The supramolecular chemistry of the sulfonate group in extended solids

Organosulfonates (RSO3−) are largely regarded as poor ligands by coordination chemists, and have typically been employed as 'non coordinating' anions in past synthetic and structural work. Indeed, the majority of transition metal aqua complexes with sulfonate counter anions show that the sulfonate group cannot readily displace water from the coordination sphere of the metal ion. There exists a strong structural analogy between the RSO3− and the phosphonate RPO32− group, a functionality which has been employed with great success in the generation of functional extended architectures. The contrast lies in the fact that individual metal–oxygen interactions with the sulfonate group are weaker, when employed with suitably soft metal cations, but may be employed cooperatively, to still yield a stable solid. This review deals with some of the functional frameworks we have reported which take advantage of the inherent coordinative pliancy of the sulfonate group to generate extended networks. Features of the discussed frameworks include sponge-like guest sorption, anion exchange, and topotactic intercalation.