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Donor‐acceptor in linear π‐conjugated systems elicits the intramolecular charge transfer which improves the optical and electronic characteristics. Nevertheless, linear arrangement of electron donor and acceptor finely tune the charge or electron transfer process divulges the device performance. Therefore, molecular engineering of appropriate D−A with precise spacer is indeed challenging. Herein, we synthesized two bispyrene derivatives and attached with benzothiadazole and phenyl group through imidazole spacer (PyBTD and PyBz). PyBTD has shown solvatochromism demonstrates the intramolecular charge transfer (ICT) from pyrene to benzothiadiazole while PyBz remains as pristine spectra. Microscopic images reveal that network‐type structures for PyBTD and elongated nanorods from self‐assemblies of PyBz. Subsequently, host‐guest interactions suggest that C60 was encapsulated in concave shaped bispyrene controls their crystallinity in nanostructures leads short nanosheets. Impedance analyses depict ICT assisted nanowires facilitate improved conductivity than host‐guest complex. Therefore, imidazole spacer between D−A systems paves the way to design such type of molecules for future generated optoelectronics. [ABSTRACT FROM AUTHOR]

Directional electron flow in the photocatalyst enables efficient charge separation, which is essential for efficient photocatalysis of H2 production. Here, we report a novel class of tetracationic cyclophanes (7) incorporating bipyridine Pt(II) and selenoviologen. X‐ray single‐crystal structures reveal that 7 not only fixes the distances and spatial positions between its individual units but also exhibits a box‐like rigid electron‐deficient cavity. Moreover, host–guest recognition phenomena are observed between 7 and ferrocene, forming host–guest complexes with a 1 : 1 stoichiometry. 7 exhibits good redox properties, narrow energy gaps, and strong absorption in the visible range (370–500 nm) due to containing two selenoviologen (SeV2+) units. Meanwhile, the femtosecond transient absorption (fs‐TA) reveals that 7 has stabilized dicationic biradical, efficient charge separation, and facilitates directional electron flow to achieve efficient electron transfer due to the formation of rigid cyclophane and electronic architecture. Then, 7 is applied to visible‐light‐driven hydrogen evolution with high hydrogen production (132 μmol), generation rate (11 μmol/h), turnover number (221), and apparent quantum yield (1.7 %), which provides a simplified and efficient photocatalytic strategy for solar energy conversion. [ABSTRACT FROM AUTHOR]

The geometrical structures of cucurbit[n]uril (CB[n], n = 5–8 and their complexes with molnupiravir (MLP) drug have been investigated using the DFT computations. The complexation energies and electronic properties of CB[n]/MLP complexes were also computed. The host–guest interactions in the complexation are occurred through the of dipole–dipole interactions which are the hydrogen bonds between the O−H or N−H of molnupiravir and oxygen atoms of CB[n]s. The CB[n]/MLP host–guest complexation in both gas and water are found to be an exothermic reaction with negative complexation energy values. By means of the NBO analysis and MEP contours, the partial charge transfers from CB[n]s to molnupiravir are displayed. After drug complexation, the electronics properties of CB[n]s are significantly changed. This means that CB[n]s can act as a host for appropriately molnupiravir guest, even in aqueous solution. [ABSTRACT FROM AUTHOR]

Lithium hexafluorophosphate (LiPF6), the most commonly used lithium battery electrolyte salt, is vulnerable to heat and humidity. Quantitative and qualitative determination the variation of LiPF6 have always relied on advanced equipment. Herein, we develop a fast, convenient, high-selective fluorescence detection method based on metal--organic cages (MOC), whose emission is enhanced by nearly 20 times in the presence of LiPF6 with good stability and photobleaching resistance. The fluorescent probe can also detect moisture in battery electrolyte. We propose and verify that the luminescence enhancement is due to the presence of hydrogen bond-induced enhanced emission effect in cages. Fluorescent excitation-emission matrix spectra and variable-temperature nuclear magnetic resonance spectroscopy are employed to clarify the role of hydrogen bonds in guest-loaded cages. Density functional theory (DFT) calculation is applied to simulate the structure of host-guest complexes and estimate the adsorption energy involved in the system. The precisely matched lock-and-key model paves a new way for designing and fabricating novel host structures, enabling specific recognition of other target compounds. [ABSTRACT FROM AUTHOR]

The excessive use of biocides has considerable environmental and economic impacts; this is why new technologies have been sought to decrease the concentration levels applied in an effort to reduce the use of these substances. Microencapsulation using cyclodextrins has been widely used in the food and pharmaceutical industries as a way of reducing the concentrations of the active substance necessary to achieve a biological effect and/or eliminate its irritating or toxicological effects. In this study, the inclusion complexation behavior and binding ability of benzothiazolinone (BIT) with different β-cyclodextrins (β-CD, HP-β-CD, and Me-β-CD) was investigated. The intermolecular interactions were examined through UV and FTIR spectroscopy, DSC, 1D 1H NMR, and 2D ROESY. The highest stability constant was observed for the BIT/Me-β-CD inclusion complex (299.5 ± 2.9 M−1). Antibacterial activity was investigated against Staphylococcus aureus and Escherichia coli, and the results revealed that the BIT/Me-β-CD inclusion complex displays a higher antibacterial activity than BIT. The acute toxicity of the biocide and inclusion complex was also examined using the photobacterium Aliivibrio fischeri. Although BIT exhibited higher toxicity than the inclusion complex, further investigation is needed due to the quorum quenching effect of β-CDs. The data found suggest that BIT microencapsulation can increase its aqueous solubility and can be used as an effective tool to improve its chemical, biological, and ecotoxicological properties. [ABSTRACT FROM AUTHOR]

Herein, we designed a chiral, axially‐twisted molecular scaffold (ATMS) using pyridine‐2,6‐dicarboxamide (PDC) unit as pivot, chiral trans‐cyclohexanediamine (CHDA) residues as linkers, and pyrene residues as fluorescent reporters. R,R‐ATMS exclusively adopted M‐helicity and produced differential response in UV‐vis, fluorescence, and NMR upon addition of tartaric acid (TA) stereoisomers allowing naked‐eye detection and enantiomeric content determination. Circular dichroism (CD) profile of R,R‐ATMS underwent unique changes during titration with TA stereoisomers ‐ while loss of CD signal at 345 nm was observed with equimolar D‐TA and meso‐TA, inversion was seen with equimolar L‐TA. Temperature increase weakened these interactions to partially recover the original CD signature of R,R‐ATMS. 2D NMR studies also indicated the significant structural changes in R,R‐ATMS in the solution state upon addition of L‐TA. Single crystal X‐ray diffraction (SCXRD) studies on the crystals of the R,R‐ATMS⊃D‐TA salt revealed the interacting partners stacked in arrays and ATMS molecules stabilized by π‐π stacking between its PDC and pyrene residues. Contrastingly, tightly‐packed supramolecular cages comprised of four molecules each of R,R‐ATMS and L‐TA were seen in R,R‐ATMS⊃L‐TA salt, and the ATMS molecules contorted to achieve CH‐π interactions between its pyrene residues. These results may have implications in modulating the helicity of topologically‐similar larger biomolecules. [ABSTRACT FROM AUTHOR]

