Crystal structures of [18]aneN6H2K[Co(CN)6].4H2O, [16]aneN4H2K[Co(CN)6] and [12]aneN4H3[Co(CN)6].2H2O. Insight into the electrostatic and hydrogen-bonding interaction in self-assembling supercomplexes

The crystal structures of [18]aneN6H2K[Co(CN)6].4H2O [potassium dihydrogen hexacyanocobaltate–1,4,7,10,13,16-hexaazacyclooctadecane–water (1/1/4)], [16]aneN4H2K[Co(CN)6] [potassium dihydrogen hexacyanocobaltate–1,5,9,13-tetraazacyclohexadecane (1/1)] and [12]aneN4H3[Co(CN)6].2H2O [trihydrogen hexacyanocobaltate–1,4,7,10-tetraazacyclododecane–water (1/1/2)] have been determined. For these supercomplexes, the [Co(CN)6]3− binding with protonated polyammonium macrocycles is dominant in the binding competition between K+ and [Co(CN)6]3−. It is suggested that the binding of [Co(CN)6]3− with protonated polyammonium macrocycles is independent of the cavity size of the macrocycle, whereas that of K+ is size-match selective. For [18]aneN6H2K[Co(CN)6].4H2O, the formation of a two-dimensional lamella may be derived from a chain-like arrangement of four-, five- and eight-membered rings in the network through the mutual balance between electrostatic and hydrogen-bonding interactions. [16]aneN4H2K[Co(CN)6] is a novel example demonstrating the anchoring of cobalticyanide through hydrogen-bonding interactions inside a zeolite-type cavity in the three-dimensional network formed by K+ and the macrocycles through Coulombic interactions. Also, a three-dimensional network was formed mainly through hydrogen-bonding interactions between [Co(CN)6]3−, protonated macrocycles and water molecules in [12]aneN4H3[Co(CN)6].2H2O.