Functionalized Calix[8]arenes, Synthesis and Self-assembly on Graphite

With the intention of building hollow tubular structures by self-assembly, we have designed and successfully synthesized a series of calix[8]arene derivatives. Their phenolic units were functionalized in p-position by various groups which are able to interact via hydrogen bonding or π−π stacking. Ethynyl, amide, urea, or imide links were chosen for the covalent attachment of these functional groups, to ensure the adjustment of an optimal distance for their interaction. Two different kinds of nanostructures self-assembled on a highly oriented pyrolytic graphite (HOPG) surface were found by scanning force microscopy:  parallel aligned nanorods in which the calixarene molecules are adsorbed edge-on on the graphite, providing evidence that these calix[8]arene derivatives stack in a tubular fashion, and micrometer long fiber bundles most probably composed of many nanorods.