Multistimuli‐responsive color‐changing materials have potential applications in areas such as chemical sensing and anti‐counterfeiting. In this work, a fluoro‐phenyl‐acetyl‐substituted viologen derivative (FPAV·Cl2) is synthesized, which can form a supramolecular inclusion complex with cucurbit[7]uril (Q[7]) via self‐assembly. Significantly, the resulting inclusion complex FPAV2+@Q[7] in the solid‐state exhibits visual color changes in response to multiple external stimuli including light, heat, and vapors of ammonia and organic amines. The electron spin resonance (ESR) and ultraviolet–visible (UV–vis) spectra analysis reveals that the photochromic, thermochromic, and vapochromic behavior of FPAV2+@Q[7] is due to the generation of FPAV+• free radicals resulting from electron transfer. Furthermore, in the solid‐state, FPAV2+@Q[7] shows controllable fluorescence regulated by its chromic process. Based on the multi stimuli‐responsive color‐changes and fluorescence properties of FPAV2+@Q[7], its practical applications in erasable inkless printing, multiple anti‐counterfeiting processes, visible ammonia/organic amines detection, and information encryption are demonstrated. The supramolecular strategy of encapsulating viologen derivatives into macrocycles provides a general method for fabricating multi stimuli‐responsive chromic materials with multiple practical applications. [ABSTRACT FROM AUTHOR]

The chemistry of hoop-shaped π-conjugated molecules has increased dramatically in recent years. We present here a computational modeling of photoinduced electron transfer processes in a series of host–guest complexes of Twin1, Twin2, and Twin3 double nanohoops with C60 fullerene. According to our findings, charge transfer from cycloparaphenylene (CPP) fragments to C60 is energetically favorable and occurs on a sub-nanosecond time scale. The slow decay of the generated charge-separated state suggests that the complexes may be of interest for organic photovoltaics. [ABSTRACT FROM AUTHOR]

In recent years, organic materials with room‐temperature phosphorescence (RTP) features have gained significant attention due to their wide applications in the fields of bioimaging, light‐harvesting materials, encryption technology, etc. Although several examples of organic RTP materials in the crystalline state and polymer‐based systems have been reported in the last decade or so, achieving organic RTP in the solution phase, particularly in the aqueous phase has remained a challenging task. Herein in this review, we summarize the progress in this direction by highlighting design strategies based on supramolecular scaffolding and host–guest complexation and the applications of such aqueous organic RTP materials in bioimaging, sensing, etc. [ABSTRACT FROM AUTHOR]

The simultaneous discrimination and detection of multiple anions in an aqueous solution has been a major challenge due to their structural similarity and low charge radii. In this study, we have constructed a supramolecular fluorescence sensor array based on three host–guest complexes to distinguish five anions (F–, Cl–, Br–, I–, and ClO–) in an aqueous solution using anionic-induced fluorescence quenching combined with linear discriminant analysis. Due to the different affinities of the three host–guest complexes for each anion the anion quenching efficiency for each host–guest complex was likewise different, and the five anions were well recognized. The fluorescence sensor array not only distinguished anions at different concentrations (0.5, 10, and 50 µM) with 100% accuracy but also showed good linearity within a certain concentration range. The limit of detection (LOD) was < 0.5 µM. Our interference study showed that the developed sensor array had good anti-interference ability. The practicability of the developed sensor array was also verified by the identification and differentiation of toothpaste brands with different fluoride content and the prediction of the iodine concentration in urine combined with machine learning. [ABSTRACT FROM AUTHOR]

The basic hydrolysis of Malachite Green (MG) in the presence of β-Cyclodextrin (β-CD) has been studied using UV-Vis spectroscopic techniques and at 20 °C. β-CD was found to catalyze the basic hydrolysis. Indeed, this basic hydrolysis is catalyzed by the interaction cyclodextrin hydroxyl group, in its deprotonated form with the carbocation in the host-guest complex. The proposed model has been successfully applied to a reaction catalyzed by CD. It considers two simultaneous pathways in the aqueous medium involving free hydroxyl ions and the substrate-CD complex. The model allows us to obtain the kinetic parameters including the bimolecular rate constant between MG and HO− in bulk water (kw = 1.47 ± 0.01 mol−1s−1), the rate constant between MG and the deprotonated hydroxyl group of β-CD inside the host-guest complex (kCD = 0.25 ± 0.03 s−1) and the binding constant of MG inside the β-CD (KS = 2500 ± 50). This behavior is like the hydrolysis of Cristal Violet (CV) in the same reaction media.

The receptor ability of diethyl N,N′‐(1,3‐phenylene)dicarbamate (1) to form host–guest complexes with theophylline (TEO) and caffeine (CAF) by mechanochemistry was evaluated. The formation of the 1–TEO complex (C12H16N2O4·C7H8N4O2) was preferred and involves the conformational change of one of the ethyl carbamate groups of 1 from the endo conformation to the exo conformation to allow the formation of intermolecular interactions. The formation of an N—H...O=C hydrogen bond between 1 and TEO triggers the conformational change of 1. CAF molecules are unable to form an N—H...O=C hydrogen bond with 1, making the conformational change and, therefore, the formation of the complex impossible. Conformational change and selective binding were monitored by IR spectroscopy, solid‐state 13C nuclear magnetic resonance and single‐crystal X‐ray diffraction. The 1–TEO complex was characterized by IR spectroscopy, solid‐state 13C nuclear magnetic resonance, powder X‐ray diffraction and single‐crystal X‐ray diffraction. [ABSTRACT FROM AUTHOR]

The basic hydrolysis of Malachite Green (MG) in the presence of β-Cyclodextrin (β-CD) has been studied using UV-Vis spectroscopic techniques and at 20 °C. β-CD was found to catalyze the basic hydrolysis. Indeed, this basic hydrolysis is catalyzed by the interaction cyclodextrin hydroxyl group, in its deprotonated form with the carbocation in the host-guest complex. The proposed model has been successfully applied to a reaction catalyzed by CD. It considers two simultaneous pathways in the aqueous medium involving free hydroxyl ions and the substrate-CD complex. The model allows us to obtain the kinetic parameters including the bimolecular rate constant between MG and HO− in bulk water (kw = 1.47 ± 0.01 mol−1s−1), the rate constant between MG and the deprotonated hydroxyl group of β-CD inside the host-guest complex (kCD = 0.25 ± 0.03 s−1) and the binding constant of MG inside the β-CD (KS = 2500 ± 50). This behavior is like the hydrolysis of Cristal Violet (CV) in the same reaction media. [ABSTRACT FROM AUTHOR]

