A system comprising cucurbit8uril (Q8) and a fluorescent molecule (E)-1-(2-hydroxyethyl)-4-(4-hydroxystyryl)pyridin-1-ium bromide (HPy) has been utilized to construct a fluorescent probe that is ...capable of detecting the pesticide tricyclazole (TC). A variety of techniques including 1H NMR spectroscopy together with fluorescence experiments have been employed to investigate the host-guest properties of the Q8/HPy system in aqueous solution. Results indicate that the system forms the stable2:1 inclusion complex HPy2@Q8, and that this inclusion complex imparts fluorescent quenching on HPy. The addition of a number of pesticides was found to have no obvious effect on the fluorescence, however on addition of tricycazole (TC), the fluorescence intensity underwent a dramatic enhancement. The linear relationship between the fluorescence intensity and the concentration of TC allowed for the facile detection of TC concentration in aqueous target solutions as well as in agricultural products. The detection limit was found to be 3.70 × 10−8 mol L−1.
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•We report a fluorescent probe system for the highly selective and sensitive detection of the pesticide tricyclazole (TC).•The encapsulation of HPy into Q 8 cavity can strongly quench the fluorescence emission because of charge-transfer.•The linear relationship between the fluorescence intensity and the concentration of TC allowed for the facile detection of TC concentration in aqueous target solutions as well as in agricultural products.
A series of 2-1-(2,6-dibenzhydryl-4-chlorophenylimino)ethyl-6-1-(arylimino)ethylpyridine ligands (L1–L5) as well as the ligand 2,6-bis1-(2,6-dibenzhydryl-4-chloro-phenylimino)ethylpyridine (L6) were ...synthesized and reacted with FeCl2·4H2O to afford the iron(II) dichloride complexes LFeCl2 (Fe1–Fe6). All new compounds were fully characterized by elemental and spectroscopic analysis, and the molecular structures of the complexes Fe1, Fe2 and Fe4 were determined by single-crystal X-ray diffraction, which revealed a pseudo-square-pyramidal geometry at iron. Upon activation with either MAO or MMAO, all iron pre-catalysts exhibited very high activity in ethylene polymerization with good thermal stability. To the best of our knowledge, the current system showed the highest activity amongst iron bis(imino)pyridine pre-catalysts reported to-date. The polymerization parameters were explored to determine the optimum conditions for catalytic activity, which were typically found to be 2500 eq. Al to Fe at 60 °C in the presence of MMAO, and 80 °C in the presence of MAO. The resultant polyethylene possessed a narrow molecular polydispersity index (PDI) consistent with the formation of single-site active species.
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•Metallocalixnarene complexes as catalysts in numerous catalytic reactions.•The presence of the calixarene cavity allows for enhanced enantioselectivity.•Cross-coupling, olefin ...oxidation and polymerization processes are the most studied.•Increased attention to the ROP of cyclic esters to produce biodegradable polymers.•Large flexible calixnarenes can adapt to the energy requirements of a process.
Aside from their applications in the fields of ion extraction, gas storage and molecular sensors, calixarenes have been extensively employed as ligands for metal complexation. Moreover, metallocalixnarenes have shown interesting catalytic activity in a plethora of reactions proving, in many cases, superior to other systems bearing different ligand scaffolds. In this review, we summarize the latest advances (post-2008) in the field, categorizing the complexes by metal center.
The binding interactions between 4-aminopyridine (4-AP) and a series of cucurbitnurils (Q5, Q6, TMeQ6, Q7, Q8) have been studied using 1H NMR spectroscopy, UV–vis absorption spectroscopy, isothermal ...titration calorimetry (ITC) and X-ray crystallography. The data indicates that the Q5@4-AP complex exhibits exo binding, which is not observed in the other four host-guest complexes. Furthermore, X-ray crystallography clearly reveals how the Qns bind with 4-AP to form complexes, for example Q5 forms an outer-surface complex, whilst Q6, TMeQ6 and Q7 formed 1:1 host and guest type complexes, and Q8 formed a stable 1:2 ternary complex due to its large cavity, which can accommodate two 4-AP molecules.
In this work, we have constructed five supramolecular host-guest systems using a series of cucurbitnurils (Q5, Q6, TMeQ6, Q7, Q8) and 4-aminopyridine (4-AP). X-ray crystallography clearly reveals how the Qns bind with 4-AP to form complexes, for example Q5 forms an outer-surface complex, whilst Q6, TMeQ6 and Q7 formed a 1:1 host and guest type complex, and Q8 formed a stable 1:2 ternary complex due to its large cavity, which can accommodate two 4-AP molecules. Display omitted
The development of simple and effective strategies to prepare electrocatalysts, which possess unique and stable structures comprised of metal/nonmetallic atoms for oxygen reduction reaction (ORR) and ...oxygen evolution reaction (OER), is currently an urgent issue. Herein, an efficient bifunctional electrocatalyst featured by ultralong N, S‐doped carbon nano‐hollow‐sphere chains about 1300 nm with encapsulated Co nanoparticles (Co‐CNHSCs) is developed. The multifunctional catalytic properties of Co together with the heteroatom‐induced charge redistribution (i.e., modulating the electronic structure of the active site) result in superior catalytic activities toward OER and ORR in alkaline media. The optimized catalyst Co‐CNHSC‐3 displays an outstanding electrocatalytic ability for ORR and OER, a high specific capacity of 1023.6 mAh gZn−1, and excellent reversibility after 80 h at 10 mA cm−2 in a Zn‐air battery system. This work presents a new strategy for the design and synthesis of efficient multifunctional carbon‐based catalysts for energy storage and conversion devices.
