Ir(â…¢) Complexes Showing Visible Light-harvesting And Long-lived Triplet Excited State:Preparation And Applications

IrⅢ complexes have attracted much attention in many fileds, for example: electroluminescence, oxygen sensing, photocatalysis and triplet-triplet annihilation (TTA) based upconversions. In this thesis, photocalalysis and TTA upconversions was studied. Traditional IrⅢ complexes show weak absorption in visible range and relatively short triplet excited state lifetimes that affect new applications (photocatalysis and TTA upconversions) of IrⅢ complexes seriously.Three series of IrⅢ complexes were synthesized in this thesis. And their photophysical properties and applications were studied by DFT calculations, steady and transient spectra.Firstly, Ir-1and Ir-3were synthesized by using6-piperidine naphthalimide-phenanthroline and9-aminophenanthroline respectively. Compared to the reference complex Ir(ppy)2(phen)(Ir-2). the absorption of Ir-1was improved by143-fold at486nm. The low-lying triplet excited states (T1) of Ir-1and Ir-3were assigned to be triplet excited states (3IL*) of coumarin while that of Ir-2was metal to ligand charge transfer triplet excited state (3MLCT*) by77K emission spectra, transient difference absorption spectra and spin density analysis. Compared to Ir-2, the lifetime of triplet excited states of Ir-1and Ir-3was improved. And the the lifetime of triplet excited states of Ir-3was improved by45-fold compared to Ir-2. The application of Ir-1and Ir-3in TTA upconversion indicated that TTA upconversion quantum yield of Ir-1and Ir-3wasl5.9%and7.8%respectively, whereas the upconversion Ir-2was neglectable at the same experimental conditions.Furthermore. Ir-4were synthesized by using modified (amino and5-alkynyl-dipyridine) Naphthalenediimide (NDI). Ir-4shows strong absorption in visible region (ε=11000M-1cm-1at542nm). in comparison the refence complex Ir(ppy)2(bpy)(Ir-5) shows the typical weak absorption in visible region (e<3000M-1cm-1above400nm). Compared to Ir-1and Ir-3, the absorption wavelength of Ir-4was improved by56nm. The result of experiment indicated that T1of Ir-4were assigned to be triplet excited slates (3’IL*) of NDI. and the lifetime of triplet excited states of Ir-4was130μs. The application of Ir-4in TTA upconversion and photooxidation indicated that TTA upconversion quantum yield of Ir-4and Ir-5was6.7%and0%, and the photooxidation rates of Ir-4was improved by63-fold and4-fold respectively, compared to Ir-5and TPP. At last, Ir-6and Ir-7were synthesized by using modified (amino and5-alkynyl-dipyridine) Naphthalimide (NI). The photophysical properties were improved. The application of Ir-6and Ir-7in TTA upconversion indicated that compared to the first two series, TTA upconversion quantum yield of Ir-6was improved to19.3%Our results show that preparation of visible light-harvesting Ir(Ⅲ) complexes can be achieved by using organic fluorophores. The lifetime of the complexes can also be extended significantly. These properties have been demonstrated to be useful for the application of the Ir(Ⅲ) complexes in photocatalysis and TTA upcovnersion.