Sensitised near-infrared emission from lanthanides using an iridium complex as a ligand in heteronuclear Ir2Ln arrays

Abstract

The iridium(III) complex Ir(ppy)₂(phen5f) [ppy = 2-phenylpyridinato-N,C^2′, and phen5f = 4,4,5,5,5-pentafluoro-1-(1′,10′-phenanthrolin-2′-yl)-pentane-1,3-dionate] has been synthesised and used as “complex ligands” to make heteronuclear d–f complexes by the attachment of Ln(NO₃)₃·xH₂O at the vacant coordination sites in the bridging ligand phen5f. The microanalyses and crystal structure characteristics confirmed the formation of the heteronuclear Ir₂Ln arrays. The measurement of the lowest triplet state energy level of Ir(ppy)₂(phen5f) indicates that it is suitable for the NIR (near-infrared) lanthanide ions, Nd^III, Yb^IIIand Er^III. Upon irradiation of the MLCT (metal-to-ligand charge transfer) absorption of Ir(ppy)₂(phen5f) at an excitation wavelength from 380–490 nm, the characteristic emission spectra of the three Ir₂Ln arrays (Ln = Nd, Yb, Er) in both the solid state and in CH₃CN solution were measured. According to the results, more Ir^III complexes will be designed for lanthanide NIR emission by the proper combination between the cyclometalated ligand and the tetradentate ancillary ligand.