Hydrogen Bonding-Driven Anion Recognition

Liping Cao, Jie Zhao, Dong Yang, Xiao-Juan Yang and Biao Wu 

Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of the Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi an 710069, China e-mail wubiao nwu.edu.cn 

Li and L. Wu (eds.). Hydrogen Bonded Supramolecular Structures, Lecture Notes in Chemistry 87, DOI 10.1007/978-3-662-45756-6 5 

Amides, bearing both H-bond acceptors (C=0) and donors (NH), play an important role in Namre (e.g., a helices and sheets of peptides and proteins, ion channels), and in technology as structural materials (e.g.. Nylons) [4]. For example, the X-ray crystal structure of the sulfate-binding protein of Salmonella typhimurium shows that the sulfate is bound by seven H-bonds, five of which involve amide NH groups of polypeptides [5]. The pXa of the amide NH is about 12-21 and becomes lower when modified with electron-deficient groups. Consequentiy, amide as an excellent H-bond donor to bind anionic species has attracted much attention of supramo-lecular, biological, and environmental chemists, especially for anion recognition, transport, and pollution remediation [6-11]. 

In early 1980s, chemists started to develop amide-based receptors for selective recognition of anions. In 1986, Pascal and co-workers reported a pioneering work about the synthesis and X-ray crystal structure of an amide-based cryptand 1 [12]. Although it was not certain that fluoride was contained within its cavity, and NMR studies suggested that 1 could bind to fluoride through H-bonding. 

---