Phosphorescent acyclic cucurbituril solid supramolecular multicolour delayed fluorescence behaviour.

Organic photoluminescent macrocyclic hosts have been widely advanced in many fields. Phosphorescent hosts with the ability to bind organic guests have rarely been reported. Herein, acyclic cucurbituril modified with four carboxylic acids (ACB-COOH) is mined to present uncommon purely organic room-temperature phosphorescence (RTP) at 510 nm with a lifetime of 1.86 µs. Its RTP properties are significantly promoted with an extended lifetime up to 2.12 s and considerable quantum yield of 6.29% after assembly with a polyvinyl alcohol (PVA) matrix. By virtue of the intrinsic self-crimping configuration of ACB-COOH, organic guests, including fluorescence dyes (Rhodamine B (RhB) and Pyronin Y (PyY)) and a drug molecule (morphine (Mor)), could be fully encapsulated by ACB-COOH to attain energy transfer involving phosphorescent acyclic cucurbituril. Ultimately, as-prepared systems are successfully exploited to establish multicolor afterglow materials and visible sensing of morphine. As an expansion of phosphorescent acyclic cucurbituril, the host afterglow color can be readily regulated by attaching different aromatic sidewalls. This study develops the fabrication strategies and application scope of a supramolecular phosphorescent host and opens up a new direction for the manufacture of intelligent long-lived luminescent materials.

Cucurbit[8]uril Confinement-Based Secondary Coassembly for High-Efficiency Phosphorescence Energy Transfer Behavior.

Aqueous supramolecular long-lived near-infrared (NIR) material is highly attractive but still remains great challenge. Herein, we report cucurbit[8]uril confinement-based secondary coassembly for achieving NIR phosphorescence energy transfer in water, which is fabricated from dicationic dodecyl-chain-bridged 4-(4-bromophenyl)-pyridine derivative (G), cucurbit[8]uril (CB[8]), and polyelectrolyte poly(4-styrene-sulfonic sodium) (PSS) via the hierarchical confinement strategy. As compared to the dumbbell-shaped G, the formation of unprecedented linear polypseudorotaxane G⊂CB[8] with nanofiber morphology engenders an emerging phosphorescent emission at 510 nm due to the macrocyclic confinement effect. Moreover, benefiting from the following secondary assembly confinement, such tight polypseudorotaxane G⊂CB[8] can further assemble with anionic polyelectrolyte PSS to yield uniform spherical nanoparticle, thereby significantly strengthening phosphorescence performance with an extended lifetime (i.e., 2.39 ms, c.f., 45.0 µs). Subsequently, the organic dye Rhodamine 800 serving as energy acceptor can be slightly doped into the polyelectrolyte assembly, which enables the occurrence of efficient phosphorescence energy transfer process with efficiency up to 80.1% at a high donor/acceptor ratio, and concurrently endows the final system with red-shifted and long-lived NIR emission (710 nm). Ultimately, the as-prepared assembly is successfully exploited as versatile imaging agent for NIR window labeling and detecting in living cells.

Aromatic Hydrocarbon Based and Space Interactions Induced Color-tunable Single-component Organic Phosphorescence.

Construction of new system and exploration of new approach are of great importance for the improvement of their photophysical properties to meet the growing various uses of phosphorescent materials. Triphenylmethane (TPM), composed only of carbon and hydrogen, exhibits excellent color tunable phosphorescence in air, with ultralong lifetime (836 ms), and wide color-tunable range (from cyan to green, then to yellow and finally to orange, 525 nm-616 nm). Through careful comparison with the single crystal diffraction structure of tetraphenylmethane (TTPM) and theoretical calculation analysis, we believe that various clusters formed through space interactions are crucial for color-tunable phosphorescence.

Phosphorescence resonance energy transfer from purely organic supramolecular assembly.

Phosphorescence energy transfer systems have been applied in encryption, biomedical imaging and chemical sensing. These systems exhibit ultra-large Stokes shifts, high quantum yields and are colour-tuneable with long-wavelength afterglow fluorescence (particularly in the near-infrared) under ambient conditions. This review discusses triplet-to-singlet PRET or triplet-to-singlet-to-singlet cascaded PRET systems based on macrocyclic or assembly-confined purely organic phosphorescence introducing the critical toles of supramolecular noncovalent interactions in the process. These interactions promote intersystem crossing, restricting the motion of phosphors, minimizing non-radiative decay and organizing donor-acceptor pairs in close proximity. We discuss the applications of these systems and focus on the challenges ahead in facilitating their further development.

