Macrocyclic Cavity Research Articles

P-71 - Scandium(III) and macrocyclic cavity of DOTA-like ligands: implications for design of chelators for scandium radioisotopes

P-71 - Scandium(III) and macrocyclic cavity of DOTA-like ligands: implications for design of chelators for scandium radioisotopes

One-dimensional architectures built from adamantane-bearing macrocycles with multiple propargyl groups

Two macrocycles having adamantane, aromatic units, and propargyl groups (1, 2) were synthesized and their molecular alignments were investigated for the purpose of creating tubular and pseudopolyrotaxane structures. Macrocycles 1 and 2 have distinct molecular sizes and shapes and possess eight and four substituents, respectively. Each macrocycle afforded two inclusion crystals from two solvent systems. The two crystals of 1 had different macrocyclic backbones and orientation of propargyl groups, and columnar or tubular structures were constructed from 1. In the two crystals of 2, the macrocyclic skeleton and the propargyl groups adopted different geometries. In one crystal of 2, two of the substituents were mutually included within the cavity of the adjacent macrocycles to afford one-dimensional polymers with pseudorotaxane-like structures. In the other crystal of 2, the macrocycles were aligned to form columnar structures. Propargyl groups interacted with other units through mainly CH···π interactions.

Loose nanofiltration membrane constructed via interfacial polymerization using porous organic cage RCC3 for dye/salt separation

Fabricating loose membranes with well-tailored porosity for effective molecular separations remains challenging. Here, we introduce RCC3, a soluble porous organic cage (POC), as an amine monomer to fabricate polyamide (PA) membrane with loose structure via interfacial polymerization and evaluate the membrane performance in dye/salt separation. RCC3 is a [4 + 6] amine molecular cage with ideal stability and sub-nanometer macrocyclic cavity (∼7 Å). The intrinsic porosity and large interchain pores formed by its participation in interfacial polymerization provide extra transport channels in membrane and contribute to realizing precise aperture sieving with high permeation flux. Meanwhile, the unique structure of RCC3 (molecular-level size, organic framework and rich –NH– groups) helps to achieve molecular-level mixing between polymer chains and individual caged molecules in the membrane, thus overcoming the problem of interfacial defects. Under the condition of optimal RCC3/PIP mass ratio, the as-prepared membrane exhibited favorable water permeability of 52.55 LMH/bar (5.2 times of PIP/TMC membrane) with good dye rejection (98.6% for MEB) and salt permeability. Due to the extremely low surface roughness (Ra = 12.5 nm), the membrane exhibited outstanding anti-fouling capacity with high and stable flux recovery rate. Furthermore, the membrane possessed excellent long-term stability, which underlined the promising potential in practical application.

Pyrazine and crown ethers: functional covalent organic polymers for (solar-assisted) high capacity and rate performance lithium-organic battery

Multifunctional two-dimensional (2D) covalent organic polymers (COPs) benefiting from unique features display great potential in lithium-organic batteries yet are rarely reported. In this work, we fabricate a novel conjugated polymer (TQ-COP) functioned with flexible crown ethers and pyrazine redox-active sites, used as an organic rechargeable battery cathode. The Fourier transform infrared spectroscopy (FT-IR) and 13C cross-polarization and magic-angle spinning nuclear magnetic resonance (MAS NMR) verify the chemical identity of redox-active units formed during polymerization. In this structure, pyrazine-redox components exhibit a maximum six-electron transfer per active site, resulting in an initial specific capacity of 162 mA h/g(20 mA/g). Because of macrocyclic cavities and preferential coordination with the alkali metal ions of crown ethers, the rate determining step is changed into a charge transfer process, urging TQ-COP to emerge with a superior rate performance (132 mA h/g at 2 C, 81% vs. 0.1 C). Furthermore, the introduction of crown ethers facilitates photo-excited charge-carriers transfer by narrowing the HOMO-LUMO gap, rendering a photo-assisted lithium-organic battery with significant photovoltage responses and ∼10% improvement of battery round-trip efficiency under illumination, demonstrating its promising capability of solar energy utilization. This work proposes new insights into multifunctional COPs for advanced lithium-organic batteries.

