Luminescence Color Change Research Articles

1D supramolecular assembly-induced emission and colorimetry toward precise onsite mercury(II) detection

Manipulation of the one-dimensional (1D) supramolecular assembly of platinum(II) terpyridyl complex is promising for achieving precise onsite mercury(II) detection in complex environments, but still challenging. Herein, by systematic molecular design of platinum(II) terpyridyl complex, chloride-mediated 1D supramolecular assembly has been successfully achieved, exhibiting not only improved recognition ability but also dual-visual signal, with turn-on red luminescence and high-contrast color change from pale-yellow to orange-red. The probe also shows excellent selectivity and anti-interference properties, fast response rate (< 1 s) and low detection limit, stretching to 20.6 fg when incorporated in a hydrogel matrix. Structure insight for the dual-visual response shows that this high detection performance derives from the ancillary ligand of -NCS, which endows the increase of ion-association ability between platinum(II) terpyridyl complex and [HgCl4]2−, leading that 1D packing mode with strengthened Pt-Pt interactions. In all, this work highlights a new strategy of 1D supramolecular assembly construction for high performance detection of heavy metal ions.

Enhancing Optical Properties of Zn-Mn Solid Solution Hybrid Halides for Wide Color Gamut Backlight Displays.

Hybrid metal halides display a range of optical properties and hold promise for various applications such as solid-state lighting, anti-counterfeiting measures, backlight displays, and X-ray detection. The incorporation of zinc into (C13H26N)2MnBr4 aims to enhance its structural rigidity and improve its narrow band green light emission properties. The resulting (C13H26N)2ZnBr4 compound exhibits an identical crystal structure to (C13H26N)2MnBr4, indicating the potential for a solid solution of varying Zn and Mn ratios within this structural framework. (C13H26N)2Zn0.2Mn0.8Br4 exhibits significantly enhanced properties, including a photoluminescence quantum yield of 92%, a minimum full width at half maximum of 43nm, and 85% retention of room temperature emission at 420K. Additionally, crystals of (C13H26N)2ZnCl4 and (C7H18N)2ZnX4 (X = Br, I) are synthesized, with (C7H18N)2ZnBr4 displaying luminescent color changes dependent on excitation. (C7H18N)2Zn0.2Mn0.8Br4 demonstrates reversible phase transitions and alterations in optical properties. A white light-emitting diode utilizing (C13H26N)2Zn0.2Mn0.8Br4 and commercial phosphors exhibited a color gamut of 112.2% of the National Television Standards Committee 1931 Standard. This investigation introduces a stable and highly efficient narrow-band green phosphor suitable for displays.

Multiple Stimulus Response Material Based on Sr-tcbpe MOF for Mechanochromism, Visualization Labeling, and Etching Toward TNP.

The abuse and excessive discharge of organic pollutants such as nitroaromatic compounds (NACs) have become a hot topic of concern for all humanity and society, and the development of fast, effective, and targeted technical means for detecting NACs also faces many challenges. Here, we reported a strontium-based metal-organic framework (MOF) {[Sr2(tcbpe)(H2O)4]}n (Sr-tcbpe), in which tcbpe represents deprotonated 4',4‴,4″‴,4‴‴-(ethene-1,1,2,2-tetrayl)tetrakis(([1,1'biphenyl]-4-carboxylic acid)). In Sr-tcbpe, Sr-O polyhedron and deprotonated tcbpe4- ligand have a staggered connection to form a self-assembled three-dimensional network structure. In addition, it is found that Sr-tcbpe undergoes no luminescent color change when grinding under solvent protection, while mechanochromic fluorescence behavior is observed when grinding directly, leading to luminescent color changes from cyan to green (Sr-tcbpe-G). Additionally, Sr-tcbpe and Sr-tcbpe-G could selectively detect PNP, DNP, and TNP, and Sr-tcbpe achieves visual fluorescence sensing detection toward TNP at a limit of detection as low as 2.25 μM. Moreover, during the detection process, unexpectedly, TNP exhibits a selective etching effect on Sr-tcbpe, which could drill nano holes with different sizes on the surface area of MOF materials to a certain extent, achieving the conversion of chemical energy to mechanical energy. In addition, the successful preparation of a portable sensor Sr-tcbpe@gypsum block provides a platform for the perfect combination of mechanochromic fluorescence behavior and visualization detection toward TNP. It lays the foundation for the practical application of MOF materials in daily life.

