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Electrochromic (EC) smart windows are an elegant alternative to dusty curtains, blinds, and traditional dimming devices. The EC energy storage smart windows and displays received remarkable attention in the optoelectronic industry as they hold promise for high energy efficiency, low power consumption, reversibility, and swift response to stimuli. However, achieving these properties remains challenging. Moreover, most EC molecules do not exhibit electrofluorochromism, which is highly essential for smart displays because its EC property can modulate the solar heat entering the building, and its electrofluorochromic (EFC) aspects can create lighting during the night. In this work, a structure‐property relationship is utilized to develop new electrochromes that can store the injected charge, and these molecules indeed exhibit electrofluorochromism. The compounds are synthesized from tetrabenzofluorene with two aromatic acceptor units, and avoids the use of widely studied heterocycles and amine derivatives. The electrochromes switches from yellow to dark hue in solution, solid, and gel state. The compounds display exceptional electrochemical stability and reversibility in 1000 cycles and capacity retention of 93–100 % in 300 charging‐discharging cycles. The proof‐of‐concept device fabrication of the self‐dimming EC smart window presented here demonstrates that it can furnish visual comfort, modulate transmitted light and glare, and reduce energy usage. [ABSTRACT FROM AUTHOR]

Redox‐active materials that exhibit both electrochromism and electrofluorochromism have great potential as multifunctional elements in optoelectronics. Here, in situ spectroelectrochemistry is presented on NU‐1000, a zirconium pyrenetetrabenzoate metal–organic framework. A thin film of NU‐1000 exhibits reversible color changes between light yellow and dark blue when subjected to an alternating electrochemical potential. In situ fluorescence excitation‐emission spectral mapping elucidates a dominant blue emission of highly fluorescent electrochromic NU‐1000 that is being quenched via an oxidation reaction. Density‐functional theory calculations reveal the forbidden optical transition between the singly occupied molecular orbital (SOMO) and the lowest unoccupied molecular orbital (LUMO) in the oxidized linker as the cause of the quenching. Double potential step chronoamperometry measures response times as fast as a dozen seconds and excellent switching stability over 500 cycles without noticeable attenuation of the color contrast. These findings provide valuable insight into the electrochromism and electrofluorochromism in metal–organic frameworks, offering exciting opportunities for developing advanced multifunctional porous materials with potential applications in optoelectronics and sensing. [ABSTRACT FROM AUTHOR]

Electrochromic/electrofluorochromic (EC/EFC) dual‐functional materials with electrochemically switchable colors and fluorescence offer the possibility of developing reflection/emission dual‐mode integrated displays in one device. However, unlike the easily adjustable multi‐color EC properties, the EFC properties with tunable fluorescence intensity are relatively broad, while those with tunable color emission are rare. Herein, two terpyridine‐attached viologen derivatives Tpy‐Vio‐1 and Tpy‐Vio‐2 are designed and synthesized for exploring the relationship between molecular structure and their EC/EFC properties. Due to the introduction of 4′‐phenyl‐2,2′:6′,2″‐terpyridine groups, Tpy‐Vio‐1 and Tpy‐Vio‐2 devices exhibited EFC characteristics in addition to EC properties. Tpy‐Vio‐1 and Tpy‐Vio‐2 devices displayed similar color and fluorescence changes after applying electric potentials. Nevertheless, compared to the Tpy‐Vio‐2 devices, the Tpy‐Vio‐1 devices possessed lower applied voltage (1.8 V), shorter response times (9.5 s for coloring and 8.5 s for bleaching), higher cyclic stability (480 cycles), and better coloration efficiency (95 cm2 C−1). This study believes that this work will provide effective guidance for the design and preparation of EC/EFC dual‐functional materials. [ABSTRACT FROM AUTHOR]

Abstract Redox‐active materials that exhibit both electrochromism and electrofluorochromism have great potential as multifunctional elements in optoelectronics. Here, in situ spectroelectrochemistry is presented on NU‐1000, a zirconium pyrenetetrabenzoate metal–organic framework. A thin film of NU‐1000 exhibits reversible color changes between light yellow and dark blue when subjected to an alternating electrochemical potential. In situ fluorescence excitation‐emission spectral mapping elucidates a dominant blue emission of highly fluorescent electrochromic NU‐1000 that is being quenched via an oxidation reaction. Density‐functional theory calculations reveal the forbidden optical transition between the singly occupied molecular orbital (SOMO) and the lowest unoccupied molecular orbital (LUMO) in the oxidized linker as the cause of the quenching. Double potential step chronoamperometry measures response times as fast as a dozen seconds and excellent switching stability over 500 cycles without noticeable attenuation of the color contrast. These findings provide valuable insight into the electrochromism and electrofluorochromism in metal–organic frameworks, offering exciting opportunities for developing advanced multifunctional porous materials with potential applications in optoelectronics and sensing.