An ultralong N,S co‐doped carbon nano‐hollow‐sphere chain with encapsulated Co nanoparticles (Co‐CNHSC) is synthesized as a bifunctional catalyst for both the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) by adopting a one‐step pyrolysis method. Benefiting from the electronic structure modulation between metal and nonmetal species, the optimized Co‐CNHSC‐3 exhibits an excellent bifunctional activity for OER and ORR and also shows superior performance for Zn‐air batteries.
A novel turn-on fluorescence probe L has been designed that exhibits high selectivity and sensitivity with a detection limit of 9.53 × 10−8 mol/L for the quantification of Zn2+. 1H-NMR spectroscopy ...and single crystal X-ray diffraction analysis revealed the unsymmetrical nature of the structure of the Schiff base probe L. An emission titration experiment in the presence of different molar fractions of Zn2+ was used to perform a Job’s plot analysis. The results showed that the stoichiometric ratio of the complex formed by L and Zn2+ was 1:1. Moreover, the molecular structure of the mononuclear Cu complex reveals one ligand L coordinates with one Cu atom in the asymmetric unit. On adding CuCl2 to the ZnCl2/L system, a Cu-Zn complex was formed and a strong quenching behavior was observed, which inferred that the Cu2+ displaced Zn2+ to coordinate with the imine nitrogen atoms and hydroxyl oxygen atoms of probe L.
From reactions involving sodium molybdate and dianilines 2,2′-(NH2)C6H42(CH2)n (n = 0, 1, 2) and amino-functionalized carboxylic acids 1,2-(NH2)(CO2H)C6H4 or 2-H2NC6H3-1,4-(CO2H)2, in the presence of ...Et3N and Me3SiCl, products adopting H-bonded networks have been characterized. In particular, the reaction of 2,2′-diaminobiphenyl, 2,2′-NH2(C6H4)2, and 2-aminoterephthalic acid, H2NC6H3-1,4-(CO2H)2, led to the isolation of (MoCl32,2′-N(C6H4)2}{HNC6H3-1-(CO2),4-(CO2H)·22,2′-NH2(C6H4)2·3.5MeCN (1·3.5MeCN), which contains intra-molecular N–H∙∙∙Cl H-bonds and slipped π∙∙∙π interactions. Similar use of 2,2′-methylenedianiline, 2,2′-(NH2)C6H42CH2, in combination with 2-aminoterephthalic acid led to the isolation of MoCl2(O2CC6H3NHCO2SiMe3)(NC6H4CH2C6H4NH2)·3MeCN (2·3MeCN). Complex 2 contains extensive H-bonds between pairs of centrosymmetrically-related molecules. In the case of 2,2′ethylenedianiline, 2,2′-(NH2)C6H42CH2CH2, and anthranilic acid, 1,2-(NH2)(CO2H)C6H4, reaction with Na2MoO4 in the presence of Et3N and Me3SiCl in refluxing 1,2-dimethoxyethane afforded the complex MoCl3{1,2-(NH)(CO2)C6H4}{NC6H4CH2CH2C6H4NH3}·MeCN (3·MeCN). In 3, there are intra-molecular bifurcated H-bonds between NH3 H atoms and chlorides, whilst pairs of molecules H-bond further via the NH3 groups to the non-coordinated carboxylate oxygen, resulting in H-bonded chains. Complexes 1 to 3 have been screened for the ring opening polymerization (ROP) of both ε-caprolactone (ε-CL) and δ-valerolactone (δ-VL) using solvent-free conditions under N2 and air. The products were of moderate to high molecular weight, with wide Ð values, and comprised several types of polymer families, including OH-terminated, OBn-terminated (for PCL only), and cyclic polymers. The results of metal-free ROP using the dianilines 2,2′-(NH2)C6H42(CH2)n (n = 0, 1, 2) and the amino-functionalized carboxylic acids 1,2-(NH2)(CO2H)C6H4 or 2-H2NC6H3-1,4-(CO2H)2 under similar conditions (no BnOH) are also reported. The dianilines were found to be capable of the ROP of δ-VL (but not ε-CL), whilst anthranilic acid outperformed 2-aminoterephthalic acid for both ε-Cl and δ-VL.
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