Tunable Multicolor Lanthanide Supramolecular Assemblies with White Light Emission Confined by Cucurbituril[7].

Macrocyclic confinement-induced supramolecular luminescence materials have important application value in the fields of bio-sensing, cell imaging, and information anti-counterfeiting. Herein, a tunable multicolor lanthanide supramolecular assembly with white light emission is reported, which is constructed by co-assembly of cucurbit[7]uril (CB[7]) encapsulating naphthylimidazolium dicarboxylic acid (G1 )/Ln (Eu3+ /Tb3+ ) complex and carbon quantum dots (CD). Benefiting from the macrocyclic confinement effect of CB[7], the supramolecular assembly not only extends the fluorescence intensity of the lanthanide complex G1 /Tb3+ by 36 times, but also increases the quantum yield by 28 times and the fluorescence lifetime by 12 times. Furthermore, the CB[7]/G1 /Ln assembly can further co-assemble with CD and diarylethene derivatives (DAE) to realize the intelligently-regulated full-color spectrum including white light, which results from the competitive encapsulation of adamantylamine and CB[7], the change of pH, and photochromic DAE. The multi-level logic gate based on lanthanide supramolecular assembly is successfully applied in anti-counterfeiting system and information storage, providing an effective method for the research of new luminescent intelligent materials.

A pillar[5]arene noncovalent assembly boosts a full-color lanthanide supramolecular light switch.

A photo-responsive full-color lanthanide supramolecular switch was constructed from a synthetic 2,6-pyridine dicarboxylic acid (DPA)-modified pillar[5]arene (H) complexing with lanthanide ion (Ln3+ = Tb3+ and Eu3+) and dicationic diarylethene derivative (G1) through a noncovalent supramolecular assembly. Benefiting from the strong complexation between DPA and Ln3+ with a 3 : 1 stoichiometric ratio, the supramolecular complex H/Ln3+ presented an emerging lanthanide emission in the aqueous and organic phase. Subsequently, a network supramolecular polymer was formed by H/Ln3+ further encapsulating dicationic G1via the hydrophobic cavity of pillar[5]arene, which greatly contributed to the increased emission intensity and lifetime, and also resulted in the formation of a lanthanide supramolecular light switch. Moreover, full-color luminescence, especially white light emission, was achieved in aqueous (CIE: 0.31, 0.32) and dichloromethane (CIE: 0.31, 0.33) solutions by the adjustment of different ratios of Tb3+ and Eu3+. Notably, the photo-reversible luminescence properties of the assembly were tuned via alternant UV/vis light irradiation due to the conformation-dependent photochromic energy transfer between the lanthanide and the open/closed-ring of diarylethene. Ultimately, the prepared lanthanide supramolecular switch was successfully applied to anti-counterfeiting through the use of intelligent multicolored writing inks, and presents new opportunities for the design of advanced stimuli-responsive on-demand color tuning with lanthanide luminescent materials.

Color-Tunable Ultralong Organic Phosphorescence: Commercially Available Triphenylmethylamine for UV-Light Response and Anticounterfeiting.

Due to the unclear mechanism and lack of effective design for color-tunable ultralong organic phosphorescence (UOP) in a single-component molecule, the development of new types of single-component UOP materials with color-tunable property remains challenging. Herein, commercially available triphenylmethylamine-based single-component phosphors featuring color-tunablity and ultralong lifetime (0.56 s) are reported. The changed afterglow colors from cyan to orange were observed after different wavelengths of UV excitation. Crystal structure and calculation studies show that multiple emission centers in the aggregated states may be responsible for the color-tunablity. In addition, visual probing of UV light (from 260 to 370 nm) and colorful anti-counterfeiting were conducted. More importantly, UV light ranging from 350 to 370 nm could be detected with the minimal interval of 2 nm. The findings provide a new type of single-component color-tunable UOP materials and shed new light on mechanism and design for such materials.

Polymerization boosting cascade energy transfer based on opened glucopyranosyl ß-cyclodextrin.

