Polycationic (Mixed) Core–Shell Dendrimers for Binding and Delivery of Inorganic/Organic Substrates

Abstract

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.

Structure–Activity Relationships of Oligocationic, Ammonium‐Functionalized Triarylphosphines as Ligands in the Pd‐Catalyzed Suzuki–Miyaura Reaction

“…The crystal structure of hexacationic 1 a (S) is in line with previously reported, related structures of similar oligocationic compounds, such as an octacationic tetra‐arylsilane derivative 20a. It shows distinct binding sites for the iodide ions, with two iodides (I1 and I4) being embedded in cationic pockets, while the other four iodides are located in voids between adjacent molecules in the crystal lattice.…”

Dendritic polyamine architectures with lipophilic shells as nanocompartments for polar guest molecules: A comparative study of their transport behavior

“…7(a,b)] if bearing sulfonate or carboxylate groups. This result can be explained with ionic interactions of the acid groups with the partly protonated PEI core as previously discussed in the literature 3, 29, 33, 34. Also very acidic OH groups, such as phenol groups, are able to facilitate the process of encapsulation.…”

“…At pH = 7 only 20% of the nitrogen atoms are protonated whereas at pH = 5 about 40% are protonated 32. The increasing amount of protonated nitrogen atoms leads to a change of the polarity of the PEI core and increasing interaction with anionic guests as discussed in case of a dendrimer with amine groups33 or addition of positive charges via alkylation 21. Therefore the pH dependence on the process of encapsulation was evaluated with PEI 6 C16 0.5 obtained via the acid chloride route.…”

Water-stable ammonium-terminated carbosilane dendrimers as efficient antibacterial agents

“…The stoichiometric reaction of dendrimer 4 containing eight units with identical equivalents of MeI gave the corresponding outermost quaternized terminal amine derivative G 2 -{[Si(CH 2 ) 3 N(Et)CH 2 CH 2 N + Me 3 ] 8 (I -) 8 } (14) with small amounts of non-methylated branches on the basis of the HMBC-{ 1 H-15 N} experiment. The stoichiometric reaction of dendrimer 4 containing eight units with identical equivalents of MeI gave the corresponding outermost quaternized terminal amine derivative G 2 -{[Si(CH 2 ) 3 N(Et)CH 2 CH 2 N + Me 3 ] 8 (I -) 8 } (14) with small amounts of non-methylated branches on the basis of the HMBC-{ 1 H-15 N} experiment.…”