Stimulus-responsive light-harvesting complexes based on the pillararene-induced co-assembly of β-carotene and chlorophyll

Arylazopyrazole as a photo-switch for controllable self-assembly of pillar[6]arene-based supramolecular amphiphiles

A photo-responsive host-guest molecular recognition between a cationic pillar[6]arene host and an arylazopyrazole derived guest was established. Based on this novel recognition motif, a photo-controllable supra-amphiphile was constructed. The spontaneous aggregation can be reversibly controlled by irradiation with UV (365 nm) and green light (520 nm), leading to a switch between spherical nanoparticles and vesicle-like aggregates.

Ultrafast Synthesis of Graphene-Embedded Cyclodextrin-Metal-Organic Framework for Supramolecular Selective Absorbency and Supercapacitor Performance

Limited by preparation time and ligand solubility, synthetic protocols for cyclodextrin-based metal-organic framework (CD-MOF), as well as subsequent derived materials with improved stability and properties, still remains a challenge. Herein, an ultrafast, environmentally friendly, and cost-effective microwave method is proposed, which is induced by graphene oxide (GO) to design CD-MOF/GOs. This applicable technique can control the crystal size of CD-MOFs from macro- to nanocrystals. CD-MOF/GOs are investigated as a new type of supramolecular adsorbent. It can selectively adsorb the dye molecule methylene green (MG) owing to the synergistic effect between the hydrophobic nanocavity of CDs, and the abundant O-containing functional groups of GO in the composites. Following high temperature calcination, the resulting N, S co-doped porous carbons derived from CD-MOF/GOs exhibit a high capacitance of 501 F g-1 at 0.5 A g-1 , as well as stable cycling stability with 90.1% capacity retention after 5000 cycles. The porous carbon exhibits good electrochemical performance due to its porous surface containing numerous electrochemically active sites after dye adsorption and carbonization. The design strategy by supramolecular incorporating a variety of active molecules into CD-MOFs optimizes the properties of their derived materials, furthering development toward the fabrication of zeitgeisty and high-performance energy storage devices.

Triazine pyridinium derivative supramolecular cascade assembly extended FRET for two-photon NIR targeted cell imaging

A triazine pyridinium derivative (TAZpy) was encapsulated into the cavity of a cucurbit[7]uril and further assembled with sulfonatocalix[4]-arene, hyaluronic acid and commercial dyes, which not only achieved fluorescence cascade enhancement and an effective FRET process based on macrocyclic confinement, but was also applied in two-photon NIR targeted cell imaging.

Shape-Persistent Triptycene-Derived Pillar[6]arenes: Synthesis, Host-Guest Complexation, and Enantioselective Recognitions of Chiral Ammonium Salts

Construction of macrocyclic hosts with a novel structure and excellent property has emerged as an intriguing undertaking for the past few years. Here, we reported the synthesis of shape-persistent triptycene-derived pillar[6]arene (TP[6]). The single crystal structure analysis revealed that the macrocyclic molecule adopts a hexagonal structure, featuring a helical and electron-rich cavity capable of encapsulating electron-deficient guests. In order to obtain chiral TP[6] from an enantiomerically pure triptycene building block, an efficient resolution of chiral triptycene was successfully developed through introducing chiral auxiliaries into triptycene skeletons. The ¹H NMR and isothermal titration calorimetry investigations demonstrated that chiral TP[6] exhibited enantioselectivity toward four pairs of chiral guests containing a trimethylamino group, implying a significant promising application in area of enantioselective recognition.

Water-soluble phosphate-pillar[5]arene (WPP5)-based artificial light-harvesting system for photocatalytic cross-coupling dehydrogenation

