Halogen‐ and chalcogen‐based σ‐hole interactions have recently received increased interest in non‐covalent organocatalysis. However, the closely related pnictogen bonds have been neglected. In this study, we introduce conceptually simple, neutral, and monodentate pnictogen‐bonding catalysts. Solution and in silico binding studies, together with high catalytic activity in chloride abstraction reactions, yield compelling evidence for operational pnictogen bonds. The depth of the σ holes is easily varied with different substituents. Comparison with homologous halogen‐ and chalcogen‐bonding catalysts shows an increase in activity from main group VII to V and from row 3 to 5 in the periodic table. Pnictogen bonds from antimony thus emerged as by far the best among the elements covered, a finding that provides most intriguing perspectives for future applications in catalysis and beyond.

In this report, we introduce synthetic anion transporters that operate with chalcogen bonds. Electron-deficient dithieno[3,2-b;2',3'-d]thiophenes (DTTs) are identified as ideal to bind anions in the focal point of the σ holes on the cofacial endocyclic sulfur atoms. Anion binding in solution and anion transport across lipid bilayers are found to increase with the depth of the σ holes of the DTT anionophores. These results introduce DTTs and related architectures as a privileged motif to engineer chalcogen bonds into functional systems, complementary in scope to classics such as 2,2'-bipyrroles or 2,2'-bipyridines that operate with hydrogen bonds and lone pairs, respectively.

Herein, we introduce catalysts that operate with chalcogen bonds. Compared to conventional hydrogen bonds, chalcogen bonds are similar in strength but more directional and hydrophobic, thus ideal for precision catalysis in apolar solvents. For the transfer hydrogenation of quinolines and imines, rate enhancements well beyond a factor of 1000 are obtained with chalcogen bonds. Better activities with deeper σ holes and wider bite angles, chloride inhibition and correlation with computed anion binding energies are consistent with operational chalcogen bonds. Comparable to classics, such as 2,2'-bipyrroles or 2,2'-bipyridines, dithieno[3,2-b;2',3'-d]thiophenes (DTTs), particularly their diimides, but also wide-angle cyclopentadithiazole-4-ones are identified as privileged motifs to stabilize transition states in the focal point of the σ holes on their two co-facial endocyclic sulfur atoms.

The tortoise and the hare: anion–π interactions are reported to selectively accelerate the intrinsically disfavored addition of malonate half thioesters.

In this communication, we introduce transmembrane anion transport with pnictogen-bonding compounds and compare their characteristics with chalcogen-and halogen-bonding analogs. Tellurium-centered chalcogen bonds are at least as active as antimony-centered pnictogen bonds, whereas iodine-centered halogen bonds are three orders of magnitude less active. Irregular, voltage-dependent single-channel currents, high gating charges, efficient dye leakage and small Hill coefficients support the formation of bulky, membrane-disruptive supramolecular amphiphiles by tris(perfluorophenyl)stibanes that bind anions "too strongly." In contrast, the chalcogen-bonding bis(perfluorophenyl)tellanes do not cause leakage and excel as carriers with nanomolar activity, P(Cl/Na) = 10.4 for anion/cation selectivity and P(Cl/NO3) = 4.5 for anion selectivity. Selectivities are lower with pnictogen-bonding carriers because their membrane-disturbing 3D structure affects also weaker binders (P(Cl/Na) = 2.1, P(Cl/NO3) = 2.5). Their 2D structure, directionality, hydrophobicity and support from proximal anion-π interactions are suggested to contribute to the unique power of chalcogen bonds to transport anions across lipid bilayer membranes. The integration of unorthodox interactions into functional systems is of fundamental importance because it promises access to new activities. 1 Synthetic transport systems 2 have emerged as an attractive tool to assess the functional relevance of such interactions. Realized examples include anion-π interactions in many variations, 1 halogen bonds 3,4 and, more recently, also chalcogen bonds. 5,6 In the following, we elaborate on anion transport with pnictogen bonds in direct comparison to chalcogen and halogen bonds. These so-called s-hole interactions 7,8 originate from highly localized areas of highly positive charge density that appear on heavier and p-block elements. Associated with s* orbitals, the s holes appear at the opposite side of the covalent bonds and deepen with increasing electron deficiency of the atom. As a result, there is one s hole available per atom for halogen bonds, 9 two for chalcogen, 10 three for pnictogen 11,12 and four for tetrel bonds (Figure 1). 7,8 Increasing with polarizability, the depth of the s holes

To integrate anion-π, cation-π, and ion pair-π interactions in catalysis, the fundamental challenge is to run reactions reliably on aromatic surfaces. Addressing a specific question concerning enolate addition to nitroolefins, this study elaborates on Leonard turns to tackle this problem in a general manner. Increasingly refined turns are constructed to position malonate half thioesters as close as possible on π-acidic surfaces. The resulting preorganization of reactive intermediates is shown to support the disfavored addition to enolate acceptors to an absolutely unexpected extent. This decisive impact on anion-π catalysis increases with the rigidity of the turns. The new, rigidified Leonard turns are most effective with weak anion-π interactions, whereas stronger interactions do not require such ideal substrate positioning to operate well. The stunning simplicity of the motif and its surprisingly strong relevance for function should render the introduced approach generally useful.

Benzodiselenazoles are introduced for efficient anion binding and unprecedented non-covalent catalysis in the focal point of neutral selenium-based chalcogen-bond donors.

Halogen-and chalcogen-based s-hole interactions have recently received increased interest in non-covalent organocatalysis.H owever,t he closely related pnictogen bonds have been neglected. In this study,w ei ntroduce conceptually simple,n eutral, and monodentate pnictogenbonding catalysts.S olution and in silico binding studies, together with high catalytic activity in chloride abstraction reactions,yield compelling evidence for operational pnictogen bonds.T he depth of the s holes is easily varied with different substituents.C omparison with homologous halogen-and chalcogen-bonding catalysts shows an increase in activity from main group VII to Vand from row 3to5inthe periodic table.Pnictogen bonds from antimony thus emerged as by far the best among the elements covered,af inding that provides most intriguing perspectives for future applications in catalysis and beyond.