A single layer of a dyad made of a cobalt(II) bis‐terpyridine complex functionalized with a Boron‐dipyrromethene (BODIPY) fluorophore on transparent Indium Tin Oxide (ITO) electrode is prepared. A modulation of the photoluminescence intensity of the fluorophore upon the application of an electric stimulus on the ITO electrode that supports 10 picomoles of molecules is demonstrated. The intensity of the fluorescence intensity decreases when the cobalt is at the oxidation state +III, due to CoIII oxidative quenching of BODIPY emission that has a higher driving force than the CoII reductive quenching initially responsible for the low fluorescence intensity of the chemisorbed dyad. [ABSTRACT FROM AUTHOR]

Viologens, a typical group of electrochromic materials, show rich color changes under the external electrical stimulus. Recently, some of the viologen derivatives are reported to exhibit good luminescent performance. However, their luminescence colors are difficult to adjust owing to the strong electron‐accepting properties of viologens, which seriously hinders their applications in smart light‐emitting devices. In this work, the color/emission dual‐switchable viologen derivative Phen‐vio is designed and synthesized by introducing fluorophore 1,10‐phenanthroline into 4,4′‐bipyridine, for multicolor large‐area and patterned electrochromic/electrofluorochromic devices. Under voltage driving of −2.3 and −2.8 V, the devices exhibited reversible color and fluorescence color changes from light yellow to dark orange to dark blue, and from yellow to orange to green, respectively. Moreover, the devices displayed a high color contrast ratio of up to 77% at 600 nm. More importantly, the driving voltages of the devices do not vary with the change of the device area, which is huge application potential in smart windows and tags. [ABSTRACT FROM AUTHOR]

The synthesis and full characterization of a family of stable λ5‐biphosphinines connected in 4,4‐position through a variety of π‐conjugated bridges is reported. The impact of the π‐bridge on the optical (absorption/emission) and redox properties was investigated using a joint experimental/theoretical approach. In contrast to the π‐extended ones, the λ5‐biphosphinines directly connected through a C−C bond in 4,4‐position display two easily accessible and reversible oxidations highlighting their multi‐stage redox character. The in situ formed radical cations are studied by spectro‐electrochemistry and electron paramagnetic resonance. Finally, electrochemical modulation of fluorescence (electrofluorochromism) was performed and revealed the potential of these intrinsically switchable electroactive fluorophores for further applications as switchable materials. [ABSTRACT FROM AUTHOR]

In this review, recent advances that exploit the intrinsic emission of organic materials for reversibly modulating their intensity with applied potential are surveyed. Key design strategies that have been adopted during the past five years for developing such electrofluorochromic materials are presented, focusing on molecular fluorophores that are coupled with redox-active moieties, intrinsically electroactive molecular fluorophores, and unconjugated emissive organic polymers. The structural effects, main challenges, and strides toward addressing the limitations of emerging fluorescent materials that are electrochemically responsive are surveyed, along with how these can be adapted for their use in electrofluorochromic devices. [ABSTRACT FROM AUTHOR]

Electrochromism/electrofluorochromism is the reversible tuning of the absorption/photoluminescence by redox processes. Dual functional electrochromic/electrofluorochromic materials can be exploited in, for example, smart windows, encryption/anticounterfeiting technologies, displays, and biomedical sensors. While electrofluorochromic materials showing tunable fluorescence intensity are relatively widespread, those with tunable color emission are not. Moreover, electrofluorochromic materials with tunable emission in the near‐infrared (NIR) range are seldom encountered. Here, this work shows a new molecular approach to afford both the above functionalities, in addition to red–NIR electrochromism, by combining the properties of highly stable arylamine radical cation mixed valence species, with those of donor–acceptor systems exhibiting the photoinduced twisted intramolecular charge transfer mechanism. [ABSTRACT FROM AUTHOR]

Two aggregation induced emission (AIE)‐active poly(acrylates) bearing triphenylvinyl‐functionalized phenylcarbazole and triphenylamine pendants, respectively, were synthesized. Their fluorescence response to nitroaromatics and electrofluorochromic (EFC) properties were studied, whereby both the presence of nitroaromatics and applied voltages led to fluorescence quenching. In a very first attempt to perform EFC detection of nitroaromatics, it was surprisingly found that after initial fluorescence quenching, the presence of nitroaromatics unexpectedly turned on fluorescence at high applied voltages (>+1.0 V), demonstrating a promising approach for the EFC detection of nitroaromatic explosives. [ABSTRACT FROM AUTHOR]

Electrochemical switching of luminescence color between magenta and blue using two types of luminescent materials and electrochromic molecules was demonstrated based on the control of excited energy transfer through an electrochromic reaction. The magenta photoluminescence, due to the integration of red luminescence from the Eu(III) complex and blue fluorescence from the anthracene derivative, was reversibly modulated to a pure-blue luminescence color by an electrochemical redox reaction. Electrofluorochromism is induced by effective excited energy transfer from the Eu(III) complex to the electrochromic molecule under a redox reaction. [ABSTRACT FROM AUTHOR]

A rhodamine-carbazole dyad has been synthesized and electropolymerized to generate thin films. The spectroelectrochemical properties of the resulting polymer are investigated both in absorption and emission. We show that the luminescence of the rhodamine unit is partially quenched by the carbazole moiety and this quenching is strongly enhanced upon oxidation. A reversible switch of the emission intensity between two redox states is demonstrated, but the stability is strongly dependent on the film thickness and proportion of carbazole in the polymerization medium. This luminescence quenching can be used to follow the electropolymerization reaction since a strong decrease of intensity occurs as soon as the oxidative coupling reaction starts. [Display omitted] • Electropolymerization of rhodamine-carbazole dyads leads to an electrofluorochromic polymer. • Oxidative electrochromism and electrofluorochromism involve the rhodamine unit. • Film thickness and electrode potential are key parameters to observe electrofluorochromism. [ABSTRACT FROM AUTHOR]

