Calix[4]pyrroles: Old yet new anion-binding agents

Recently, as the result of our work with polypyrrole macrocycles, it occurred to us that the porphyrinogens, a venerable class of molecules, might serve as such easy to make anion binding agents. The present results lead us to suggest that there could be a rich molecular recognition chemistry associated with the calixpyrroles. Presently we are exploring whether the calix[4]pyrroles might to also serve as receptors for neutral substrates or as chelating agents for more complex negatively charged materials(e.g.,polyanions such as DNA). We are also working to produce yet larger (i.e., expanded) calixpyrroles based on the incorporation of more than four pyrrolic substrates into a porphyrinogen-like framework/ or the use of bi- or terpyrrolic starting materials. The results of these investigations will be reported in due course.