HIGH-EFFICIENCY THERMALLY ACTIVATED DELAYED FLUORESCENCE OF A COPPER(I) COMPLEX BASED ON OCTACHLORO-1,10-PHENANTHROLINE

A [Cu(phen-Cl-8)(Xantphos)]PF6 center dot 2CH(2)Cl(2) (1 center dot 2CH(2)Cl(2)) complex based on octachloro-1,10-phenanthroline (phen-Cl-8) and 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (Xantphos) is prepared and studied. At 298 K, the crystalline form of the complex exhibits intense thermally activated delayed fluorescence (TADF) in the orange-red region with a quantum yield of 67% and a decay time of 2 mu s. Upon cooling down to 77 K, the emission maximum exhibits a bathochromic shift from 622 nm to 650 nm, and the decay time increases up to 550 mu s. Photoluminescence of the synthesized complex is additionally studied in the poly(methyl methacrylate) (PMMA) matrix and in a CH2Cl2 solution; the complex is shown to be X-ray luminescent. The spectral data and quantum chemical calculations show that the observed TADF is due to the charge transfer from the metal and phosphine ligand to the diimine group.