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.

Uncommon Supramolecular Phosphorescence-Capturing Assembly Based on Cucurbit[8]uril-Mediated Molecular Folding for Near-Infrared Lysosome Imaging.

The construction of highly effective phosphorescence energy transfer capturing system still remains great challenge in aqueous phase. Herein, a high-efficiency supramolecular purely organic room temperature phosphorescence (RTP)-capturing system via a secondary assembly strategy by taking advantage of cucurbit[8]uril (CB[8]) and amphiphilic calixarene (SC4AH) is reported. Comparing with free bromonaphthalene-connected methoxyphenyl pyridinium salt (G), G⊂CB[8] exhibits an emerging RTP emission peak at 530 nm. Moreover, G⊂CB[8] further interacts with SC4AH to form the ternary assembly G⊂CB[8]  @  SC4AH accompanied by remarkably enhanced RTP emission. Interestingly, RTP-capturing systems with delayed near-infrared (NIR) emissive performance (635, 675 nm) are feasibly acquired by introducing Nile Red (NiR) or Nile Blue (NiB) as the acceptor into hydrophobic layer of G⊂CB[8] @ SC4AH, possessing ultrahigh antenna effects (352.9, 123.5) at a high donor/acceptor ratio (150:1, 300:1). More importantly, cell experiments indicate that G⊂CB[8]  @  SC4AH/NiB not only hold low cytotoxicity but also can successfully realize NIR lysosome-targeted imaging of A549 cancer cells. This RTP-capturing system of delayed NIR emission via multistage assembly strategy offers a new approach for NIR imaging in living cells.

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.

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.

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.

Photooxidation-Driven Purely Organic Room-Temperature Phosphorescent Lysosome-Targeted Imaging.

The construction of host-guest-binding-induced phosphorescent supramolecular assemblies has become one of increasingly significant topics in biomaterial research. Herein, we demonstrate that the cucurbit[8]uril host can induce the anthracene-conjugated bromophenylpyridinium guest to form a linear supramolecular assembly, thus facilitating the enhancement of red fluorescence emission by the host-stabilized charge-transfer interactions. When the anthryl group is photo-oxidized to anthraquinone, the obtained linear nanoconstructs can be readily converted into the homoternary inclusion complex, accompanied by the emergence of strong green phosphorescence in aqueous solution. More intriguingly, dual organelle-targeted imaging abilities have been also distinctively achieved in nuclei and lysosomes after undergoing photochemical reaction upon UV irradiation. This photooxidation-driven purely organic room-temperature phosphorescence provides a convenient and feasible strategy for supramolecular organelle identification to track specific biospecies and physiological events in the living cells.

Ultrahigh Supramolecular Cascaded Room-Temperature Phosphorescence Capturing System.

An ultrahigh supramolecular cascaded phosphorescence-capturing aggregate was constructed by multivalent co-assembly of cucurbit[7]uril (CB[7]) and amphipathic sulfonatocalix[4]arene (SC4AD). The initial dibromophthalimide derivative (G) generated a weak phosphorescent emission at 505 nm by host-guest interaction with CB[7], which further assembled with SC4AD to form homogeneously spherical nanoparticles with a dramatic enhancement of both phosphorescence lifetime to 1.13 ms and emission intensity by 40-fold. Notably, this G⊂CB[7]@SC4AD aggregate exhibited efficient phosphorescence energy transfer to Rhodamine B (RhB) and benzothiadiazole (DBT) with high efficiency (ϕET ) of 84.4 % and 76.3 % and an antenna effect (AE) of 289.4 and 119.5, respectively, and then each of these can function as a bridge to further transfer their energy to second near-IR acceptors Cy5 or Nile blue (NiB) to achieve cascaded phosphorescence energy transfer. The final aggregate with long-range effect from 425 nm to 800 nm and long-lived photoluminescence was further employed as an imaging agent for multicolour cell labeling.

A General Supramolecular Approach to Regulate Protein Functions by Cucurbit[7]uril and Unnatural Amino Acid Recognition.

