Cyclodextrin Derivatives Research Articles

Structural Architectural Features of Cyclodextrin Oligoesters Revealed by Fragmentation Mass Spectrometry Analysis.

Cyclodextrins (CDs) were used in the present study for the ring-opening oligomerization (ROO) of l-lactide (LA) in order to synthesize biodegradable products with possible applications in pharmaceutical and medical fields. The practical importance of ROO reactions may reside in the possibility of synthesizing novel CD derivatives with high purity due to the dual role played by CDs, the role of the initiator through the hydroxylic groups, and the role of the catalyst by monomer inclusion in the CD cavity. The analyzed compounds were CDs modified with oligolactides obtained through ROO reactions of l-lactide in dimethylformamide. The resulting CD isomeric mixtures were investigated using classical characterization techniques such as gel permeation chromatography and nuclear magnetic resonance. Moreover, advanced mass spectrometry (MS) techniques were employed for the determination of the average number of monomer units attached to the cyclodextrin and the architecture of the derivatives (if the monomer units were attached as a single chain or as multiple chains). Thus, fragmentation studies effectuated on two different instruments (ESI Q-TOF and MALDI TOF) allowed us to correlate the size of the oligolactide chains attached to the CD with the observed fragmentation patterns.

Cyclodextrin complexes: Perspective from drug delivery and formulation.

Cyclodextrins (CDs) have been widely investigated as a unique pharmaceutical excipient for past few decades and is still explored for new applications. They are highly versatile oligosaccharides which possess multifunctional characteristics, and are mainly used to improve the physicochemical stability, solubility, dissolution rate, and bioavailability of drugs. Stability constant, factors affecting complexation, techniques to enhance complexation efficiency, the preparation methods for molecular inclusion complexes and release of guest molecules are discussed in brief. In addition, different CD derivatives and their pharmacokinetics are elaborated. Further, the significance of CD complex in aqueous solubility, dissolution and bioavailability, stability, and taste masking is explained. The recent advancement of CDs in developing various drug delivery systems is enlightened. Indeed, the potential of CDs by means of inclusion complex formation have widen the applicability of these materials in various drug delivery systems including ocular, osmotic, mucoadhesive, transdermal, nasal, and targeted delivery systems. Feasibility studies have been performed on the benefit of these cyclic oligomers as nanocarriers, a strategy that can modify the drugs with improved physicochemical properties. Studies also demonstrated the feasibility of CDs to self-assemble in the form of stable nanoaggregates, which may extend the scope of CDs in drug delivery to the continually expanding list of new drug entities.

Synthesis of substituted cyclodextrins

Cyclodextrins are naturally occurring, non-toxic and biodegradable cyclic oligosaccharides. The main feature of cyclodextrins is the ability to encapsulate lipophilic compounds, which has led to many applications. Although many cyclodextrin derivatives have become available on the market, their price is in the range of fine chemicals, and thus, they are still often synthesised in laboratories. The actual number of cyclodextrin derivatives exceeds 11,000, but new cyclodextrin derivatives are still needed for more advanced applications. Therefore, many beginners in cyclodextrin chemistry struggle with a reliable choice of a synthetic route. This review focuses on cyclodextrin derivatives that can be subsequently modified. Indeed, the modification of an already substituted cyclodextrin with a suitable functional group is much easier than the optimisation of the substitution for every new cyclodextrin derivative desired. This review describes the synthesis of different types of cyclodextrin derivatives: persubstituted, randomly substituted, persubstituted at selected positions, selectively substituted and monosubstituted cyclodextrins.

