Structure, conformation, and dynamics of P,N-containing cyclophanes in solution.

3D structures in solution of highly symmetrical N,P-containing macrocycles were established by a variety of 2D NMR correlation techniques. It was shown that a number of magnetically equivalent fragments in such symmetrical systems can be estimated by NMR diffusion measurement. The title compounds adopt a helical conformation of the macrocycles in solution. The extent of twisting and the size of the intramolecular cavity are determined by steric hindrance of the aromatic substituents on the exocyclic phosphorus atoms with phenylene and dimethylmethylene groups forming the macrocycle. In solution these macrocycles host aromatic guests inside the cavity.