Photoresponsive Piperazine Macrocycles

The photoresponsive macrocyclic phanes 3, 7a, 7b, 10 were prepared. The (E) and (Z) isomers of 7b could be separated from each other by column chromatography. The X‐ray structure of the 31‐membered cycle (E)‐7b and the 54‐membered cycle (E,E)‐10 shows a tendency toward self‐assembly to a dimeric structure (7b) and a tubular structure (10) in the crystalline state. Additionally, both structures demonstrate inclusion of solvent molecules into the cavity (diameter 5 Å, 7b) and tube (diameter 11 Å, 10) respectively. A variable‐temperature 1H‐NMR study of 7b showed that the piperazine ring inversion is restricted at lower temperatures.