(Invited) Photo Stimuli Responsive Supramolecular Actuators Constructed By Non-Covalent or Topological Crosslinkers

Various kinds of biological molecular motors, such as myosin, kinesin, and dynein, realize the conversion of energy in ATP hydrolysis into mechanical work. These mechanical motions inspired supramolecular chemist to realize polymeric materials with supramolecular materials. Two structural approaches may realize supramolecular actuators through host–guest interactions: a method with a linear main chain and one with a side chain in the polymer structure (Fig. 1).1) We have prepared photo responsive supramolecular actuators by integrating host–guest interactions on the polymer side chains (Fig. 1a). The association and dissociation of inclusion complexes as crosslinking units on the polymer side chains demonstrate contraction and expansion motions due to changes in the crosslinking density. A plate-shaped actuator bent against the incident ultraviolet (UV) light. 2) Herein we hypothesize that polymer chains crosslinked with [c2]daisy chains would realize a novel supramolecular actuator whose volume contracts upon UV light irradiation but expands upon visible (Vis) light irradiation. This contraction would bend the flat plate actuator toward the incident UV light because UV irradiation causes the shrinkage of the end-to-end distance of the [c2]daisy chain to shrink polymeric materials due to desorption of the solvent on the exposed surface (Fig. 1b). Supramolecular hydrogels containing CD-based [c2]daisy chains as crosslinkers contract and expand through photoresponsive sliding motions of the [c2]daisy chain (Fig. 1c).3) The photogenerated supramolecular artificial muscle is reminiscent of contraction and expansion motions of biological skeletal muscle. Figure 1. Supramolecular actuators using cyclodextrin derivatives. These supramolecular actuators show macroscopic contraction–expansion and flexing behaviors. References (1) Harada, A.; Takashima, Y.; Nakahata, M. Acc. Chem. Res. 2014, 47, 2128-2140. (2) Takashima, Y.; Hatanaka, S.; Otsubo, M.; Nakahata, M.; Kakuta, T.: Hashidzume, A.; Yamaguchi, H.; Harada, A. Nat. Commun. 2012, 3, 1270. (3) Iwaso, K.; Takashima, Y.; Harada, A. Nat. Chem. 2016, 8 , 625–632. (4) Takashima, Y.; Harada, A. J. Incl. Phenom. Macrocycl. Chem. 2017, 87, 313-330. Figure 1

COMPARATIVE STUDIES WITH DIFFERENT CYCLODEXTRIN DERIVATIVES IN IMPROVING THE SOLUBILITY AND DISSOLUTION OF SAQUINAVIR

Objective: The present study was aimed to perform comparative studies with different cyclodextrin (CD) derivatives and to study the effect of different methods of preparation in improving the solubility and dissolution of saquinavir (SQV).Methods: Phase solubility studies were performed with beta CD (βCD), hydroxypropyl βCD, randomly methylated βCD, and sulfobutyl ether βCD (SBE7βCD). Complexes were prepared using physical mixture, coevaporation, kneading, spray drying, and freeze-drying techniques. For complexes prepared by spray drying, process parameters were optimized based on percentage yield. The prepared complexes were characterized using Fourier-transform infrared spectroscopy, differential scanning calorimetry, X-ray diffraction studies, nuclear magnetic resonance spectroscopy, and scanning electron microscopy. In vitro drug release study was conducted in phosphate buffer pH 6.8 and mean dissolution time (MDT) was calculated for all freeze-dried complexes.Results: Phase solubility studies showed a linear relationship with an increase in CD concentration and phase diagrams were of AL type. Highest stability constant was observed with SQV-SBE7βCD (8281.28/M). All characterization studies proved complexation. Among four CD derivatives, SQV complexed with SBE7βCD by freeze-drying showed maximum drug release and low MDT of 20.67.Conclusion: Among different CDs, SBE7βCD proved as ideal CD derivative, and among different methods of preparations, freeze-drying method was found to be useful in improving the solubility and dissolution of SQV.