A novel water-soluble phosphate-pillar[5]arene (WPP5)-based artificial light-harvesting system (LHS) was successfully fabricated through the supramolecular assembly of phenyl-pyridyl-acrylonitrile derivative (PBT), WPP5, and organic pigment Eosin Y (ESY). Initially, after host-guest interaction, WPP5 could bind well with PBT and form WPP5 ⊃ PBT complexes in water, which further assembled into WPP5 ⊃ PBT nanoparticles. WPP5 ⊃ PBT nanoparticles performed an outstanding aggregation-induced emission (AIE) capability because of the J-aggregates of PBT in WPP5 ⊃ PBT nanoparticles, which were appropriate as fluorescence resonance energy transfer (FRET) donors for artificial light-harvesting. Moreover, due to the emission region of WPP5 ⊃ PBT overlapped well with the UV-Vis absorption of ESY, the energy of WPP5 ⊃ PBT (donor) could be significantly transferred to ESY (acceptor) via FRET process in WPP5 ⊃ PBT-ESY nanoparticles. Notably, the antenna effect (AE_{WPP5⊃PBT-ESY}) of WPP5 ⊃ PBT-ESY LHS was determined to be 30.3, which was much higher than that of recent artificial LHSs for photocatalytic cross-coupling dehydrogenation (CCD) reactions, suggesting a potential application in photocatalytic reaction. Furthermore, through the energy transfer from PBT to ESY, the absolute fluorescence quantum yields performed a remarkable increase from 14.4% (for WPP5 ⊃ PBT) to 35.7% (for WPP5 ⊃ PBT-ESY), further confirming their FRET processes in WPP5 ⊃ PBT-ESY LHS. Subsequently, in order to output the harvested energy for catalytic reactions, WPP5 ⊃ PBT-ESY LHSs were used as photosensitizers to catalyze the CCD reaction of benzothiazole and diphenylphosphine oxide. Compared to free ESY group (21%), a significant cross-coupling yield of 75% in WPP5 ⊃ PBT-ESY LHS was observed, because more UV region energy of PBT was transferred to ESY for CCD reaction, which suggested more potential in improving the catalytic activity of organic pigment photosensitizers in aqueous systems.

Macrocycle with Equatorial Coordination Sites Provides New Opportunity for Structure-Diverse Metallacages

Reported here is the synthesis of a macrocycle with equatorial coordination sites for the construction of self-assembled metallacages. The macrocycle is prepared via a post-modification on the equator of biphen[n]arene. Utilizing this macrocycle as a ligand, three prismatic cages and one octahedral cage were synthesized by regulating the geometric structures and coordination number of metal acceptors. The multi-cavity configuration of prismatic cage was revealed by single-crystal structure. We prove that a macrocycle with equatorial coordination sites can be an excellent building block for synthesizing structure-diverse metallacages. Our results provide a typical example and a general method for the design and synthesis of metallacages.

Pillararenes as Promising Carriers for Drug Delivery

Since their discovery in 2008 by N. Ogoshi and co-authors, pillararenes (PAs) have become popular hosts for molecular recognition and supramolecular chemistry, as well as other practical applications. The most useful property of these fascinating macrocycles is their ability to accommodate reversibly guest molecules of various kinds, including drugs or drug-like molecules, in their highly ordered rigid cavity. The last two features of pillararenes are widely used in various pillararene-based molecular devices and machines, stimuli-responsive supramolecular/host-guest systems, porous/nonporous materials, organic-inorganic hybrid systems, catalysis, and, finally, drug delivery systems. In this review, the most representative and important results on using pillararenes for drug delivery systems for the last decade are presented.

Novel Strategy of Constructing Artificial Light-Harvesting System with Two-Step Sequential Energy Transfer for Efficient Photocatalysis in Water

An efficient artificial light-harvesting system with a two-step sequential energy transfer was fabricated in the aqueous solution based on the host-guest interactions between cyano-substituted p-phenylenevinylene derivative (PPTA) and a water-soluble pillar[5]arene (WP5). PPTA-WP5 complex could self-assemble into nanoparticles, and two fluorescent dyes eosin Y (EY) and Nile Red (NIR) are employed as acceptors to realize sequential energy transfer. The PPTA-WP5-EY-NIR system could achieve efficient two-step sequential energy transfer process from PPTA-WP5 to EY and then to NIR (67% for the first step and 66% for the second step). Moreover, to make full use of the harvested energy, the hydrophobic microenvironment in the assembled nanoparticles is used to promote the aerobic cross-dehydrogenative coupling (CDC) reaction in aqueous medium with 88% yield after 12 h of irradiation. To our knowledge, this is the first example of artificial LHS with two-step energy transfer used to catalyze the CDC reaction in aqueous medium. This work directly mimics the function of photosynthesis in nature of converting solar energy into chemical energy in aqueous solution.

