Chloride capture using a C–H hydrogen-bonding cage

A C–H bonding trap for chloride Part of the reason salt dissolves so well in water is that the polarized O–H bonds attract the negatively charged chloride ions. It has therefore been common to include O–H or N–H bonds in molecular receptors designed to capture anions such as chloride. Liu et al. report the surprising finding that sufficiently polarized C–H bonds can work even better (see the Perspective by Bowman-James). They designed a cage with triazole rings that directed C–H bonds inward to encapsulate chloride with a remarkable attomolar affinity in dichloromethane. Science , this issue p. 159 ; see also p. 124