Toward Expanded Diversity of Host–Guest Interactions via Synthesis and Characterization of Cyclodextrin Derivatives

Researchers developing software to predict the binding constants of small molecules for proteins have, in recent years, turned to host–guest systems as simple, computationally tractable model systems to test and improve these computational methods. However, taking full advantage of this strategy requires aqueous host–guest systems that probe a greater diversity of chemical interactions. Here, we advance the development of an experimental platform to generate such systems by building on the cyclodextrin (CD) class of hosts. The secondary face derivative mono-3-carboxypropionamido-β-cyclodextrin (CP-β-CD) was synthesized in a one-pot strategy with 87% yield, and proved to have much greater aqueous solubility than native β-CD. The complexation of anionic CP-β-CD with the cationic drug rimantadine hydrochloride was explored using one- and two-dimensional nuclear magnetic resonance; NOESY analysis showed secondary face binding of the ammonium moiety of the guest, based on cross-correlations between the amic acid functionality and the side-chain of rimantadine. Isothermal titration calorimetry was furthermore used to determine the standard Gibbs energy and enthalpy for this binding reaction, and the results were compared with those of rimantadine with native β-CD.

Characterization of Inclusion Complexes between Miconazole and Different Cyclodextrin Derivatives

Abstract Objective: Miconazole, an imidazole antifungal derivative, is a very hydrophobic compound, a major drawback in obtaining topical pharmaceutical formulations with optimal bioavailability. Cyclodextrins (CDs) may increase local drug delivery by enhancing the drug release and/or permeation. The aim of the study is the characterization of inclusion complexes between miconazole and different CD derivatives. Methods: Several CD derivatives were tested in the experiments. The binary systems between miconazole and different CDs were prepared in 1:1 molar ratios by physical-mixture and kneading methods. Differential scanning calorimetry (DSC) and Fourier transformed-infrared spectroscopy (FT-IR) methods were used to characterize solid state interactions between miconazole and CDs in their binary systems. Results: The FT-IR analysis suggests the formation of a new solid phase, indicating a molecular interaction between the components. The DSC analysis sustains the hypothesis of formation of partial inclusion complexes between miconazole nitrate and CD. Conclusion: The thermic behaviour of the complexes depends both on the preparation method and the composition of the products.

Bridging β-Cyclodextrin Prevents Self-Inclusion, Promotes Supramolecular Polymerization, and Promotes Cooperative Interaction with Nucleic Acids.

A bridge to assemble: Cyclodextrins bridged with an ammonium linker bearing a hydrophobic substituent can efficiently form supramolecular polymers and avoid the competing self-inclusion and head-to-head processes. Furthermore, the self-assembling cyclodextrin derivative interacts in a highly cooperative manner with DNA, as demonstrated by compaction experiments. It also interacts cooperatively with siRNA and allows its transfection.

Noncovalent Monolayer Modification of Graphene Using Pyrene and Cyclodextrin Receptors for Chemical Sensing

Surprisingly few details have been reported in the literature that help the experimentalist to determine the conditions necessary for the preparation of self-assembled monolayers on graphene with a high surface coverage. With a view to graphene-based sensing arrays and devices and, in particular, in view of graphene-based varactors for gas sensing, graphene was modified in this work by the π–π interaction-driven self-assembly of 10 pyrene and cyclodextrin derivatives from solution. The receptor compounds were pyrene, pyrene derivatives with hydroxyl, carboxyl, ester, ammonium, amino, diethylamino, and boronic acid groups, and perbenzylated α-, β-, and γ-cyclodextrins. Adsorption of these compounds onto graphene was quantified by contact-angle measurements and X-ray photoelectron spectroscopy. Data thus obtained were fitted with the Langmuir adsorption model to determine the equilibrium constants for surface adsorption and the concentrations of self-assembly solutions needed to form dense monolayers on graphene. The equilibrium constants of all pyrene derivatives fell into the range from 103.4 to 104.6 M–1. For the perbenzylated α-, β-, and γ-cyclodextrins, the equilibrium constants are 103.24, 102.97, and 102.95 M–1, respectively. Monolayers of 1-pyrenemethylammonium chloride on graphene were confirmed to be stable under heating to 100 °C in a high vacuum (2 × 10–5 Torr).