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 β-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 β-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.

Supramolecular Detoxification of Macromolecular Biotoxin through the Complexation by a Large-Sized Macrocycle

Biotoxins are diverse, complex, and hypertoxic, ultimately serving as grave and lasting menaces to humanity. Here, it is aimed to introduce a new detoxification methodology for macromolecular biotoxin through complexation by a very large macrocycle. A 25-mer peptide isolated from Lycosa erythrognatha spider venom (LyeTxI) is selected as the model macromolecular biotoxin. Quaterphen[4]arene, with a side length of ≈1.6 nm, has a sufficient cavity to bind LyeTxI. Hence, the water-soluble derivative of Quaterphen[4]arene (H) is designed and synthesized. H exhibits an overall host-guest complexation toward LyeTxI, resulting in a considerably high association constant of (7.01 ± 0.18) × 10⁷  m^-1 . This encapsulation of peptide is interesting as traditional macrocycles can only engulf the amino acid residues of peptides due to their limited cavity size. In vitro assay verifies that complexation by H inhibits the interactions of LyeTxI with cell membranes, thereby reducing its cytotoxicity, suppressing hemolysis, and decreasing the release of lactate dehydrogenase. Notably, the intravenous administration of H has a significant therapeutic effect on LyeTxI-poisoned mice, alleviating inflammation and tissue damage, and markedly improving the survival rate from 10% to 80%. An efficient and potentially versatile approach is provided to detoxify macromolecular biotoxins, with giant macrocycle serving as an antidote.

Controlled release of drug molecules by pillararene-modified nanosystems

Stimuli-responsive nanosystems have attracted the interest of researchers due to their intelligent function of controlled release regulated by a variety of external stimuli and have been applied in biomedical fields. Pillar[n]arenes with the advantages of a rigid structure, electron holes and easy functionalization are considered as excellent candidates for the construction of host-guest nanosystems. In recent years, many pillararene modified nanosystems have been reported in response to different stimuli. In this feature article, we summarize the advance of stimuli-responsive pillararene modified nanosystems for controlled release of drugs from the perspectives of decomposition release and gated release, focusing on the control principles of these nanosystems. We expect that this review can enlighten and guide investigators in the field of stimuli-responsive controlled release.

Pillar[5]arene-Based Fluorescent Sensor Array for Biosensing of Intracellular Multi-neurotransmitters through Host-Guest Recognitions

Neurotransmitters are very important for neuron events and brain diseases. However, effective probes for analyzing specific neurotransmitters are currently lacking. Herein, we design and create a supramolecular fluorescent probe (CN-DFP5) by synthesizing a dual-functionalized fluorescent pillar[5]arene derivative with borate naphthalene and aldehyde coumarin recognition groups to identify large-scale neurotransmitters. The developed probe can detect seven model neurotransmitters by generating different fluorescence patterns through three types of host-guest interactions. The obtained signals are statistically processed by principal component analysis, thus the high-throughput analysis of neurotransmitters is realized under dual-channel fluorescence responses. The present probe combines the advantages of small-molecule-based probes to easily enter into living neurons and cross-reactive sensor arrays. Thus, the selective binding enables this probe to identify specific neurotransmitters in biofluids, living neurons, and tissues. High selectivity and sensitivity further demonstrate that the molecular device could extend to more applications to detect and image neurotransmitters.

Effective taste masking of alkaloids by a water-soluble terphen[3]arene

The synthesis of first water-soluble 2,2’’,4,4’’-terphen[3]arene bearing sulphonatopropoxy moieties (STP3), and its effective alleviation of aversive response to alkaloids in vitro and in vivo by forming supramolecular complexes has been...

