The convergent synthesis of a series of polycationic aryl ether den-drimers has been accomplished by a convenient procedure involving quantitative quaternarization of aryl(poly)-amine core molecules. The series has been expanded to the preparation of the first polycationic, mixed core ± shell den-drimer. All these dendrimers consist of an apolar core with a peripheral ionic layer which is surrounded by a less polar layer of dendritic wedges. These cation-ic, macromolecular species have been investigated for their ability to form assemblies with (anionic) guest molecules. The results obtained from UV/Vis and NMR spectroscopies, and MALDI-TOF-MS demonstrate that all the cat-ionic sites throughout the dendrimer core are involved in ion pair formation with anionic guests giving predefined guest/host ratios up to 24. The large NMR spectroscopic shifts of resonances correlated with the groupings located in the core of the dendrimers, together with the relaxation time data indicate that the anionic guests are associated with the cationic core of these dendrim-ers. The X-ray molecular structure of the octacationic, tetra-arylsilane model derivative [Si(C 6 H 3 {CH 2 NMe 3 } 2-3,5) 4 ] 8‡´88‡´ 8‡´8 I À shows that the iodide counterions are primarily located near the polycat-ionic sphere. The new polycationic den-drimers have been investigated for their catalytic phase-transfer behavior and substrate delivery over a nanofiltration membrane.

Ionic core-shell dendrimers with an octacationic core have been applied as noncovalent supports for homogeneous catalysts. Catalytically active arylpalladium complexes, which bear a tethered sulfato group, were noncovalently attached to the ionic core-shell dendritic supports via a straightforward ionexchange reaction under mild conditions. Diagnostic shifts in 1 H NMR and Overhauser contacts show that the sulfato groups of the catalysts are located close to the octacationic core of the dendritic support in the resulting assemblies. The location of the catalytic Pd(II) sites has been varied via two strategies: by increasing the dendrimer generation and/or by shortening of the sulfato tether. In addition, a metallodendritic assembly was prepared, which bears an alternative shell of apolar dodecyl groups. Both the dendrimer size and the nature of the dendritic shell have no influence on the binding properties of the dendritic supports, i.e., the octacationic dendrimers of generations 1-3 form discrete 1:8 assemblies with the arylpalladium complexes. The structural aspects and the nature of the metallodendritic assemblies have been studied by means of pulse gradient spin-echo NMR diffusion methods, Overhauser spectroscopy, and electron microscopy (TEM). These techniques showed that the dendritic supports and arylpalladium complexes are strongly associated in solution to give unimolecular assemblies of nanoscopic dimensions. Membrane dialysis can recover these metallodendritic assemblies due to their nanoscopic size. The catalytic performances of the metallodendritic assemblies are comparable, but slightly lower than the performance of the unsupported catalyst.

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