High incorporation of magnetite nanoparticles inside tetraaza macrocyclic Schiff base cavity: spectroscopic characterization and modeling by DFT calculation

This work presents a simple synthesis of tetraaza macrocyclic Schiff base ligand (C40H28N4), its complex [(C40H28N4)@Fe(II)], and a novel complex of magnetite Fe3O4NPs incorporated inside tetraaza macrocyclic cavity [(C40H28N4)@Fe3O4NPs] by the co-precipitation method in order to obtain well-dispersed nanoparticles, controlled size and prevent the aggregation of Fe3O4 NPs due to strong dipole–dipole magnetic attractions and interactions between particles. The characterization and structural identification were carried out by X-ray spectroscopy as well by 1H NMR, 13C and DEPT 135 NMR spectroscopy, FT-IR, UV–visible, EDX, TGA, and finally by VSM using both experimental and theoretical methods. XRD measurements indicate that the presence of Schiff's bases does not modify the crystal structure of the nanoparticles (11.05 nm). All the NMR spectra suggested the success of the synthesis of all structures with high purity. FTIR was used to illuminate the presence of Fe3O4NPs in tetrahedral and octahedral sites as well as their coordination with imine (C = N) of tetraaza macrocyclic. The UV–visible spectra and frontier molecular orbitals (FMOs) of the title compounds were calculated at TD-DFT/CAM-B3LYP-D3/6–311 G (d, p) level of theory. The corresponding calculated result yield shows a good agreement with the experimental data. The morphological characterization of the nanoparticles was carried out by SEM, which revealed that the shape of the NPs was generally spherical. The SEM images also show that the nanoparticles prepared by in situ with co-precipitation method were able to form stable complexes. Thermal characterization by TGA shows that there are 64% of the magnetite nanoparticles formed in situ, which corresponds to a grafting density of 25 mmol.g−1. The VSM analysis displays a similar magnetic hysteresis loop shape compared to free Fe3O4 NPs, which confirmed a ferromagnetic character due to the significant decrease in saturated magnetization.Graphical abstract

C–H⋯S Hydrogen Bond Assisted Supramolecular Encapsulation of Fullerenes with Nanobelts

C–H⋯S Hydrogen Bond Assisted Supramolecular Encapsulation of Fullerenes with Nanobelts

Molecular-Level Control over Ionic Conduction and Ionic Current Direction by Designing Macrocycle-Based Ionomers.

Poor ionic conductivity of the catalyst-binding, sub-micrometer-thick ionomer layers in energy conversion and storage devices is a huge challenge. However, ionomers are rarely designed keeping in mind the specific issues associated with nanoconfinement. Here, we designed nature-inspired ionomers (calix-2) having hollow, macrocyclic, calix[4]arene-based repeat units with precise, sub-nanometer diameter. In ≤100 nm-thick films, the in-plane proton conductivity of calix-2 was up to 8 times higher than the current benchmark ionomer Nafion at 85% relative humidity (RH), while it was 1–2 orders of magnitude higher than Nafion at 20–25% RH. Confocal laser scanning microscopy and other synthetic techniques allowed us to demonstrate the role of macrocyclic cavities in boosting the proton conductivity. The systematic self-assembly of calix-2 chains into ellipsoids in thin films was evidenced from atomic force microscopy and grazing incidence small-angle X-ray scattering measurements. Moreover, the likelihood of alignment and stacking of macrocyclic units, the presence of one-dimensional water wires across this macrocycle stacks, and thus the formation of long-range proton conduction pathways were suggested by atomistic simulations. We not only did see an unprecedented improvement in thin-film proton conductivity but also saw an improvement in proton conductivity of bulk membranes when calix-2 was added to the Nafion matrices. Nafion–calix-2 composite membranes also took advantage of the asymmetric charge distribution across calix[4]arene repeat units collectively and exhibited voltage-gating behavior. The inclusion of molecular macrocyclic cavities into the ionomer chemical structure can thus emerge as a promising design concept for highly efficient ion-conducting and ion-permselective materials for sustainable energy applications.

