A cyclometallated fluorenyl Ir(iii) complex as a potential sensitiser for two-photon excited photodynamic therapy (2PE-PDT)Electronic supplementary information (ESI) available: Stern-Volmer analysis of IrppyL1 with O2, overlay of one photon and two photon emission spectra of IrppyL1, spectroelectrochemistry of IrppyL1 and single crystal X-ray data in cif format of [Ir(ppy)2(L1)][PF6]. CCDC 1401349. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c5dt01855b

A new Ir( iii ) cyclometallated complex bearing a fluorenyl 5-substituted-1,10-phenanthroline ligand ([Ir(ppy) 2 ( L1 )][PF 6 ], ppy = 2-phenylpyridine) is presented which exhibits enhanced triplet oxygen sensing properties. The efficacy of this complex to act as a photosensitiser for altering the morphology of C6 Glioma cells that represent malignant nervous tumours has been evaluated. The increased heavy metal effect and related spin-orbit coupling parameters on the photophysical properties of this complex are evidenced by comparison with Ru( ii ) analogues. The complex [Ir(ppy) 2 ( L1 )][PF 6 ] is shown to exhibit relatively high two-photon absorption efficiencies for the lowest energy MLCT electronic transitions with two-photon absorption cross sections that range from 50 to 80 Goeppert-Mayer units between 750 to 800 nm. Quantum yields for the complex were measured up to 23% and the Stern-Volmer quenching constant, K SV was determined to be 40 bar −1 in acetonitrile solution, confirming the high efficiency of the complex as a triplet oxygen sensitiser. Preliminary in vitro experiments with C6 Glioma cells treated with [Ir(ppy) 2 ( L1 )][PF 6 ], show that the complex is an efficient sensitizer for triplet oxygen, producing cytotoxic singlet oxygen ( 1 O 2 ) by two-photon excitation at 740 nm resulting in photodynamic effects that lead to localised cell damage and death. A cyclometallated fluorenyl Ir( iii ) complex that exhibits enhanced triplet oxygen sensing properties for two photon photodynamic therapy is reported.