Rational Design of Organically Functionalized Polyoxopalladates and Their Supramolecular Properties

The SrII‐centered 12‐palladate(II) open‐cube {SrPd12(OAc)3} has been systematically evolved by substitution of the three acetate ligands by a library of saturated carboxylic acids with increasing chain lengths leading to four novel polyoxopalladates(II) with the formula [SrPd12O6(OH)3(PhAsO3)6(L)3]4− (SrPd12L3, L=CnH2n+1COO, n=2 to 5). These first examples of surfactant‐type polyoxopalladates with a hydrophilic metal‐oxo unit and three hydrophobic alkyl chains were characterized in the solid state (single‐crystal XRD, FTIR, TGA), in solution (1H, 13C NMR spectroscopy), and in the gas phase (ESI‐MS). The two polyanions SrPd12L3 with chain lengths of 5 and 6 are the first examples of polyoxopalladates that are soluble and stable in organic media. The Na salts of the amphiphilic polyoxopalladates SrPd12L3 were shown to self‐assemble into “blackberry”‐type spherical supramolecular structures in dilute solutions, of which an unusual “volcano”‐shaped trend of assembly size versus solvent polarity is chiefly influenced by directional hydrogen bonding interactions. Polyoxometalates: Four surfactant‐type polyoxo‐12‐palladates(II) SrPd12L3 with three carboxylate ligands L (chain lengths from 3 to 6) were prepared, resulting in discrete polyanions, which exhibit aqueous and organic solubility and unprecedented supramolecular interactions.