Bredereck oxazole synthesis was utilized to create a series of novel D-A polymers based on the triphenylamine (TPA) derivative, 4,4′-Diformyltriphenylamine (DPA), 4,4′-((4-bromophenyl)azanediyl)dibenzaldehyde (BPA), and oxamide/dithiooxamide. The obtained novel polymers exhibited impressive solution processabilities and excellent thermal stabilities. In the entire processes of electrochemical oxidation, these polymer films exhibited excellent electrochromic (EC) performances, high optical contrasts (49.6–52.8 %), high coloration efficiencies (362–451 cm2·C−1), and excellent cycling stabilities (18.6–33.9 % decay) with a cycle time of 20 s. By applying voltage, electrofluorochromic (EFC) performance can also be adjusted. Furthermore, these polymers showed fluorescence (PL) in solvents and solvatochromic effects in absorption. The outcome was indicative of the addition of oxazole[5,4- d ]oxazoles (OzOz) and thiazolo[5,4- d ]thiazoles (TzTz), whose highly conjugate rigid planar structures can significantly increase molecule stabilities and minimizing volume shrinking during charge transfer. In addition, due to introducing bromine atoms, the p-π conjugations enhanced the conjugation degrees of the molecules, which facilitated the electron transfers. Experimental results show that these improvement schemes will pave a way for obtaining multi-function optoelectronic devices with long-term cyclic stabilities. [Display omitted] • The electrochromic stability was optimized by introducing TzTz-type/OzOz-type group to the polymers. • Polymers were synthesized using fewer steps and cheap raw materials. • The introduction of fluorescent chromophore the fluorescence properties of the polymer and increased their potential purposes. [ABSTRACT FROM AUTHOR]

In this review, recent advances that exploit the intrinsic emission of organic materials for reversibly modulating their intensity with applied potential are surveyed. Key design strategies that have been adopted during the past five years for developing such electrofluorochromic materials are presented, focusing on molecular fluorophores that are coupled with redox-active moieties, intrinsically electroactive molecular fluorophores, and unconjugated emissive organic polymers. The structural effects, main challenges, and strides toward addressing the limitations of emerging fluorescent materials that are electrochemically responsive are surveyed, along with how these can be adapted for their use in electrofluorochromic devices.

Electrochemical switching of luminescence color, that is, electrofluorochromism, has received increasing attention because of its extensive applications. In this study, we investigate the combination of a luminescent EC molecule and a blue luminescent molecule to achieve electrochemical control of luminescence color by controlling the energy transfer through an electrochromic reaction. We employed a functional leuco dye (Yellow‐1), which shows yellow coloration and green emission by electrochemical oxidation, and 2,5‐bis(5‐tert‐butyl‐benzoxazol‐2‐yl)thiophene (BBT), which shows strong blue luminescence upon photoexcitation. Using this combination, the blue photoluminescence of the BBT molecule can be electrochemically modulated by the EC reaction of the Yellow‐1 molecule, allowing the control of the luminescence color between blue and green emissions through electrochemical reactions. [ABSTRACT FROM AUTHOR]

Covalent organic framework (COF) film with electrofluorochromic (EFC) and electrochromic (EC) properties has been synthesized by using triphenylamine-based monomers. The film exhibited a high maximum fluorescence contrast of 151 when subjected to a drive voltage of 0.75 V vs the Ag/AgCl electrode, causing the fluorescence to be quenched, which resulted in the EFC process's "fluorescence off" state. The switching times for the fluorescence on and off states were 0.51 and 7.79 s, respectively. Over the same voltage range, the COF film also displayed EC properties, achieving a contrast of 50.23% and a coloration efficiency of 297.4 cm 2 C -1 at 532 nm, with switching times of 18.6 s for coloration and 0.7 s for bleaching. Notably, the quenched fluorescence of the COF film could be restored by adding dopamine as a reductant. This phenomenon enabled the implementation of a NAND logic gate using the applied potential as a physical input and dopamine addition as a chemical input. This study demonstrates the successful development of COF films with bifunctional EFC and EC properties, showcasing their potential for use in constructing advanced optoelectronic devices.

