Host–Guest Chemistry: Oxoanion Recognition Based on Combined Charge‐Assisted C−H or Halogen‐Bonding Interactions and Anion⋅⋅⋅Anion Interactions Mediated by Hydrogen Bonds

Abstract

Several bis-triazolium-based receptors have been synthesized and their anion-recognition capabilities have been studied. The central chiral 1,1'-bi-2-naphthol (BINOL) core features either two aryl or ferrocenyl end-capped side arms with central halogen- or hydrogen-bonding triazolium receptors. NMR spectroscopic data indicate the simultaneous occurrence of several charge-assisted aliphatic and heteroaromatic C-H noncovalent interactions and combinations of C-H hydrogen and halogen bonding. The receptors are able to selectively interact with HP2 O7 (3-) , H2 PO4 (-) , and SO4 (2-) anions, and the value of the association constant follows the sequence: HP2 O7 (3-) >SO4 (2-) >H2 PO4 (-) . The ferrocenyl end-capped 7(2+) ⋅2 BF4 (-) receptor allows recognition and differentiation of H2 PO4 (-) and HP2 O7 (3-) anions by using different channels: H2 PO4 (-) is selectively detected through absorption and emission methods and HP2 O7 (3-) by using electrochemical techniques. Significant structural results are the observation of an anion⋅⋅⋅anion interaction in the solid state (2:2 complex, 6(2+) ⋅[H2 P2 O7 ](2-) ), and a short C-I⋅⋅⋅O contact is observed in the structure of the complex [8(2+) ][SO4 ]0.5 [BF4 ].

Halogen Bonding in Solution: Anion Recognition, Templated Self‐Assembly, and Organocatalysis

“…In 2015, the first example of XB‐based redox‐active receptors and their electrochemical anion‐sensing properties were reported by the Beer research group . Subsequently, XB motifs were also successfully integrated into other redox‐active receptor frameworks containing, for example, ferrocene or tetrathiafulvalene units …”

“…Electrochemical sensors have received much attention because of their innate high sensitivity and facile integration into applicable devices.I n2 015, the first example of XBbased redox-active receptors and their electrochemical anionsensing properties were reported by the Beer research group. [39] Subsequently,X Bm otifs were also successfully integrated into other redox-active receptor frameworks containing,f or example,f errocene [40][41][42][43] or tetrathiafulvalene units. [44] Thef undamental studies of Lim et al [39][40][41] concentrated, in particular,o nf errocene as the redox-active motif because of its chemical stability,w ide synthetic repertoire,a sw ell as favorable voltammetric properties.T heir initial studies concerned different ferrocene motifs directly connected to the anion binding sites of 10 and 11 (X = H, I; Figure 7), [39] which were analyzed by 1 HNMR spectroscopy and electrochemical voltammetric investigations in organic and aqueous solvents.…”

Expanding reversible chalcogenide binding: supramolecular receptors for the hydroselenide (HSe−) anion

“…Synthetic supramolecular receptors have been used with great success for investigating the solution binding of biologically- and environmentally-relevant anions 1–5. By using reversible, mostly non-covalent interactions such as hydrogen bonding, electrostatic interactions, and anion–π interactions, a diverse palette of anions can be bound ranging from relatively inert anions such as halides and oxoanions6–10 to highly reactive anions 11–16. Although targeting the latter poses many challenges, reversible binding in supramolecular hosts can be used to stabilize high-energy anions through non-covalent interactions in a manner reminiscent of certain active sites in proteins 17.…”

Relationships between hydrogen bonds and halogen bonds in biological systems

“…Interest in halogen bonds (XBs) has seen a revival in the past couple of decades, as the potential to exploit their unique properties has become better recognized (Erdé lyi, 2012;Gilday et al, 2015;Cavallo et al, 2016). XBs are widely applied to the chemical engineering of crystals and supramolecular assemblies (Metrangolo & Resnati, 2001;Metrangolo et al, 2005), including designing liquid crystals (Nguyen et al, 2004;Bruce, 2008;Chen et al, 2014;Fernandez-Palacio et al, 2016), and organometallic frameworks (Maharramov et al, 2016), stabilizing volatile liquids (Aakerö y et al, 2015), synthesizing organic catalysts (Coulembier et al, 2010;Jungbauer & Huber, 2015;Matsuzawa et al, 2016), designing anion receptors (Sarwar, Dragisic, Sagoo et al, 2010;Kilah et al, 2011;Tepper et al, 2015;Amendola et al, 2016;Wageling et al, 2016;Mullaney et al, 2016;Hoque & Das, 2016), and in host-guest assemblies (Dumele et al, 2015;Noa et al, 2015Noa et al, , 2016Gonzá lez et al, 2016;Puttreddy et al, 2016). In biology (Auffinger et al, 2004;Scholfield et al, 2013), XBs are seen to direct DNA macromolecular conformations (Voth, Hays & Ho, 2007), to increase the affinity of agonists (Rohde et al, 2012) and antagonists to protein targets (Lam et al, 2009;Lu, Shi et al, 2009;Hardegger et al, 2011;Scholfield et al, 2013;Xu et al, 2014;…”