Artificial light-harvesting systems based on macrocycle-assisted supramolecular assembly in aqueous media

Light-harvesting, which involves the conversion of sunlight into chemical energy by natural systems such as plants, bacteria, is one of the most universal routine activities in nature. Thus far, various artificial light-harvesting systems (LHSs) have been fabricated toward solar energy utilization through mimicking natural photosynthesis in simplified and altered ways. Macrocycles are supramolecular hosts with unique cavities, in which specific guest molecules can be recognized based on non-covalent interactions. They have been widely employed in constructing LHSs due to their ability to form supramolecular assembly and dynamic molecular activity. In this review, we mainly focus on some representative examples reported by our group and other groups. Specifically, the fabrication of LHSs and their related discussions, such as a high donor/acceptor ratio, driving force for the formation of supramolecular assemblies and energy transfer mechanisms using different water-soluble macrocycles such as cyclodextrins (CD), pillararenes (PA), calixarenes (CA), cucurbiturils (CB), and other macrocycles will be included. In addition, how the resulting supramolecular self-assembled LHSs could be potentially utilized for photocatalysis, sensing, and imaging is also explained in detail. Challenges and developing trends for photochemical solar energy conversion will also be presented.

Supramolecular Polymerization-Induced Nanoassemblies for Self-Augmented Cascade Chemotherapy and Chemodynamic Therapy of Tumor

The clinical application of chemodynamic therapy is impeded by the insufficient intracellular H2 O2 level in tumor tissues. Herein, we developed a supramolecular nanoparticle via a simple one-step supramolecular polymerization-induced self-assembly process using platinum (IV) complex-modified β-cyclodextrin-ferrocene conjugates as supramolecular monomers. The supramolecular nanoparticles could dissociate rapidly upon exposure to endogenous H2 O2 in the tumor and release hydroxyl radicals as well as platinum (IV) prodrugs in situ, which is reduced into cisplatin to significantly promote the generation of H2 O2 in the tumor tissue. Thus, the supramolecular nanomedicine overcomes the limitation of conventional chemodynamic therapy via the self-augmented cascade radical generation and drug release. In addition, dissociated supramolecular nanoparticles could be readily excreted from the body via renal clearance to effectively avoid systemic toxicity and ensure long term biocompatibility of the nanomedicine. This work may provide new insights on the design and development of novel supramolecular nanoassemblies for cascade chemo/chemodynamic therapy.

A supramolecular complex of hydrazide-pillar[5]arene and bisdemethoxycurcumin with potential anti-cancer activity

Pillar[5]arene complexes of the naturally occurring compound bisdemethoxycurcumin (BDMC) were acquired for improving the water solubility and stability of BDMC. As a family member of curcuminoid compounds, BDMC has many interesting therapeutic properties. However, its low aqueous solubility and stability resulted in poor availability and restricted the clinical efficacy. Pillar[5]arenes with hydrophilic ends and a hydrophobic cavity could include with BDMC based on size matching. The synthesized hydrazide-pillar[5]arene (HP5A) and BDMC had a strong host-guest interaction with a 1:1 binding stoichiometry. Furthermore, the HP5A ⊃ BDMC complex could self-assemble into well-defined fibers in water/ethanol solution. This supramolecular complex worked well in vitro for inhibiting the proliferation of hepatoma carcinoma cells HepG2. Remarkably, this method of complexation with pillar[5]arenes visibly reduced the undesirable side effects on normal cells without weakening the anti-cancer activity of the drugs. We expected that the obtained host-guest complex and fibrous assembly would provide a promising platform for delivering drugs with low water solubility.

Insight into functionalized-macrocycles-guided supramolecular photocatalysis

Due to the unique characteristics of macrocycles (e.g., the ease of modification, hydrophobic cavities, and specific guest recognition), they can provide a suitable environment to realize photocatalysis via noncovalent interactions with different substrates. In this minireview, we emphasized the photochemical transformation and catalytic reactivity of different guests based on the binding with various macrocyclic hosts as well as on the role of macrocyclic-hosts-assisted hybrid materials in energy transfer. To keep the clarity of this review, the macrocycles are categorized into the most commonly used supramolecular hosts, including crown ethers, cyclodextrins, cucurbiturils, calixarenes, and pillararenes. This minireview not only summarizes the role that macrocycles play in photocatalytic reactions but also clarifies the photocatalytic mechanisms. Finally, the future research efforts and new pathways to apply macrocycles and supramolecular hybrid materials in photocatalysis are also discussed.