Multimodal anti-counterfeiting and optical storage application based on luminescence reversible modification and color change of photochromic phosphor

Reversible upconversion luminescence (RUCL) modification based on photochromism has received considerable interest due to its potential applications in optical storage and invisible optical anti-counterfeiting. Herein, white β-Ba2ScAlO5: Yb3+, Er3+ (β-BSAO-YE) phosphor was irradiated with 254 nm light, which caused the phosphor to turn blue due to the increase of oxygen vacancy. The blue β-BSAO-YE phosphor returns to its original color upon stimulation with 808 nm laser light or 125 °C, exhibiting a double photo-induced reversible photochromic change. The green and red upconversion luminescence (UCL) of the β-BSAO-YE were reversibly modified according to their photochromic properties. The UCL modification changes the luminescence color of the pattern, indicating that β-BSAO-YE phosphor is an ideal compound anti-counterfeit agent. The light information recorded on the β-BSAO-YE binary photochromic dot matrix can be read under ultraviolet (UV) and near-infrared (NIR) excitation, demonstrating the potential application of β-BSAO-YE phosphors as optical data storage media. In addition, the cyclic experiment showed good photochromic and UCL modulation repeatability. The new luminescent β-BSAO-YE not only proposes a new way to exploring upconversion red light materials, but also provides new materials for optical storage, optical information and optical anti-counterfeiting.

Organic Mechanochromic Luminescent Materials with Self-Recovering Characters.

Recently, applied research on stimuli-responsive materials with luminescence-switching characteristics has been conducted in various fields. A representative phenomenon of stimuli-responsive luminescent materials is mechanochromic luminescence (MCL), which exhibits luminescent color change induced by mechanical stimuli such as grinding. These materials are among the most prominent candidates for security and sensing applications. Interestingly, some mechanochromic luminescent materials have shown self-recovery character, in which their original luminescent color can be recovered by just standing under ambient conditions after grinding. Although there are more and more reports of such materials in recent years, the fundamental principles of molecular design still remain elusive. In this concept, we summarize distinctive advances in mechanochromic luminescent materials with self-recovery according to the core structures of luminescent molecules. Controlling amorphous state by introducing substituents such as alkyl or polar groups is effective method to provide self-recovering properties.

Up-conversion luminescence and thermal sensing properties of LuYO3: Er3+/Yb3+ phosphor

A series of LuYO3: Er3+/Yb3+ phosphors with different Yb3+ concentrations were prepared through a melting zone method with CO2 laser. The samples emit bright up-conversion luminescence (UCL) under a 980 nm laser. The UCL intensity and the luminescence color change significantly when Yb3+ concentration changes. Besides, when doped with 3 mol% Yb3+, the UCL intensity is maximal. The thermal sensing properties of LuYO3: Er3+(0.5 mol%)/Yb3+(3 mol%) were studied using the fluorescence intensity ratio (FIR) method from 298 K to 848 K. The maximum absolute and relative sensitivities are 0.0050 K−1 at 366 K and 0.0167 K−1 at 298 K, respectively. Thus, the LuYO3: Er3+(0.5 mol%)/Yb3+(3 mol%) fluorescent material is very suitable for thermal sensing because of the wide temperature range and the high sensitivity.

Ratiometric visualization fluorescence temperature sensing based on dual-lanthanide metal-organic frameworks

High-performance optical temperature sensors play an important role in various fields, and lanthanide metal-organic frameworks (Ln-MOFs) are expected to be luminescent temperature sensors due to their distinctive luminescent properties. Herein, a new three-dimensional (3D) Ln-MOF [Tb(TCA)(Phen)]·DEF (1) (H3TCA = 4,4′,4′'-nitrilotribenzoic acid, Phen = 1,10-phenanthroline, DEF= N, N-diethylformamide) is constructed with a rtl topology based on {Tb2(COO)4} secondary building units (SBUs). Meanwhile, dual-lanthanide Ln-MOFs [TbxEu1-x(TCA)(Phen)]·DEF (2-6) are also synthesized by varying the ratio of Tb3+: Eu3+ in the reaction mixture, which can be applied in practical LED applications originating from their visual luminescent color changes. Among them, 4 is an efficient ratiometric fluorescent thermometer over a wide temperature range from 283 to 393 K and has a large relative sensitivity Sr of 4.2407 % K−1 at 393 K with good repeatability. Furthermore, the emission color of 4 gradually changes from yellow (283 K) to orange-red (393 K) as temperature increases for visual colorimetric temperature measurements, which attributed to the energy transfer between Tb3+ and Eu3+ ions.