P-114 - Potential protective effects of hydroxypropyl-β-cyclodextrin on Aβ (1–42)-induced neurotoxicity

The presence of amyloid β (Aβ) peptide plaques is one of the key events for the neuropathogenesis of Alzheimer disease (AD). High membrane cholesterol concentration promotes Aβ incorporation into membrane and increases the cytosolic calcium concentration leading to cell death. Oxidative stress is an early factor in AD pathogenesis that can lead to cell signaling impairments and increased production of Aβ. In turn, Aβ aggregation reciprocally augment the oxidative stress. Potential interactions between Aβ and “lipid rafts” may affect the activity of CREB signaling system which plays an important role for memory process. The aim of this work was to examine the effect of hydroxypropyl-β-cyclodextrin (HP-β-CD), is a cyclodextrin derivative and capable to deplete cholesterol from cell membranes, on the levels of total oxidant status (TOS) and mRNA expressions of CREB-controlled molecules, and “lipid raft” protein Caveolin-1 (Cav-1) in Aβ (1–42) induced rat model of AD. Our results showed that TOS levels, and CREB, BDNF and Cav-1 mRNA expressions were significantly regulated by HP-β-CD treatment against Aβ (1–42) in the rat hippocampus. Accordingly, these results may reflect the potential protective effect of HP-β-CD against Aβ peptide- induced neurotoxicity.

Comprehensive evaluation of solubilization of flavonoids by various cyclodextrins using high performance liquid chromatography and chemometry

Flavonoids have many pharmacological activities, but the water solubility is poor, Cyclodextrin (CD) can be used to increase the solubility of flavonoids through making flavonoids into their cavities. While various CDs have different solubilization effects on flavonoids. Therefore, the purpose of this study was to evaluate the solubilization of flavonoids by three classes of cyclodextrins by Chemometrics (I native CDs: alpha-cyclodextrin (α-CD), beta-cyclodextrin (β-CD) and gamma-cyclodextrin (γ-CD); II hydrophilic CD derivatives: methyl-β-cyclodextrin (Me-β-CD) and 2-hydroxypropyl-β-cyclodextrin (HP-β-CD); III ionic CD derivative: sulfobutyl ether β-cyclodextrin (SBE-β-CD)). All selected CDs had significant solubilization effects (P < 0.01). The solubilization coefficients of six kinds of CDs on flavonoids were α-CD: 41.77, γ-CD: 61.81, β-CD: 143.45, HP-β-CD: 415.43, Me-β-CD: 558.53, SBE-β-CD: 709.56, respectively. Phase solubility study indicated that six kinds of CDs and kaempferide can form inclusion complexes with 1:1 M ratio, association constants (Ka) of inclusion compounds were kaempferide-α-CD: 808 L/mol, kaempferide-β-CD: 1541 L/mol, kaempferide-γ-CD: 1191 L/mol, kaempferide-HP-β-CD: 9335 L/mol, kaempferide-Me-β-CD: 10,421 L/mol, kaempferide-SBE-β-CD: 12,502 L/mol, respectively. The study showed that SBE-β-CD has the best solubilization effect on flavonoids, therefore, SBE-β-CD may be widely used as a solubilizing agent for flavonoids.

MRI probes based on C6-peracetate β-cyclodextrins: Synthesis, gadolinium complexation and in vivo relaxivity studies

The initial synthesis of two β-cyclodextrin derivatives bearing seven carboxylate ligands was optimized in order to improve the production of contrast agents. A speciation study using potentiometric analysis was performed on a gadolinium(III) complex. The in vivo myocardic activity was evaluated on mice. This study highlights the best efficiency for the cyclodextrin derivative having free hydroxyl groups and validated the biomedical potential of the flexible cyclodextrin scaffold as a cardiac MRI probe.

Supramolecular Organocatalysis in Water Mediated by Macrocyclic Compounds.

