Strategic modulation of the photonic properties of conjugated organometallic Pt–Ir polymers exhibiting hybrid CT-excited states

Abstract

Polymer 6, ([trans-Pt(PBu3)2(C≡C)2]-[Ir(dFMeppy)2(N^N)](PF6))n, (([Pt]-[Ir](PF6))n; N^N = 5,5′-disubstituted-2,2′-bipyridyl; dFMeppy = 2-(2,4-difluoro-phenyl)-5-methylpyridine) is prepared along with model compounds. These complexes are investigated by absorption and emission spectroscopy and their photophysical and electrochemical properties are measured and compared with their corresponding non fluorinated complexes. Density functional theory (DFT) and time-dependent DFT computations corroborate the nature of the excited state as being a hybrid between the metal-to-ligand charge transfer (1,3MLCT) for the trans-Pt(PBu3)2(C≡CAr)2 unit, [Pt] and the metal-to-ligand/ligand-to-ligand′ charge transfer (1,3ML′CT/LL′CT) for [Ir] with L = dFMeppy. Overall, the fluorination of the phenylpyridine group expectedly does not change the nature of the excited state but desirably induces a small blue shift of the absorption and emission bands along a slight decrease in emission quantum yields and lifetimes.