Supramolecular [M4L4] Tetrahedra Based on Triangular Acylhydrazone Catechol Ligands

The ligands 1-H6 and 2-H6 are prepared by condensation of the triangular triamines 5 and 2,3-dihydroxybenzoic acid hydrazide 7. The ligands form container-type tetrahedral coordination compounds Mx [(1 or 2)4M′4] (M = Li, Na, K; M′ = Ti, x = 8; M′ = Ga, x = 12). The complexes are characterized by NMR spectroscopy and ESI mass spectrometry. Despite the relatively labile acyl hydrazone unit, the complexes show high stability in water. Ligand 3-H6 is prepared from the trisacyl hydrazide 8 and 2,3-dihydroxybenzaldehyde 9 but does not form well-defined coordination compounds with gallium(III) or titanium(IV) ions.