Carbon quantum dots from hemicucur[6]bit and the application for the detection of Pb.

A macrocyclic compound, hemicucurbit[6]uril (HemiQ[6]), is employed as the carbon source to produce a novel sort of carbon quantum dots (CQDs) with blue fluorescence in aqueous solution. The CQDs are fully identified by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Nuclear Magnetic Resonance (NMR), zeta potential, ultraviolet/visible (UV-vis) and photoluminescence spectroscopy (PL). The nanomaterial is developed for the analysis of Pb in the light of the Resonance Rayleigh scattering (RRS) changes with the increasing Pb concentration.

Cucurbit[7]uril-Catalyzed Beckmann Rearrangement of Arylketoximes.

With the existence of cucurbit[7]uril (Q[7]), a supramolecular catalysis strategy for the Beckmann rearrangement of aryl ketoximes to -substituted amides was successfully established. The cavity of Q[7] was found to be essential for substrate encapsulation and the rearrangement reaction through comparative experiments and studies on host-guest interactions. This supramolecular strategy provides an efficient route for the rearrangement reaction incorporating a carbonation intermediate.

Synthesis of Dihydroquinoxalinones from Biomass-Derived Keto Acids and -Phenylenediamines.

A novel catalyst-free cascade amination/cyclization/reduction reaction was developed for the synthesis of various Dihydroquinoxalinones under mild conditions from accessible biomass-derived keto acids and 1,2-phenylenediamines with ammonia borane as a hydrogen donor. This single-step approach enables a simple and eco-friendly route toward the direct synthesis of 12 kinds of Dihydroquinoxalinones in moderate to excellent yields in the green solvent dimethyl carbonate. The results of deuterium-labeling experiments and density function calculations demonstrate that the reductive process proceeds along a double hydrogen transfer pathway.

Preparation and Biomedical Applications of Cucurbit[n]uril-Based Supramolecular Hydrogels.

The cucurbit[n]uril supramolecular hydrogels are driven by weak intermolecular interactions, of which exhibit good stimuli responsiveness and excellent self-healing properties. According to the composition of the gelling factor, supramolecular hydrogels comprise Q[n]-cross-linked small molecules and Q[n]-cross-linked polymers. According to different driving forces, hydrogels are driven by the outer-surface interaction, the host-guest inclusion interaction, and the host-guest exclusion interaction.

Supramolecule-Controlled Enantioselectivity for Electrochemical Asymmetric Hydrogenation of Coumarins with a Chiral Macrocyclic Compound.

The supramolecular strategy was subjected to the asymmetric hydrogenation of 4-methylumbelliferone by electrochemical reduction in the presence of a chiral macrocyclic multifarane[3,3], which offered a l-7-hydroxy-4-methylchroman-2-one product with a chemical yield of 65% and enantioselectivity up to >99% ee. The high stability of the developed chiral supramolecular electrode guaranteed the recyclability and repeatability in the electrolysis, and therefore, the application was extended to more coumarin derivatives to provide satisfactory chemical yields and enantioselectivities.

Supramolecular Assembly of Tetramethylcucurbit[6]uril and 2-Picolylamine.

The supramolecular assembly of symmetrical tetramethylcucurbit[6]uril (TMeQ[6]) and 2-picolylamine (AMPy) has been investigated via various techniques, including ultraviolet-visible (UV-vis) and nuclear magnetic resonance spectroscopy, isothermal titration calorimetry (ITC), and X-ray crystallography. The results indicated that TMeQ[6] could encapsulate the AMPy guest molecule to form a stable inclusion complex. The rotational restriction of the guest in the cavity of TMeQ[6] resulted in a large negative value of entropy.

Recent Breakthroughs in Supercapacitors Boosted by Macrocycles.