In the last decades many efforts have been devoted to design supramolecular organocatalysts able to work in water as the reaction medium. The use of water as solvent provides promising benefits with respect to environmental impact. In this context, macrocyclic compounds played a role of primary importance thanks to their ease of synthesis and their molecular recognition abilities toward the reactants. The aim of this review is to give an overview of the recent advances in the field of supramolecular organocatalysis in water, focusing the attention on calixarene and cyclodextrins derivatives. Calixarenes and cyclodextrins, thanks to their hydrophobic cavities, are able to host selectively the substrates isolating they from the reaction environment. In addition, the synthetic versatilities of these macrocycles permits to introduce useful functional groups in close proximity of the hydrophobic binding sites. Regarding the cyclodextrins (CDs), we have here reviewed the their most recent uses as organocatalysts for the synthesis of heterocyclic compounds, in multi-component reactions and in carbon-carbon bond forming reactions. Examples have been reported in which CD catalysts are able to drive the regiochemistry of common organic reactions. In addition, cyclodextrins bearing catalytically active chiral groups, have shown excellent enantioselectivity in the catalysis of organic reactions. Recently reported results have shown that calixarene derivatives are able to accelerate organic reaction under “on-water” conditions with a significant selectivity toward the reactants. Under “on-water conditions” the hydrophobic effect, induced by insoluble calixarene derivatives, forces the reactants and the catalyst to aggregate and thus accelerating the reaction between them thanks to an amplification of weak secondary interactions. Regarding the use of water-soluble calixarene organocatalysts, we have here reviewed their role in the acceleration of common organic reactions.

Supramolecular Assembly of Thiolated Cyclodextrin and Ferrocene Derivative for Controlled Drug Delivery

AbstractConstruction of biocompatible nanoparticles is a significant topic of research at the chemistry/biology interface. Presently, more and more researchers have focused on supramolecular amphiphiles constructed by macrocycle‐induced aggregation, a feasible and universal strategy in the fabrication of functional nanomaterials. In this work, we report a pH‐responsive nanoparticle through a noncovalent complexation between per‐6‐thiolated β‐cyclodextrin sodium salt (SACD) and amphiphilic ferrocene derivative (FC12+Br−) in water. The formation and composition of the obtained supramolecular nanoparticles were comprehensively characterized by UV/Vis absorption, dynamic laser scattering, and microscopic observations. Furthermore, the drug loading and release studies demonstrated that the supramolecular binary nanoparticles could efficiently encapsulate doxorubicin hydrochloride (DOX) in their nanoparticulate cores, and the entrapped DOX could be rapidly released in a low pH environment. The present study suggests that the obtained binary supramolecular amphiphiles with good stability, tunable assembling/disassembling behaviors, and controlled drug loading/release properties have great potential in the construction of on‐demand drug‐delivery systems.

Predicting the Binding Mode of 2-Hydroxypropyl-β-cyclodextrin to Cholesterol by Means of the MD Simulation and the 3D-RISM-KH Theory.

It has been found that a cyclodextrin derivative, 2-hydroxypropyl-β-cyclodextrin (HPβCD), has reasonable therapeutic effect on Niemann-Pick disease type C, which is caused by abnormal accumulation of unesterified cholesterol and glycolipids in the lysosomes and shortage of esterified cholesterol in other cellular compartments. We study the binding affinity and mode of HPβCD with cholesterol to elucidate the possible mechanism of HPβCD for removing cholesterol from the lysosomes. The dominant binding mode of HPβCD with cholesterol is found based on the molecular dynamics simulation and a statistical mechanics theory of liquids, or the three-dimensional reference interaction site model theory with Kovalenko-Hirata closure relation. We examine the two types of complexes between HPβCD and cholesterol, namely, one-to-one (1:1) and two-to-one (2:1). It is predicted that the 1:1 complex makes two or three types of stable binding mode in solution, in which the βCD ring tends to be located at the edge of the steroid skeleton. For the 2:1 complex, there are four different types of the complex conceivable, depending on the orientation between the two HPβCDs: head-to-head (HH), head-to-tail (HT), tail-to-head (TH), and tail-to-tail (TT). The HT and HH cyclodextrin dimers show higher affinity to cholesterol compared to the other dimers and to all the binding modes of 1:1 complexes. The physical reason why the HT and HH dimers have higher affinity compared to the other complexes is discussed based on the consistency with the 1:1 complex. On the one hand, in case of the HT and HH dimers, the position of each CD in the dimer along the cholesterol chain comes right on or close to one of the positions where a single CD makes a stable complex. On the other hand, one of the CD molecules is located on unstable region along the cholesterol chain, for the case of TH and TT dimers.