An injectable polysaccharide supramolecular hydrogel was successfully fabricated from opened D-glucopyranosyl ß-cyclodextrin with four aldehyde groups (ACD) cross-linked with biomacromolecule chitosan (CS), which was not only beneficial to the clustering-triggered emission of CS with high quantum yield (32.25%), but also could co-assemble with a first stage acceptor triphenylamine derivative (TPA) and encapsulate Cyanine 5 (Cy5) or Nile blue (NiB) achieving supramolecular cascade energy transfer from the cross-linked polymer to the dyes, leading to fluorescence emission at 673 nm or 680 nm, and could be further applied in cell imaging.

Nanoreactor Based on Cyclodextrin for Direct Electrocatalyzed Ammonia Synthesis.

The high-efficiency transition metal-free electrocatalytic nitrate reduction reaction (NO3-RR) for ammonia synthesis has received more attention because of its green and environmentally friendly characteristics. Here, we report an efficient electrochemical NH3 synthesis directly from purely organic macrocyclic compounds α-, ß-, and γ-cyclodextrins (CDs)-catalyzed transition metal-free electroreduction of nitrate under ambient conditions. In comparison with α-, and ß-CDs, parent γ-CD presented uncommon catalytic performance with a relatively higher NH3 yield that can reach up to 2.28 mg h-1 cm-2 with a Faradaic efficiency (FE) of 63.2% at -0.9 V versus a reversible hydrogen electrode in alkaline medium, and the potassium ion-coordinated γ-CD complex can achieve a maximum NH3 production rate up to 4.66 mg h-1 cm-2 with an NH3 FE of 79.3%. Further comparison with permethyl-γ-CD, d-glucose, and poly(vinyl alcohol) for the NO3-RR indicated that the typical torus-shaped cyclic conformation and edge hydroxyl groups of parent CDs play important roles in the electrocatalytic process. The K+-mediated 3D γ-CD-K+ frameworks containing six CDs as nanoreactors greatly strengthen the enrichment effect of nitrate through hydrogen-bonding interaction and electrostatic interaction and promote the mass transfer, thus leading to the efficient NO3-RR in an alkaline electrolyte. This work provides a convenient, green, and economic method for high-performance NO3-RR, which has potential applications in the fields of environment, energy, and industry.

Generation of Tunable Ultrastrong White-Light Emission by Activation of a Solid Supramolecule through Bromonaphthylpyridinium Polymerization.

Herein, we reported solid supramolecular bromonaphthylpyridinium polymers (P-BrNp), which exhibit tunable phosphorescence emission in the amorphous state enabled by sulfobutylether-ß-cyclodextrin (SBE-ß-CD) and diarylethene derivatives. The monomer BrNp gave single fluorescence emission at 490 nm, while an apparent room-temperature phosphorescence (RTP) at 550 nm emerged for P-BrNp copolymers with various feed ratios. Through fluorescence-phosphorescence dual emission, P-BrNp-0.1 displayed an ultrahigh white-light emission quantum yield of 83.9 %. Moreover, the subsequent assembly with SBE-ß-CD further enhanced the phosphorescent quantum yield of P-BrNp-0.1 from 64.1 % to 71.3 %, accompanied by the conversion of photoluminescence emission from white to yellow. Diarylethene monomers were introduced as photoswitches to realize reversible RTP emission, which can be used in switchable data encryption and multifunctional writing ink.

A tunable full-color lanthanide noncovalent polymer based on cucurbituril-mediated supramolecular dimerization.

The construction of lanthanide multicolor luminescent materials with tunable photoluminescence properties has been developed as one of the increasingly significant topics and shown inventive applications in miscellaneous fields. However, fabricating such materials based on synergistically assembly-induced emission rather than simple blending of different fluorescent dyes together still remains a challenge. Herein, we report a europium-based noncovalent polymer with tunable full-color emission, which is constructed from the 2,6-pyridinedicarboxylic acid-bearing bromophenylpyridinium salt. This rationally designed bifunctional component can concurrently serve as a guest molecule and a chelating ligand to associate with cucurbit[8]uril and europium ions, thus leading to the formation of a trichromatic (red-green-blue, RGB) photoluminescent polypseudorotaxane-type noncovalent polymer in aqueous solution. Meanwhile, the full-color emission enclosed within the RGB color triangle could be readily produced by simply tuning the molar ratio of cucurbit[8]uril and europium ions. The lanthanide supramolecular polymer featuring tricolor emission, long lifetime, high photoluminescence efficiency and low cytotoxicity could be further applied in multicolor imaging in a cellular environment. These results provide a new and feasible strategy for the construction of full-color single lanthanide self-assembled nanoconstructs.

