Gold-Based Coronands as Hosts for M(3+) Metal Ions: Ring Size Matters

The controlled, self-assembled synthesis of multinuclear coordination compounds can be performed via different approaches. Frequently, steric, geometric and/or electronic factors located at the ligand systems predefine the way in which metal ions can assemble them to large aggregates. For the compounds in the present paper, also the Pearson’s acidities and preferred coordination geometries of the metal ions were used as organization principles. The ligand under study, 2,6-dipicolinoylbis(N,N-diethylthiourea), H(2)L1(ethyl), possesses ‘soft’ sulfur and ‘hard’ nitrogen and oxygen donors. One-pot reactions of this compound with [AuCl(tht)] (tht = tetrahydrothiophene) and M(3+) salts (M = Sc, Y, La, Ln, Ga, In) give products with gold-based {Au(3)(L1(ethyl))(3)}(3+) or {Au(2)(L1(ethyl))(2)}(2+) coronands, which host central M(3+) ions. The formation of such units is templated by the M(3+) ions and the individual size of the coronand rings is dependent on the ionic radii of the central ions in a way that small ions such as Ga(3+) form a [Ga⊂{Au(2)(L1(ethyl))(2)}](+) assembly, while larger ions (starting from Sc(3+)/In(3+)) establish neutral [M⊂{Au(3)(L1(ethyl))(3)}] units with nine-coordinate central ions.