Stepwise assembly of mixed-metal coordination cages containing both kinetically inert and kinetically labile metal ions: introduction of metal-centred redox and photophysical activity at specific sites.

摘要: Stepwise preparation of the heterometallic octanuclear coordination cages [(Ma)4(Mb)4L12]16+ is reported, in which Ma = Ru or Os and Mb Cd Co (all their +2 oxidation state). This requires initial kinetically inert mononuclear complexes [(Ma)L3]2+ L a ditopic ligand with two bidentate chelating pyrazolyl-pyridine units: one terminus each bound to metal ion, such that complex has three pendant sites at cage assembly can propagate by additional labile ions separate step. Thus, combination four units [Mb]2+ results complete ion lies eight vertices, bridging spans twelve edges, cube. The different types necessarily alternate around periphery type. All have been structurally characterised: Ru(II)/Cd(II) (reported recent communication) Ru(II) Cd(II) are crystallographically distinct; other [Ru(II)/Co(II), Os(II)/Cd(II) Os(II)/Co(II), reported here] disordered every site refines as 50 : 50 mixture atom types. incorporation Os(II) into both redox activity [a reversible Os(II)/Os(III) couple for all simultaneously, modest potential] luminescence [the luminescent 3MLCT excited states will be good photo-electron donors] being incorporated superstructure.