Dyes Based on Iridium Complexes and Method of Tethering Ligands

Dyes Based on Iridium Complexes and Method of

Tethering Ligands

Carlo Nervi, Roberto Gobetto

Dipartimento di Chimica, Università di Torino, via P. Giuria 7, 101265 Torino, Italy The photophysical properties of cationic iridium cyclometalated heteroleptic complexes have attracted much interest during last years due to their photostability, photophysical properties and applications in DSSC and light emitting devices. In the last decade conversion of solar energy has been recognized as one of the most important research topic.1 _{Conversion of sunlight into energy}

can be pursued via a direct (i.e. by DSSCs), or indirect (i.e. by energy storage via artificial photosynthesis) approaches. In particular, Ir(III) derivatives have been outlined as superior alternatives to the photo-sensitizer [Ru(bpy)3]+-type complexes for hydrogen production via

water-splitting reactions, due to their tunable photophysical and electrochemical properties, and to their ability to generate long-lived excited states after irradiation.2

We herein report the synthesis of novel monocationic iridium(III) photosensitizers (Ir-PSs) with the general formula [IrIII_(C^N)

2(N^N)]+ (C^N = cyclometalating benzilpyridine ligand, N^N =

4,4’-substituted bipyridine) as potential photosensitizers.

Ir-PS 1 R = H R’ = H Ir-PS 2 R = CH3 R’ = CH3

Ir-PS 3 R = OCH3 R’ = OCH3

Ir-PS 4 R = COOH R’ = COOH Ir-PS 5 R = COOCH3 R’ = COOCH3

Structurally similar, but easily functionalizable Ir complexes containing dipyridylketone unit were also synthesized with the aim to show how to tether ligands able to give the desired properties (i.e. greater solubility, surface-anchoring groups, light-harvesting properties, etc…) to the photosensitizer.3

References

[1] _{V.Balzani, A.Credi, M.Venturi, ChemSusChem 2008, 1, 26 – 58.}

[2] _{a) P.N.Curtin, L.L.Tinker, C.M.Burgess, E.D.Cline, S.Bernhard, Inorg. Chem., 2009, 48, 10498; b) F.Gartner,}

D.Cozzula, S.Losse, A.Boddien, G.Anilkumar, H.Junge, T.Schulz, N.Marquet, A.Spannenberg, S.Gladiali, M.Beller, Chem. Eur. J. 2011, 17, 6998.

[3] _{We are indebted to G.Volpi and C.Garino for assistance. a) G.Volpi, C.Garino, E.Breuza, R.Gobetto, C.Nervi,}