Supercapacitors are essential for electrochemical energy storage because of their high-power density, good cycle stability, fast charging and discharging rates, and low maintenance cost. Macrocycles, including cucurbiturils, calixarene, and cyclodextrins, are cage-like organic compounds (with a nanocavity that contains O and N heteroatoms) with unique potential in supercapacitors. Here, we review the applications of macrocycles in supercapacitor systems, and we illustrate the merits of organic macrocycles in electrodes and electrolytes for improving the electrochemical double-layer capacitors and pseudocapacitance via supramolecular strategies.

Graphitic carbon nitride (g-CN)-based photocatalytic materials for hydrogen evolution.

The semiconductors, such as TiO, CdS, ZnO, BiVO, graphene, produce good applications in photocatalytic water splitting for hydrogen production, and great progress have been made in the synthesis and modification of the materials. As a two-dimensional layered structure material, graphitic carbon nitride (g-CN), with the unique properties of high thermostability and chemical inertness, excellent semiconductive ability, affords good potential in photocatalytic hydrogen evolution. However, the related low efficiency of g-CN with fast recombination rate of photogenerated charge carriers, limited visible-light absorption, and low surface area of prepared bulk g-CN, has called out the challenge issues to synthesize and modify novel g-CN-block photocatalyst.

Paired electrocatalysis in 5-hydroxymethylfurfural valorization.

5-Hydroxymethylfurfural (HMF) has aroused considerable interest over the past years as an important biomass-derived platform molecule, yielding various value-added products. The conventional HMF conversion requires noble metal catalysts and harsh operating conditions. On the other hand, the electrocatalytic conversion of HMF has been considered as an environmentally benign alternative.

A label-free electrochemical sensor constructed with layer-by-layer assembly of GCE-AuNPs-Q[7]·HAuCl for detection of diphenylamine.

Metal-organic frameworks (MOFs) including cucurbit[7]uril block (Q[7]·HAuCl) were employed to develop a diphenylamine (DPA) sensor in electrochemical method, the presence of HAuCl improved the conductivity of the macrocyclic compound. To further enhance of the sensitivity, Au nanoparticles were inserted between the surface of glassy carbon electrode and Q[7]·HAuCl MOFs (GCE-AuNPs-Q[7]·HAuCl). Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV) were applied for evaluation on the electrochemical behavior.

Improved electrochemical properties of polypyrrole with cucurbit[6]uril supramolecular interactions.

A supramolecular polymer was developed through the encapsulation of polypyrrole by cucurbit[6]uril (PPy@Q[6]), which was employed as the electrode material to improve the capacitor ability of conductive polypyrrole. In the optimized ratio of 2 : 1 ( : ), the capacitor properties of the supramolecular material were evaluated, and a high specific capacitance of 414 F g at 10 mV s was obtained, which was 3.1 times higher than that of pure polypyrrole (132 F g).

Synthesis of a novel aminobenzene-containing hemicucurbituril and its fluorescence spectral properties with ions.

A novel hemicucurbituril-based macrocycle, alternately consisting of amidobenzene and 2-imidazolidione moieties was designed and synthesized. Based on the fragment coupling strategy, nitrobenzene-containing hemicucurbituril was firstly prepared facilely under alkaline environment, and reduction of the nitro groups produced the desired amidobenzene-containing hemicucurbituril. As an original fluorescent chemosensor, it exhibited strong interactions with Fe over other metal cations.

A high-sensitive sensor with HEPES-enhanced electrochemiluminescence of benzo[3]uril for Fe and its application in human serum.

An electrochemiluminescence (ECL) sensor based on a benzo[3]uril-modified glassy carbon electrode with sensitized luminescence, with the coexistence of 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) as the coreactant, was successfully constructed. The sensitization mechanism was proposed by analyzing the results of the control experiments for establishing the relationship of the luminescence effect with the concentration of HEPES. Under the optimized conditions, the fabricated sensor system was applied for the detection of Fe in an aqueous solution with good sensitivity and selectivity.

The high selective chemo-sensors for TNP based on the mono- and di-substituted multifarene[2,2] with different fluorescence quenching mechanism.

