process was blocked and obvious fluorescence enhancement centred at ca. 450 nm was observed. Moreover, during the detection process, fluorescent behavior of probe 1oo could be modulated upon alternate irradiations of UV and Vis light, ascribed to photochromic diarylethene molecules in the C^N ligands could play the part of fluorescent switch. Probe 1oo exhibited excellent sensitivity (LOD: 2.43 μM), selectivity and rapid response (15 min) to thiophenol.

Loading Photochromic Molecules into a Luminescent Metal-Organic Framework for Information Anticounterfeiting.

Stimuli-responsive photoluminescent materials have attracted considerable attention owing to their potential applications in security protection because the information recorded directly in materials with static luminescent outputs are usually visible under either ambient or UV light. Herein, we realize reversible information anticounterfeiting by loading a photoswitchable diarylethene derivative into a lanthanide metal-organic framework (MOF). Light triggers the open- and closed-form isomerization of the diarylethene unit, which respectively regulates the inactivation and activation of the photochromic FRET process between the diarylethene acceptor and lanthanide donor, resulting in reversible luminescence on-off switching of the lanthanide emitting center in the MOF host. This photoresponsive host-guest system allows for reversible multiple information pattern visible/invisible transformation by simply alternating the exposure to UV and visible light.

Loading Photochromic Molecules into a Luminescent Metal–Organic Framework for Information Anticounterfeiting

AbstractStimuli‐responsive photoluminescent materials have attracted considerable attention owing to their potential applications in security protection because the information recorded directly in materials with static luminescent outputs are usually visible under either ambient or UV light. Herein, we realize reversible information anticounterfeiting by loading a photoswitchable diarylethene derivative into a lanthanide metal–organic framework (MOF). Light triggers the open‐ and closed‐form isomerization of the diarylethene unit, which respectively regulates the inactivation and activation of the photochromic FRET process between the diarylethene acceptor and lanthanide donor, resulting in reversible luminescence on–off switching of the lanthanide emitting center in the MOF host. This photoresponsive host–guest system allows for reversible multiple information pattern visible/invisible transformation by simply alternating the exposure to UV and visible light.

Novel multi-responsive fluorescence switch for Hg2+ and UV/vis lights based on diarylethene-rhodamine derivative

A new multi-responsive fluorescent switch DTE-Pip-Rho 1O has been designed and synthesized in this study. For this molecule, the reactive site of spirolactam ring is far away from the diarylethene unit through the intramolecular piperazine. It exhibited high selectivity and sensitivity to Hg2+ in addition to obvious color change (colorless-pink) and fluorescence “off-on” (dark-orange) during this process. It is believed that the color change is due to Hg2+-assisted hydrolysis of rhodamine hydrazide. Therefore, the new molecule can be used as colorimentric and fluorescent chemosensor for Hg2+ with high selectivity. The detection limits of absorbance and fluorescence for Hg2+ were calculated to be 1.15 μM and 1.16 μM, respectively. The resulting DTE-Pip-Rho 1O-Hg2+ could also function as a reversible fluorescence photo-switch in response to UV/vis light owing to FRET mechanism. Moreover, it has been demonstrated that the photo-switchable system displayed excellent fatigue resistance and remarkable anti-photobleaching capability.

Chromogenic and fluorogenic detection of selected anions by bis-terpyridine Fe(II) complex through displacement approach

Abstract This paper deals with synthesis, characterization and anion recognition properties of a homoleptic bis-terpyridine Fe(II) complex covalently coupled with diarylethene unit. The recognition event was examined in both organic as well as mixed aqueous–organic medium through different optical channels and spectroscopic techniques by taking advantage of metal–ligand interaction in the complex. The complex acts as sensor for \(\hbox {F}^{-}\), \(\hbox {OAc}^{-}\) and \(\hbox {CN}^{-}\) among the other studied anions (\(\hbox {F}^{-}\), \(\hbox {Cl}^{-}\), \(\hbox {Br}^{-}\), \(\hbox {I}^{-}\), \(\hbox {CN}^{-}\), \(\hbox {OAc}^{-}\), \(\hbox {H}_{2}\hbox {PO}_{4}^{-}\), \(\hbox {SCN}^{-}\), \(\hbox {BF}_{4}^{-}\) and \(\hbox {ClO}_{4}^{-})\) without selectivity. In contrast to acetonitrile, the complex acts as highly selective chromogenic and fluorogenic sensor for only \(\hbox {CN}^{-}\) in water. Detection limit of the metalloreceptor towards \(\hbox {CN}^{-}\) was determined from the absorption and emission titration data and the observed values lie in the order of \(10^{-9}\) M in acetonitrile and \(10^{-8}\) M in mixed aqueous–organic media.Graphical AbstractSYNOPSIS Anion sensing property of a bis-terpyridine Fe(II) complex was thoroughly investigated in both acetonitrile and water–acetonitrile (100:1, v/v) media through different optical channels and spectroscopic techniques. Interestingly, the complex acts as chromogenic and fluorogenic receptor for cyanide in predominantly aqueous medium with very low detection limit.