The derivatization of pillar[n]arenes is a prerequisite for endowing them with functions, as well as enriching the application of pillar[n]arene materials in advanced material science. Herein, we report the self‐assembly of amphiphilic rim‐differentiated pillar[5]arene (H1). One side of the pillar[5]arene is composed of hydrophilic poly(ethylene oxide) chains, benzene and azobenzene groups connected with ether bonds, and the other side is composed of ethoxy groups. In CHCl3 solvent, the amphiphile H1 self‐assembled into spherical micelles, while in H2O/THF mixed solvent H1 self‐assembled into nanorod‐like assemblies. Interestingly, addition of a guest molecule composed of tetraphenylethene and hexanenitrile groups (G1) to the CHCl3 solution of H1 produces large sheet aggregates via the strong π–π stacking of rod segments. The reversible transformation between the nanosheet assemblies of host–guest complexes and nanoparticles is achieved by addition of the guest molecule 1,4‐butylamine (G2) and pillar[5]arene with ethoxy groups as competitive molecules. Notably, worm‐like and nanorod micelles of H1 were constructed in H2O/THF solution triggered by light irradiation, which assemblies can be used as photosensitive erasable writing materials. © 2023 Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

The excessive use of biocides has considerable environmental and economic impacts; this is why new technologies have been sought to decrease the concentration levels applied in an effort to reduce the use of these substances. Microencapsulation using cyclodextrins has been widely used in the food and pharmaceutical industries as a way of reducing the concentrations of the active substance necessary to achieve a biological effect and/or eliminate its irritating or toxicological effects. In this study, the inclusion complexation behavior and binding ability of benzothiazolinone (BIT) with different β-cyclodextrins (β-CD, HP-β-CD, and Me-β-CD) was investigated. The intermolecular interactions were examined through UV and FTIR spectroscopy, DSC, 1D 1H NMR, and 2D ROESY. The highest stability constant was observed for the BIT/Me-β-CD inclusion complex (299.5 ± 2.9 M−1). Antibacterial activity was investigated against Staphylococcus aureus and Escherichia coli, and the results revealed that the BIT/Me-β-CD inclusion complex displays a higher antibacterial activity than BIT. The acute toxicity of the biocide and inclusion complex was also examined using the photobacterium Aliivibrio fischeri. Although BIT exhibited higher toxicity than the inclusion complex, further investigation is needed due to the quorum quenching effect of β-CDs. The data found suggest that BIT microencapsulation can increase its aqueous solubility and can be used as an effective tool to improve its chemical, biological, and ecotoxicological properties.

A novel supramolecular complex C44H71Cl2N26O22 (CB[6]@Pipa·2HCl) of the “host-guest” type has been synthesized. It is based on cucurbit[6]uril (CB[6]) with dihydrochloride 1,4-bis(2-hydroxyethyl)piperazine (Pipa·2HCl) localized within the portals of the macrocycle. Based on 1H NMR and X-ray crystallography, the host–guest ratio in the complex under the specified conditions was determined to be 1:1. Further evidence of complex formation was observed through IR spectroscopy, where a shift in the absorption band of carbonyl vibrational frequencies of cucurbit[6]uril by 36 cm−1 towards the longer wavelength region was detected in CB[6]@Pipa·2HCl compared to the original CB[6]. TGA/DSC analysis results indicated an increase in thermal stability by 55 °C for the obtained CB[6]@Pipa·2HCl complex compared to the initial 1,4-bis(2-hydroxyethyl)piperazine dihydrochloride. The structure of the synthesized CB[6]@Pipa·2HCl complex was confirmed using single-crystal XRD.

The family of cucurbiturils (CBs), the unique pumpkin-shaped macrocycles, has received great attention over the past four decades owing to their remarkable recognition properties. They have found diverse applications including biosensing and drug delivery technologies. The cucurbituril complexation of guest molecules can modulate their pKas, improve their solubility in aqueous solution, and reduce the adverse effects of the drugs, as well as enhance the stability and/or enable targeted delivery of the drug molecule. Employing twelve cationic styryl dyes with N-methyl- and N-phenylpiperazine functionality as probes, we attempted to understand the factors that govern the host–guest complexation of such molecules within CB[7] and CB[8] host systems. Various key factors determining the process were recognized, such as the pH and dielectric constant of the medium, the cavity size of the host, the chemical characteristics of the substituents in the guest entity, and the presence/absence of metal cations. The presented results add to our understanding (at the molecular level) of the mechanism of encapsulation of styryl dyes by cucurbiturils, thus shedding new light on various aspects of the intriguing complexation chemistry and the underlying recognition processes. [ABSTRACT FROM AUTHOR]

In the present study, a host–guest complex was obtained between a modified Chalcone (CHC) with anti T. cruzi activity and hydroxypropyl beta-cyclodextrin (HpBCD). This approach was chosen due to the low water solubility of CHC, in a drug delivery approach against Chagas disease. The complexes CHC:HpBCD were obtained by three synthetic routes: lyophilization, grinding method and calcinated method. TG assays point to the formation of an in situ complex of CHC with HpBCD. The 1H NMR assays give an idea of how the inclusion of CHC in HpBCD occurs and give the association constant of these species, that is around 60. UV–vis measurements demonstrate that the stoichiometry of complexation is 1:1. The FTIR and PXRD results show that solid state complex formation was successfully formed. Biological assays were carried out and demonstrate that the obtained complexes have antiparasitic activity against T. cruzi, having the advantage of a better water solubility and requiring a smaller mass amount of CHC to work. [ABSTRACT FROM AUTHOR]

