Dithiolate-containing macrocyclic complexes in which there is no thiolate bridging: synthesis, structure and electrochemistry of some dizinc(II) complexes

The synthesis of three dizinc(II) Schiff base macrocyclic complexes, [Zn2L1](CF3SO3)2 (1), [Zn2L2](CF3SO3)2 (2) and [Zn2L3](CF3SO3)2 (3), from 2,6-diformyl-4-methyl-thiophenolate, the appropriate amine (diethylenetriamine, N-(3-aminopropyl)-1,3-diaminopropane and triethylenetetramine respectively) and zinc template ions, is detailed. Complex 1 is unstable in solution. Single crystal structure analysis of 2 and 3 reveals tetrahedral and five coordinate zinc(II) atoms, respectively, and shows that the two thiolate donors within each macrocycle do not bridge the metal ions. Rather, in each case the macrocycle twists over on itself, utilising the flexibility of the lateral chains, such that the two phenyl rings form favourable π–π stacking interactions. NMR studies indicate that this structure is retained in solution. Complexes 2 and 3 are electrochemically inactive in dry MeCN but if traces of water are present two irreversible oxidation processes are observed.