Anionic Complexes of the Perfluorinated Three‐Mercury Anticrown (o,o’‐C6F4C6F4Hg)3. Dependence of the Anion Coordination Type on Counter‐Cation in Case of Chloride and Bromide Anions

AbstractThe interaction of the macrocycle (o,o′‐C6F4C6F4Hg)3 (1) containing three mercury centres with arylphosphonium salts ([Ph4P]Cl or [Ph4P]Br) yields halide complexes, [Ph4P]{[(o,o′‐C6F4C6F4Hg)3](η1:η1‐X)} (X=Cl, Br) having infinite polymer chain structure in the crystal. In both adducts, the halide anion is situated outside of the cavity of the three‐mercury anticrown 1 and bridged by two mercury centres of neighbouring anticrown moieties. At the same time, when mercuracycle 1 interacts with tetraalkylammonium salts ([nBu4N]Cl or [nBu4N]Br), then the discrete 1 : 1 complexes [nBu4N]{[(o,o′‐C6F4C6F4Hg)3](η3‐X)} (X=Cl, Br) of completely different structure are formed. In these halide complexes the anion is located inside the cavity of macrocycle 1 and coordinates the three mercury atoms symmetrically. The synthesized halide complexes [nBu4N]{[(o,o′‐C6F4C6F4Hg)3](η3‐X)} (X=Cl, Br) are the first example of complexes of the macrocycle 1 where it behaves as anticrown.

Modular Introduction of endo‐Binding Sites in a Macrocyclic Cavity towards Selective Recognition of Neutral Azacycles

AbstractMacrocycles with a functionalized interior, which is a general cavity feature of bioreceptors, are relatively hard to synthesize. Here we report a modular strategy to customize diverse endo‐binding sites in the macrocycle cavity. Only two steps are needed. First, one V‐shaped functional module bearing an embedded binding site and two 2,5‐dimethoxyphenyls as reaction modules are connected. Then the condensation of the resulting monomer and paraformaldehyde directly produces the designed macrocycle. V‐shaped monomers are deliberately used to guarantee the binding sites equatorially directing inward into the cavity and 2,5‐dimethoxyphenyls standing axially as macrocycle sidewalls. More than a dozen endo‐functionalized macrocyclic receptors have been constructed. Host–guest complexation studies show that macrocycle BP1‐decorated interior OH moieties can strongly encapsulate neutral azacycles by forming inner hydrogen bonds, giving a high association constant of 4.59×104 M−1 in non‐polar media.

Modular Introduction of endo-Binding Sites in a Macrocyclic Cavity towards Selective Recognition of Neutral Azacycles.

Macrocycles with a functionalized interior, which is a general cavity feature of bioreceptors, are relatively hard to synthesize. Here we report a modular strategy to customize diverse endo-binding sites in the macrocycle cavity. Only two steps are needed. First, one V-shaped functional module bearing an embedded binding site and two 2,5-dimethoxyphenyls as reaction modules are connected. Then the condensation of the resulting monomer and paraformaldehyde directly produces the designed macrocycle. V-shaped monomers are deliberately used to guarantee the binding sites equatorially directing inward into the cavity and 2,5-dimethoxyphenyls standing axially as macrocycle sidewalls. More than a dozen endo-functionalized macrocyclic receptors have been constructed. Host-guest complexation studies show that macrocycle BP1-decorated interior OH moieties can strongly encapsulate neutral azacycles by forming inner hydrogen bonds, giving a high association constant of 4.59×104 M-1 in non-polar media.