Abstract Variable-temperature cryogenic ion mobility-mass spectrometry (VT-Cryo-IM-MS) was developed to examine the conformations of host-guest complexes. The VT-Cryo-IM-MS consists of an electrospray ionization source, a quadrupole ion trap, a cryogenic ion drift tube, and a time-of-flight mass spectrometer. The ion drift tube was cooled to 83 K with liquid nitrogen. Two sets of ion funnels are installed at the source and the drift tube to focus the ion beam. We used Li+-encapsulated fullerene (Li+@C60) as a reference ion to examine the ion-mobility resolution of the VT-Cryo-IM-MS apparatus because this ion has a rigid structure with a single conformer. The temperature dependence of collision cross section (CCS) of Li+@C60 and the resolution of the apparatus were determined at each temperature. We examined the conformations of host-guest complexes of a series of metal ions (M = Ca2+, Na+, Ag+, K+, Rb+, and Cs+) with dibenzo-24-crown-8 (DB24C8) by Cryo-IM-MS. All CCS distributions were fitted with two Gaussian functions which are assigned to closed and open conformers. These closed and open conformers have different distances between the two benzene rings of DB24C8. The abundance ratio of closed conformers for these M(DB24C8) complex ions depends on the guest M ion with an order, Ca2+ < Na+ < Ag+ < Cs+ < Rb+ < K+. The stability of the closed conformer of K+(DB24C8) originates from the benzene ring positional relationship which is quite close to that of the free benzene dimer. This special benzene dimer-like conformation produces the strong π-π interaction between the benzene rings of K+(DB24C8).

3D hydrogel structures fabricated by two‐photon polymerization (TPP) have become attractive in biomedical fields. Generally, conventional organic solvents are toxic and the residues left in the fabricated 3D structures are harmful to cells. Hence, anion ionic carbazole‐based water‐soluble two‐photon initiator (TPI) 3,6‐bis[2‐(1‐methylpyridinium)vinyl]‐9‐methylcarbazole ditosylate (BT) is proposed to construct arbitrary 3D hydrogel structures. Cucurbit[7]uril (CB7) and BT form a host‐guest complex (CB7/BT) with a binding ratio of 1:1, which further improves the water solubility, biocompatibility and nonlinear absorption property of TPI. A water‐soluble photoresist consisting of photoinitiator CB7/BT and monomer poly(ethylene glycol) diacrylate is prepared to explore the TPP fabrication capacity. The electron paramagnetic resonance measurement shows that CB7/BT initiates photopolymerization by alkyl radicals. The laser threshold power of the photoresist is 6.3 mW and the feature size is 127 nm in TPP at 780 nm. The initiator with p‐toluenesulfonate anion exhibits higher binding energy, larger two‐photon absorption cross‐section and two‐photon fabrication resolution compared with the previous work using iodide as an anion, indicating a promising way to improve the fabrication capacity of water‐soluble TPI through changing the anion ionic group. The proposed strategy will provide high potential for the further application in the biomedical field. [ABSTRACT FROM AUTHOR]

There is huge demand for developing guests that bind β‐CD and can conjugate multiple cargos for cellular delivery. We synthesized trioxaadamantane derivatives, which can conjugate up to three cargos per guest. 1H NMR titration and isothermal titration calorimetry revealed these guests form 1 : 1 inclusion complexes with β‐CD with association constants in the order of 103 M−1. Co‐crystallization of β‐CD with guests yielded crystals of their 1 : 1 inclusion complexes as determined by single‐crystal X‐ray diffraction. In all cases, trioxaadamantane core is buried within the hydrophobic cavity of β‐CD and three hydroxyl groups are exposed outside. We established biocompatibility using representative candidate G4 and its inclusion complex with β‐CD (β‐CD⊂G4), by MTT assay using HeLa cells. We incubated HeLa cells with rhodamine‐conjugated G4 and established cellular cargo delivery using confocal laser scanning microscopy (CLSM) and fluorescence‐activated cell sorting (FACS) analysis. For functional assay, we incubated HeLa cells with β‐CD‐inclusion complexes of G4‐derived prodrugs G6 and G7, containing one and three units of the antitumor drug (S)‐(+)‐camptothecin, respectively. Cells incubated with β‐CD⊂G7 displayed the highest internalization and uniform distribution of camptothecin. β‐CD⊂G7 showed higher cytotoxicity than G7, camptothecin, G6 and β‐CD⊂G6, affirming the efficiency of adamantoid derivatives in high‐density loading and cargo delivery. [ABSTRACT FROM AUTHOR]

The new Lewis acid–base adducts of general formula X(nad)B←NC5H4-C5H4N→B(nad)X [nad = 1,8-O2C10H6, X = C6H5 (2c), 3,4,5-F3-C6H2 (2d)] were synthesized in high yields via reactions of 1,8-dihydroxy naphthalene [nadH2] and 4,4′-bipyridine with the aryl boronic acids C6H5B(OH)2 and 3,4,5-F3-C6H2B(OH)2, respectively, and structurally characterized by multi-nuclear NMR spectroscopy and SCXRD. Self-assembled H-shaped Lewis acid–base adduct 2d proved to be effective in forming thermally stable host–guest complexes, 2d × solvent, with aromatic hydrocarbon solvents such as benzene, toluene, mesitylene, aniline, and m-, p-, and o-xylene. Crystallographic analysis of these solvent adducts revealed host–guest interactions to primarily occur via π···π contacts between the 4,4′-bipyridyl linker and the aromatic solvents, resulting in the formation of 1:1 and 1:2 host–guest complexes. Thermogravimetric analysis of the isolated complexes 2d × solvent revealed their high thermal stability with peak temperatures associated with the loss of solvent ranging from 122 to 147 °C. 2d, when self-assembled in an equimolar mixture of m-, p-, and o-xylene (1:1:1), preferentially binds to o-xylene. Collectively, these results demonstrate the ability of 1,8-dihydroxy naphthalene to serve as an effective building block in the selective self-assembly to supramolecular aggregates through dative covalent N→B bonds. [ABSTRACT FROM AUTHOR]

This paper reports a stimuli-responsive designer supramolecular polymer gel in dimethylsulphoxide (DMSO)/water (1:2) based on a dipeptide amphiphile and β-cyclodextrin (β-CD) The dipeptide amphiphile contains caproic acid at the N terminus and methyl ester at the C terminus. From X-ray single crystal diffraction, the amphiphile adopts a kink-like conformation. The amphiphile self-assembled to form a parallel sheet-like structure stabilized by multiple intermolecular hydrogen bonds. Moreover, the parallel sheet-like structure is also stabilized by edge-to-edge π–π stacking interactions. In higher-order packing, it forms a corrugated sheet-like structure stabilized by hydrophobic interactions. The dipeptide amphiphile interacts with β-cyclodextrin and forms gel through supramolecular polymer formation in (DMSO)/water (1:2) by a simple heating-cooling cycle. The sol-to-gel transformation is because of a host–guest complex between compound 1 and β-CD and the formation of supramolecular polymer accompanied by microstructure changes from nanofibers to microrods. The gel is temperature responsive with a Tgel of 70 °C. The supramolecular polymer gel is also responsive to stimuli such aspicric acid and HCl. The extensive spectroscopic studies show that the aromatic hydrophobic side chain of compound 1 forms a host–guest complex with β-CD. These results will be helpful for the design of advanced programable eco-friendly functional materials.

