A Ruthenium( II )‐Complexed Rotaxane Whose Ring Incorporates a 6,6′‐Diphenyl‐2,2′‐bipyridine: Synthesis and Light‐Driven Motions

By incorporating a 6,6'‐diphenyl‐2,2'‐bipyridine (dpbipy) fragment in a ring, endo coordination of a ruthenium(II) center is performed selectively and almost quantitatively. The threaded system, containing a helical fragment, could be fully characterized. When the terminal functions of the rod‐shaped helical complex threaded through the macrocycle are phenol groups, the complete rotaxane is prepared by the classical Williamson stoppering reaction in moderate yield. Light‐induced motions of the unstoppered system (pseudorotaxane) and the real rotaxane have been studied. Under visible light irradiation, quantitative decoordination of the dpbipy‐containing ring is observed, leading to the separate fragments (ring and helical thread) or to a new rotaxane (uncoordinated ring threaded by the dumbbell). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)