Role In Supramolecular Chemistry Research Articles

Quinoacridane[4]arenes─Very Large Conformationally Restricted Macrocycles.

Phenol-based macrocycles play a fundamental role in supramolecular chemistry, but their size has been rather limited. Here we report a novel class of very large, bowl-shaped macrocycles with a diameter of 21.8 Å. These quinoacridane[4]arenes are 150% larger than the current record holders, the acridane[4]arenes, and three times the size of resorcin[4]arene. We expect the quinoacridane[4]arenes to be a useful platform for the construction of molecular containers.

Chiral Self‐Discrimination Induced Luminescence Vapochromism of Binaphthol Imides for Anti‐Counterfeiting and Data Encryption

AbstractChiral self‐discrimination plays a critical role in supramolecular chemistry and materials science. However, an ideal strategy for achieving chiral self‐discrimination remains elusive due to the inevitable nonspecific binding of incorrect enantiomers, and insufficient intrinsic optical activity of chiral molecules. Herein, a novel 1,1′‐binaphthol (BINOL) derivative with an imide group fused at the peri‐position of one naphthol scaffold is developed, which combines the dual functionalities of aggregation‐induced emission characteristic of BINOLs, and high emission of 1,8‐naphthalimides. The multiple molecular recognition between two hydroxyl groups in BINOL units and two carbonyl groups in 1,8‐naphthalimide moieties endows the precise chiral self‐discrimination behaviors. As expected, the homochiral aggregates exhibit reversible phase transitions, switching from non‐emission to bright green emission upon absorption and desorption of methanol vapor. In contrast, the heterochiral conglomerates exhibit irreversible yellow emission changes due to the impact of chiral self‐discrimination. Such chiral self‐discrimination‐induced luminescence vapochromism can be further applied to high‐level anti‐counterfeiting and data encryption. This work provides a new perspective on smart chiral organic materials based on chiral self‐discrimination.

Supramolecular Assemblies of 3/4-Chlorobenzoic Acid and Amino-Chloropyridine Derivatives: Synthesis, X-ray Diffraction, DFT Calculations, and Biological Screening

Organic acids (3-chlorobenzoic acid and 4-chlorobenzoic acid) were treated with 4-amino-2-chloropyridine and 2-amino-4-chloropyridine as coformers for cocrystallization. Acid/base pairs afforded a cocrystal (3-chlorobenzoic acid and 4-amino-2-chloropyridine, compound 1) and molecular salts (2-amino-4-chloropyridinium 3-chlorobenzoate, 2; 2-amino-4-chloropyridinium 4-chlorobenzoate, 3). The products were characterized with the help of FT-IR, UV/visible spectroscopy, PXRD, and SC-XRD. The position of the Cl-substituent on the phenyl ring was explored with respect to proton transfer between acid/base pairs, and its role in supramolecular chemistry is discussed in detail. The existence of supramolecular assemblies was further reproduced using DFT calculations. Further, frontier molecular orbital (FMO), molecular electrostatic potential (MEP), and noncovalent interaction index (NCI) analyses were performed to gain insight into the electronic properties and nature of noncovalent interactions. The prepared compounds were examined for their biological activities against selected Gram-positive and Gram-negative bacterial strains and were also tested as antioxidant agents (DPPH free radical scavenging). Structural parameters determined experimentally and theoretically are within the expected range, and the biological activities of the resultant compounds are moderate.

Design and Synthesis of New Type of Macrocyclic Architectures Used for Optoelectronic Materials and Supramolecular Chemistry.