Selective binding and controlled release of anticancer drugs by polyanionic cyclodextrins

The binding stoichiometry, binding constants, and inclusion mode of some water-soluble negatively charged cyclodextrin derivatives, i.e. heptakis-[6-deoxy-6-(3-sulfanylpropanoic acid)]-β-cyclodextrin(H1), heptakis-[6-deoxy-6-(2-sulfanylacetic acid)]-β-cyclodextrin(H2), mono-[6-deoxy-6-(3-sulfanylpropanoic acid)]-β-cyclodextrin (H3) and mono-[6-deoxy-6-(2-sulfanylacetic acid)]-β-cyclodextrin (H4), with three anticancer drugs, i.e. irinotecan hydrochloride; topotecan hydrochloride; doxorubicin hydrochloride, were investigated by means of 1H NMR, UV–Vis spectroscopy, mass spectra and 2D NMR. Polyanionic cyclodextrins H1-H2 showed the significantly high binding abilities of up to 2.6 × 104–2.0 × 105 M−1 towards the selected anticancer drugs, which were nearly 50–1000 times higher than the corresponding Ks values of native β-cyclodextrin. In addition, these polyanionic cyclodextrins also showed the pH-controlled release behaviors. That is, the anticancer drugs could be efficiently encapsulated in the cyclodextrin cavity at a pH value similar to that of serum but sufficiently released at an endosomal pH value of a cancer cell, which would make these cyclodextrin derivatives the potential carriers for anticancer drugs.

Inhibition of interaction between epigallocatechin-3-gallate and myofibrillar protein by cyclodextrin derivatives improves gel quality under oxidative stress

High levels of polyphenols can interact with myofibrillar proteins (MPs), causing damage to a MP emulsion gel. In this study, β-cyclodextrins were used to reduce covalent and non-covalent interaction between epigallocatechin-3-gallate (EGCG) and MPs under oxidative stress. The loss of both thiol and free amine groups and the unfolding of MPs caused by EGCG (80 μM/g protein) were significantly prevented by β-cyclodextrins, and the structural stability and solubility were improved. MP emulsion gel treated with EGCG (80 μM/g protein) had the highest cooking loss (68.64%) and gel strength (0.51 N). Addition of β-cyclodextrins significantly reduced cooking loss (26.24–58.20%) and improved gel strength (0.31–0.41 N) of MP emulsion gel jeopardized by EGCG under oxidative stress. Damage to the emulsifying properties of MPs caused by EGCG was significantly prevented by addition of β-cyclodextrins. β-cyclodextrins reduced interaction between EGCG and MPs in the order Methyl-β-cyclodextrin > (2-Hydroxypropyl)-β-cyclodextrin > β-cyclodextrin. In absence of EGCG, addition of β-cyclodextrins partly protected MPs from oxidative attack and improved its solubility. It is concluded that β-cyclodextrins does not markedly reduce the antioxidant ability of EGCG according to carbonyl analysis, and can effectively increase EGCG loading to potentially provide more durable antioxidant effect for meat products during processing, transportation and storage.

Polysaccharide Submicrocarrier for Improved Pulmonary Delivery of Poorly Soluble Anti-infective Ciprofloxacin: Preparation, Characterization, and Influence of Size on Cellular Uptake.