A series of novel hinge‐like molecules, namely dipyrrolo‐1,4‐dithiins (PDs), were prepared and fully characterized by NMR, UV/vis, cyclic voltammogram, ESR, and single crystal X‐ray diffraction (SCXRD) analysis. The lateral fusion of pyrroles with 1,4‐dithiins has led to not only retained key features of a dithiin, but also enhanced redox‐activity with increased susceptibility to radical cations via redox or chemical oxidation. Stabilization of their radicals are observed for the N,N‐tert‐butyl or N,N‐triphenylmethyl PD as evidenced by ESR measurements. DFT calculations and SCXRD analysis revealed PDs are extremely flexible with adaptive molecular geometries that can be mechanically regulated via crystal packing or host–guest complexation. The excellent donor nature of PDs renders inclusion complexes with the cyclophane bluebox (cyclobis(paraquat‐p‐phenylene)), featuring association constants up to 104 M−1. Additionally, a planarized transition intermediate associated with inversion dynamics of a PD has been preserved in the pseudorotaxane structure with assistances of π⋅⋅⋅π and S⋅⋅⋅π interactions. The hinged structure, excellent redox‐activity, and adaptive nature of PDs could further enable accesses to exotic redox switchable host–guest chemistry and functional materials. [ABSTRACT FROM AUTHOR]

Variable-temperature cryogenic ion mobility-mass spectrometry (VT-Cryo-IM-MS) was developed to examine the conformations of host-guest complexes. The VT-Cryo-IM-MS consists of an electrospray ionization source, a quadrupole ion trap, a cryogenic ion drift tube, and a time-of-flight mass spectrometer. The ion drift tube was cooled to 83 K with liquid nitrogen. Two sets of ion funnels are installed at the source and the drift tube to focus the ion beam. We used Li+-encapsulated fullerene (Li+@C60) as a reference ion to examine the ion-mobility resolution of the VT-Cryo-IM-MS apparatus because this ion has a rigid structure with a single conformer. The temperature dependence of collision cross section (CCS) of Li+@C60 and the resolution of the apparatus were determined at each temperature. We examined the conformations of host-guest complexes of a series of metal ions (M = Ca2+, Na+, Ag+, K+, Rb+, and Cs+) with dibenzo-24-crown-8 (DB24C8) by Cryo-IM-MS. All CCS distributions were fitted with two Gaussian functions which are assigned to closed and open conformers. These closed and open conformers have different distances between the two benzene rings of DB24C8. The abundance ratio of closed conformers for these M(DB24C8) complex ions depends on the guest M ion with an order, Ca2+ < Na+ < Ag+ < Cs+ < Rb+ < K+. The stability of the closed conformer of K+(DB24C8) originates from the benzene ring positional relationship which is quite close to that of the free benzene dimer. This special benzene dimer-like conformation produces the strong π-π interaction between the benzene rings of K+(DB24C8). [ABSTRACT FROM AUTHOR]

Supramolecular host‐guest chemistry has provided many opportunities for the design and construction of new fluorescent systems in various applications, particularly in the field of sensing. Owing to the special structure and fascinating utilities, cucurbit[n]urils (CB[n]s) existing themselves as a young family of molecular vessels, it construction a stable host‐guest supramolecular complex with a variety of fluorescent dyes and indicators, that has been used as a powerful fluorescent probe and is widely used in sensing and related research fields. Therefore, in this review article, we will outline and attention on the recent advances in the progress of various CB[n] ⋅ guest‐based fluorescent probes, it can provide a general overview of the construction, detection mechanism and fluorescence sensing of certain metal ions, biomolecules and toxic chemicals. Examples of the selection of other types of CB[n]‐based supramolecular assemblies and coordination polymers will also be covered. Finally, we will also provide important views on fluorescent CB[n] ⋅ guest‐based inclusion complex for metal ion and biomolecular sensors. [ABSTRACT FROM AUTHOR]

This paper reports a stimuli-responsive designer supramolecular polymer gel in dimethylsulphoxide (DMSO)/water (1:2) based on a dipeptide amphiphile and β-cyclodextrin (β-CD) The dipeptide amphiphile contains caproic acid at the N terminus and methyl ester at the C terminus. From X-ray single crystal diffraction, the amphiphile adopts a kink-like conformation. The amphiphile self-assembled to form a parallel sheet-like structure stabilized by multiple intermolecular hydrogen bonds. Moreover, the parallel sheet-like structure is also stabilized by edge-to-edge π–π stacking interactions. In higher-order packing, it forms a corrugated sheet-like structure stabilized by hydrophobic interactions. The dipeptide amphiphile interacts with β-cyclodextrin and forms gel through supramolecular polymer formation in (DMSO)/water (1:2) by a simple heating-cooling cycle. The sol-to-gel transformation is because of a host–guest complex between compound 1 and β-CD and the formation of supramolecular polymer accompanied by microstructure changes from nanofibers to microrods. The gel is temperature responsive with a Tgel of 70 °C. The supramolecular polymer gel is also responsive to stimuli such aspicric acid and HCl. The extensive spectroscopic studies show that the aromatic hydrophobic side chain of compound 1 forms a host–guest complex with β-CD. These results will be helpful for the design of advanced programable eco-friendly functional materials. [ABSTRACT FROM AUTHOR]

Cucurbiturils are magnificent macrocycles that are used as precise molecules for the fabrication of supramolecular chemotherapeutic agents through host-guest molecular recognition. In the present work, the host-guest complex of cucurbit[6]uril (CB[6]) with 5-fluorouracil (Flu, an anticancer drug) is synthesized and its structural study was carried out using UV, XRD, and TG/DTA techniques. The UV-Vis spectrum of the inclusion complex exhibited maximum absorbance with a blue shift at 302 nm whereas the maximum absorbance for free CB[6] was observed at 318 nm. This notable shift in wavelength proves the formation of the inclusion complex of CB[6] with fluorouracil. The host-guest complex of fluorouracil with CB[6] shows sharp endothermic peaks at 403.30C with a heat flow of -0.5 mW/mg the peak covers partially an area of 528.2 J/g, The large variations observed in the DSC curves of the complex compared with free host CB[6] confirm the formation of a stable host-guest complex. The XRD pattern of the host-guest complex is different from the parent compound and this reaffirms the formation of host-guest complex. The cytotoxic effect of 5-fluorouracil and the host-guest complex of CB[6] with fluorouracil on KB cells was determined by MTT assay and the cytotoxicity of anticancer drug Flu towards cancer cells significantly increases by encapsulating 5-fluorouracil into the hydrophobic cavity of CB[6], The ROS generation study was carried out by measurement of intracellular ROS using fluorescent and chemiluminescent probe. The ROS generation of anticancer drugs against cancer cells is significantly increased by encapsulating 5-fluorouracil into the hydrophobic cavity of CB[6], The inclusion complex of cucurbituril with fluorouracil treatment in KB cells showed higher anticancer potential than fluorouracil treatment in KB cells when compared to the control. The IC50 value of 5-flurouracil was found to be higher compared to the inclusion complex of cucurbituril with fluorouracil. The interesting results obtained, might open new avenues for the use of CB[6] host-guest complexes in anticancer and drug delivery studies. [ABSTRACT FROM AUTHOR]