Utilizing a water-stable terbium (III) metal-organic framework for luminescent sensing of nitroimidazole antibiotics

A new 3D terbium (III)-based metal–organic framework, [Tb(TDC)(µ2-CH3COO)(H2O)] (Tb-MOF, H2TDC = 2,5-thiophenedicar-boxylic acid), was obtained with Tb3+ ions as metal source and TDC ligands as the auxiliary ligand through self-assemble mode. The Tb-MOF features a 3D network constructed by bridging a 2D wave-like network connected by TDC ligands with monodentate coordination mode, which results in the formation of a 3D net framework. The luminescent properties and sensing antibiotics experiments were extensively investigated for the Tb-MOF. Remarkably, the Tb-MOF exhibits a substantial quantum yield (QY) at 55.0 % and an average photoluminescence lifetime of 534 µs. Furthermore, the Tb-MOF shows selective luminescence quenching for nitroimidazole antibiotics, including metronidazole (MDZ), dimetridazole (DTZ), and ornidazole (ODZ), with a particularly strong response for MDZ (Ksv = 5.49 × 104 M−1, LOD value is 7.9 × 10−5 M). Finally, the Tb-MOF enables a simple and convenient test paper that allows luminescent color changes to be observed with the naked eye for detecting MDZ.

Multidimension‐Regulated Dynamic Timing Control Over Multicolor Emission of Host–Guest Assemblies for Information Encryption and Advanced Anti‐Counterfeiting

AbstractDynamical control over molecular luminescence, especially in a time‐dependent manner, holds great promise for the development of smart luminescent materials for anti‐counterfeiting and preventing information leakage. Herein, a series of self‐assembled systems are reported using pillar[5]arene (DMP[5]) and spiropyran derivatives (SP‐C4‐Py). The assemblies rely on the time‐encoded locking and unlocking ring‐switching and fluorescence resonance energy transfer (FRET) units for information camouflage and multilevel encryption. DMP[5] with cyan solid fluorescence color acts as the host and energy transfer (EnT) donor, while photochromic SP‐C4‐Py with the ring‐opened and closed isomers acts as guest and EnT acceptor. When irradiated, the assemblies undergo a time‐dependent luminescence color change ranging from cyan to yellow to red through a FRET process. The molar ratio of host and guest in the assembly systems affects the FRET efficiency, and the power of the irradiation source influences the isomerization degree and rate of SP‐C4‐Py, allowing for precise control over the fluorescent color transition time. The combination of molecular composition and external stimuli governs the kinetics of color change, resulting in a difference in the appearance time of a specific fluorescent color pre‐designed as correct authorized information. By combining these diverse assembles in one label, information encryption and dynamic information identification are achieved in the dimensions of time, ratio, and light power. This time‐dependent feature offers the assembly materials with a multilevel security and provides new possibilities for anti‐counterfeiting and blocking information leakage.

Hybrid MPA-CdSe quantum dots-based luminescent hydrogel: White light emission regulation and Cu2+ recognition

In this study, a novel CdSe@PEI-PVP luminescent hydrogel was constructed by using MPA-CdSe quantum dots (QDs) as a single emitter and hydrogen bond cross-linking network between highly branched polyethyleneimine (PEI) and polyvinylpyrrolidone (PVP) as a hydrogel skeleton, in which PEI also works as a passivation ligand for MPA-CdSe quantum dots. Utilizing the dual emission of MPA-CdSe quantum dots and adjusting the surface state of MPA-CdSe with PEI and Cd2+, CdSe@PEI-PVP hydrogel can emit bright white light as a whole. Furthermore, CdSe@PEI-PVP shows specific recognition for Cu2+, luminescent color changes from bright white to orange when Cu2+ is added, which enables CdSe@PEI-PVP hydrogel to serve as a fluorescent probe for ion detection. The luminescent hydrogel has great self-healing ability and reversible morphological thermal responsiveness, existing as a white luminescent hydrogel at room temperatures and transforming into a pale green luminescent solution at high temperatures.

