Neutral CH and cationic CH donor groups as anion receptors

Abstract

The design and synthesis of anion selective receptors and chemosensors continues to attract considerable interest within the supramolecular community. In recent years, increasing attention has focused on the use of neutral and cationic CH hydrogen bond donors as anion recognition elements. Over the last five years, motifs that support CHX (X = anion) hydrogen bonds have been actively used in various shape persistent macrocycles, foldamers and "molecular machines". This tutorial review highlights recent developments in host-guest chemistry based on the use of neutral and cationic CH hydrogen bond donors. Also discussed are various structural classifications, including alkyl CH, phenyl CH, triazole-based CH, imidazolium (CH)(+) and triazolium (CH)(+) hydrogen bond donor systems.

Substituent Effects in CH Hydrogen Bond Interactions: Linear Free Energy Relationships and Influence of Anions

“…1,2 CH donors play important and previously unrecognized roles in the multidisciplinary fields of molecular biology, supramolecular chemistry, 3–5 and catalysis. 1,6 CH⋯O HBs are common in protein folding and are found in the minor groove of DNA. 7,8 Catalysts have also been found to include CH⋯O HBs as an important factor in stereoselectivity.…”

“…7,8 Catalysts have also been found to include CH⋯O HBs as an important factor in stereoselectivity. 6 Chemists are now widely using CH groups as HB donors in designed systems for anion capture 1,9–11 and catalysis. 12,13 …”

Selective anion receptor for fluoride detection using ferrocenyl–boronate derivative

“…2. However, the color was changed obviously from faint yellow to pink rather than yellow (the color of receptor 1 alone in CH 3 Fig. 3a (inset)).…”

“…The receptor 1 was soluble in common organic solvents such as CH 3 Cl, dichloromethane (DCM), THF, CH 3 CN and DMSO, etc. To investigate the optical properties of receptor 1, UVevis spectra changes of receptor 1 (c ¼ 5 Â 10 À5 M) in CH 3 CN upon addition of anions (F À , Cl À , Br À , AcO À , HSO 4 À , and H 2 PO 4 À ) were carried out.…”

“…(a) UVevis absorption spectra of receptor 1 (1 Â 10 À4 mol L À1 in CH 3 CN) with 10 equivalents' F À ion by increasing the amount of water gradually; (b) color changes of receptor 1 (c ¼ 5 Â 10 À4 mol L À1 ) in CH3 CN with 1 equivalent of F À , OAc À and H 2 PO 4 À upon the addition of 15% aqueous solution of CH 3 CN:H 2 O ¼ 85:15. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)…”