There have been an increasing number of materials developed that show multifunctional chromogenic properties (such as electrochromism, electrofluorochromism, or photochromism), but to date, few materials have shown all three properties. Materials that are electrochemically and optically active are attractive for a diverse set of applications that include smart‐windows, lighting, sensing, energy production, and conservation. This is especially attractive for building developers interested in adaptive or environmentally responsive façades. Achieving systems made from cost‐effective, readily synthesized materials will make them easy to utilize in a variety of fields. Low‐cost devices are developed using water‐soluble, chromogenic thiazolo(5,4‐d)thiazole (TTz) dyes that show high device performance in three areas: electrochromism, electrofluorochromism, and photochromism and are all contained within a highly fluorescent aqueous polyvinyl alcohol/borax hydrogel device. The dyes incorporate a rigid, heterocyclic TTz structure that enables the development of devices with excellent reversibility and stable cycling for 250 cycles. The TTz hydrogel‐containing devices also exhibit photochromism under illumination, which can be electrochemically cycled back to the colorless state. In addition, coupling photochromism with electrochromism lowers the power necessary for a comparable electrochromic color change. Last, the hydrogel‐containing devices also show electrofluorochromism, where fluorescence can be turned off by > 90%. [ABSTRACT FROM AUTHOR]

A new and simple strategy towards electric‐field‐driven multiple chirality switching device has been designed and fabricated by combining a newly synthesized base‐responsive chiroptical polymer switch (R‐FLMA) and p‐benzoquinone (p‐BQ) via proton‐coupled electron transfer (PCET) mechanism. Clear and stable triple chirality states (silence, positive, negative) of this device in visible band can be regulated reversibly (>1000 cycles) by adjusting voltage programs. Furthermore, such chiral switching phenomena are also accompanied by apparent changes of color and fluorescence. More importantly, the potential application of this device for a spatial light modulator has also been demonstrated. [ABSTRACT FROM AUTHOR]

Responsive chromogenic materials have attracted increasing interest among researchers; however, up until now, few materials have exhibited multifunctional chromogenic properties. The coordination polymers (CPs) provide intriguing platforms to design and construct multifunctional materials. Here, a multifunctional photo/electricity responsive CP named Zn−Oxv, which is based on the “extended viologen” (ExV) ligand, was synthesized. The Zn−Oxv exhibited reversible photochromism, photomodulated fluorescence, electrochromism and electrofluorochromism. Furthermore, we prepared Zn−Oxv thin films and investigated electrochromic (EC) properties of viologen−based CPs for the first time. Zn−Oxv thin films showed excellent EC performance with a rapid switching speed (both coloring and bleaching time within 1 s), high coloration efficiency (102.9 cm2/C) and transmittance change (exceeding 40%). Notably, the Zn−Oxv is by far the fastest CP EC material based on redox−active ligands ever reported, indicating that the viologen−based CPs could open up a new field of materials for EC applications. Therefore, viologen−based CPs are attractive candidates for the design of novel multi−responsive chromogenic materials and EC materials that could promise creative applications in intelligent technology, dynamic displays and smart sensors.

The phenomenon of electrofluorochromism occurs whenever the fluorescence of a material can be reversibly modulated, both in terms of intensity and color change, through the application of an electrical stimulus. Electrofluorochromic (EFC) materials have gained a great interest in the last decade, since they offer access to the development of different optoelectronic devices. Great efforts have been made to achieve highly performing EFC materials either as small organic molecules or as polymers. A critical overview of the most recent materials progress development is presented here, trying to guide the reader toward the most remarkable advancements in this field in the last years. This synoptic frame is completed by the recognition of the weak progress done on the development of the related EFC devices, which cannot be achieved without the identification of the most interesting applications. Among the many issues that are still open, it is necessary to correctly define the performance metrics for a suitable characterization of EFC materials and devices. Indeed, most of the published data are not homogeneous and the lack of standardized procedures really hampers a performance comparison among the various systems. Thus, standardized procedures are desirable and would allow for an easier transfer of this technology. [ABSTRACT FROM AUTHOR]

Electrofluorochromic devices (EFCDs) that allow the modulation of the light emitted by electroactive fluorophores are very attractive in the research field of optoelectronics. Here, the electrofluorochromic behaviour of a series of squaraine dyes was studied for the first time. In solutions, all compounds are photoluminescent with maxima located in the range 665–690 nm, characterized by quantum yields ranging from 30% to 4.1%. Squaraines were incorporated in a polymer gel used as an active layer in all-in-one gel switchable EFCDs. An aggregation induced quenching occurs in the gel phase, causing a significant decrease in the emission quantum yield in the device. However, the squaraines containing the thieno groups (thienosquaraines, TSQs) show a panchromatic emission and their electrofluorochromism allows the tuning of the fluorescence intensity from 500 nm to the near infrared. Indeed, the application of a potential difference to the device induces a reversible quenching of their emission that is significantly higher and occurs at shorter switching times for TSQs-based devices compared to the reference squaraine dye (DIBSQ). Interestingly, the TSQs fluorescence spectral profile becomes more structured under voltage, and this could be explained by the shift of the aggregates/monomer equilibrium toward the monomeric species, due to electrochemical oxidation, which causes the disassembling of aggregates. This effect may be used to modulate the colour of the fluorescence light emitted by a device and paves the way for conceiving new electrofluorochromic materials based on this mechanism.