Inverse emulsion-crosslinked cyclodextrin polymer nanoparticles for selective adsorption and chemiresistive sensing of BTEX

Macrocyclic molecules, such as cyclodextrins, possess selective host-guest binding properties and can be incorporated into larger architectures for adsorption or sensing applications. An inverse emulsion approach was developed for the synthesis of crosslinked polymer nanoparticles of cyclodextrins (CD-PNP) without the employment of any additional linker or spacer. The macrocyclic cavity of cyclodextrin endows CD-PNP with the ability to selectively bind benzene, toluene, ethylbenzene, and xylenes (BTEX) molecules according to their size and shape, while the cross-linked porous network enables high adsorption capacities (e.g. 378.1 mg/g for benzene). The solution processability of nanoparticles enables feasible incorporation of CD-PNP, together with carbon nanotubes (CNT), into composite chemiresistive sensor devices. These sensors exhibit high sensitivity and excellent selectivity in response to the exposure of various BTEX vapors.

Fabricating a novel supramolecular light-activated platform based on internal-driven forces induced by the UV-light

Recently, exploiting a novel supramolecular fabrication pathway have drawn great attention. To this endeavor, we firstly designed and reported an original light-activated platform based on the internal-driven forces of macrocyclic host by hiring the pillar[5]arene as the host molecule (H) and phenazine derivatives acting as an energetic guest molecule (G). Surprisingly, after adding the H solution into G system, the intensive fluorescence emission of the G molecule rapidly decreased under the irradiation of the UV-light (254 nm) until absolutely quenching. Delightfully, different from the traditional supramolecular host-guest interaction, the fluorescent emission of G molecule could be recovered after irradiating under the nature light. In view of this interesting observations, the interaction mechanism was carefully investigated by a series of characterizations. Those results suggested that the G molecule was easily threaded into the macrocyclic cavity (H) under the internal-driven forces induced by the UV-light irradiation, forming a 1:1 host-guest complex. Moreover, taking advantage of this especial feature, the light-activated platform of host–guest complex was further applied for ink-free light-driven printing materials, exhibiting great potential in the real application.

Inclusion of Pentamidine in Carboxylated Pillar[5]arene: Late Sequential Crystallization and Diversity of Host–Guest Interactions

Here we describe the inclusion of the minor-groove binding drug pentamidine in its extended conformation into the macrocyclic cavity of water-soluble carboxylated pillar[5]arene. The artificial host–guest system is manifested as an ensemble of three crystalline forms differing in the pillar[5]arene–pentamidine interaction mode, solvation type, and even stoichiometry. The strong hydrogen bonds of various types of amidinium–carboxylate (between pentamidine and pillar[5]arene) and carboxylic–carboxylate (between adjacent pillar[5]arenes) are realized in all complexes, rigidifying the assembly. However, it seems that more subtle effects, such as local solvation/desolvation, a certain degree of flexibility of both the host and guest, and variable protonation/deprotonation state of the pillar[5]arene substituents, play significant roles in the peculiar crystallization behavior of the system. The snapshots of three crystal structures highlighting various binding geometries and intermolecular interaction modes between the same host and guest present exciting opportunities in terms of more holistic models of the host–guest systems, shifting from focusing our attention on “visible interactions” in one crystal structure to the appreciation of many subtle effects playing a combined role in the host–guest chemistry.

SYNTHESIS, ELECTROCHEMICAL, ANTIMICROBIAL AND THEORETICAL STUDIES OF FE AND NI MACROCYCLIC COMPLEXES

Macrocyclic compounds have got recognition in modern science and technologies because of their potential applications in energy, catalysis, material science, biochemistry, and pharmaceutical. The most interesting feature of macrocyclic complexes is their adjustable macrocyclic cavity which opens many possibilities for the development of various important fields. Herein, we synthesized two MN4-macrocyclic complexes (M = Fe(III) and Ni(II) by using template method, and characterized by employing multiple techniques like molar conductance, FTIR, UV–Vis and mass spectra. On the basis of characterization results, a saddle shaped octahedral geometry can be attributed to theses complexes. The “saddle shape” geometry of these complexes is due to the steric repulsions between the benzenoid and amidic moieties on the macrocyclic framework as suggested by theoretical investigations. Further, the electrochemical investigations carried out using cyclic voltammetry in methanol at the Pt electrode indicated that the unusual oxidation state of metal ion could stabilize the macrocyclic framework of the complex. Moreover, these complexes were also evaluated for their antibacterial activities against several pathogens using Gentamycin as standard drug. The results suggested that these complexes did have significant antimicrobial activity.