A mitochondria-targeted phosphorescent probe for sequentially detecting Cu2+ and cysteine and its imaging in living cells and in vivo

This study reported a unique mitochondria-targetable phosphorescent 'on-off-on' probe, Ir-DPA, based on an iridium(III) complex derivative for the sequential and specific detection of Cu2+ and Cys in vitro and in vivo. Probe Ir-DPA was constructed by a lipophilic cation unit as the chromophore as well as the mitochondria biomarker and a dipicolylamine (DPA) group as the recognition unit for Cu2+, followed by removal of Cu2+ specifically in the presence of Cys. The probe itself was strongly emissive at 570 nm. Upon addition of Cu2+, marked quenching occurred as result of the binding of Cu2+ with DPA moiety of this probe, accompanied by a distinct naked-eye luminescence color change from orange yellow to colorless. Additionally, further addition of Cys, the displacement of Cu2+ from in situ generated Ir-DPA-Cu ensemble because of the large nucleophilicity of cysteine toward Cu2+ led to the release of probe, giving rise to the luminescence recovery, as well as a relevant chromogenic change from colorless to orange yellow. Ir-DPA showed a large Stokes shift of 200 nm and high selectivity and sensitivity for the rapid detection of Cu2+ and Cys under physiological conditions, with low detection limits of 0.04 μM and 1.21 μM for Cu2+ and Cys, respectively. More importantly, the probe successfully targeted mitochondria, sensitively detected Cu2+ and exogenously or endogenously generated Cys both in mitochondria of living cells and zebrafish. Finally, Ir-DPA was capable of quantifying Cu2+ level in water samples and the in situ generated ensemble identifying Cys in human serum. These results indicated the great potential of Ir-DPA for monitoring Cu2+ and Cys in environmental, biological systems, and mitochondrial processes.

Designing multi-mode optical thermometers via Sb3+/Er3+ co-doped Cs2NaInCl6 lead-free double perovskite microcrystals

Contactless optical thermometers are widely studied in scientific research and technology because of their apparent advantages. The combination of multi-mode thermometric techniques can realize self-referenced temperature sensing, making temperature monitoring signals more accurate. Herein, a series of Cs2NaInCl6: Sb3+, Er3+ microcrystals (MCs) were prepared via the ligand-assisted reprecipitation method. Under 320 nm excitation, the energy transfer from the self-trapped excitons (STEs) to Er3+ is established, which leads to the blue emission of STEs and intrinsic emissions of Er3+. Additionally, the MCs can also produce up-conversion green emissions under the excitation of NIR laser. Based on this, a multi-mode thermometer is developed, including the luminescence intensity ratio of two thermally coupled levels of Er3+ (2H11/2/4S3/2), the luminescence intensity ratio of a non-thermally coupled system of STEs and Er3+(4S3/2), and fluorescence lifetime of Er3+(4S3/2). Moreover, the MCs exhibit thermochromic properties, the luminescent color changes from blue to green as the temperature increases. To monitor the temperature more objectively by color variation, a novel sensing mode is constructed via the relationship between chromatic coordinates and temperature. The favorable thermometry performances for four-mode temperature sensing reveal that Cs2NaInCl6: Sb3+/Er3+ MCs are good candidates for thermometric materials for the novel multi-mode design.

Stimuli-Responsive π-Conjugated Polymers Showing Solid-State Emission Based on Boron-Fused Azomethine Complexes with NNO-Tridentate Ligands.

We report stimuli-responsive luminescent π-conjugated polymers involving the boron-fused azomethine (BAm) structure with the NNO-tridentate ligands and demonstrate their application to film-type sensors. The acid-responsive properties of the polymers are provided by the free lone-pair electrons of the nitrogen atom on the BAm unit. The polymer films showed red shifts in emission wavelengths under acid vapor, and the responses were reversible and corresponded to deprotonation. Furthermore, owing to environmental sensitivity in the film state, unique luminescent color changes were observed. The bilayer films of the BAm polymer coated by poly(n-butyl methacrylate) exhibited vapochromic luminescence with gradual blue shifts (orange → yellow → green) by vapor annealing with chloroform depending on the exposure time. We demonstrated that these changes were applicable for evaluating solvent-vapor permeability of target membranes. This study shows that nitrogen substitution into existing organic compounds is effective for creating stimuli-responsive materials.

Three-Dimensional Viologen-Based Lanthanide-Organic Frameworks: Photochromism and Fluorescence Detection of Quinolone Antibiotics.

