Effect of protonation and PAMAM dendrimer size on the complexation and dynamic mobility of 2-naphthol

The supramolecular dynamics of triplet excited states of the 2-naphthol@den drimer (2-NpOH@n-SBD) noncovalently bound complex have been studied by fluo rescence spectroscopy and laser flash photolysis. By varying the acidity an d dendrimer size, polyamidoamine dendrimers are shown to possess both nonsp ecific and specific binding properties. For example, the studies show that 2-naphthol binds preferentially to the tertiary amine groups within the den drimer interior and can be released by lowering the pH of the solution. On a per binding site basis, studies of the dynamics of (3)2-NpOH*@n-SBD revea l that the overall dynamics (entry and exit rate constants) are enhanced by increasing the acidity of the solution. Furthermore, the amount of protona tion of tertiary amine groups within 2-SBD, 4-SBD, and 6-SBD was determined to be similar to 12%, similar to 10%, and <1%, respectively, at pH 6. The results presented here demonstrate that, in addition to being able to compl ex transition metals, organic molecules that are capable of hydrogen bondin g to the internal amine moieties can also be bound to dendrimers.