Regulation of specific protein function is of great importance for both research and therapeutic development. Many small or large molecules have been developed to control specific protein function, but there is a lack of a universal approach to regulate the function of any given protein. We report a general host-guest molecular recognition approach involving modification of the protein functional surfaces with genetically encoded unnatural amino acids bearing guest side chains that can be specifically recognized by cucurbit[7]uril. Using two enzymes and a cytokine as models, we showed that the activity of proteins bearing unnatural amino acid could be turned off by host molecule binding, which blocked its functional binding surface. Protein activity can be switched back by treatment with a competitive guest molecule. Our approach provides a general tool for reversibly regulating protein function through molecular recognition and can be expected to be valuable for studying protein functions.

High-Efficiency Synergistic Effect of Supramolecular Nanoparticles Based on Cyclodextrin Prodrug on Cancer Therapy.

Novel cyclodextrin-prodrug supramolecular nanoparticles (NPs) with cooperative-enhancing cancer therapy were constructed from a reduction-sensitive disulfide bond-linked permethyl-ß-cyclodextrin-camptothecin prodrug, water-soluble adamantane-porphyrin photosensitizer, and hyaluronic acid grafted by triphenylphosphine and ß-cyclodextrin through an orthogonal host-guest recognition strategy, displaying uniform nanoparticles with a diameter around 100 nm as revealed by dynamic light scattering, transmission electron microscopy, scanning electron microscopy, and atomic force microscopy. Compared with 293T normal cells, the supramolecular NPs could be easily taken up by mitochondria of A549 cancer cells, then release the active anticancer drug camptothecin (CPT) in situ via the cleavage of the disulfide bond by the overexpressed glutathione, and could initiate the effective singlet oxygen (1O2) generation by porphyrin under light irradiation, ultimately resulting in severe mitochondrial dysfunction and a rising cell death rate with increasing micromolar concentration of NPs. These multicomponent supramolecular nanoassemblies effectively combined the two-step synergistic chemo-photodynamic therapy of reduction-release of CPT and light-triggered 1O2 generation within cancer cells presenting the synergistic effect of supramolecular nanoparticles on cancer therapy, which provide a new approach for efficient step-by-step cancer therapy.

Controllable Singlet Oxygen Generation in Water Based on Cyclodextrin Secondary Assembly for Targeted Photodynamic Therapy.

The construction of supramolecular assembly whose singlet oxygen (1O2) generation capability can be controllably regulated in water still remains challenging. Herein, a novel cyclodextrin secondary assembly was fabricated from the photochromic-switch moiety diarylethene-bridged dicyclodextrin, the adamantane-polypyridyl ruthenium photosensitizer, and the cancer-cell-targeting ligand ß-cyclodextrin-grafted hyaluronic acid, which not only possessed cancer-cell-targeting ability but also served as cell imaging and photodynamic therapy agents with noninvasive controllability. In virtue of the multivalent interactions between the three components, they could self-assemble in two stages to form uniform spherical nanoparticles (OF-NPs) with average diameters of about 80 nm, as indicated by scanning electron microscopy, high-resolution transmission electron microscopy, atomic force microscopy, and dynamic light scattering. Significantly, the prepared OF-NPs exhibited excellent photochromic performance and can transform into their ring-closed form (CF-NPs), accompanied by the efficient energy transfer from donor 2 to CF-1 and gradual quenching of 1O2 generation. Cellular imaging experiments showed that OF-NPs could specifically target the mitochondria of A549 cancer cells, while CF-NPs displayed a negligible red fluorescence signal in A549 cells due to the energy-transfer process. Furthermore, in vitro cytotoxicity tests revealed that upon irradiation with 450 nm light, OF-NPs with 10 µM concentration displayed a remarkable higher cytotoxicity with the cell death rate of up to 88% toward A549 cancer cells, which was approximately 4.4 times higher than that of CF-NPs. Additionally, the apoptosis rate of A549 cells induced by OF-NPs under light irradiation was 4.68 times higher than that of CF-NPs. These well-designed cyclodextrin secondary assemblies successfully achieve noninvasive control over the generation of 1O2 both in water and in cancer cells by irradiation at distinct wavelengths and are further applied in targeted PDT, which avoid the inadvertent photosensitizer activation and provide a new approach for cancer therapy with more safety and high efficiency.

Alkyl-Substituted Cucurbit[6]uril Bridged ß-Cyclodextrin Dimer Mediated Intramolecular FRET Behavior.

