Proton Conduction in Tröger's Base-Linked Poly(crown ether)s

Reaction Site Designation by Intramolecular Electric Field in Tröger's-Base-Derived Conjugated Microporous Polymer for Near-Unity Selectivity of CO2 Photoconversion

To facilitate solar-driven overall CO₂ and H₂ O convsersion into fuels and O₂ , a series of covalent microporous polymers derived from Tröger's base are synthesized featuring flexural backbone and unusual charge-transfer properties. The incorporation of rigid structural twist Tröger's base unit grants the polymers enhanced microporosity and CO₂ adsorption/activation capacity. Density function theory calculations and photo-electrochemical analyses reveal that an electric dipole moment (from negative to positive) directed to the Tröger's base unit is formed across two obliquely opposed molecular fragments and induces an intramolecular electric field. The Tröger's base unit located at folding point becomes an electron trap to attract photogenerated electrons in the molecular network, which brings about suppression of carrier recombination and designates the reaction site in synergy with the conjugated network. In response to the discrepancy in reaction pathways across the reaction sites, the product allocation in the catalytic reaction is thereby regulated. Optimally, CMP-nTB achieves the highest photocatalytic CO production of 163.53 µmol g^-1 h^-1 with approximately unity selectivity, along with H₂ O oxidation to O₂ in the absence of any photosensitizer or co-catalyst. This work provides new insight for developing specialized artificial organic photocatalysts.

Ultrafast and selective separation of 99mTc from molybdenum matrix using DBDGA deliberately tailored macrocyclic crown-ethers

Technetium-99m (^99mTc) is an important medical radionuclide. Due to the crisis in supply of molybdenum-99 (⁹⁹Mo), production of ^99mTc directly via the ¹⁰⁰Mo (p, 2 n) reaction by cyclotron was proposed. In this process, the most critical challenge is to rapidly and efficiently separate ^99mTc from high concentration of molybdenum. In this work, a novel ligand, bis(N,N-dibutyldiglycolamide)dibenzo-18-crown-6 (BisDBDGA-DB18C6) was successfully synthesized and used for extraction of TcO₄^- /ReO₄^- from molybdenum. The results demonstrated that BisDBDGA-DB18C6 expressed excellent selectivity for TcO₄^- with a high separation factor of 1.6 × 10⁵ against Mo, a fast extraction kinetic (within 45 s), and a high extraction capacity of 211 mmol ReO₄^- (⁹⁹TcO₄^-)/per mole of extractant. The extraction mechanism was proposed as a co-interaction of macrocyclic crown ether and N,N-dibutyldiglycolamide group through slope analysis, FT-IR, ESI-MS, ¹H NMR titration and theory calculations. Importantly, ⁹⁹Tc in the organic phase can be quantitatively (> 99%) and easily back-extracted using deionized water, which can be directly used for medical applications.

Tröger's Base Chemistry in Solution and in Zr(IV)-Based Metal-Organic Frameworks

Tröger's base (TB) and its derivatives have been studied extensively due to their unique concave shape stemming from the endomethylene strap. However, the strap-clipped TB chemistry has been largely overlooked in metal-organic framework (MOF) solids, leading to a gap in our knowledge within this field. In this work, we report the in situ strap elimination of a carboxylate-carrying TB in the presence of formic acid, both in solution and in Zr(IV)-based MOFs. In the solution system, the methanodiazocine nucleus can be exclusively transformed into an N,N'-diformyl-decorated phenhomazine derivative, regardless of the solvent used (DMF, DMA, or DEF), as unambiguously uncovered by single crystal X-ray crystallography. In contrast, while in the MOF synthetic system, the degree of derivatization reaction can be effectively controlled to give either the secondary diamine or formyl-decorated diamine, depending on the solvent used (DMF or DEF), resulting in the formation of two Zr-MOFs with 8-connected bcu (NU-1900) and 12-connected fcu (NU-407) topologies, respectively. The derivatization mechanism is proposed to be topology-guided and dependent on the local acid concentration during the MOF formation processes. Moreover, we discovered a novel post-synthetically water-induced in situ linker formylation process in NU-1900 through sequential formic acid elimination, migration, and condensation processes, affording an isostructural framework with the same linker as in NU-407, which further corroborates our proposed mechanism. Additionally, the highly defective NU-1900 with abundant accessible Zr sites was demonstrated to be an outstanding catalyst for the detoxification of a nerve agent simulant with a half-life of less than 1 min.