Role of Functionalized Pillararene Architectures in Supramolecular Catalysis

The many useful features possessed by pillararenes (PAs; e.g. rigid, capacious, and hydrophobic cavities, as well as exposed functional groups) have led to a tremendous increase in their popularity since their first discovery in 2008. In this Minireview, we emphasize the use of functionalized PAs and their assembled supramolecular materials in the field of catalysis. We aim to provide a fundamental understanding and mechanism of the role PAs play in catalytic process. The topics are subdivided into catalysis promoted by the PA rim/cavity, PA-based nanomaterials, and PA-based polymeric materials. To the best of our knowledge, this is the first overview on PA-based catalysis. This Minireview not only summarizes the fabrications and applications of PAs in catalysis but also anticipates future research efforts in applying supramolecular hosts in catalysis.

Pilot-scale cultivation of Chlorella sorokiniana FZU60 with a mixotrophy/photoautotrophy two-stage strategy for efficient lutein production

Chlorella sorokiniana FZU60, a lutein-enriching microalga, was cultivated in 50 L column photobioreactor to evaluate its potential for lutein production. Initial cell concentration, phosphate concentration and aeration rate were optimized, and results showed that optimal conditions of these three parameters were 0.10 g/L, 0.06 g/L and 0.02 vvm (2.5% CO₂), respectively. In addition, a novel two-stage strategy was successfully developed, in which algae were firstly cultivated under fed-batch mixotrophic condition to achieve high biomass concentration, and then shifted to photoautotrophic condition for enhancing lutein accumulation. Moreover, dissolved oxygen was found to be an efficient indicator of acetate depletion in fed-batch stage. The obtained lutein content, production and productivity reached 9.51 mg/g, 33.55 mg/L and 4.67 mg/L/d, respectively, which were greater than those reported in other pilot-scale studies. This proposed strategy provided a cost-effective approach for high-efficient microalgae-based lutein production at pilot-scale, indicating great potential for commercial production.

An efficient artificial light-harvesting system with tunable emission in water constructed from a H-bonded AIE supramolecular polymer and Nile Red

With the aid of CTAB amphiphile, water-phase artificial light-harvesting systems were fabricated as nanoparticles by the self-assembly of two low-molecular-weight organic molecules: a UPy-functionalized TPE derivative 1 with both supramolecular polymerization and AIE capabilities as a donor and a fluorescent chromophore NiR as an acceptor. Owing to the flexibility of supramolecular self-assembly, tunable emissions including white-light emission could be easily realized with high energy transfer efficiency and the antenna effect.

Recent developments in the construction and applications of platinum-based metallacycles and metallacages via coordination

Coordination-driven suprastructures have attracted much interest due to their unique properties. Among these structures, platinum-based architectures have been broadly studied due to their facile preparation. The resultant two- or three-dimensional (2D or 3D) systems have many advantages over their precursors, such as improved emission tuning, sensitivity as sensors, and capture and release of guests, and they have been applied in biomedical diagnosis as well as in catalysis. Herein, we review the recent results related to platinum-based coordination-driven self-assembly (CDSA), and the text is organized to emphasizes both the synthesis of new metallacycles and metallacages and their various applications.

Peptoid Helix Displaying Flavone and Porphyrin: Synthesis and Intramolecular Energy Transfer

Natural light-harvesting complexes (LHCs) absorb a broad spectrum of sunlight using a collection of photosynthetic pigments whose spatial arrangement is controlled by a protein matrix and exhibit efficient energy transfer. We constructed a novel light-harvesting protein mimic, which absorbs light in the UV to visible region (280-700 nm) by displaying flavone and porphyrin on a peptoid helix. First, an efficient synthesis of 4'-derivatized 7-methoxyflavone (7-MF, 3 and 4) was developed. The flavone-porphyrin-peptoid conjugate (FPPC) was then prepared via Miyaura borylation on a resin-bound peptoid followed by Suzuki coupling between the peptoid and pigment. Circular dichroism spectroscopy indicated that the FPPC underwent helix-to-loop conversion of the peptoid scaffold upon changing the solvent conditions. A distinct intramolecular energy transfer was observed from 7-MF to porphyrin with greater efficiency in the helix than that in the loop conformation of the peptoid, whereas no clear evidence of energy transfer was obtained for unstructured FPPC. We thus demonstrate the value of the helical peptoid, which provided a controlled orientation for 7-MF and porphyrin and modulated the energy transfer efficiency via conformational switching. Our work provides a way to construct a sophisticated LHC mimic with enhanced coverage of the solar spectrum and controllable energy transfer efficiency.