Folic Acid-Modified Cyclodextrin Multivalent Supramolecular Assembly for Photodynamic Therapy.

The construction of supramolecular multivalent assemblies with unique photoluminescence behaviors and biological functions has become a research hot spot recently in the biomaterial field. Herein, we report an adaptive supramolecular assembly via a multivalent co-assembly strategy prepared in two stages by using an adamantane-connected pyrenyl pyridinium derivative (APA2), sulfonated aluminum phthalocyanine (PcS), and folic acid-modified ß-cyclodextrin (FA-CD) for efficient dual-organelle targeted photodynamic cancer cell ablation. Benefiting from π-π and electrostatic interactions, APA2 and PcS could first assemble into non-fluorescent irregular nanoaggregates because of the heterodimer aggregation-induced quenching and then secondarily assemble with FA-CD to afford targeted spherical nanoparticles (NPs) with an average diameter of around 50 nm, which could be specifically taken up by HeLa cancer cells through endocytosis in comparison with 293T normal cells. Intriguingly, such multivalent NPs could adaptively disaggregate in an intracellular physiological environment of cancer cells and further respectively and selectively accumulate in mitochondria and lysosomes, which not only displayed near-infrared two-organelle localization in situ but also aroused efficient singlet oxygen generation under light irradiation to effectively eliminate cancer cells up to 99%. This supramolecular multivalent assembly with an adaptive feature in a specific cancer cell environment provides a feasible strategy for precise organelle-targeted imaging and an efficiently synergetic photodynamic effect in situ for cancer cell ablation.

Ultralarge Stokes Shift Phosphorescence Artificial Harvesting Supramolecular System with Near-Infrared Emission.

A two-step sequential phosphorescence harvesting system with ultralarge Stokes shift and near-infrared (NIR) emission at 825 nm is successfully constructed by racemic 1,2-diaminocyclohexan-derived 6-bromoisoquinoline (BQ), cucurbit[8]uril (CB[8]), and amphipathic sulfonatocalix[4]arene (SC4AD) via cascaded assembly strategy in aqueous solution. In virtue of the confinement effect of CB[8] with rigid cavity, BQ can generate an emerging phosphorescent emission at 555 nm. Subsequently, the binary BQ⊂CB[8] further assemblies with SC4AD to form close-packed spherical aggregate, which contributes to the dramatic enhancement of phosphorescence emission intensity ≈30 times with prolonged lifetime from 21.3 µs to 0.364 ms. Notably, the BQ⊂CB[8]@SC4AD assembly can serve as an energy donor to conduct stepwise phosphorescence harvesting process through successive introduction of primary acceptors, cyanine 5 (Cy5) or nile blue (NiB), and secondary acceptor, heptamethine cyanine (IR780). The final aggregate with remarkable ultralarge Stokes shift (≈525 nm) and long-lived NIR photoluminescence (PL) emission at 825 nm is further employed as imaging agent for NIR cell labeling.

Noncovalent Polymerization-Activated Ultrastrong Near-Infrared Room-Temperature Phosphorescence Energy Transfer Assembly in Aqueous Solution.

