Building [2]catenanes around a tris(diimine)ruthenium(2+) ([Ru(diimine)3]2+) complex core used as template

In the course of the last two decades, the use of transition metals as templates for constructing catenanes has almost exclusively been restricted to tetrahedral copper(I). The present work is dealing with an octahedral metal, ruthenium(II), coordinated to three bidentate chelates. Incorporation of two chelates (1,10-phenanthroline) in a ring allows to prepare a C-2-symmetric ruthenium complex, the two chelates being disposed cis to one another (see 14(2+) and 16(2+) in Scheme 5 and 6, resp.). The ring is large enough to accomodate a third chelate, thus allowing the metal-directed threading of a long fragment containing the third chelate (2,2'-bipyridine derivative; see 23(2+) and 24(2+) in Scheme 8). The last step consists of a ring-closing metathesis reaction with two terminal olefins. The two ruthenium(II)-complexed catenanes 25(2+) and 26(2+) were prepared by using this strategy, each containing a 42-membered ring interlocked to a larger macrocycle (50- or 63-membered ring) incorporating the two 1,10-phenanthroline chelates. It is expected that these catenanes can be set in motion under light-irradiation, thus behaving as photochemically driven molecular machines.