Synthesis, Structural Characterization, and Luminescence Switching of Diarylethene-Conjugated Ru(II)-Terpyridine Complexes by trans-cis Photoisomerization: Experimental and DFT/TD-DFT Investigation.

We synthesized and thoroughly characterized a new family of diarylethene-conjugated mononuclear Ru(II)-terpyridine complexes and investigated in detail their photophysical, electrochemical, and spectroelectrochemical behaviors. Interestingly, the compounds show moderately strong room-temperature luminescence predominantly from their 3MLCT state with luminescence lifetime varying between 8.43 and 22.82 ns. Because of the presence of diarylethene unit, all the monometallic complexes underwent trans-to-cis photoisomerization upon interaction with UV light with substantial changes in their absorption and luminescence spectra. Reverting back from the cis to the trans form is also made possible upon treatment with visible light or by heat. Trans-to-cis isomerization leads to almost complete quenching of luminescence, while backward cis-to-trans isomerization gives rise to restoration of the original luminescence for all the complexes. Thus, "on-off" and "off-on" emission switching was made possible upon successive interaction of the complexes with UV and visible light. Computational investigation involving density functional theory (DFT) and time-dependent DFT methods was done for proper assignment of the experimental absorption and emission spectral bands in the complexes. Finally, experimentally observed trend on the absorption and emission spectral behaviors of the complexes upon photoisomerization was also compared with the calculated results.

A multi-responsive diarylethene-rhodamine 6G derivative for sequential detection of Cr3+ and CO32−

A new unsymmetrical diarylethene derivative (1o) with rhodamine 6G as a functional group has been designed and synthesized. It displayed good physicochemical properties induced by lights and chemical stimuli. 1o could sensitively detect towards Cr3+ with a 1:1 stoichiometry, and exhibit an obviously fluorescence (from dark to light cyan) and color (from colorless to pink) changes during the recognition process. The limit of detection was determined to be 27 nM and 8.5 nM via UV/vis and fluorescence methods, respectively. More importantly, the resulting complex 1o-Cr3+ (1o') could be served as a potential fluorescent probe to selectively and sensitively recognize toward CO32−, the limit of detection was determined to be 0.88 μM and 0.26 μM via UV/vis and fluorescence methods, respectively. Moreover, the quenching of fluorescence intensity can reach 95% due to the perfect FRET processes between the excited open-ring rhodamine 6G moiety and the closed-ring diarylethene unit.

DFT/TDDFT, NPA, and AIM-based study of the molecular switching properties of photocyclization and metallochromism of the DAE complexes

Diarylethene (DAE), the ubiquitous photochromic unit, is one of the most promising candidates for well-recognized optoelectronic applications. In this paper, the relationship between reversible photoisomerization/metallochromic properties and second-order nonlinear optical (NLO) responses for a new photochromism based on DAE with a benzyl-linked 8-aminoquinoline-2-aminomethylpyridine unit (1O) has been systematically investigated by using density functional theory. Our results show that closed-ring (1C) comprising DAE unit was shown to be capable of exhibiting both large static first hyperpolarizabilities βtot (1.075 × 10−28 esu) and large switch ratio βratio ~ 31 with corresponding open-ring because of the better delocalization of the π-electron system, the more obvious degree of charge transfer and the smaller transition energy in the closed-ring. When the metal ions have been injected in open-ring (1O*M), we observed a larger NLO response compared with the corresponding open-ring 1O. However, it can slightly decrease the βtot values in 1C*M. Natural bonding orbital and atom in molecules analysis provide a better understanding for the property differences in metallochromic process. We hope this research would be beneficial for further theoretical and experimental studies on large second-order NLO switches applications.

Synthesis, Characterization, and Properties of Iron(II) Spin-Crossover Molecular Photoswitches Functioning at Room Temperature.

Spin-crossover molecular switches [FeII(H2B(pz)2)2L] (L = novel phenanthroline-based ligands featuring photochromic diarylethene units; pz = 1-pyrazolyl) were synthesized and thoroughly characterized by variable-temperature X-ray crystallography, Mössbauer spectroscopy, and magnetic measurements. The effect of substituents introduced into the phenanthroline backbone (L2) and into the photochromic diarylethene unit (L3) on photophysical properties of metal-free ligands and spin-crossover iron(II) complexes 2 and 3, respectively, were investigated in detail. Both ligands and complexes could be switched with light in solution at room temperature. The photocyclization of 2 was accompanied by a high-spin to low-spin photoconversion determined at 19%. The closed-ring isomers of L3 and 3 reveal the lifetimes in the range of minutes, whereas those of L2 and 2 are thermally stable for days in solutions at room temperature. The reversibility of the photoswitching can be improved by avoiding the photostationary states. Prospective introduction of anchoring groups to the phenanthroline backbone might allow the construction of chemisorbed self-assembled monolayers of spin-crossover species switchable with light at room temperature.