Molecular Tweezer Based on Perylene and Crown Ether for Selective Recognition of Fullerenes

A molecular tweezer trans-di(perylene-3-ylmethanaminobenzo)-18-crown-6 (DP-18C6) incorporating two perylene subunits in a single crown ether core was designed and synthesized as a host for fullerenes. Through the cooperative effect of the perylene subunits and the crown ether moiety, DP-18C6 can efficiently recognize fullerenes including C₆₀, C₇₀, and C₇₆. ¹H NMR titration and fluorescence titration experiments demonstrated that DP-18C6 can effectively grasp the fullerene molecule to form a 1:1 host-guest complex. Density functional theory calculations revealed the presence of intermolecular π-π interactions between the perylene subunits of DP-18C6 and the fullerene molecule. More importantly, DP-18C6 exhibited remarkably high binding selectivity for higher fullerenes over C₆₀, revealing potential application for the separation of fullerenes by means of host-guest interactions.

K+-Responsive Crown Ether-Based Amphiphilic Copolymer: Synthesis and Application in the Release of Drugs and Au Nanoparticles

Due to unique chelating and macrocyclic effects, crown ether compounds exhibit wide application prospects. They could be introduced into amphiphilic copolymers to provide new trigger mode for drug delivery. In this work, new amphiphilic random polymers of poly(lipoic acid-methacrylate-co-poly(ethylene glycol) methyl ether methacrylate-co-N-isopropylacrylamide-co-benzo-18-crown-6-methacrylamide (abbrev. PLENB) containing a crown ether ring and disulphide bond were synthesized via RAFT polymerization. Using the solvent evaporation method, the PLENB micelles were formed and then used to load substances, such as doxorubicin hydrochloride (DOX) and gold nanoparticles. The results showed that PLENB exhibited a variety of lowest critical solution temperature (LCST) in response to the presence of different ions, such as K+, Na+ and Mg2+. In particular, the addition of 150 mM K+ increased the LCST of PLENB from 31 to 37 °C and induced the release of DOX from the PLENB@DOX assemblies with a release rate of 99.84% within 12 h under 37 °C. However, Na+ and Mg2+ ions could not initiate the same response. Furthermore, K+ ions drove the disassembly of gold aggregates from the PLENB-SH@Au assemblies to achieve the transport of Au NPs, which is helpful to construct a K+-triggered carrier system.

Multiple Enhancement Effects of Crown Ether in Tröger's Base Polymers on the Performance of Anion Exchange Membranes

The development of anion exchange membranes (AEMs) is hindered by the trade-off of ionic conductivity, alkaline stability, and mechanical properties. Tröger's base polymers (Tb-polymers) are recognized as promising membrane materials to overcome these obstacles. Herein, the AEMs made from Tb-poly(crown ether)s (Tb-PCEs) show good comprehensive performance. The influence of crown ether on the conductivity and alkaline stability of AEMs has been investigated in detail. The formation of hydronium ion-crown ether complexes and an obvious microphase-separated structure formed by the existence of crown ether can enhance the conductivity of the AEMs. The maximum OH^- conductivity of 141.5 mS cm^-1 is achieved from the Tb-PCEs based AEM (Tb-PCE-1) at 80 °C in ultrapure water. The ion-dipole interaction of the Na⁺ with crown ether can protect the quaternary ammonium from the attack of OH^- to improve the alkaline stability of AEMs. After 675 h of alkaline treatment, the OH^- conductivity of Tb-PCE-1 decreases by only 6%. The Tb-PCE-1-based single cell shows a peak power density of 0.202 W cm^-2 at 80 °C. The prominent physicochemical properties are attributed to the well-developed microstructure of the Tb-PCEs, as revealed by TEM, AFM, and SAXS observations.

Adjustable chiral self-sorting and self-discriminating behaviour between diamond-like Tröger's base-linked cryptands

Adjustable chiral self-sorting and self-discriminating behaviour between diamond-like Tröger's base-linked cryptands was reported, which could be regulated by external stimuli easily.