Ultrafast excited state dynamics of iridium() complexes and their changes upon immobilisation onto titanium dioxide layers

Time-resolved spectroscopy was applied to investigate the excited state dynamics of two heteroleptic Ir( iii ) complexes with the general formula [Ir(C^N) 2 (N^N)] + , where C^N and N^N represent different cyclometalating and diimine ligands, respectively. The excited state relaxation is influenced by the ligand substitution as well as the light polarisation. Vibrational relaxation occurs in the sub-ps timescale and interligand charge transfer results in polarisation dependent signal dynamics with a time constant of about 30 ps. Electron injection from the iridium dye to TiO 2 is analysed with respect to potential applications in solar energy conversion. The unprecedented polarisation dependent excited state dynamics of iridium photosensitisers: new features of a well-known dye family.