A highly efficient light-harvesting system with sequential energy transfer based on a multicharged supramolecular assembly

A highly efficient light-harvesting system with two-step sequential energy transfer was designed by the nonconvalent interaction of pillar[5]arene with pyridinium modified tetraphenylethene, sulforhodamine 101 and sulfonated aluminum phthalocyanine.

Constructing Artificial Light-Harvesting Systems by Covalent Alignment of Aggregation-Induced Emission Molecules

The characteristics of chloroplasts harvesting solar energy and conducting energy transfer have inspired chemists to mimic similar processes. However, accurate manipulation to gain regularly displayed antenna chromophores in mimicking chloroplasts is a great challenge. Herein, a rational design is presented that combines orderly arranged chromophores with aggregation-induced emission (AIE) to develop artificial light-harvesting systems. Tetraphenyl ethylene (TPE) molecules, which exhibited strong AIE properties, are considered as building blocks to fabricate high emissive 2D nanosheets and nanovesicles, respectively. Furthermore, the well-aligned TPE molecules are also developed as donor chromophores in light-harvesting processes. After subsequent surface modification by porphyrin molecules as acceptor chromophores, an efficient light-harvesting system has been integrally constructed. This study demonstrates a novel strategy to utilize AIE feature to mimic chloroplasts process in nature.

Effect of scaffold structures on the artificial light-harvesting systems: a case study with an AIEE-active pillar[5]arene dyad

The presence of a supramolecular polymeric scaffold structure enhanced the energy transfer capacity of the artificial light-harvesting nanoparticles.

Assembly of Metallacages into Soft Suprastructures with Dimensions of up to Micrometers and the Formation of Composite Materials

This work provides a platform for the rapid generation of superstructure assemblies with a wide range of lengths that can be used to access a variety of metal-organic complex-based soft superstructures. Metallacage-based microneedles that are nanometers in diameter and millimeters in length were generated in dichloromethane and ethyl acetate; their size could be controlled by adjusting the ratio of the two solvents. Interestingly, microflower structures could be formed by further assembly of the microneedles during solvent evaporation. Our study establishes a feasible method designed to broaden the range of suprastructures with emissions from blue and green to red through the co-assembly of lysine-modified perylene. Similar to the co-assembly of lysine-modified perylene with microflowers, chlorophyll-a and vitamin B₁₂ were introduced into the microflowers during the assembly process, which may be exploited in studies of energy capture and nerve repair in the future.

Self-Assembly of Metallacages into Multidimensional Suprastructures with Tunable Emissions

Cubic metallacages were arranged into multidimensional (one-, two-, and three-dimensional) suprastructures via multistep assembly. Four new shape-controllable, hybrid metallacages with modified substituents and tunable electronic properties were prepared using dicarboxylate ligands with various substituents (sodium sulfonate, nitro, methoxyl, and amine), tetra-(4-pyridylphenyl) ethylene, and cis-(PEt3)2Pt(OTf)2. The as-prepared metallacages were used as building blocks for further assembly. Diverse suprastructures with tunable emissions (λmax from 451 to 519 nm) and various substituents (-SO3Na, -NO2, -OCH3, and -NH2) were prepared depending on the substituents and solvents used.

A biomimetic chiral-driven ionic gate constructed by pillar[6]arene-based host-guest systems

Inspired by glucose-sensitive ion channels, herein we describe a biomimetic glucose-enantiomer-driven ion gate via the introduction of the chiral pillar[6]arene-based host-guest systems into the artificial nanochannels. The chiral nanochannels show a high chiral-driven ionic gate for glucose enantiomers and can be switched "off" by D-glucose and be switched "on" by L-glucose. Remarkably, the chiral nanochannel also exhibited a good reversibility toward glucose enantiomers. Further research indicates that the switching behaviors differed due to the differences in binding strength between chiral pillar[6]arene and glucose enantiomers, which can lead to the different surface charge within nanochannel. Given these promising results, the studies of chiral-driven ion gates may not only give interesting insight for the research of biological and pathological processes caused by glucose-sensitive ion channels, but also help to understand the origin of the high stereoselectivity in life systems.

