Sensitisation of Eu(III)- and Tb(III)-based luminescence by Ir(III) units in Ir/lanthanide dyads: evidence for parallel energy-transfer and electron-transfer based mechanisms.

A series of blue-luminescent Ir(III) complexes with a pendant binding site for lanthanide(III) ions has been synthesized and used to prepare Ir(III)/Ln(III) dyads (Ln = Eu, Tb, Gd). Photophysical studies were used to establish mechanisms of Ir→Ln (Ln = Tb, Eu) energy-transfer. In the Ir/Gd dyads, where direct Ir→Gd energy-transfer is not possible, significant quenching of Ir-based luminescence nonetheless occurred; this can be ascribed to photoinduced electron-transfer from the photo-excited Ir unit (*Ir, (3)MLCT/(3)LC excited state) to the pendant pyrazolyl-pyridine site which becomes a good electron-acceptor when coordinated to an electropositive Gd(III) centre.

Luminescent cyanometallates based on phenylpyridine-Ir(III) units: solvatochromism, metallochromism, and energy-transfer in Ir/Ln and Ir/Re complexes.

[Ir(ppy)(2)(CN)(2)](-) (ppy = anion of 2-phenylpyridine) and some substituted derivatives have been investigated for their ability to interact with additional metal cations, both in solution and the solid state, via the externally-directed cyanide lone pairs, and to act as energy-donors in the resulting assemblies. [Ir(ppy)(2)(CN)(2)](-) is slightly solvatochromic, showing a blue-shift of the lowest energy absorption manifold in water compared to organic solvents, and the solubilised (t)Bu-substituted analogue [Ir((t)Buppy)(2)(CN)(2)](-) [(t)Buppy = anion of 2-(4-(t)Bu-phenyl)pyridine] is also metallochromic with coordination of the cyanide lone pairs to two M(II) cations in MeCN (M = Ba, Zn) resulting in blue-shifts of the lowest-energy absorption and emission maxima. These effects are however modest because of (i) the presence of only two cyanide groups, and (ii) the fact that the lowest-energy excited state has a substantial (3)LC component and is therefore not purely charge-transfer in nature.