The majority of the currently used and developed anti-infectives are poorly water-soluble molecules. The poor solubility might lead to limited bioavailability and pharmacological action of the drug. Novel pharmaceutical materials have thus been designed to solve those problems and improve drug delivery. In this study, we propose a facile method to produce submicrocarriers (sMCs) by electrostatic gelation of anionic ß-cyclodextrin (aß-CD) and chitosan. The average hydrodynamic size ranged from 400 to 900 nm by carefully adjusting polymer concentrations and N/C ratio. The distinct host-guest reaction of cyclodextrin derivative is considered as a good approach to enhance solubility, and prevent drug recrystallization, and thus was used to develop sMC to improve the controlled release profile of a poorly soluble and clinically relevant anti-infective ciprofloxacin. The optimal molar ratio of ciprofloxacin to aß-CD was found to be 1:1, which helped maximize encapsulation efficiency (∼90%) and loading capacity (∼9%) of ciprofloxacin loaded sMCs. Furthermore, to recommend the future application of the developed sMCs, the dependence of cell uptake on sMCs size (500, 700, and 900 nm) was investigated in vitro on dTHP-1 by both flow cytometry and confocal microscopy. The results demonstrate that, regardless of their size, an only comparatively small fraction of the sMCs were taken up by the macrophage-like cells, while most of the carriers were merely adsorbed to the cell surface after 2 h incubation. After continuing the incubation to reach 24 h, the majority of the sMCs were found intracellularly. However, the sMCs had been designed to release sufficient amount of drug within 24 h, and the subsequent phagocytosis of the carrier may be considered as an efficient pathway for its safe degradation and elimination. In summary, the developed sMC is a suitable system with promising perspectives recommended for pulmonary extracellular infection therapeutics.

Metallocyclodextrins in medicinal chemistry.

This review focuses on metal complexes of cyclodextrin (CyD)derivatives designed for application as therapeutics or diagnostics. We discuss examples of metalloprotein models (hemoglobin, superoxide dismutase and catalase) based on cyclodextrins. The hydrophobic microenvironment of CyDs stabilizes the Fe(II) porphyrin system that can reversibly bind O2 or CO in water. Superoxide dismutase/catalase mimetics exploit functionalization with CyDs, which increase their solubility and biological activity. Furthermore, CyDs have been used as scaffolds to obtain multicenter metal complexes: paramagnetic systems act as high-performance contrast agents for magnetic resonance imaging applications. Finally, we review CyD ligands, whose use appears promising in metal chelation therapy, as CyD moiety confers additional properties to the ligands.

Amorphous Metal-Free Room-Temperature Phosphorescent Small Molecules with Multicolor Photoluminescence via a Host-Guest and Dual-Emission Strategy.

Metal-free room-temperature phosphorescence (RTP) materials offer unprecedented potentials for photoelectric and biochemical materials due to their unique advantages of long lifetime and low toxicity. However, the achievements of phosphorescence at ambient condition so far have been mainly focused on ordered crystal lattice or on embedding into rigid matrices, where the preparation process might bring out poor repeatability and limited application. In this research, a series of amorphous organic small molecular compounds were developed with efficient RTP emission through conveniently modifying phosphor moieties to β-cyclodextrin (β-CD). The hydrogen bonding between the cyclodextrin derivatives immobilizes the phosphors to suppress the nonradiative relaxation and shields phosphors from quenchers, which enables such molecules to emit efficient RTP emission with decent quantum yields. Furthermore, one such cyclodextrin derivative was utilized to construct a host-guest system incorporating a fluorescent guest molecule, exhibiting excellent RTP-fluorescence dual-emission properties and multicolor emission with a wide range from yellow to purple including white-light emission. This innovative and universal strategy opens up new research paths to construct amorphous metal-free small molecular RTP materials and to design organic white-light-emitting materials using a single supramolecular platform.