Supramolecular chemistry has received much attention for decades. Macrocyclic architectures as representative receptors play a vital role in supramolecular chemistry and are applied in many fields such as supramolecular assembly and host-guest recognition. However, the classical macrocycles generally lack functional groups in the scaffolds, which limit their further applications, especially in optoelectronic materials. Therefore, developing a new design principle is not only essential to better understand macrocyclic chemistry and the supramolecular behaviors, but also further expand their applications in many research fields. In recent years, the doping compounds with main-group heteroatoms (B, N, S, O, P) into the carbon-based π-conjugated macrocycles offered a new strategy to build macrocyclic architectures with unique optoelectronic properties. In particular, the energy gaps and redox behavior can be effectively tuned by incorporating heteroatoms into the macrocyclic scaffolds. In this Minireview, we briefly summarize the design and synthesis of new macrocycles, and further discuss the related applications in optoelectronic materials and supramolecular chemistry.

Bismacrocycle: Structures and Applications.

In the past half-century, macrocycles with different structures and functions, have played a critical role in supramolecular chemistry. Two macrocyclic moieties can be linked to form bismacrocycle molecules. Compared with monomacrocycle, the unique structures of bismacrocycles led to their specific recognition and assembly properties, also a wide range of applications, including molecular recognition, supramolecular self-assembly, advanced optical material construction, etc. In this review, we focus on the structure of bismacrocycle and their applications. Our goal is to summarize and outline the possible future development directions of bismacrocycle research.

N]Cycloparaphenylene-Pillar[5]arene Bismacrocycles: Their Circularly Polarized Luminescence and Multiple Guest Recognition Properties.

Both pillar[n]arenes (P[n]As) and [n]cycloparaphenylenes ([n]CPPs) play an important role in supramolecular chemistry. Herein, we report the precise synthesis of two multifunctional bismacrocycles [n]CPP-P[5]A by integrating P[5]A into the [n]CPP backbone. The photoluminescence quantum yield (ΦF ) of the bismacrocycles was found to show a dramatic increase relative to the corresponding [n]CPPs. The chiral enantiomers (pR)/(pS)-[8]CPP-P[5]A were successfully isolated by chiral HPLC, and showed promising properties of circularly polarized luminescence (glum ≈0.02). In addition, [n]CPP-P[5]A bismacrocycles are capable of binding pyridinium salts and fullerene derivatives with high affinity and specificity within the two distinct cavities. Transient absorption studies showed that photo-induced electron transfer occurs in [10]CPP-P[5]A⊃C60 complex. Our results suggest that [n]CPP-P[5]A are potentially useful in CPL-active materials, multiple guest recognition and supramolecular polymer preparation.

N]Cycloparaphenylene‐Pillar[5]arene Bismacrocycles: Their Circularly Polarized Luminescence and Multiple Guest Recognition Properties

AbstractBoth pillar[n]arenes (P[n]As) and [n]cycloparaphenylenes ([n]CPPs) play an important role in supramolecular chemistry. Herein, we report the precise synthesis of two multifunctional bismacrocycles [n]CPP‐P[5]A by integrating P[5]A into the [n]CPP backbone. The photoluminescence quantum yield (ΦF) of the bismacrocycles was found to show a dramatic increase relative to the corresponding [n]CPPs. The chiral enantiomers (pR)/(pS)‐[8]CPP‐P[5]A were successfully isolated by chiral HPLC, and showed promising properties of circularly polarized luminescence (glum≈0.02). In addition, [n]CPP‐P[5]A bismacrocycles are capable of binding pyridinium salts and fullerene derivatives with high affinity and specificity within the two distinct cavities. Transient absorption studies showed that photo‐induced electron transfer occurs in [10]CPP‐P[5]A⊃C60 complex. Our results suggest that [n]CPP‐P[5]A are potentially useful in CPL‐active materials, multiple guest recognition and supramolecular polymer preparation.

Tetraphenylethene-based macrocycles with dual-ring topology: synthesis, structures, and applications

This review focuses on the eight-shaped double ring structure of tetraphenylethylene, summarizes the research progress of structures, ionic molecular structures and metal molecular structures, and looks forward to its future development direction.

