PHOTORESPONSIVE PIPERAZINE MACROCYCLES

The photoresponsive macrocyclic phanes 3, 7a, 7b, 10 were prepared. Th e (E) and (Z) isomers of 7b could be separated from each other by colu mn 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-assem bly to a dimeric structure (7b) and a tubular structure (10) in the cr ystalline state. Additionally, both structures demonstrate inclusion o f solvent molecules into the cavity (diameter 5 angstrom, 7b) and tube (diameter 11 angstrom, 10) respectively. A variable-temperature H-1-N MR study of 7b showed that the piperazine ring inversion is restricted at lower temperatures.