Highly substituted Δ3‐1,2,3‐triazolines can be prepared by reaction of triarylvinyl Grignard reagents with functionalized organic azides. The heterocycles are fluorescent in the solid state, and—depending on the substituents—they can display aggregation‐induced emission. Upon oxidation, the triazolines form stable radical cations with altered photophysical properties. Therefore, they represent rare examples of solid‐state emitters with intrinsic electrofluorochromic behavior. [ABSTRACT FROM AUTHOR]

Abstract A combined experiment of fluorescence and electrochemical microscopies was performed to highlight the possibility of using a unique water-soluble molecule as the redox mediator and fluorescence reporter. Resorufin was selected as it owns a highly luminescent redox state which can be easily converted into a non-emissive one by reduction at moderately negative potentials. In the feedback mode of Scanning Electrochemical Microscopy (SECM), it is shown that the fluorescence modulation amplitude is sensitive to the nature of the substrate as well as to the tip-substrate distance and can thus be utilized to record optical approach curves. Changing the polarization of the ITO substrate enables to move from positive to negative feedback and the fluorescence modulation amplitude is also sensitive to this change. Substrate generation-tip collection mode was also investigated showing that fluorescence intensity can be used to detect at the tip the species produced at the substrate with a higher accuracy than the electrochemical current. [ABSTRACT FROM AUTHOR]

Abstract We describe the synthesis of two new polymerizable monomers, and the subsequent polymers functionalized by tetrazine pendant groups, along with their electrochemical behaviour and fluorescence properties. In all cases a very stable conducting polymer is obtained, featuring both the redox activity of the main chain in oxidation and of the tetrazine functional group upon reduction. One of the polymers in addition exhibits an electrofluorochromic behaviour. Highlights • Elaboration of an electropolymerized conducting polymer from a functionalized TBT monomer for the first time • A new electroactive polymer with grafted tetrazines • First example of the modulation of a grafted fluorophore by the redox state of a conducting polymer [ABSTRACT FROM AUTHOR]

Graphical abstract This comprehensive review describes the recent development of triphenylamine-based advanced materials for various optoelectronic applications, such as electrochromic, electrofluorochromic, and polymeric memory devices. We herein systemically discuss the structural design, optical and electrical properties of different kinds of triphenylamine-containing high-performance polymers that will be beneficial for polymer chemists and scientific community to have deeper and broader understanding about the recent developments and further prompt the engineering and conceptual design of materials for a number of emerging applications (data storage, displays, and flexible electronics). Abstract This comprehensive review describes the recent development of triphenylamine-based advanced materials for various optoelectronic applications, such as electrochromic, electrofluorochromic, and polymeric memory devices. We herein systemically discuss the structural design, optical and electrical properties of different triphenylamine-containing high-performance polymers that will be beneficial for polymer chemists and scientific community to have deeper and broader understanding of the recent developments and further prompt the engineering and conceptual design of materials for a number of emerging applications (data storage, displays, and flexible electronics). Finally, perspectives on applications beyond the state-of-the-art are also included. [ABSTRACT FROM AUTHOR]

Dual functional electrochromic (EC)/electrofluorochromic (EFC) materials play a pivotal role in wearable and smart electronic equipments. Developing new materials with high performance of EC/EFC properties is still a big challenge. Here a new D-A structure polymer PPDOTTPD based on thieno(3,4-c)pyrrole-(4,6)dione (TPD) was synthesized by Stille coupling, and the EC/EFC properties were investigated for the first time. PPDOTTPD film exhibits reversible color changes from purple neutral state to transparent colored state in the process of reversible redox. Photophysical and electrochemical studies revealed that the polymer has outstanding EC properties, including high optical contrast (52%), fast response time (0.5 s/0.7 s), high coloring efficiency (427.1 cm2 C−1) and good stability. What's more, PPDOTTPD exhibited EFC phenomenon. PPDOTTPD film showed an intense red near-infrared fluorescence with a peak of 672 nm, which gradually doped with the increase of applied potential with a maximum contrast ratio of 12.9. The EC/EFC dual-functional device based on PPDOTTPD was also successfully fabricated, which exhibited high optical and fluorescence contrast. The fine dual-functional performance indicates TPD can be further explored as potential acceptors for synthesizing high performance D-A molecules for intelligent optical devices. [Display omitted] • A dual functional polymer based on thieno[3,4- c ]pyrrole-4,6-dione was synthesized. • It shows outstanding EC properties with reversible color from purple to transparent. • It shows EFC properties in the red-NIR region with high quenching efficiency. • Thieno[3,4-c]pyrrole-4,6-dione is explored as a new building block in the EC/EFC materials. [ABSTRACT FROM AUTHOR]

Graphical abstract Unlabelled Image Highlights • Design of an original ferrocene-appended rhodamine dyad • Redox switchable rhodamine-ferrocene dyad • Fluorescence is tuned from the redox state of ferrocene. • The fluorescence of the dyad was turned on in the presence of cancer cells. [ABSTRACT FROM AUTHOR]

Abstract Novel polythiophene derivatives containing trans -stilbene and fumaronitrile groups have been designed and synthesized. These polymers emit intense fluorescence in both solution and film states, attributing to the restriction of intramolecular rotation caused by multiple C—H···π bonds existed in the neighboring polymer backbones. Driven by different applied potentials, the polymer films show reversible electrochemical oxidation-reduction reactions with colors changing from yellow-green to sky-blue and red to rufous respectively, furthermore, electrofluorochromism between fluorescent state and non-fluorescent state happens synchronously. In addition, these polymers represent excellent thermal stability, good solubility and fast switching time, making them special candidates for electrochemical fluorescence and electrochromic applications. Graphical abstract Image 1 Highlights • The polymers achieve dual-state emission via introducing multiple C—H···π bonds. • The polymers can realize electrofluorochromism and electrochromism simultaneously. • The polymers represent excellent thermal stability, good solubility and fast switching time. [ABSTRACT FROM AUTHOR]

