A novel strategy for the recognition of anions in water using charge-neutral σ-hole halogen bonding and chalcogen bonding acyclic hosts is demonstrated for the first time. Exploiting the intrinsic hydrophobicity of halogen and chalcogen bond donor atoms integrated into a foldamer structural molecular framework containing hydrophilic functionalities, a series of water-soluble receptors were constructed for anion recognition investigation. Isothermal titration calorimetry (ITC) binding studies with a range of anions revealed the receptors to display very strong and selective binding of large, weakly hydrated anions such as Iand ReO4-. This is achieved through the formation of 2:1 host-guest stoichiometric complex assemblies, resulting in an encapsulated anion stabilized by cooperative, multidentate convergent σ-hole donors, as shown by molecular dynamics simulations carried out in water. Importantly, the combination of multiple σ-hole-anion interactions and hydrophobic collapse results in Iaffinities in water that exceed all known σ-hole receptors, including cationic systems (β2 up to 1.68 × 10 11 M-2). Furthermore, the anion binding affinities and selectivity trends of the first example of an all-chalcogen bonding anion receptor in pure water are compared with halogen bonding and hydrogen bonding receptor analogues. These results further advance and establish halogen and chalcogen bond donor functions as new tools for overcoming the challenging goal of anion recognition in pure water.

Organocatalytic enantioselective desymmetrisation of achiral or meso compounds is a powerful strategy for the construction of enantiomerically enriched complex molecules, often with multiple stereocentres and in high selectivities. Recent years have seen increasing use of organocatalysts in desymmetrisation methodology, in contrast to traditional metal- or enzyme-catalysed reactions, with many impressive advances made in the current decade. This review will provide an overview of the field since 2010, with the aim of highlighting both the practical applications and elegance of enantioselective desymmetrisation to the wider synthetic community.

Neutral tetradentate halogen bond donor foldamers were synthesised and exhibit enhanced anion affinities over their hydrogen bonding analogues, displaying iodide selectivity over lighter halide, carboxylate and dihydrogen phosphate anions. A foldamer with a chiral (S)-binaphthol motif was demonstrated to distinguish between enantiomers of chiral anions.Halogen bonding (XB) is the attractive non-covalent interaction between a terminal s-hole on an electron deficient halogen atom and a Lewis base.1 Its strength and directionality have led to several applications in materials science and, more recently, in supramolecular chemistry 2,3 and organocatalysis. 4 In particular, XB donors have been successfully used in anion receptors for molecular recognition and sensing applications. 5 Many of these have shown enhanced binding properties over their hydrogen bonding (HB) analogues.6,7The electron-deficient 8 1,2,3-triazole motif has been exploited for anion recognition as an effective C-H hydrogen bond donor when integrated into multidentate macrocycles 9 and acyclic foldamers. [10][11][12] While the related 5-iodotriazole unit has been used as XB donor for anion binding, such XB anion hosts are rare in the literature. 13 No tetradentate XB donor foldamers have been described to date; the closest examples are a tridentate halopyridinium 14 and the use of triazole foldamers as XB acceptor hosts for organohalogens. 15Herein we sought to apply the potency of XB to enhance the anion affinity of the known triazole-based HB foldamer framework. Thus, XB foldamers with four 5-iodo-1,2,3-triazole XB donors were synthesized (Fig. 1) and their anion binding properties probed in comparison with HB analogues. A few variants were prepared: 1 and 2 contain triethylene glycol (TEG) chains for improved solubility, while in 3 and 4 9-anthrylmethyl termini have been introduced to provide a fluorescent response. 15,16 System 4 also includes a chiral (S)-binaphthol core in order to investigate XB chiral recognition, which has only previously been observed in a bidentate receptor. 17 Importantly, the XB foldamers exhibited overall stronger anion affinity than their HB analogs with the chiral XB host 4b displaying chiral discrimination with bulky amino acid anions. XB and HB foldamers 1-4 were synthesized via Cu(I)-catalysed azide-(iodo)alkyne cycloaddition (CuAAC) reactions (Scheme 1) using Cu(MeCN) 4 PF 6 in the presence of tris(benzyltriazolylmethyl) amine (TBTA) ligand. For the preparation of 1a and 2a an alternative benzyltriazolylmethylamine (BTA) ligand 18 was used as these compounds co-eluted with TBTA during chromatographic purification. As seen in Scheme 1, a terminal azide synthon 5-7 was reacted statistically with an excess of bis-alkyne 8a or 8b to afford an arm fragment 9-11. Two equivalents of 9-11 were then coupled under CuAAC conditions with a bis-azide core synthon 12 or 13 to give the anion receptors 1-4. The cycloadditions proceeded in moderate to high yields of 64-88% for 5H-triazole and 46-85% for 5I-triazole formation (s...

A novel halogen-bonding foldamer molecular film was utilised to achieve anion sensing in pure water via non-faradaic capacitance spectroscopy.

Replication and compartmentalization are fundamental to living systems and may have played important roles in life's origins. Selection in compartmentalized autocatalytic systems might provide a way for evolution to occur and for life to arise from non-living systems. Herein we report selection in a system of self-reproducing lipids where a predominant species can emerge from a pool of competitors. The lipid replicators are metastable and their out-of-equilibrium population can be sustained by feeding the system with starting materials. Phase separation is crucial for selective surfactant formation as well as autocatalytic kinetics; indeed, no selection is observed when all reacting species are dissolved in the same phase. Selectivity is attributed to a kinetically controlled process where the rate of monomer formation determines which replicator building blocks are the fittest. This work reveals how kinetics of a phase-separated autocatalytic reaction may be used to control the population of out-of-equilibrium replicators in time.

Review: 247 refs.