Synthesis, Characterization, and Electrochemistry of Copper Dibenzoporphyrin(2.1.2.1) Complexes.

Three copper dibenzoporphyrin(2.1.2.1) complexes having two dipyrromethene units connected through o-phenylen bridges and 4-MePh, Ph, or F5Ph substituents at the meso positions of the dipyrrins were synthesized and characterized according to their spectral, electrochemical, and structural properties. As indicated by the single-crystal X-ray structures, all three derivatives have highly bent molecular structures, with angles between each planar dipyrrin unit ranging from 89° to 85°, indicative of a nonaromatic molecule. The insertion of copper(II) into dibenzoporphyrins(2.1.2.1) induced a change in the macrocyclic cavity shape from rectangular in the case of the free-base precursors to approximately square for the metalated copper derivatives. Solution electron paramagnetic resonance (EPR) spectra at 100 K showed hyperfine coupling of the Cu(II) central metal ion and the N nucleus in the highly bent molecular structures. Electrochemical measurements in CH2Cl2 or N,N-dimethylformamide (DMF) containing 0.1 M tetrabutylammonium perchlorate (TBAP) were consistent with ring-centered electron transfers and, in the case of reduction, were assigned to electron additions involving two equivalent π centers on the bent nonaromatic molecule. The potential separation between the two reversible one-electron reductions ranged from 230 to 400 mV in DMF, indicating a moderate-to-strong interaction between the equivalent redox-active dipyrrin units of the dibenzoporphyrins(2.1.2.1). The experimentally measured highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gaps ranged from 2.14 to 2.04 eV and were smaller than those seen for the planar copper tetraarylporphyrins(1.1.1.1), (Ar)4PCu.

Molecular Assemblies Offering Hydrogen-Bonding Cavities: Influence of Macrocyclic Cavity and Hydrogen Bonding on Dye Adsorption.

This work presents a set of Hg macrocycles of amide-phosphine-based ligands offering H-bonding cavities of different dimensions. Such macrocycles are shown to selectively adsorb anionic dyes followed by neutral dyes as well as Prontosil, a biologically relevant antibiotic, within their cavities with the aid of H-bonding-assisted encapsulation. Kinetic experiments supported by spectroscopic and docking studies illustrate the importance of the cavity structure as well as H-bonds for the selective adsorption of dyes.

Diametric calix[6]arene-based phosphine gold(I) cavitands.

We report the synthesis and characterization, in low polarity solvents, of a novel class of diametric phosphine gold(I) cavitands characterized by a 1,2,3-alternate geometry. Preliminary catalytic studies were performed on a model cycloisomerization of 1,6-enynes as a function of the relative orientation of the bonded gold(I) nuclei with respect to the macrocyclic cavity.

Phenanthrene cyclocarbonylation – core post-synthetic modification of phenanthriporphyrin

The unique [Fe(CO)5]-induced cyclocarbonylation of the phenanthriporphyrin core is an intriguing example of a post-synthetic modification of the macrocyclic cavity.

Fine-tuning macrocycle cavity to selectively bind guests in water for near-infrared photothermal conversion

A class of water-soluble macrocycles with gradually extended cavities were synthesized to selectively bind size-matched guests. One of the host–guest products exhibited excellent near-infrared photothermal activity.

Whither Second-Sphere Coordination?

Whither Second-Sphere Coordination?