Recognition Selectivities of Lasso-Type Pseudorotaxane Based on a Mono-Ester-Functionalized Pillararene.
ABSTRACT: Two types of mono-ester-functionalized pillararenes, P1 and P2, bearing different side-chain groups, were synthesized. Their host-guest complexation and self-inclusion properties were studied by 1H NMR and 2D nuclear overhauser effect spectroscopy (NOESY) NMR measurements. The results showed that the substituents on their phenolic units have a great influence on the self-assembly of both pillararenes, although they both could form stable pseudorotaxanes at room temperature. When eight bulky 4-brombutyloxy groups were capped on the cavity, instead of methoxy groups, pseudorotaxane P1 became less stable and its locked ester group in the inner space of cavity was not as deep as P2, leading to distinctly different host-guest properties between P1 and P2 with 1,6-dibromohexane. Moreover, pillararene P1 displayed effective molecular recognition toward 1,6-dichlorohexane and 1,2-bromoethane among the guest dihalides. In addition, the self-complex models and stabilities between P1 and P2 were also studied by computational modeling and experimental calculations.
Project description:Control of single-walled carbon nanotube dispersion properties is of substantial interest to the scientific community. In this work, we sought to investigate the effect of a macrocycle, pillararene, on the dispersion properties of a polymer-nanotube complex. Pillararenes are a class of electron-rich macrocyclic hosts capable of forming inclusion complexes with electron-poor guests, such as alkyl nitriles. A hydroxyl-functionalized pillararene derivative was coupled to the alkyl bromide side chains of a polyfluorene, which was then used to coat the surface of single-walled carbon nanotubes. Noncovalent functionalization of carbon nanotubes with the macrocycle-containing conjugated polymer significantly enhanced nanotube solubility, resulting in dark and concentrated nanotube dispersions (600 ?g mL<sup>-1</sup>), as evidenced by UV-vis-NIR spectroscopy and thermogravimetric analysis. Differentiation of semiconducting and metallic single-walled carbon nanotube species was analyzed by a combination of UV-vis-NIR, Raman, and fluorescence spectroscopy. Raman spectroscopy confirmed that the concentrated nanotube dispersion produced by the macrocycle-containing polymer was due to well-exfoliated nanotubes, rather than bundle formation. The polymer-nanotube dispersion was investigated using <sup>1</sup>H NMR spectroscopy, and it was found that host-guest chemistry between pillararene and 1,6-dicyanohexane occurred in the presence of the polymer-nanotube complex. Utilizing the host-guest capability of pillararene, the polymer-nanotube complex was incorporated into a supramolecular organogel.
Project description:Pillar[n]arenes are a new type of macrocyclic compounds, which were first reported in 2008 by Ogoshi. They not only have cylindrical, symmetrical, and rigid structures, but also have many advantages, including easy functionalization and rich host-guest properties. On the other hand, mechanically interlocked molecules (MIMs) exist extensively in nature which have been artificially synthesized and widely applied in the fields of nanotechnology and biology. Although pillararene-based MIMs have been investigated much over recent years, pillararene-based rotaxanes are very limited. In this report, we synthesized a series of amide-linked pillararene-based rotaxanes with ferrocene unit as the stopper. Under the catalysis of HOBT/EDCL, the mono-amido-functionalized pillararenes were amidated with ferrocene carboxylic acid to constructed ferrocene-based rotaxanes, respectively. The structure of the rotaxanes were characterized by 1H NMR, 13C NMR, 2D NMR, mass spectroscopy, and single-crystal X-ray structural determination. In the experiment, the monofunctionalized pillararene was synthesized with a self-inclusion property, which allows for forming a pseudo-rotaxane. The key role is the length of the imine chain in this process. The formation of a rotaxane was realized through amidation of ferrocene dicarboxylic acid, which acted as a plug. In addition, due to the ferrocene units, the pillararene-based rotaxanes perform electrochemically reversible property. Based on this nature, we hope these pillararene-based rotaxanes can be applied in battery devices in the future.
Project description:Planar-chiral pillararenes bearing ?-D-galactose substituents on both rims have been successfully synthesized and effectively separated by silica gel chromatography with a high yield. The obtained (S p )- and (R p )-?-D-galactose functionalized pillararenes [(S p-D )-GP5 and (R p-D )-GP5] exhibit the S p and R p planar chirality. Furthermore, (S p-D )-GP5 and (R p-D )-GP5 can not racemize according to dynamic 1H NMR and CD spectra. Notably, GP5 is able to capture a guest molecule (DNS-CPT) to form a host-guest supramolecular amphiphile, which can further self-assemble into chiral nanoparticles with the S p and R p planar chirality of (S p-D )-GP5 and (R p-D )-GP5 still being retained, suggesting GP5 could be as reliable chiral sources to transfer the S p and R p planar chirality.
