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 (L1) and dimethyl-dipyrido[3,2-a:2′,3′-c]phenazine (L2) 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 (λex 400 nm) for Yb(III), resulting in characteristic near-IR emission at 950–1050 nm. The incorporation of dppz-type ligands into cyclometalated IrIII complexes of the general type [Ir(epqc)2(Ln)](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 YbIII can be sensitised using visible light.