Three rhodamine derivatives exhibiting electrofluorochromic properties were investigated by cyclic voltammetry and UV–Vis/fluorescence spectroelectrochemistry. Rhodamine 101 (Rh101, compound 1 ) was used as a reference model. In compound 2 , the carboxylate anion of Rh101 was replaced by an alkyne moiety to allow further functionalization. The compound 3 was prepared from 2 by conversion of the alkyne to a triazole group bearing an alkyl chain with an alcohol function. These three rhodamine derivatives exhibited similar electrochemical behaviors. Their mono-electronic reductions produced the corresponding radical species which were stable on the time-scale of cyclic voltammetry. Additional reduction of electrogenerated radicals produced unstable anions which underwent subsequent chemical reaction, most likely protonation. Based on cyclic voltammetry investigations, absorption and fluorescence spectroelectrochemistry were then performed on compounds 1 , 2 , 3 and their parent reduced radicals 1a , 2a , 3a . UV–Vis spectroelectrochemistry, combined with TD-DFT calculation, confirmed the formation of radicals upon mono-electronic reduction of starting rhodamines. Fluorescence spectroelectrochemistry showed that, contrary to their parent molecules, electrogenerated radicals were non-fluorescent. Electrochemical fluorescence extinction was successfully achieved with all studied compounds. Moreover, compound 1 underwent on/off switching between fluorescent and non-fluorescent states repeatedly. Also, recovery of fluorescence in compound 3 was observed, which open interesting opportunities for the development of versatile rhodamine-based probes. [ABSTRACT FROM AUTHOR]

In this work, a series of AEE-active polyamides containing methylsulfonyltriphenylamine units were prepared from a newly synthesized diamine “4,4′-diamine-4″-methylsulfonyltriphenylamine” and three dicarboxylic acids, which were highly soluble in various organic solvents and exhibited outstanding thermostability. The resulting polymer films showed one reversible redox couple along with apparent color changing from colorless to purple. The polymer solutions revealed relatively weak fluorescence with quantum yields in the range of 2.2–26.2%, which could be enhanced by induced aggregation in poor solvents. Furthermore, the bright fluorescence of the solid polymer film could be reversibly tuned by direct electrochemical redox of triphenylamine with a high contrast ratio ( I off / I on ) of 234. Overall, this comprehensive investigation of their interesting electrochromic and electrofluorochromic bifunctional properties not only supplies a deep understanding of the optical essence upon electrical stimuli but also paves the way for their future intelligent applications. [ABSTRACT FROM AUTHOR]

The introduction of novel materials with multifunctional chromogenic properties, such as electrochromic/electrofluorochromic (EC/EFC) properties, has recently attracted prospective interest in the development of various optoelectronic devices and smart windows. In this study, a novel Zn(II)-based metallo-supramolecular polymer ( polyZn ) has been developed as an ON/OFF switchable EFC application with prominent EC behavior. In this regard, the polymeric chain of polyZn was first synthesized by 1:1 complexation in a zigzag manner with Zn(II) ions at the metal center and 4,4'-[bis(2,2':6',2″-terpyridinyl)benzene]triphenylamine ( L TPY-TPA ) as the redox-active ditopic ligand. The polyZn exhibits excellent solubility in organic solvents and can form a very good uniform thin film on an indium tin oxide/glass substrate by spin-coating. In a neutral state, transparent polyZn exhibits a bright yellow color to the naked eye (absorption at ∼325 nm). The electroactive triphenylamine (TPA) core of L TPA-TPY , however, undergoes reversible single-electron oxidation when a positive bias of +1.6 V vs Ag/Ag + is applied, generating radical cations (TPA ↔ TPA •+ ) with a significant drop in transparency (77%). A noticeable chromic shift in the hue of the film from brilliant yellow to green was observed with the appearance of a near-infrared absorption band at ∼897 nm with a tail of 1300-1600 nm. Interestingly, in addition to this EC phenomenon, the fabricated solid-state polyZn film exhibits intense, high-contrast reddish-orange photoluminescence with λ em = 650 nm, which is significantly desired as a molecular probe for bioimaging. Both the TPA core and the redox-inactive Zn(II)-terpyridine core emit orange-red photoluminescence in polyZn , which is significantly quenched upon the oxidation of the film and is re-emitted at 0.0 V vs Ag/Ag + . This ON/OFF EFC transition was sustained for several cycles. This study should motivate to design and create distinctive new unique materials with combined EC/EFC behavior for the fabrication of optoelectronic devices by combining a metal-fluorescent core with a redox-active spacer.

