{Δ-1,4,7,10-Tetrakis[(S)-2-hydroxypropyl-κO]-1,4,7,10-tetraazacyclododecane-κ4N}cadmium(II) salicylate perchlorate hemihydrate

Crystallization of [Cd(S-thpc12)](ClO4)(2).H2O {S-thpc12 is 1,4,7,10-tetrakis[(S)-2-hydroxypropyl]-1,4,7,10-tetraazacyclo- dodecane} in the presence of sodium salicylate (sodium o-hydroxybenzoate) forms a receptor complex, namely the title compound, [Cd(C20H44N4O4)(C7H5O3)]ClO4.0.5H(2)O, in which salicylate is hydrogen bonded, via each of its two carboxylate O atoms, to pairs of cis-related pendant hydroxyl groups which, together with the four N atoms, are themselves bound to Cd-II in an approximately square anti-prismatic arrangement. The diastereoselectivity of the complex-forming process is apparent from the fact that only molecules having Delta helicity, associated with the spiralling of the pendant arms, are formed.