The fluoride anion has recently gained well deserved attention among the scientific community for its importance in many fields of human activities, but also for concerns on its effect on health and ...the environment. Although surprisingly overlooked in systematic studies in the past, fluoride has nowadays become a topical target in the field of anion recognition. A multitude of scientific reports are published every year where the establishment of efficient and specific interaction with fluoride is sought in polar and aqueous media. Here, the emphasis is directed to a detailed description of the most interesting contemporary studies in the field, with a particular focus given to those published in the last few years.
A carefully designed strategy is presented for the construction of ternary cocrystals, based on the orthogonality of two supramolecular interaction modes: hydrogen bonding between crown ethers and ...thioureas and the halogen bonding between thioureas and perfluorohalocarbons. Tested on a set comprising two crown ethers, two thioureas and five halogen bond donors, the strategy resulted in a high, 75% success rate, with 15/20 component combinations yielding at least one cocrystal. Crystal structure analysis revealed the interplay between the hydrogen and halogen bonding motifs, also shedding light on the variables affecting their formation.
An asymmetric organocatalytic domino oxa‐Michael/1,6‐addition reaction of ortho‐hydroxyphenyl‐substituted para‐quinone methides and isatin‐derived enoates has been developed. In the presence of 5 mol ...% of a bifunctional thiourea organocatalyst, this scalable domino reaction affords 4‐phenyl‐substituted chromans bearing spiro‐connected oxindole scaffolds and three adjacent stereogenic centers in good to excellent yields (up to 98 %) and with very high stereoselectivities (up to >20:1 d.r., >99 % ee).
Hydroxy‐substituted para‐quinone methides were successfully used in an asymmetric organocatalytic oxa‐Michael/1,6‐addition domino reaction. In the presence of a bifunctional thiourea organocatalyst, this reaction afforded a wide range of 4‐aryl‐substituted chromans with an oxindole scaffold and three contiguous stereocenters in high yields and stereoselectivities.
We report a new air‐stable PdI dimer, Pd(μ‐I)(PCy2tBu)2, which triggers E‐selective olefin migration to enamides and styrene derivatives in the presence of multiple functional groups and with ...complete tolerance of air. The same dimer also triggers extremely rapid C−C coupling (alkylation and arylation) at room temperature in a modular and triply selective fashion of aromatic C−Br, C−OTf/OFs, and C−Cl bonds in poly(pseudo)halogenated arenes, displaying superior activity over previous PdI dimer generations for substrates that bear substituents ortho to C−OTf.
A novel air‐stable PdI dimer is reported that triggers E‐selective olefin migration to enamides and styrene derivatives in the presence of multiple functional groups and with complete tolerance of air. The same dimer also triggers extremely rapid C−C coupling (alkylation and arylation) at room temperature in a modular and triply selective fashion.
The study of the structures and properties of atomically precise gold nanoclusters is the object of active research worldwide. Recently, research has been also focusing on the doping of metal ...nanoclusters through introduction of noble metals, such as platinum, and less noble metals, such as cadmium and mercury. Previous studies, which relied extensively on the use of mass spectrometry and single-crystal X-ray crystallography, led to the assignment of the location of each of these foreign-metal atoms. Our study provides new insights into this topic and, particularly, compelling evidence about the actual position of the selected metal atoms M = Pt, Pd, Hg, and Cd in the structure of Au24M(SR)18 0. To make sure that the results were not dependent on the thiolate, for SR we used both butanethiolate and phenylethanethiolate. The clusters were prepared according to different literature procedures that were supposed to lead to different doping positions. Use of NMR spectroscopy and isotope effects, with the support of mass spectrometry, electrochemistry, and single-crystal X-ray crystallography, led us to confirm that noble metals indeed dope the cluster at its central position, whereas no matter how the doping reaction is conducted and the nature of the ligand, the position of both Cd and Hg is always on the icosahedron shell, rather than at the central or staple position, as often reported. Our results not only provide a reassessment of previous conclusions, but also highlight the importance of NMR spectroscopy studies and cast doubts on drawing conclusions mostly based on single-crystal X-ray crystallography.
A simple terpyridine-Zn(II) complex is shown to act as an efficient and highly selective fluorescent sensor for pyrophosphate in water at physiological pH. The sensor complex showed an unprecedented ...fluorescence response (∼500 fold increase) and a record nanomolar sensitivity (detectable fluorescent response at 20 nM and LOD ∼ 0.8 nM). It has successfully been used to stain and record confocal fluorescence microscopy images of HeLa cells. Moreover, the complex was found to self-assemble into a hydrogel which was subsequently used to coat disposable paper strips for easy, low-cost detection of pyrophosphate.
The air-sensitive nature of white phosphorus underlies its destructive effect as a munition: Tetrahedral P₄ molecules readily react with atmospheric dioxygen, leading this form of the element to ...spontaneously combust upon exposure to air. Here, we show that hydrophobic P₄ molecules are rendered air-stable and water-soluble within the hydrophobic hollows of self-assembled tetrahedral container molecules, which form in water from simple organic subcomponents and iron(II) ions. This stabilization is not achieved through hermetic exclusion of O₂ but rather by constriction of individual P₄ molecules; the addition of oxygen atoms to P₄ would result in the formation of oxidized species too large for their containers. The phosphorus can be released in controlled fashion without disrupting the cage by adding the competing guest benzene.
A Halogen-Bonded Dimeric Resorcinarene Capsule Beyeh, Ngong Kodiah; Pan, Fangfang; Rissanen, Kari
Angewandte Chemie (International ed.),
June 15, 2015, Letnik:
54, Številka:
25
Journal Article
Recenzirano
Iodine (I2) acts as a bifunctional halogen‐bond donor connecting two macrocyclic molecules of the bowl‐shaped halogen‐bond acceptor, N‐cyclohexyl ammonium resorcinarene chloride 1, to form the ...dimeric capsule (1,4‐dioxane)3@12(I2)2. The dimeric capsule is constructed solely through halogen bonds and has a single cavity (V=511 Å3) large enough to encapsulate three 1,4‐dioxane guest molecules.
All in a nut shell: An entirely halogen‐bonded dimeric capsule is isolated from the combination of I2 as the bifunctional halogen‐bond donor and N‐cyclohexyl ammonium resorcinarene chloride as the tetravalent halogen‐bond acceptor. Three 1,4‐dioxane molecules as guests are bound in the single extended cavity (see picture; red molecules in center). Atom colors: C=gray; H=white; Cl=green; I=purple; O=red (edges).
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