The synthesis and full characterization of a family of stable λ 5 -biphosphinines connected in 4,4-position through a variety of π-conjugated bridges is reported. The impact of the π-bridge on the optical (absorption/emission) and redox properties was investigated using a joint experimental/theoretical approach. In contrast to the π-extended ones, the λ 5 -biphosphinines directly connected through a C-C bond in 4,4-position display two easily accessible and reversible oxidations highlighting their multi-stage redox character. The in situ formed radical cations are studied by spectro-electrochemistry and electron paramagnetic resonance. Finally, electrochemical modulation of fluorescence (electrofluorochromism) was performed and revealed the potential of these intrinsically switchable electroactive fluorophores for further applications as switchable materials., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

[Display omitted] • Electrofluorochromic materials are improved ICT characteristics by the structure modification. • Electrofluorochromic materials have good thermal stability. • Electrofluorochromic devices achieve blue-to-yellow fluorescence conversion. • Electrofluorochromic devices achieve color change at low voltages, down to 0.6 V. Five donor–acceptor (D-A) small organic molecule compounds were designed and synthesized by using triphenylamine (TPA) as the donor and imidazole as the acceptor. Through introducing different substituent groups at the para position of TPA, the excited state characteristics were adjusted, and a reversible and stable color change was obtained. These compounds exhibited good thermal properties. All five compounds were evaluated as small organic molecule materials for electrofluorochromism (EFC) and achieved luminescence conversion from blue to yellow at low voltages, and the compound 4e realized electroluminescence conversion at only 0.6 V due to the introduction of –OCH 3. The stability of the EFC devices was demonstrated by the CV curves for 400 cycles. The color-changing voltages of EFC can be effectively reduced by adjusting the characteristics of ICT. This rational structural design of small organic molecules provides a new design strategy for the preparation of EFC materials. [ABSTRACT FROM AUTHOR]

π-Extended viologen derivatives of SHP , THP and FHP with selenophene, thiophene and furan units between two pyridine moieties, respectively, as chromophores, were synthesized. Compared with conventional viologen of DHP using bipyridines as the chromophore, the three compounds of SHP , THP , and FHP possess extended conjugation lengths and narrowed bandgaps. All-in-one electrochromic devices (ECDs) were assembled using these four viologen derivatives and investigated systematically. Due to the different electronic properties of the chromophores, the devices exhibited different colored states, blue, blue-violet, magenta and red. Furthermore, the electrochromic response of SHP , THP , and FHP extended into near-infrared (NIR) region due to the long conjugation as compared with that of DHP. Further, the ECDs possessing SHP , THP and FHP displayed faster response speed and relatively higher coloration efficiency than that of DHP. Among them, ECD based on FHP has shown the most excellent stability, which retains 95.7% optical contrast of its initial state after continuous working for 20000 cycles. Additionally, upon applying a switching potential, electrofluorochromic (EFC) properties of the devices based on THP and FHP were observed. This study revealed structure-property relations and demonstrated that manipulation of chromophores offers an effective route to obtain multicolor and multifunctional ECDs, which provides potential applications for colorful displays and smart windows. [Display omitted] •π-extended viologen derivatives containing selenophene, thiophene, and furan units were synthesized. •Four ECDs showed different colored states, including blue, blue-violet, magenta and red. • ECD-O retains 95.2% of its initial optical contrast up to 20000 switching cycles. • ECD-S and ECD-O exhibited dual functions of electrochromism and electrofluorescence. [ABSTRACT FROM AUTHOR]

Electrofluorochromic molecules share the unique property that their fluorescence changes as a function of their oxidation state. This makes them interesting from a fundamental perspective as molecular dyads are designed and synthesized to tune the interplay of electrochemical and luminescent properties of molecules. Electrofluorochromic systems also find applications in sensing because a fluorescent signal can be detected with high sensitivity. Moreover, in the recent years the interest in redox-switchable fluorescent polymers has strongly increased due to their applicability in display devices. Here, we review electrofluorochromic molecules and polymers; we emphasize their structures and functional principles and point to specific applications. [ABSTRACT FROM AUTHOR]

Modulation of luminescent color or intensity by varying external stimuli, such as temperature, light, ion concentration, etc., has received increasing attention recently because of numerous applications such as sensors, bioanalysis, optical imaging and memories. For instance, electrically induced luminescent switching - electroluminochromism (ELC) - is one of the most powerful and promising approaches to implement controllable emission due to its facile and precise operation. Recent years have witnessed significant advances in ELC research in the context of materials development and device optimizations. This feature article reviews the fundamentals and recent progress in this emerging field, focusing on working mechanisms, materials, devices and performance improvements. Perspectives for future ELCs are also outlined. [ABSTRACT FROM AUTHOR]

