Controlled self-assembly by mono-p-sulfonatocalix[n]arenes and bis-p-sulfonatocalix[n]arenes

The complexation-induced critical aggregation concentrations of 1-pyrenemethylaminium by mono-p-sulfonatocalix[n]arenes and bis-p-sulfonatocalix[n]arenes (n=4, 5) were systemically measured by fluorescence spectroscopy. In all cases, the complexation-induced critical aggregation concentration decreases by about 3 times upon addition of p-sulfonatocalix[n]arenes. However, the optimal molar ratios for the aggregation of 1-pyrenemethylaminium by mono-p-sulfonatocalix[n]arenes and bis-p-sulfonatocalix[n]arenes are distinctly different: For mono-p-sulfonatocalix[n]arenes, the optimum mixing ratio for the aggregation of 1-pyrenemethylaminium is 1:4 mono-p-sulfonatocalix[n]arenes/1-pyrenemethylaminium, whereas only 2.5 molecules of 1-pyrenemethylaminium can be bound by one cavity of bis-p-sulfonatocalix[n]arenes. The intermolecular complexation of mono-p-sulfonatocalix[n]arenes and bis-p-sulfonatocalix[n]arenes with 1-pyrenemethylaminium led to the formation of two distinctly different nanoarchitectures, which were shown to be nanoscale vesicle and rod aggregates, respectively, by using dynamic laser scattering, TEM, and SEM. This behavior is also different from the fiber-like aggregates with lengths of several micrometers that were formed by 1-pyrenemethylaminium itself above its critical aggregation concentration. Furthermore, the obtained nanoaggregates exhibit benign water solubility, self-labeled fluorescence, and, more importantly, temperature responsiveness.