| Autor: |
Broeren MA; Laboratory of Macromolecular and Organic Chemistry, Eindhoven University of Technology. P.O. Box 513, 5600 MB Eindhoven, The Netherlands., de Waal BF, van Genderen MH, Sanders HM, Fytas G, Meijer EW |
| Jazyk: |
angličtina |
| Zdroj: |
Journal of the American Chemical Society [J Am Chem Soc] 2005 Jul 27; Vol. 127 (29), pp. 10334-43. |
| DOI: |
10.1021/ja052074m |
| Abstrakt: |
A new way to analyze supramolecular dendritic architectures is reported by making use of (13)C NMR and (31)P NMR. Two ethylene glycol guest molecules have been synthesized containing a (13)C labeled carboxylic acid headgroup (2) and a phosphonic acid headgroup (3). The binding of these guests to urea-adamantyl modified poly(propylene imine) dendrimers has been investigated with (13)C NMR and (31)P NMR next to 1D and 2D (1)H NMR techniques. Different amounts of guest 2 have been added to fifth generation dendrimer 1e, and the observed chemical shift values in (13)C NMR were fitted to a model that assumes 1:1 binding between guest and binding site. An association constant of 400 +/- 95 M(-)(1) is obtained for guest 2 with 41 binding sites per dendrimer. When different amounts of phosphonic acid guest 3 are added to dendrimer 1e, two different signals are observed in (31)P NMR. Deconvolution gives the fractions of free and bound guest, resulting in an association constant of (4 +/- 3) x 10(4) M(-)(1) and 61 +/- 1 binding sites. A statistical analysis shows that guest 2 forms a "polydisperse supramolecular aggregate", while guest 3 is able to form a "monodisperse supramolecular aggregate" when the amount of guest is high enough. The NMR results are compared with dynamic light scattering experiments, and a remarkable agreement is found. Phosphonic acid guest 3 is able to exchange with guest 2, which is in agreement with the obtained association constants, and shows that these techniques can be used to analyze multicomponent dendritic aggregates. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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