Pseudorotaxanes and rotaxanes incorporating diarylcycloheptatriene stations

The nature of the interaction between the tetracationic cyclophane cyclobis(paraquat-4,4'-biphenylene) and molecular threads incorporating arylcycloheptatriene units as stations was studied through the differences between the proton resonances observed in the NMR spectra of free molecular threads and in those of corresponding pseudorotaxanes and rotaxanes (CIS values). Molecular threads of different lengths possessing one or two recognition stations and incorporating two different isomeric arylcycloheptatriene units were used for pseudorotaxanes and rotaxanes. The main contribution to the driving forces behind the complexation of pseudorotaxanes and the co-conformation of rotaxanes was deduced from the CIS values of distinct parts of the molecular threads. The unusual signal dispersion of the cyclophane proton resonances is attributed to the asymmetry caused by the molecular thread incorporating the asymmetric cycloheptatriene ring. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).