Unsymmetrical Triangular Schiff Base Macrocycles with Cone Conformations

Two new unsymmetrical Schiff base macrocycles with isosceles triangle shapes have been prepared. The macrocycles adopt cone-shaped conformations that rapidly interconvert at high temperature. Dynamic NMR studies show that the macrocycle that is tautomerized to the keto-enamine isomer is slower to flip than is the one in the enol-imine state. These macrocycles are good hosts for binding organic cations in their interiors.