Supramolecular Hybrid Material Constructed from Graphene Oxide and Pillar[6]arene-Based Host-Guest Complex as a Ultrasound and Photoacoustic Signals Nanoamplifier

Photoacoustic imaging combines the merits of ultrasound imaging and optical imaging that allows a fascinating imaging paradigm with deeper tissue penetration than optical imaging and higher spatial resolution than ultrasound imaging. Herein, we develop a supramolecular hybrid material composed of graphene oxide (GO) and a pillar[6]arene-based host-guest complex (CP6⊃PyN), which can be used as a ultrasound (US) and photoacoustic (PA) signal nanoamplifier. Triggered by the near-infrared (NIR) light mediated photothermal effect, CO2 nanobubbles are generated on the surface of GO@CP6⊃PyN due to the decomposition of bicarbonate counterions, thus strongly amplifying its US and PA performances. Our study, for the first time, demonstrates enhanced US and PA activity in supramolecular hybrid material on the basis of host-guest chemistry as a photoacoustic nanoplatform.

Warm/cool-tone switchable thermochromic material for smart windows by orthogonally integrating properties of pillar[6]arene and ferrocene

Functional materials play a vital role in the fabrication of smart windows, which can provide a more comfortable indoor environment for humans to enjoy a better lifestyle. Traditional materials for smart windows tend to possess only a single functionality with the purpose of regulating the input of solar energy. However, different color tones also have great influences on human emotions. Herein, a strategy for orthogonal integration of different properties is proposed, namely the thermo-responsiveness of ethylene glycol-modified pillar[6]arene (EGP6) and the redox-induced reversible color switching of ferrocene/ferrocenium groups are orthogonally integrated into one system. This gives rise to a material with cooperative and non-interfering dual functions, featuring both thermochromism and warm/cool tone-switchability. Consequently, the obtained bifunctional material for fabricating smart windows can not only regulate the input of solar energy but also can provide a more comfortable color tone to improve the feelings and emotions of people in indoor environments.

Materials for smart windows usually possess single functionality, thus developing materials that regulate solar energy whilst changing color to affect human emotion is desirable. Here the authors combine pillar[6]arenes and ferrocene/ferrocenium groups to produce warm/cool tone-switchable thermochromic materials.

Artificial light-harvesting supramolecular polymeric nanoparticles formed by pillar[5]arene-based host-guest interaction

Artificial light-harvesting nanoparticles were prepared from supramolecular polymers comprised of pillar[5]arene with anthracene-derived donors and acceptors through host-guest interactions. The resulting water-dispersible nanoparticles displayed efficient energy transfer and excellent light harvesting ability in part because the steric bulk of pillar[5]arene suppressed the self-quenching of the chromophores.

Successive energy transfer within multiple photosensitizers assembled in a hexameric hemoprotein scaffold

An assembly of multiple photosensitizers is demonstrated by development of a hexameric hemoprotein (HTHP) scaffold as a light harvesting model to replicate the successive energy transfer occuring within photosensitizer assemblies of natural systems. In our model, six zinc protoporphyrin IX (ZnPP) molecules are arrayed at the heme binding site of HTHP by supramolecular interactions and five fluorescein (Flu) molecules and one Texas Red (Tex) molecule as donor and acceptor photosensitizers, respectively, are attached to the HTHP protein surface with covalent linkages. The flow of excited energy from photoexcited Flu to Tex occurs via two pathways: direct energy transfer from Flu to Tex (path 1) and energy transfer via ZnPP (path 2). Steady state and time-resolved fluorescence measurements reveal that the energy transfer ratio of these pathways (path 1 : path 2) is 39 : 61. These findings indicate that the excited energy originating at five Flu and six ZnPP molecules is collected at one Tex molecule as a funnel-like bottom for light harvesting. The present system using the hexameric hemoprotein scaffold is a promising candidate for construction of an artificial light harvesting system having multiple photosensitizers to promote efficient use of solar energy.

Recognition and optical sensing of amines by a quartz-bound 7-chloro-4-quinolylazopillar[5]arene monolayer

Pillar[5]arene-decorated quartz slides for the direct detection of linear amines and diamines are now available.