Well-defined assemblies of adamantyl-terminated poly(propylene imine) dendrimers and beta-cyclodextrin in water

J.J. Michels, M.W.P.L. Baars, E.W. Meijer, J. Huskens, D.N. Reinhoudt

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Abstract

Adamantyl-terminated poly(propylene imine) dendrimers 1–5 were dissolved in water in the presence of -cyclodextrin through strong non-covalent interaction between the -cyclodextrin and adamantyl groups. The solubilization of the dendrimer by -cyclodextrin is most effective at pH = 2, because at this pH there is complete protonation of the tertiary amino groups present in the dendritic cores, which causes the dendrimers to adopt a stretched conformation. The dendrimers remain in solution at pH 7, but precipitate under basic conditions, except for 1, which remains in solution. The stoichiometries of the -cyclodextrin complexes of 1–4 at pH = 2 are 1·(-CD)4, 2·(-CD)8, 3·(-CD)16, and 4·(-CD)32, respectively. For steric reasons not all 64 adamantyl groups of 5 can be complexed by -cyclodextrin. The stoichiometry of the 5·(-CD)n complex is about 140 (pH = 2). Steric arguments confirm that the outer surface area of 5 is too small to allow complete coverage by -cyclodextrins. Qualitative fluorescence measurements at pH = 1 using 8-anilinonaphthalene-1-sulfonate (ANS) as a probe showed that the assemblies of 2–5 with -cyclodextrin act as supramolecular hosts for ANS in water. The binding of ANS is electrostatically driven and increases for higher generations.
Original languageEnglish
Pages (from-to)1914-1918
Number of pages5
JournalJournal of the Chemical Society. Perkin Transactions II : Physical Organic Chemistry
Issue number9
DOIs
Publication statusPublished - 2000

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