The chem-sensors, based on the triazole-CH-anthracene-functionalized multifarene[2,2] were successfully synthesized, which could efficiently and rapidly detect 2,4,6-trinitrophenol (TNP). The high specificities of the proposed macrocyclic sensors were achieved by selective response for TNP in the existence of other competing phenolic compounds, and the limits of detection in ∼10 mol/L range were produced to confirm the high sensitivities of the chem-sensors, which could be attributed to the mechanism of electron and resonance energy transfer processes in the complexes with the supramolecular interactions. H NMR titration analysis revealed the actual binding position should be the triazole rings of sensors with the hydroxyl group on TNP to offer a hydrogen bonding.

Recognition of silver cations by multifarene[2,2] chemosensors with unexpected fluorescence response.

Fluorescent chemosensors based on a new macrocyclic compound, multifarene[2,2], with modification by triazole-linked pyrene or anthracene were synthesized. These macrocyclic sensors exhibited high affinity and selectivity toward Ag over other metal ions, with ratiometric or enhanced response of their fluorescence emissions depending upon the substituent species for coordination to Ag, and an unexpected response to a concentration threshold of the metal cations was discovered. The experimental evidences of fluorescence spectra, H NMR titration, IR spectra, and high-resolution mass spectra suggested the coordination behaviors of the sensors with Ag, that is, the 1:1 complexes were formed with moderate association constants of about 10 L·mol, and the sulfur atoms on macrocyclic ligand should affinite to the metal cations.

Copper-Mediated Annulation of Phosphorus-Containing Arenes with Alkynes: An Approach to Phosphindolium Salts.

A novel method for the synthesis of π-conjugated phosphindolium salts via copper-mediated C-H functionalization of trisubstituted phosphines with alkynes in a single step is reported. The reactions are highly regioselective with unsymmetrical aryl-alkyl-substituted alkynes. This protocol provides an unprecedented atom- and step-efficient access to valuable phosphindolium salts.

Synthesis of Conjugated Polycyclic Quinoliniums by Rhodium(III)-Catalyzed Multiple C-H Activation and Annulation of Arylpyridiniums with Alkynes.

A simple method for the efficient synthesis of highly substituted pyrido[1,2-a]quinolinium- and quinolizino[3,4,5,6-ija]quinolinium-based polyheteroaromatic compounds via rhodium(III)-catalyzed multiple C-H activation annulation reactions has been developed. Moreover, some of the quinolizino[3,4,5,6-ija]quinolinium salts exhibit intense fluorescence and have potential application in optoelectronic materials.

Synthesis of substituted benzo[ij]imidazo[2,1,5-de]quinolizine by rhodium(III)-catalyzed multiple C-H activation and annulations.

The cascade oxidative annulation reactions of aryl imidazoles with two molecules of alkynes via multiple C-H activation proceed efficiently in the presence of [Cp*RhCl2]2 and Cu(OAc)2·H2O to give substituted benzo[ij]imidazo[2,1,5-de]quinolizine-based polyheteroaromatic compounds. This method is compatible with various functional groups, which are very useful for further synthetic transformations.

Rhodium(III)-catalyzed cascade oxidative annulation reactions of aryl imidazolium salts with alkynes involving multiple C-H bond activation.

The cascade oxidative annulation reactions of aryl imidazolium salts with alkynes proceed efficiently in the presence of [Cp*RhCl2]2 and Cu(OAc)2·H2O to give substituted imidazo[1,2-a]-quinolinium salts and benzo[ij]imidazo[2,1,5-de]quinolizinium salts. The reactions were through the normal and abnormal N-heterocyclic carbene (NHC)-directed cyclometalation, alkyne insertion into the Rh-C bond, and reductive elimination of alkenyl and NHC ligands. The reactions are highly regioselective with unsymmetrical alkynes and can be achieved stepwise by controlling the reaction conditions.