Project description:Novel water-soluble multifunctional pillararenes containing amide-ammonium-amino acid moiety were synthesized. The compounds demonstrated a superior ability to bind (1S)-(+)-10-camphorsulfonic acid (S-CSA) and methyl orange dye depending on the nature of the substituent, resulting in the formation one-to-one complexes with both guests. The formation of host-guest complexes was confirmed by ultraviolet (UV), circular dichroism (CD) and 1H NMR spectroscopy. This work demonstrates the first case of using S-CSA as a chiral template for the non-covalent self-assembly of architectures based on pillararenes. It was shown that pillararenes with glycine or L-alanine fragments formed aggregates with average hydrodynamic diameters (d) of 165 and 238 nm, respectively. It was established that the addition of S-CSA to the L-alanine-containing derivative led to the formation of micron-sized aggregates with d of 713 nm. This study may advance the design novel stereoselective catalysts and transmembrane amino acid channels.
Project description:A series of mono-amide-functionalized pillararenes with different lengths of N-?-aminoalkyl groups as the side chain on the rim were designed and synthesized, which all formed pseudorotaxanes in the crystal state. And these pseudorotaxanes could be transformed into rotaxanes or open forms in the crystal state. In addition, they were also studied in solution by (1)H NMR spectroscopy.
Project description:The pillararene mono- and di(oxyalkoxy)benzoic acids were successfully prepared in high yields by sequential alkylation of ?-bromoalkoxy-substituted pillararenes with methyl or ethyl p-hydroxybenzoate followed by a hydrolytic reaction under basic conditions. Under catalysis of HOBt/EDCl, the amidation reaction of pillararene mono(oxybutoxy)benzoic acid with monoamido-functionalized pillararenes afforded diamido-bridged bis-pillararenes. 1H NMR and 2D NOESY spectra clearly indicated that rotaxanes were formed by insertion of longer diaminoalkylene unit into the cavity of one pillararene with another pillararene acting as a stopper. The similar catalysed amidation reaction of pillararene di(oxybutoxy)benzoic acid with monoamido-functionalized pillararenes resulted in the diamido-bridged tris-pillararenes, which successfully form the unique bis-rotaxanes bearing longer than diaminopropylene diamido bridges.
Project description:Tiaraarenes (Ts), a new class of five-fold symmetric oligophenolic macrocycles that are not accessible from the addition of formaldehyde to phenol, were synthesized for the first time. These pillararene-derived structures display both unique conformational freedom, differing from that of pillararenes, with a rich blend of solid-state conformations and excellent host-guest interactions in solution. Finally we show how this novel macrocyclic scaffold can be functionalized in a variety of ways and used as functional crystalline materials to distinguish uniquely between benzene and cyclohexane.
Project description:The design and synthesis of extended concave host P2 by fusion of two concave phosphorus-containing units is reported. Co-crystallization of P2 and the fullerene guests C60 and C70 afforded the 2?:?1 host-guest complexes (P2)2 ? C60 and (P2)2 ? C70, in which the two concave surfaces of P2 encapsulate the convex surface of the fullerenes in a sandwich fashion. Interestingly, the orientation of the two P2 molecules with respect to each other was observed to be flexible, resulting in the formation of a variety of cavity shapes. MALDI-TOF mass, NMR, and UV-vis absorption spectra supported the formation of host-guest complexes between P2 and the fullerenes in solution. The affinity of P2, containing two phosphorus atoms, towards fullerenes was significantly enhanced relative to P1 with one phosphorus atom.
Project description:The separation of styrene (St) and ethylbenzene (EB) mixtures is important in the chemical industry. Here, we explore the St and EB adsorption selectivity of two pillar-shaped macrocyclic pillar[n]arenes (EtP5 and EtP6; n = 5 and 6). Both crystalline and amorphous EtP6 can capture St from a St-EB mixture with remarkably high selectivity. We show that EtP6 can be used to separate St from a 50:50 v/v St:EB mixture, yielding in a single adsorption cycle St with a purity of >99%. Single-crystal structures, powder X-ray diffraction patterns, and molecular simulations all suggest that this selectivity is due to a guest-induced structural change in EtP6 rather than a simple cavity/pore size effect. This restructuring means that the material "self-heals" upon each recrystallization, and St separation can be carried out over multiple cycles with no loss of performance.
Project description:Supramolecular host-guest interaction and sensing between cationic pillararenes (CP5) and L-carnitine were developed by the competitive host-guest recognition for the first time. The fluorescence sensing platform was constructed by CP5 functionalized Au nanoparticles (CP5@Au-NPs) as receptor and probe (rhodamine 123, R123), which shown high sensitivity and selectivity for L-carnitine detection. Due to the negative charge and molecular size properties of L-carnitine, it can be highly captured by the CP5 via electrostatic interactions and hydrophobic interactions. The host-guest mechanism between PP5 and L-carnitine was studied by ¹H NMR and molecular docking, indicating that more affinity binding force of CP5 with L-carnitine. Therefore, a selective and sensitive fluorescent method was developed. It has a linear response of 0.1?2.0 and 2.0?25.0 ?M and a detection limit of 0.067 ?M (S/N = 3). The fluorescent sensing platform was also used to detect L-carnitine in human serum and milk samples, which provided potential applications for the detection of drugs abuse and had path for guarding a serious food safety issues.