Water-soluble, luminescent iridium(III)-ytterbium(III) complexes using dipyrido[3,2-a:2′,3′-c] phenazine derivatives as bridging units

Amino-substituted dipyrido[3,2-a:2',3'-c]phenazine (L-1) and dimethyl-dipyrido[3,2-a:2',3'-c]phenazine (L-2) have been investigated as: (i) chromophores in cyclen-based ligands for lanthanide(III) ions; (ii) ancillary co-ligands in cyclometalated iridium(III) complexes; (iii) bridging, linker units in covalently linked, water-soluble bimetallic lanthanide(III) iridium(III) hybrid complexes. The dipyrido[3,2-a:2',3'-c]-phenazine (dppz) derivatives can act as sensitising chromophores (lambda(ex) 400 nm) for Yb(III), resulting in characteristic near-IR emission at 950-1050 nm. The incorporation of dppz-type ligands into cyclometalated Ir-III complexes of the general type [Ir(epqc)(2)(L-n)](PF6) (where epqc = ethylphenylquinoline carboxylate) gave luminescent species with solvent-sensitive emission properties. Steady state and time-resolved luminescence measurements on the water-soluble d-f hybrid species showed that Yb-III can be sensitised using visible light.