Assembly of three sulfonylcalix[4]arene-based multinuclear complexes: Tunable structures and guest encapsulation properties

Understanding and controlling the structure of polymetallic clusters plays a fundamental role in supramolecular chemistry. Herein we describe the preparation of three sulfonylcalix[4]arenebased multinuclear cluster complexes, namely, [Fe4(TBSC)2(DMF)4(µ3-H2O)2(H2O)2·2MeCN] (1), [Fe2Na4(TBSC)2(DMF)4(µ6-H2O)(H2O)2] (2), and [Fe4(TBSC)(Py)4(µ4-H2O)] (3) from trivalent iron ions and p-tert-butylsulfonylcalix[4]arene ligands by the metal-directed assembly. These complexes exhibit interesting tunable core structures, exo cavities, supramolecular packing characteristics in the solid state. As a result, the three multinuclear complexes exhibit selective molecular recognition toward the dye molecules.

Formation of supramolecular structures in aqueous medium by noncovalent interactions between surfactant and resorcin[4]arene

Self-assembly of molecular elements through non-covalent interactions plays a central role in supramolecular chemistry. The intermolecular interactions between macrocyclic and open-chain amphiphilic building blocks have been of large interest for last decade, since their mixed assembly is an example of building nanostructures by supramolecular bottom-up synthesis. Here we report that noncovalent interactions of viologen-based resorcin[4]arene cavitand with sodium dodecyl sulphate can enable self-assembly into highly-ordered supramolecular structures. A set of physicochemical methods was used to study the aggregation and binding properties of the supramolecular system based on these components. It was found that in this system the morphological transitions are observed depending on the ratio of the components of the system. The effectiveness of the mixed compositions as carriers for hydrophilic doxorubicin and hydrophobic antioxidants rutin and quercetin was evaluated, and a high loading efficiency of drugs and the ability to sustained release were found for the equimolar system. This study demonstrates features of such supramolecular structures, highlighting their potential applications in drug delivery.

Synthesis and characterization of a porphyrin-crown ether conjugate as a potential intermediate for drug delivery application

The development of synthetic strategies for functional building units plays a central role in supramolecular chemistry. Both porphyrin and crown ethers have attracted the attention of researchers worldwide owing to their unique properties. It is envisioned that the integration of the two molecules will result in hybrid materials with potential applications in many fields. In the present study, a new porphyrin derivative 3 appended with four 18-crown-6 (18C6) ether moieties was synthesized through the Suzuki-Miyaura coupling of boronic ester porphyrin 1 and 4-bromobenzo-18-crown-6 2 in 80% yield. Porphyrin 3 was fully characterized by 1H/[Formula: see text]C NMR spectroscopy and high resolution mass spectrometry. The tendency of the 18C6 to form host-guest complexes with ammonium cations was exploited to assemble cation responsive hybrid material of porphyrin 3 and ammonium immobilized mesoporous silica nanoparticles (MSNs). Furthermore, the potential application of the 3/MSNs conjugate as a cation-responsive drug delivery vehicle was investigated in solution by UV-vis and fluorescence spectroscopies.

The interplay between anion-π and H-bonding interactions in X−···s-Triazine···(HF)n(HCl)3-n (X = F−, Cl− and CN−) complexes: DFT and DFT-D study

ABSTRACT Anion-π interactions play an important role in supramolecular chemistry. The aim of this work is to explore the effect of H-bonding between s-Triazine and separated molecules (HF)n(HCl)3-n on the strength of anion-π interaction in X−–s-Triazine–(HF)n(HCl)3-n (X− = F–, Cl– and CN–) complexes. The M06-2X/6-311++G(d,p) binding energies (BEs) were corrected by using B2PLYP, mPW2PLYP, M06-2X-GD3 and B2PLYP-GD3 functionals. The molecular electrostatic potential (MESP) analysis revealed that involving multiple binding sites in s-Triazine (TA) through N···H H-bonding can enhance the MESP value over the ring centre of TA so that for H-bonding complexes containing HF is greater than those of HCl. The BE results revealed that the stability of X−–TA–(HF)n(HCl)3-n anion-π complexes in each series increases as the number of HF involved in H-bonding increases. The results showed that the complexes owning F– anion with higher interaction energies display the strong cooperativity effects in the ternary systems. B2PLYP functional showed stronger intramolecular dispersion effects than M06-2X one. Besides, a correlation was found between BE, MESP, bond distances, natural bond orbitals (NBO) and atoms in molecules (AIM) data.