Noncovalent macrocycle-confined supramolecular purely organic room-temperature phosphorescence (RTP) is a current research hotspot. Herein, a high-efficiency noncovalent polymerization-activated near-infrared (NIR)-emissive RTP-harvesting system in aqueous solution based on the stepwise confinement of cucurbit[7]uril (CB[7]) and ß-cyclodextrin-grafted hyaluronic acid (HACD), is reported. Compared with the dodecyl-chain-bridged 6-bromoisoquinoline derivative (G), the dumbbell-shaped assembly G⊂CB[7] presents an appeared complexation-induced RTP signal at 540 nm via the first confinement of CB[7]. Subsequently, benefitting from the stepwise confinement encapsulation of the ß-cyclodextrin cavity, the subsequent noncovalent polymerization of the binary G⊂CB[7] assembly enabled by HACD can contribute to the further-enhanced RTP emission intensity approximately eight times in addition to an increased lifetime from 59.0 µs to 0.581 ms. Moreover, upon doping a small amount of two types of organic dyes, Nile blue or tetrakis(4-sulfophenyl)porphyrin as an acceptor into the supramolecular confinement assembly G⊂CB[7] @ HACD, efficient RTP energy transfer occurs accompanied by a long-lived NIR-emitting performance (680 and 710 nm) with a high donor/acceptor ratio. Intriguingly, the prepared RTP-harvesting system is successfully applied for targeted NIR imaging of living tumor cells by utilizing the targeting ability of hyaluronic acid, which provides a new strategy to create advanced water-soluble NIR phosphorescent materials.

Conformationally Confined Emissive Cationic Macrocycle with Photocontrolled Organelle-Specific Translocation.

The optimization of molecular conformation and aggregation modes is of great significance in creation of new luminescent materials for biochemical research and medical diagnostics. Herein, a highly emissive macrocycle (1) is reported, which is constructed by the cyclization reaction of triphenylamine with benzyl bromide and exhibits very distinctive photophysical performance both in aqueous solution and the solid state. Structural analysis reveals that the 1 can form self-interpenetrated complex and emit bright yellow fluorescence in the crystal lattice. The distorted yet symmetrical structure can endow 1 with unique two-photon absorption property upon excitation by near-infrared light. Also, 1 can be utilized as an efficient photosensitizer to produce singlet oxygen (1 O2 ) both in inanimate milieu and under cellular environment. More intriguingly, due to the strong association of 1 with negatively charged biomacromolecules, organelle-specific migration is achieved from lysosome to nucleus during the 1 O2 -induced cell apoptosis process. To be envisaged, this conformationally confined cationic macrocycle with photocontrolled lysosome-to-nucleus translocation may provide a feasible approach for in situ identifying different biospecies and monitoring physiological events at subcellular level.

In Situ Coassembly Induced Mitochondrial Aggregation Activated Drug-Resistant Tumor Treatment.

Macrocyclic supramolecular coassembly is the current research hotspot for tumor treatment. Herein, we report a multivalent supramolecular coassembly strategy, which not only acquires long-time phosphorescent labeling of mitochondrial aggregation but also strongly enhances chemotherapeutic efficiency against drug-resistant tumors. The mitochondrial aggregation depends on cucurbit[8]uril-mediated cross-linkage of the hyaluronic acid polymer grafted by 4-bromophenylpyridium and mitochondrion-targeting peptide (HABMitP) residing on the mitochondria, taking advantage of the 2:1 homoternary host-guest complexation between cucurbit[8]uril and 4-bromophenylpyridium with an extraordinary binding constant (6.24 × 1012 M-2). In cisplatin-resistant MCF-7 tumor cells, the assembly induced mitochondrial aggregation substantially enhances the antitumor efficiency of cisplatin, with the ratio of apoptotic cells increasing from 43% to 96% compared to treatment with cisplatin alone, and thoroughly inhibits tumor growth in vivo. This study provides a novel way for biological phosphorescent imaging and treatment of drug-resistant cancers.

A Highly Efficient Phosphorescence/Fluorescence Supramolecular Switch Based on a Bromoisoquinoline Cascaded Assembly in Aqueous Solution.

Despite ongoing research into photocontrolled supramolecular switches, reversible photoswitching between room-temperature phosphorescence (RTP) and delayed fluorescence is rare in the aqueous phase. Herein, an efficient RTP-fluorescence switch based on a cascaded supramolecular assembly is reported, which is constructed using a 6-bromoisoquinoline derivative (G3 ), cucurbit[7]uril (CB[7]), sulfonatocalix[4]arene (SC4A4), and a photochromic spiropyran (SP) derivative. Benefiting from the confinement effect of CB[7], initial complexation with CB[7] arouses an emerging RTP signal at 540 nm for G3 . This structure subsequently coassembles with amphiphilic SC4A4 to form tight spherical nanoparticles, thereby further facilitating RTP emission (≈12 times) in addition to a prolonged lifetime (i.e., 1.80 ms c.f., 50.1 µs). Interestingly, following cascaded assembly with a photocontrolled energy acceptor (i.e., SP), the efficient light-driven RTP energy transfer occurs when SP is transformed to its fluorescent merocyanine (MC) state. Ultimately, this endows the final system with an excellent RTP-fluorescence photoswitching property accompanied by multicolor tunable long-lived emission. Moreover, this switching process can be reversibly modulated over multiple cycles under alternating UV and visible photoirradiation. Finally, the prepared switch is successfully applied to photocontrolled multicolor cell labeling to offer a new approach for the design and fabrication of novel advanced light-responsive RTP materials in aqueous environments.