The terpyridine Eu(III) complex with an alkyl-substituted phenyl-capped aniline dimer shows ternary electrofluorochromic behavior under different potentials. [Display omitted] • Terpyridine Eu(III) complexes with multiple redox states. • The resulted complex displays an unique electrofluorochromic behavior. • With ternary conversion among orange, dark-blue and pale-yellow colors. • And red, deep-blue and greenish-blue PL emissions. Three new terpyridine Eu(III) complexes, [(L 1-3)Eu(HFA) 3 ] (where L 1 = 4′-phenyl-2,2′:6′,2″-terpyridine, L 2 = 4′-{[ p -(N-butyl-N-phenyl)amino]-phenyl}-2,2′:6′,2″-terpyridine}, L 3 = 4′-{ p -[ p -(N,N′-dibutyl-N′-phenyl)-phenyldiamino]-phenyl}-2,2′:6′,2″-terpyridine, and HFA = hexafluoroacetylacetone), have been successfully synthesized and characterized by UV–vis absorption spectrum, FTIR, MALDI-TOF MS and elemental analysis. The X-ray crystallography of complex [(L 2)Eu(HFA) 3 ] shows that the europium(III) ion is nine-coordinated with N3O6 donors in normal ranges. Owing to the antenna effect, complex [(L 1)Eu(HFA) 3 ] (Ф = 0.44) possesses ca. 3 times enhancement of the metal-centered red emission intensity compared to that of precursor Eu(HFA) 3 (Ф = 0.16). The most interesting is that complex [(L 3)Eu(HFA) 3 ] displays an unique electrofluorochromic behavior with the ternary absorption (orange/dark-blue/pale-yellow) and PL emission (red/deep-blue/greenish-blue) conversions, in which the ICT, cation radicals-related and Eu(III)-centered electronic transitions are involved. [ABSTRACT FROM AUTHOR]

A highly fluorescent electrofluorochromic gel with quantum yields as high as 67% is prepared by incorporating the thienoviologen fluorophore 4,4′-(2,2′-bithiophene-5,5′-diyl) bis(1-nonylpridinium)bistriflimide into a polymeric matrix. The fluorescent emission spectrum of the gel at low percentages of thienoviologen shows a strong band at 530 nm. A new intense fluorescence band at 630 nm can be induced by fluorophore aggregation. Single layer electrofluorochromic devices were readily prepared by sandwiching the polymer gels between two indium tin oxide (ITO) electrodes. The fluorescence intensity can be easily modulated between a fluorescent and a quenched state, in a wide visible spectral range, by direct electrochemical reduction of the thienoviologen fluorophore. It exhibits three reduction states, each with different emission properties. The reversible interconversion among these states leads to a high electrofluorochromic stability of the device, exhibiting switching times of a few seconds and, to the best of our knowledge, the highest contrast ratio (337). [ABSTRACT FROM AUTHOR]

The synthesis, photophysical and electrochemical properties as well as theoretical calculation studies of a newly designed triphenylamine derivative are described. This original compound displays one neutral form, three oxidized forms, and two protonated forms with distinct photophysical characteristics. The interplay of the emission with the protonation or the redox state (electrofluorochromism) has been explored and an on-off-on-off fluorescence switching was observed in the case of oxidation and an on-on-off fluorescence switching in the case of protonation. [ABSTRACT FROM AUTHOR]

• Highly luminescent polymers were obtained by introducing a typical aggregation-induced emission (AIE) side group triphenylacrylonitrile with polyaniline backbones. • The polymers demonstrate highly-performed integrated electrochromic and electrofluorochromic properties. • The polymers exhibit fast switching speed, large fluorescent on/off contrast, and high cycle stability. • Reasonable control of polymer energy band gap along with AIE-featured geometry leads to both satisfactory electrochemical activity and luminescent capacity. Recent years have witnessed rapid developments in electrochromic/ electrofluorochromic (EC/EFC) materials. Though highly efficient ECs have been realized in a lot of systems, the synchronous EFC performance is still severely limited by the low luminescent efficiency (Φ f) and slow response. In this work, we designed and synthesized conjugated polymers PDTEC and PTEC, which are composed of polyaniline-like main chains and triphenylacrylonitrile (TPAN) side chains. Both polymers exhibit remarkable color changes between yellow, orange and blue, and fluorescent on/off switchings upon applied potentials. Notably, especially high Φ f (44.2%), fluorescent contrast (I on/off =4339) and fast response (0.18s) are simultaneously accomplished, which is rarely found in EFC materials due to the difficulty in balancing both electrochemical activity and luminescent capacity in polymers. Such fascinating comprehensive EC/EFC performance will render these polymers promising candidates for versatile applications in smart optical devices and biosensors. [Display omitted] [ABSTRACT FROM AUTHOR]

A novel electrochromism (EC) and photoluminescence (PL)-active poly(4-cyanotriphenylamine) ( CN-PTPA) is prepared by oxidative coupling polymerization from 4-cyanotriphenylamine (CN-TPA) using FeCl3 as an oxidant. The high-performance electrofluorochromic (EFC) devices using CN-PTPA thin film with photoluminescent quantum yield of 21.9% as active layer are readily fabricated and reveal the highest fluorescent contrast ratio ( Ioff/ Ion) of 242 between the fluorescent (neutral) state and the non-fluorescent (oxidized) state, rapid response time shorter than 0.4 s, and excellent EFC stability longer than 9000 s. Furthermore, by introducing viologen into electrolyte as a counter EC layer for charge balance, the resulting EFC device exhibits notable improvement in reducing oxidation potential (from 2.30 V to 1.55 V) and switching recovery time (from 78 to 38 s) with enhanced fluorescent contrast ratio during pulse on/off multi-cyclic scanning. These results demonstrate that incorporation of the EC and PL-active CN-PTPA is a facile and feasible approach to prepare highly efficient EFC devices. [ABSTRACT FROM AUTHOR]