Quinolone antibiotic residues, norfloxacin (NORF) and ciprofloxacin (CIP), have attracted more attention due to their frequent detection in surface water and food field, which seriously threaten the health of animals and humans. Rapid and efficient detection of NORF and CIP is critical for environmental testing and ecosystems. Herein, two novel isostructural viologen-functionalized Ln(III) complexes [Ln2L0.5(IPA)3]n (Ln = Eu, 1; Tb, 2; L = N,N'-bis (2-carboxyethyl)-4,4'-bipyridridylium dichloride, H2IPA = isophthalic acid) with a three-dimensional structure have been synthesized solvothermally. Complexes 1 and 2 exhibited reversible photochromism under UV light. In addition, complex 1 exhibits excellent pH tolerance and can be seen as an efficient fluorescent probe for the detection of NORF and CIP with detection limits of 7.90 × 10-7 and 9.48 × 10-7 M, respectively. Furthermore, the good photoresponsive and outstanding fluorescent properties of 1 were further exploited in dual-function paper involving erasable inkless printing and detection of NORF and CIP. Our work reports a new strategy for recognizing NORF and CIP based on the luminescent color change of the viologen-based Ln-MOFs, providing a new direction for the development of multifunctional materials.

Tb-MOF-based luminescent recovery probe for rapid and facile detection of an anthrax biomarker

Rapidly detecting 2, 6-dipicolinic acid (DPA, an anthrax biomarker) in a highly sensitive manner is vital due to DPA being highly lethal to human beings and animals. However, most reported DPA probes are ‘‘turn-on’ type, while luminescent recovery probes (LRPs) are still rare. Herein, a unique Tb-MOF (1) LRP was tailor-made, and its function is achieved via an energy transfer regulation strategy. In 1, the characteristic luminescence from Tb3+ is not sensitized due to the lack of energy transfer from the carefully chosen ligand that also induces steric effects to allow solvent molecules to be coordinated to Tb3+. During detection, DPA replaces the solvent molecules and thus effectively sensitizes the emission from Tb3+, achieving recovery response. 1 exhibits highly selective sensing of DPA down to 1.7 μM, and displays an obvious luminescence color change visible to naked eyes. Furthermore, a regular smartphone platform installed with a Color Recognizer App can achieve sensitive, real-time, and on-site detection of DPA. The probe can also be used for the effective detection of DPA in tap water, rainwater, and human serum. The work not only provides a route to the preparation of recovery probes but also proves the potential of such probes.

Characteristic vapochromic detection of platinum(II) 3,8-bis-(2-triisopropylsilylethynyl)-phenanthroline organometallic complexes with bis-arylethynyl derivatives

The vapochromism of square-planar platinum(II) complexes has been widely studied because of its potential as a useful chemical sensor of harmful volatile organic compounds (VOCs). We synthesized six platinum(II) organometallic complexes with 3,8-bis-(triisopropylsilyl)ethynyl-1,10-phenanthroline (PhenTIPS) and six respective arylethynyl ligands with different substituents (Pt(PhenTIPS)(-Ph-R)2: R = 4-Me (1TIPS), 4-CF3 (2TIPS), 4-t-Bu (3TIPS), 3,5-di-Me (4TIPS), 3,5-di-CF3 (5TIPS), 3,5-di-t-Bu (6TIPS)), as well as two complexes with 3,8-bis-(trimethylsilyl)ethynyl-1,10-phenanthroline (PhenTMS) and 3,8-bis-(triethylsilyl)ethynyl-1,10-phenanthroline (PhenTES) including a 3,5-dimethyl-phenylethynyl ligand: Pt(PhenTMS)(-Ph-3,5-di-Me)2 (4TMS) and Pt(PhenTES)(-Ph-3,5-di-Me)2 (4TES). These complexes were characterized by their luminescence in solution and in the solid state by photoluminescence spectroscopy and showed the phosphorescence from the mixed transition of triplet metal-to-ligand charge transfer (3MLCT)/triplet ligand-to-ligand charge transfer (3LLCT) or the transition of a triplet metal-metal-to-ligand charge transfer (3MMLCT) including the Pt-Pt interaction in the solid state. In vapoluminescence experiments, we found that three complexes (3TIPS, 4TIPS, and 4TMS) in the solid state showed unique luminescent color changes against the vapors of specific VOCs. Also, in vapoluminescence experiments, the solid-state photoluminescence spectra of 3TIPS and 4TMS showed a blue shift in phosphorescence from the 3MMLCT transition to the 3MLCT/3LLCT mixed transition against the vapors of specific VOCs. The vapoluminescence experiment with 4TIPS against 13 species of VOCs showed only the characteristic selective detection against CHCl3 with a bright green emission.

