Geometrical and inclusion considerations in the formation of hexagonal nanotubes of calix[4]arene di-methoxycarbonyl methyl ester and acid

The crystal structures of calix[4]arene di-methoxycarbonyl-methyl ester and carboxylic acid have been resolved. Interestingly, the packing for both molecules is in the form of crystal symmetry defined hexagonal helical nanotube architecture, but with the methyl ester derivative showing an extended form of the helix with regard to that formed by the carboxylic acid derivative. The addition of one carbon in the ester group leads to inclusion of the ethyl ester within a neighbouring calixarene cavity, and in consequence the packing becomes radically different.