Macrocyclic Arenes Functionalized with BODIPY: Rising Stars among Chemosensors and Smart Materials

Macrocycles play a crucial role in supramolecular chemistry and the family of macrocyclic arenes represents one of the most important types of hosts. Among them, calixarenes, resorcinarenes and pillararenes are the most commonly encountered macrocyclic arenes, and they have received considerable attention. Boron-dipyrromethene (BODIPY) dyes are fascinating compounds with multiple functionalization sites and outstanding luminescence properties including high fluorescence quantum yields, large molar absorption coefficients and remarkable photo- and chemical stability. The combination of macrocyclic arenes and BODIPY dyes has been demonstrated to be an effective strategy to construct chemosensors for various guests and smart materials with tailored properties. Herein, we firstly summarize the recent advances made so far in macrocyclic arenes substituted with BODIPY. This review only focuses on the three macrocyclic arenes of calixarenes, resorcinarenes and pillararenes, as there are no other macrocyclic arenes substituted BODIPY units at the present time. Hopefully, this review will not only afford a guide and useful information for those who are interested in developing novel chemosensors and smart materials, but also inspire new opportunities in this field.

Template-Free Self-Assembly of Molecular Trefoil Knots and Double Trefoil Knots Featuring Cp*Rh Building Blocks.

Understanding and controlling the topology of self-assembled structures plays a fundamental role in supramolecular chemistry. Herein, the preparation of a series of tetranuclear metallarectangles and hexanuclear trefoil knots featuring Cp*Rh building blocks by template-free self-assembly with four different rigid and flexible ligands is described. Transformations between the trefoil knots and the corresponding macrocycles can be induced by using concentration effects. Remarkably, the hexanuclear trefoil knot 5 was shown to assemble further to provide rare examples of [12+1] heteronuclear double trefoil knots (5 a/5 b/5 c/5 d) through coordination of the amide oxygen atoms to the secondary metal ions Na+ /K+ /Ca2+ /Cd2+ . The synthetic results are supported by single-crystal XRD.

Macrocycles containing azo groups: recognition, assembly and application

Macrocyclic compounds play an important role in supramolecular chemistry accounting for their unique recognition and self-assembly properties and potential applications in biomedicine and material science. Azo compounds display promising capability in fields of molecular switches, polymers, smart materials and molecular machines because of their photoactive and electroactive properties. Introducing azo groups into macrocycles gives them signal moieties, additional recognition sites, photo-responsive properties, and so on. Herein, we comprehensively review the structures of azo-containing macrocyclic compounds reported up to now. Then we describe representative works on azo macrocycles with their molecular recognition, self-assembly and application emphasized.

Carboxylate cross-linked cyclodextrin: A nanoporous scaffold for enhancement of rosuvastatin oral bioavailability

Cyclodextrins play an important role in supramolecular chemistry acting as building blocks than can be cross-linked by various linker molecules forming nano-porous structures called nanosponges (NS). NS have the ability to enhance the stability, solubility and bioavailability of various actives. This work aimed at elaborating rosuvastatin (ROS) loaded NS to improve its oral bioavailability. Carboxylate-linked NS were synthesized by reacting β-CD with pyromellitic dianhydride (PDA) at different molar ratios under specific conditions. ROS-loaded NS were prepared by lyophilisation technique and characterized for particle size, zeta potential, entrapment efficiency and drug release. Occurrence of cross-linking and ROS incorporation within the NS were assessed by DSC, FT-IR and SEM micrographs. NS prepared at a molar ratio of 1:6 of β-CD: PDA demonstrated the highest entrapment efficiency (88.76%), an optimum particle size of 275nm, a narrow size distribution (PDI of 0.392), and zeta potential of −61.9 indicating good colloidal stability. In vivo oral pharmacokinetics study in male Sprague Dawley rats showed that ROS-NS provided an outstanding enhancement in oral bioavailability compared to drug suspension and marketed tablets besides their physicochemical stability for 3month. Accordingly, ROS-NS represent a superior alternative to the conventional marketed formulation for effective ROS delivery.