Hypoxia accompanies many human diseases and is an indicator of tumor aggressiveness. Therefore, measuring hypoxia in vivo is clinically important. Recently, complexes of calix[4]arene were identified as potent hypoxia markers. The subject of this paper is new hypoxia-sensitive host–guest complexes of thiacalix[4]arene. We report a new high-yield synthesis method for thiacalix[4]arene with four anionic carboxyl azo fragments on the upper rim (thiacalixarene L) and an assessment of the complexes of thiacalixarene L with the most widespread cationic rhodamine dyes (6G, B, and 123) sensitivity to hypoxia. Moreover, 1D and 2D NMR spectroscopy data support the ability of the macrocycles to form complexes with dyes. Rhodamines B and 123 formed host–guest complexes of 1:1 stoichiometry. Complexes of mixed composition were formed with rhodamine 6G. The association constant between thiacalixarene L and rhodamine 6G is higher than for other dyes. Thiacalixarene L-dye complexes with rhodamine 6G and rhodamine B are stable in the presence of various substances present in a biological environment. The UV-VIS spectrometry and fluorescence showed hypoxia responsiveness of the complexes. Our results demonstrate that thiacalixarene L has a stronger binding with dyes compared with the previously reported azo-calix[4]arene carboxylic derivative. Thus, these results suggest higher selective visualization of hypoxia for the complexes with thiacalixarene L. [ABSTRACT FROM AUTHOR]

The supramolecular interactions in water between β-cyclodextrin and the open and closed photochromic forms of two bis-cationic dithienylethenes, characterized by different electronic properties, were investigated aiming at underlying the key aspects of the recognition process. The dithienylethene equipped with the cyclopentenyl unit showed a difference in binding free energies to the β-cyclodextrin between the open and closed photochromic forms of about 1 kJ/mol. Conversely, the dithienylethene equipped with the perfluorinated cyclopentenyl unit not only was a better guest but showed a three times higher difference in the binding of free energies between the open and closed isomers.

Chemiluminescence (CL) bioassay is one of the most advanced and used detection method in clinical diagnosis and biomedical research because of the advantages of low background, easy operation, and wide-field imaging without a light source or microscope. The luminol/hydrogen peroxide/horseradish peroxidase (luminol/H 2 O 2 /HRP) system is the most popular CL system, but its application in high-throughput imaging detection is challenged due to its low luminescence efficiency and flash-type emission which is difficult in ensuring the reproducibility and consistency of detection results. We reported a glow-type CL system of luminol@CD/H 2 O 2 /HRP by using a supramolecular enhancer of cyclodextrin (CD). This luminol@CD/H 2 O 2 /HRP system exhibited a luminescence lifetime of 41 min for sensitive and accurate imaging analysis. The long-lasting CL emission was attributed to the formation of a 1:1 host–guest complex between luminol and CD, which could stabilize the emitter and effectively reduce nonradiative relaxation. The formation of luminol@CD complex was determined through NMR experiments and theoretical analysis. Under optimum conditions, the luminol@CD/H 2 O 2 /HRP system showed higher sensitivity and much better precision than classical luminol/H 2 O 2 /HRP system for imaging detection of HRP. Especially, this glow-type luminol@CD/H 2 O 2 /HRP system realized CL imaging of microwell arrays on microfluidic chips. In addition, the luminol@CD/H 2 O 2 /HRP system was successfully applied for point-of-care detection of 17 β- estradiol based on a competitive mechanism of host–guest recognition. An efficient CL system is crucial for obtaining reproducible and consistent results for accurate detection. Our luminol@CD/H 2 O 2 /HRP system emitted strong and persistent luminescence, resulting in reliability and efficiency at both CL macroscopic and microscopic imaging detection. We expected the luminol@CD/H 2 O 2 /HRP CL system to be applied in various detection fields. [Display omitted] • A glow-type chemiluminescence system of luminol@CD/H 2 O 2 /HRP was presented by using a supramolecular enhancer of cyclodextrin. • The luminol@CD/H 2 O 2 /HRP system exhibited a luminescence lifetime of 41 min. • The luminol@CD/H 2 O 2 /HRP system realized both CL macroscopic and microscopic imaging detection of HRP with high sensitivity and good precision. • The luminol@CD/H 2 O 2 /HRP system enabled point-of-care detection of 17 β- estradiol. [ABSTRACT FROM AUTHOR]

The family of cucurbiturils (CBs), the unique pumpkin-shaped macrocycles, has received great attention over the past four decades owing to their remarkable recognition properties. They have found diverse applications including biosensing and drug delivery technologies. The cucurbituril complexation of guest molecules can modulate their pKas, improve their solubility in aqueous solution, and reduce the adverse effects of the drugs, as well as enhance the stability and/or enable targeted delivery of the drug molecule. Employing twelve cationic styryl dyes with N-methyl- and N-phenylpiperazine functionality as probes, we attempted to understand the factors that govern the host–guest complexation of such molecules within CB[7] and CB[8] host systems. Various key factors determining the process were recognized, such as the pH and dielectric constant of the medium, the cavity size of the host, the chemical characteristics of the substituents in the guest entity, and the presence/absence of metal cations. The presented results add to our understanding (at the molecular level) of the mechanism of encapsulation of styryl dyes by cucurbiturils, thus shedding new light on various aspects of the intriguing complexation chemistry and the underlying recognition processes.

The widespread conversion of synthetic receptors into luminescent sensors has been achieved via the use of fluorescent-indicator displacement assays (F-IDAs). Due to their rigid structures and efficient binding affinities, cucurbit[n]urils, combined with a variety of fluorescent guests, have gained extensive utilization in fluorescent-indicator displacement assays for sensing non-fluorescent or weakly fluorescent organic compounds (analytes) in a selective and specific manner. This mini-review summarizes recent advances in the design of cucurbit[n]uril-based fluorescent-indicator displacement assays and discusses the current challenges and future prospects in this area.

