Crowned dendrimers: pH-responsive pseudorotaxane formation.
With the end goal of incorporating the unique structural and physical properties of dendrimers into supramolecular assemblies, bis(m-phenylene)-32-crown-10-functionalized poly(propyleneimine) dendrimers of the first and third generations have been synthesized and their interaction with paraquat diol has been investigated. Using (1)H NMR, we determined that binding to the 4 or 16 crown ether sites occurred in an anti-cooperative fashion, most likely a result of steric influences. Upon protonation of the tertiary amines in the dendritic interior, binding became independent, i.e., statistical, and the average apparent association constant increased by nearly 5-fold; this effect is attributed to rigidification of the dendrimer, which makes its binding sites more accessible and less crowded.
Jones
Jason W
JW
Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061-0212, USA.
Bryant
William S
WS
Bosman
Anton W
AW
Janssen
Rene A J
RA
Meijer
E W
EW
Gibson
Harry W
HW