Arjunolic Acid: A Promising Antioxidant Moiety with Diverse Biological Applications

Arjunolic acid (AA) is a triterpenoid saponin isolated mainly from Terminalia arjuna bark. Arjunolic acid is associated with the various important physiological functions viz. antioxidant, antimicrobial, cardioprotective, hepatoprotective, and plays important role in supramolecular chemistry, etc. Arjunolic acid exhibits important function in maintaining the level of various antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), glutathione reductase (GR) and glutathione peroxidase (GPx), level of cellular metabolites, reduced glutathione (GSH), oxidized glutathione (GSSG) and thereby reduces the oxidative stress. Its protective effect on liver, pancreas and kidney has also been the key property of arjunolic acid. Hence, arjunolic acid has potential to treat various disorders and this review may provide valuable information about arjunolic acid. Keywords: Oxidative stress, arjunolic acid, Terminalia arjuna, reactive oxygen species (ROS), reactive nitrogen species (RON).

ChemInform Abstract: Diketopyrrolopyrrole: Brilliant Red Pigment Dye‐Based Fluorescent Probes and Their Applications

AbstractReview: 51 refs.

How Small Can a Catenane Be?

Catenanes are playing an increasingly important role in supramolecular chemistry. In attempting to identify the minimum number of carbon atoms in a viable catenane, the B3LYP, BP86, M06-2X, MM3, and MM4 methods were applied to study representative [2]catenane models, which consist of two mechanically interlocked saturated n-cycloalkanes ([CnH2n]2). The structures, energy variations, and electron density differences vary nearly monotonically from n = 18 to 11. For example, the B3LYP/DZP++ dissociation energies [CnH2n]2 → 2CnH2n are 101, 121, 159, 191, 222, 252, 290, and 323 kcal/mol from n = 18 to 11, respectively. However, there is much variation among the energetic predictions with the B3LYP, BP86, M06-2X, MM3, and MM4 methods. The distances of the longest C-C single bond in each catenane are 1.593 (n = 18), 1.604 (n = 17), 1.631 (n = 16), 1.640 (n = 15), 1.667 (n = 14), 1.669 (n = 13), 1.680 (n = 12), and 1.689 Å (n = 11). These results display something of a shoulder in the vicinity of n = 14. This may suggest that [C15H30]2 is the smallest catenane that will resist fragmentation under specified laboratory conditions.

Hydrogen‐Bond Dynamics of CH⋅⋅⋅O Interactions: The Chloroform⋅⋅⋅Acetone Case

Spectroscopic evidence for C-H...O hydrogen bonding in chloroform...acetone [Cl(3)CH...O=C(CH(3))(2)] mixtures was obtained from vibrational inelastic neutron scattering (INS) spectra. Comparison between the INS spectra of pure samples and their binary mixtures reveals the presence of new bands at about 82, 130 and 170 cm(-1). Assignment of the 82 cm(-1) band to the nuO...H anti-translational mode is considered and discussed. In addition, the betaC-H mode of CHCl(3) at 1242 cm(-1) is split in the spectra of the mixtures, and the high-wavenumber component is assigned to the hydrogen-bonded complex. The plot of the integrated intensity of this component shows a maximum for x=0.5, in agreement with the 1:1 stoichiometry of the chloroformacetone complex, with a calculated complexation constant of 0.15 dm(3) mol(-1). Results also show that the complex behaves as an independent entity, that is, despite being weak, such interactions play a key role in supramolecular chemistry.