The highly unstable 1-methylcyclopropene (1-MCP) is used as an agrochemical in the form of supramolecular complexes with various receptors to extend the shelf life of fruits and vegetables. To control the content of 1-MCP in the complex with cucurbit[6]uril, a new analytical method involving the release of 1-MCP from the complex, its chemical transformation into a more stable derivative, and subsequent HPLC analysis of the latter was developed in this study. The reaction of 1-MCP with dimethyl acetylenedicarboxylate leading to the formation of dimethyl 2-(2-methylcycloprop-2en-1-yl)maleate was adopted from the literature, but the reaction conditions were significantly improved, making it suitable for routine analyses. To make this reaction suitable for the quantitative determination of 1-MCP in complex with cucurbit[6]uril, a multistep procedure was developed that allows the release of the gas from the complex upon dissolution, extraction and derivatization of 1-MCP in a suitable organic solvent, separation, evaporation and drying of the organic layer, and analysis of the residue (crude dimethyl 2-(2-methylcycloprop-2en-1-yl)maleate) by high-performance liquid chromatography (HPLC). The elaborated methodology allows reliable quantitative determination of 1-MCP in a supramolecular complex with cucurbit[6]uril, involving a relatively simple synthesis procedure using commercially available reagents and subsequent HPLC analysis of the derivative, which is non-volatile and stable for at least 10 days under normal storage conditions. [ABSTRACT FROM AUTHOR]

Intermolecular complexes with calixarenes are intriguing because of multiple possibilities of noncovalent binding for both polar and nonpolar molecules, including docking in the calixarene cavity. In this contribution calix[6]arenes interacting with amino acids are studied with an additional aim to show that tools such as symmetry-adapted perturbation theory (SAPT), functional-group SAPT (F-SAPT), and systematic molecular fragmentation (SMF) methods may provide explanations for different numbers of noncovalent bonds and of their varying strength for various calixarene conformers and guest molecules. The partitioning of the interaction energy provides an easy way to identify hydrogen bonds, including those with unconventional hydrogen acceptors, as well as other noncovalent bonds, and to find repulsive destabilizing interactions between functional groups. Various other features can be explained by energy partitioning, such as the red shift of an IR stretching frequency for some hydroxy groups, which arises from their attraction to the phenyl ring of calixarene. Pairs of hydrogen bonds and other noncovalent bonds of similar magnitude found by F-SAPT explain an increase in the stability of both inclusion and outer complexes. [ABSTRACT FROM AUTHOR]

The values of the apparent binding constants for β‐cyclodextrin complexes of betulin derivatives determined by mobility shift affinity capillary electrophoresis were found to be independent of the composition of the two background electrolytes used (tetraborate buffer, pH 9.18, and phosphate buffer, pH 8.00, both of them with 20 mM ionic strength). It has been found that if there is not a constant plateau on the binding curve then four independent parameters can be determined: binding constants (also referred to as stability, association, or formation constants) and ionic mobilities of 1:1 and 1:2 complexes. However, at least 10–12 data points in the binding curve should be used to reliably estimate the parameters. For the first time, the apparent binding constants for complexes of ester betulin derivatives with dimethyl‐β‐cyclodextrin have been determined by mobility shift affinity capillary electrophoresis. The logarithms of the constants for 1:1 and 1:2 complexes at 25°C for betulin 3,28‐diphthalate with a 95% confidence interval are 4.98 (4.95–5.01) and 7.52 (7.26–7.68); for betulin 3,28‐disulfate, the values are 4.97 (4.89–5.03) and 8.24 (6.82–8.52). It has been found that betulin 3,28‐disuccinate forms only a 1:1 complex and the binding constant logarithm is 5.25 ± 0.02. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of a novel class of pillar[4]arene[1]thioarenes (P[4]A[1]SMe) are reported. An oxidation–thionation strategy was used to replace a single dialkoxybenzene panel in the parent pillar[5]arene.1 H NMR spectroscopic titration experiments, supported by density functional theory computational studies, revealed that P[4]A[1]SMe show starkly modulated host–guest binding properties for electron-deficient aliphatic guests. [ABSTRACT FROM AUTHOR]

Cyclodextrins (CDs) are a family of cyclic oligosaccharides, consisting of a macrocyclic ring of glucose subunits linked by α-1,4 glycosidic bonds. The shape of CD molecules is similar to a truncated cone with a hydrophobic inner cavity and a hydrophilic surface, which allows the formation of inclusion complexes with various molecules. This review article summarises over 200 reports published by the end of 2021 that discuss the complexation of CDs with antibiotics and antibacterial agents, including beta-lactams, tetracyclines, quinolones, macrolides, aminoglycosides, glycopeptides, polypeptides, nitroimidazoles, and oxazolidinones. The review focuses on drug-delivery applications such as improving solubility, modifying the drug-release profile, slowing down the degradation of the drug, improving biological membrane permeability, and enhancing antimicrobial activity. In addition to simple drug/CD combinations, ternary systems with additional auxiliary substances have been described, as well as more sophisticated drug-delivery systems including nanosponges, nanofibres, nanoparticles, microparticles, liposomes, hydrogels, and macromolecules. Depending on the desired properties of the drug product, an accelerated or prolonged dissolution profile can be achieved when combining CD with antibiotics or antimicrobial agents. [ABSTRACT FROM AUTHOR]

Macrocyclic arenes-based fluorescent indicator displacement assays (F-IDAs) offer a unique and innovative approach to chemosensing, taking molecular recognition in host-guest chemistry to a higher level. Because of their special architecture and versatile host–guest binding properties, macrocyclic arenes, principally calix[n]arenes and, in recent years, pillar[n]arenes, in combination with various fluorophores, are widely used in F-IDAs for the specific and selective sensing of cationic, anionic, and neutral analytes. In this paper, we review recent progress in the development of F-IDAs based on macrocyclic arenes and outline the prospects and remaining challenges relating to macrocyclic arenes-based F-IDAs.

A widely used class of synthetic receptors are resorcin[4]arene-based cavitands. A collection of the most representative studies in this field is reported here, from organic-soluble receptors to those that are water-soluble. Intermolecular forces involved in complex formation – hydrogen bonds, halogen bonds and solvophobic interactions – are discussed with emphasis on the relationship between guest conformation and reactivity in the cavity. The applications of hosts as reaction vessels, chaperones, templates and protecting groups in organic and aqueous media are explored, highlighting how synthetic receptors are modern tools to explore the behavior of molecules in confined spaces.