A novel triazolyl bridged cucurbituril (CB)-cyclodextrin (CD) dimer was synthesized via click reaction of monopropargyl modified octamethylcucurbit[6]uril and mono-6-azido-ß-cyclodextrin. Moreover, it could form stable supramolecular inclusion complexes possessing efficient fluorescence resonance energy transfer, which benefited from the fact that CD and CB can bind amantadine- and pyridinium-containing fluorophores simultaneously. The supramolecular inclusion complex behaviors were investigated by NMR spectroscopy, UV-vis absorption, and fluorescence spectroscopy.

Guest-induced supramolecular chirality transfer in [2]pseudorotaxanes: experimental and computational study.

To reveal the factors governing the chirality transfer from a chiral unimolecule to a supramolecular assembly, we constructed a series of [2]pseudorotaxanes through the intermolecular noncovalent interaction of a pair of chiral binaphthalene crown ethers with achiral secondary ammonium salts with different chromophores, and found that the binaphthalene groups can induce new circular dichroism (CD) signals only in the [2]pseudorotaxane structures between the host crown ethers and the guest molecule with the anthryl group. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations show that the generation of the new CD signal is mainly due to the intermolecular chiral induction between the anthryl group in the guest and the naphthalene groups in the host.

In Situ Photoconversion of Multicolor Luminescence and Pure White Light Emission Based on Carbon Dot-Supported Supramolecular Assembly.

Constructing multicolor photoluminescence materials that allow for the integration of suitable external stimuli in order to control luminescence color conversions is a challenging objective. Multicolor luminescent output that is regulated in an in situ photo-controlled manner is not a common phenomenon. Herein, a photoluminescent supramolecular assembly, prepared in two stages, is described that displays in situ photo-tuning broad-spectrum output. Benefiting from the reversible photo-switched constitutional interconversion of diarylethenes, the fluorescence of a guest molecule, styrylpyridinium-modified diarylethene, can be switched on/off by alternating ultraviolet and visible light irradiation. Upon complexation of this guest with a host, cucurbit[8]uril, the fluorescence intensity of the resulting binary supramolecular nanofiber shows a drastic enhancement when compared with that of the free guest, which can also be quenched and recovered reversibly by light irradiation. Significantly, such cationic supramolecular nanofibers also interact with anionic carbon dots to form broad-spectrum output ternary supramolecular assemblies, the fluorescence of which can be changed efficiently from yellow to blue in an in situ photo-controlled manner. Pure white light emission can be realized expediently in the luminescence color-conversion process. The use of light as an external stimulus to regulate fluorescent color conversion provides us with an opportunity to design and construct more advanced anti-counterfeiting materials as well as visual display instruments.

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.

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.

Achieving Near-Infrared Phosphorescence Supramolecular Hydrogel Based on Amphiphilic Bromonaphthalimide Pyridinium Hierarchical Assembly.

Phosphorescent supramolecular hydrogels are currently a prevalent topic for their great promise in various photonic applications. Herein, an efficient near-infrared (NIR) phosphorescence supramolecular hydrogel is reported via the hierarchical assembly strategy in aqueous solution, which is fabricated from amphiphilic bromonaphthalimide pyridinium derivative (G), exfoliated Laponite (LP) nanosheets, and polymeric polyacrylamide (PAAm). Initially, G spontaneously self-aggregates into spherical nanoparticles covered with positively charged pyridinium units and emits single fluorescence at 410 nm. Driven by electrostatic interactions with negatively charged nanosheets, the nanoparticles subsequently function as the cross-linked binders and coassemble with LP into supramolecular hydrogels with an engendered red room-temperature phosphorescence (RTP) up to 620 nm. Benefiting from hydrogen-bonding interactions-mediated physical cross-linkage, the further introduction of PAAm not only significantly elevates the mechanical strength of the hydrogels showing fast self-healing capability, but also increases phosphorescence lifetime from 2.49 to 4.20 ms, especially generating phosphorescence at even higher temperature (τ 363 K = 2.46 ms). Additionally, efficient RTP energy transfer occurs after doping a small amount of organic dye heptamethine cyanine (IR780) as an acceptor into hydrogels, resulting in a long-lived NIR emission at 823 nm with a high donor/acceptor ratio, which is successfully applied for cell labeling in the NIR window.

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.

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.

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.