Enantioseparation and determination of triazole fungicides in fruit juice by aqueous biphasic system coupled with HPLC-MS/MS.

The aqueous biphasic system based on choline ionic liquids and ethylene/propylene oxide copolymer coupled with high-performance liquid chromatography-tandem mass spectrometry was developed for the simultaneous determination of the enantiomers of two fungicides: myclobutanil and tebuconazole. The influence of mass fractions of ionic liquids and the copolymer on the extraction efficiency of the target fungicides was investigated. The analytes are mainly concentrated in the bottom, copolymer-rich phase. The extraction efficiencies of the selected fungicides were significantly affected by the concentrations of the copolymer, and their extraction efficiencies decreased with the higher mass fractions of the copolymer, while the mass fraction of ionic liquids had little effect on their extraction behavior. Excellent extraction efficiency was achieved using the aqueous biphasic system based on choline L-lysinate and the copolymer. At three spiked concentrations of 0.01, 0.05, and 0.1 mg/kg, the average recoveries of the selected fungicides ranged from 80 to 89%, with the relative standard deviations in the range of 2.1-5.3%. Limits of quantitation for the enantiomers of tebuconazole and myclobutanil were 0.5 and 5.0 µg/kg, respectively. The developed system could be successfully applied to the analysis of triazole fungicides residue in real samples.

An unusual macrocyclization reagent for highly selective one-pot synthesis of strained macrocyclic aromatic hexamers.

One-pot, multi-molecular macrocyclization allows the highly selective preparation of strained macrocyclic aromatic hexamers structurally stabilized by an inward-pointing continuous hydrogen-bonding network.

Shape-persistent H-bonded macrocyclic aromatic pentamers.

The use of multiple-center intramolecular H-bonds for the efficient construction of macrocycles of varying structures and functions is among the newest and the most noteworthy additions to the toolbox for macrocycle synthesis. This strategy has allowed the creation of sizable interior cavities as small as 2.8 Å and as large as 15 Å in radius in these H-bonded macrocycles with a number of them expressing tailor-made functions. While concentrating on our recent contributions to this fast-growing field, we will further summarize the latest advances on the design, synthesis, structure and function of these shape-persistent H-bonded macrocyclic foldamers that have helped to create a whole new dimension of scientific research, markedly expanding both the structural and functional repertoires of shape-persistent macrocycles.

Locking high energy 1D chain of dichloromethane molecules containing abnormally short Cl···Cl contacts of 2.524 Å inside organic crystals.

1D helical channels can be created by "sticky" end-mediated formation of 1D helical stacks composed of short cavity-containing helices and are able to host 1D chains of dichloromethane molecules containing extraordinarily short intermolecular Cl···Cl contacts of 2.524 Å in length that computationally destabilize the host-guest complex by 14.94 kcal mol(-1).