The structural geometries of cucurbit[n]uril CB[n] with n = 6–9 and their complexes with oseltamivir (OST) drug were obtained using the density functional theory computations. The stationary points of the most stable complexes were confirmed using vibrational frequency calculation. The complexation energies and electronic properties of CB[n]/OST complexes were investigated. The calculated results indicate that the intermolecular interactions in all the studied complexes occur via a large number of dipole–dipole interactions, especially hydrogen bonds between oxygen atoms of CB[n] and hydrogen atoms of amine of oseltamivir drug. The negative complexation energies of CB[n]/OST complexes in both gas and water phases indicate that the host–guest complexes are exothermic process and the complexes are more stable than its bare CB[n]. In addition, the CB[7]/OST complex is more stable than that of all studied CB[n]/OST complexes. The frequency calculation results of the most stable complexes for each of CBs indicate that complexations occur via a spontaneous process. The NBO analysis of complexes shows the transferring of partial charge from CB[n]s to oseltamivir which correspond to their MEP contours. The HOMO and the LUMO orbitals are localized on the oseltamivir in CB[n]/OST complexes. After drug complexation, the electronic properties also display that the energy gaps of CB[n] are significantly changed. All of the complexation properties point out that CB[n]s can act as a host for appropriately oseltamivir guest, even in aqueous solution. [ABSTRACT FROM AUTHOR]

The supramolecular interactions in water between β-cyclodextrin and the open and closed photochromic forms of two bis-cationic dithienylethenes, characterized by different electronic properties, were investigated aiming at underlying the key aspects of the recognition process. The dithienylethene equipped with the cyclopentenyl unit showed a difference in binding free energies to the β-cyclodextrin between the open and closed photochromic forms of about 1 kJ/mol. Conversely, the dithienylethene equipped with the perfluorinated cyclopentenyl unit not only was a better guest but showed a three times higher difference in the binding of free energies between the open and closed isomers. [ABSTRACT FROM AUTHOR]

This study aimed to design and fabricate novel hydroxypropyl-β-cyclodextrin-based hypercrosslinked polymers, called nanosponges, as carriers for anticancer hydrophobic agents and compare them with host–guest complexes of hydroxypropyl-β-cyclodextrin, a remarkable solubilizer, to investigate their application in improving the pharmaceutical properties of the flavonoid naringenin, a model hydrophobic nutraceutical with versatile anticancer effects. For this purpose, three new nanosponges, crosslinked with pyromellitic dianhydride, citric acid, and carbonyldiimidazole, were fabricated. The carbonate nanosponge synthesized by carbonyldiimidazole presented the highest naringenin loading capacity (≈19.42%) and exerted significantly higher antiproliferative effects against MCF-7 cancer cells compared to free naringenin. Additionally, this carbonate nanosponge formed a stable nanosuspension, providing several advantages over the naringenin/hydroxypropyl-β-cyclodextrin host–guest complex, including an increase of about 3.62-fold in the loading capacity percentage, sustained released pattern (versus the burst pattern of host–guest complex), and up to an 8.3-fold increase in antiproliferative effects against MCF-7 cancer cells. Both naringenin-loaded carriers were less toxic to L929 murine fibroblast normal cells than MCF-7 cancer cells. These findings suggest that hydroxypropyl-β-cyclodextrin-based carbonate nanosponges could be a good candidate as a drug delivery system with potential applications in cancer treatment. [ABSTRACT FROM AUTHOR]

Sensitive and rapid monitoring of cholesterol levels in the human body are highly desirable as they are directly related to the diagnosis of cardiovascular diseases. By using the nanoarchitectonic approach, a novel fluorescent conjugated oligofluorene (OFP-CD) functionalized with β-cyclodextrin (β-CD) was assembled for "Turn-On" fluorescence sensing of cholesterol. The appended β-CD units in OFP-CD enabled the forming of host-guest complexes with dabsyl chloride moieties in water, resulting in fluorescence quenching of the oligofluorene through intermolecular energy transfer. In the presence of cholesterol molecules, a more favorable host-guest complex with stoichiometry 1 cholesterol: 2 β-CD units was formed, replacing dabsyl chloride in β-CD's cavities. This process resulted in fluorescence recovery of OFP-CD, owing to disruption of energy transfer. The potential of this nanoarchitectonic system for "Turn-On" sensing of cholesterol was extensively studied by fluorescence spectroscopy. The high selectivity of the sensor for cholesterol was demonstrated using biologically relevant interfering compounds, such as carbohydrates, amino acids, metal ions, and anions. The detection limit (LOD value) was as low as 68 nM, affirming the high sensitivity of the current system. [ABSTRACT FROM AUTHOR]

Due to the diseases that people face today, scientists dedicate a part of their research to the synthesis, characterization, and study of functional compounds for controlled drug delivery. On the one hand, resorcinarenes are macrocycles obtained by condensation reactions of resorcinol and aldehyde. They include an upper and a lower rim functioning with different groups that confer solubility to the macrocycle and favor interactions with other compounds, therefore the hydroxyl groups on the upper rim improve the formation of hydrogen bonds. Additionally, resorcinarenes feature a cavity studied for forming host-guest complexes. SBA-15, on the other hand, is a mesoporous silica characterized by ordered pores in its structure and a large surface area. As a result of its properties, it has been used for several purposes, including absorbents, drug delivery, catalysis, and environmental processes. This review shows the recent advances in synthesis methods, characterization, micelle formation, interaction with other compounds, and host-guest procedures, as well as techniques for evaluating toxicity, drug retention, and their preliminary uses in pharmacology for macrocycles, such as resorcin[4]arenes and SBA-15. [ABSTRACT FROM AUTHOR]

The current study investigated host-guest complexation in 6-p-toluidinylnaphthalene-2-sulfonate (TNS), a fluorescence probe used to investigate hydrophobic regions that contain the water-soluble cationic pillar[6]arene (CP6). After complexation with CP6, the fluorescence intensity of TNS was significantly increased. The decreases in the fluorescence intensity of the TNS•CP6 complex when phenolic food-additives are added have been used in indicator displacement assays to detect food additives in the water.

Umbrella sampling along a one-dimensional order parameter in combination with Hamiltonian replica exchange was employed to calculate the binding free energy of five guest molecules with known affinity to cucurbit[8]uril. A simple empirical approach correcting for the overestimation of the affinity by the GAFF force field was proposed and subsequently applied to the seven guest molecules of the "Drugs of Abuse" SAMPL8 challenge. Compared to the uncorrected binding free energies, the systematic error decreased but quantitative agreement with experiment was only reached for a few compounds. From a retrospective analysis a weak point of the correction term was identified. [ABSTRACT FROM AUTHOR]