Multivalent supramolecular assembly with ultralong organic room temperature phosphorescence, high transfer efficiency and ultrahigh antenna effect in water.

Multivalent supramolecular assemblies have recently attracted extensive attention in the applications of soft materials and cell imaging. Here, we report a novel multivalent supramolecular assembly constructed from 4-(4-bromophenyl)pyridine-1-ium bromide modified hyaluronic acid (HABr), cucurbit[8]uril (CB[8]) and laponite® clay (LP), which could emit purely organic room-temperature phosphorescence (RTP) with a phosphorescence lifetime of up to 4.79 ms in aqueous solution via multivalent supramolecular interactions. By doping the organic dyes rhodamine B (RhB) or sulfonated rhodamine 101 (SR101) into the HABr/CB[8]/LP assembly, phosphorescence energy transfer was realized with high transfer efficiency (energy transfer efficiency = 73-80%) and ultrahigh antenna effect (antenna effect value = 308-362) within the phosphorescent light harvesting system. Moreover, owing to the dynamic nature of the noncovalent interactions, a wide-range spectrum of phosphorescence energy transfer outputs could be obtained not only in water but also on filter paper and a glass plate by adjusting the donor-acceptor ratio and, importantly, white-light emission was obtained, which could be used in the application of information encryption.

Induced Near-Infrared Emission and Controlled Photooxidation based on Sulfonated Crown Ether in Water.

Regulation of physio-chemical properties and reaction activities via noncovalent methodology has become one of increasingly significant topics in supramolecular chemistry and showed inventive applications in miscellaneous fields. Herein, we demonstrate that sulfonated crown ether can form very stable host-guest complexes with a series of push-pull-type photosensitizers, eventually leading to the dramatic fluorescence enhancement in visible and near-infrared regions. Meanwhile, severe suppression in singlet oxygen (1 O2 ) production is found, mainly due to the higher energy barriers between the excited single and triple states upon host-guest complexation. Moreover, such complexation-induced tuneable 1 O2 generation systems has been utilized in adjusting the photochemical oxidation reactions of polycyclic aromatic hydrocarbons (anthracene) and sulfides ((methylthio)benzene) in water. This supramolecularly controlled photooxidation based on the selective molecular binding of crown ether with photosensitizers may provide a feasible and applicable strategy for monitoring and modulating many photocatalysis processes in aqueous phase.

Multivalent Supramolecular Assembly Based on a Triphenylamine Derivative for Near-Infrared Lysosome Targeted Imaging.

Near-infrared (NIR) targeted cell imaging has become a research hotspot due to the advantages of deeper tissue penetration, minimal interference from the background signals, and lower light damage. Herein, we report a multivalent supramolecular aggregate with NIR fluorescence emission, which was fabricated from triphenylamine derivatives (TPAs), cucurbit[8]uril (CB[8]), Si-rhodamine (SiR), and hyaluronic acid (HA). Interestingly, possessing a rigid luminescent core and cationic phenylpyridinium units linked by flexible alkyl chains, the tripaddle hexacationic TPA could bind with CB[8] at a 2:3 stoichiometric ratio to form a network-like multivalent assembly with enhanced red luminescence. Such organic two-dimensional network-like aggregate further co-assembled with the energy acceptor SiR and cancer cell targeting agent HA, leading to nanoparticles with NIR emission at 675 nm via an intermolecular energy transfer pathway. Furthermore, the obtained multivalent supramolecular aggregate was successfully applied in lysosome targeted imaging toward A549 cancer cells, which provides a convenient strategy for NIR targeted cell imaging.