Color-Tunable Upconversion-Emission Switch Based on Cocrystal-to-Cocrystal Transformation.

Cocrystal engineering, involving the assembly of two or more components into a highly ordered solid-state superstructure, has emerged as a popular strategy for tuning the photophysical properties of crystalline materials. The reversible co-assembly and disassembly of multicomponent cocrystals and their reciprocal transformation in the solid state remain challenging objectives. Herein, we report a color-tunable upconversion-emission switch based on the interconversion between two cocrystals. One red- and one yellow-emissive cocrystal, composed of an electron-deficient naphthalenediimide-based triangular macrocycle and different electron donors, have been obtained. The red- and yellow-emissive cocrystals undergo reversible transformations on exchanging the electron donors. Benefiting from intermolecular charge transfer interactions, the two cocrystals display superior two-photon excited upconversion emission. Accompanying the interconversion of the two cocrystals, their luminescent color changes between red and yellow, forming a dual-color upconversion-emission switch. This research provides a rare yet critical example involving precise control of cocrystal-to-cocrystal transformation and affords a reference for fabricating color-tunable nonlinear optical materials in the solid state.

Time-resolved encryption via photochromic and mechanochromic system based on silane-substituted spiropyran

With the continuous progress of forgery and decryption, the traditional static encryption technology is becoming more and more inadequate, which also strongly demands the development of multilevel anti-counterfeiting materials and advanced multi-dimensional encryption strategies and technologies. Here a new strategy to realize time-resolved encryption based on a silane-substituted spiropyran is presented, which exhibits tunable dynamic photochromic features caused by the reversible photochromic and mechanochromic properties with exceptional reversible absorption/luminescence modulation ability both in powder and crystal state. This compound shows excellent photochromic properties, including extremely rapid response time, high contrast color change, high reversibility etc. In addition, the growth of large-size needle-like single crystal by solution evaporation is helpful to further explore the mechanism of grinding discoloration of the compound. What's more, it is possible to modulate the luminescence emission and color change by simply changing the ultraviolet light stimulation time or grinding time, providing fine and adjustable time-related characteristics for the material, which can not only be used for data processing with more extended information, but also be used to construct confidential materials by time-resolved multidimensional encryption and dynamic anti-counterfeiting.

A dual-emission Eu(Ⅲ) functionalized multi-ligand MOFs for wide range pH sensing

Reliable sensing of pH is very important in daily life. Herein, we construct a luminescent material Eu(BTA)@CPP3 for wide range pH sensing (1.19–13.90) with blue (∼430 nm) and red (∼613 nm) luminescent centers. First, amino-terephthalic acid (BDC-NH2) is partially replaced by 1,2,4-Benzenetricarboxylic acid (BTC) to construct multi-ligand UiO-66-NH2. Second, using the coordinating post-synthetic method, we successfully incorporate a red emission center (Eu-BTA, benzoyltrifluoroacetone) into the frameworks of multi-ligand UiO-66-NH2. To obtain the best luminescent material, all the parameters during the synthesis process are adjusted. Interestingly, Eu(BTA)@CPP3 shows three types of luminescent response modes in the process of pH sensing, including red emission quenching (1.19 < pH < 7.56), red emission quenching while blue emission enhancing (8.36 < pH < 12.04), and blue emission quenching (12.20 < pH < 13.98). The response mechanisms of each mode are discussed carefully. The luminescent color changes from red (natural and acidic solution) to blue (base solution), which can be identified by the naked eye. Furthermore, a luminescent pH test paper based on Eu(BTA)@CPP3 is prepared and is used to determine the pH practically.

A copper(I) thiolate coordination polymer with thermochromic and mechanochromic luminescence

A luminescent copper(I) thiolate coordination polymer named [Cu(pot)]n has been synthesized by the employment of the thiol ligand of 5-(3-pyridyl)-1,3,4-oxadiazole-2-thiol (Hpot). The maximum emission peak of [Cu(pot)]n at room temperature is located at 609 nm. The compound shows superb luminescent stability toward acidic/alkaline conditions and organic solvents. [Cu(pot)]n exhibits an interesting thermochromic behavior with the luminescence changing from saffron at 77 K to orange at 297 K and yellowish green at 497 K. Meanwhile, its luminescent color changes from orange to red after grinding. Thus, the compound represents a rare example of copper(I) thiolate coordination polymers possessing thermochromic and mechanochromic luminescence simultaneously.