Half-lantern Pt(ii) complexes in deep-red hybrid light-emitting diodes

Abstract

A series of Pt(II) complexes [Pt(piq)(μ-N^S)]₂ (piq = 1-phenylisoquinolinate) [N^S = Spy (pyridine-2-thiolate), Spy-CF₃ (5-trifluoromethylpyridine-2-thiolate), S-Q (quinoline-2-thiolate) and Spy-N (pyrimidine-2-thiolate)] are presented. They display a “half-lantern” disposition with two “Pt(piq)” fragments connected by a double pyridine thiolate bridge and remarkable short Pt⋯Pt distances (2.8–2.9 Å). The strong bonding interaction between the Pt(II) centers endows them with bright (up to 15% quantum yield (QY)) deep-red (down to 740 nm) phosphorescence in both powder and PMMA coatings. Theoretical calculations based on time-dependent density functional theory (TD-DFT) highlight that the nature of the emitting exciting state is related to a ³MMLCT [dσ*(Pt–Pt) → π*(piq)] transition. However, the emission shifts noticeably towards the NIR region (up to 850 nm) in solution, depending on the type of complex and the concentration. Besides, dual emission was noted related to a high energy ³MLCT [d(Pt) → π*(piq)] structured emission feature and the low-energy and broad ³MMLCT emission band, highlighting the versatility of the half-lantern structure. Given their photophysical properties, the complexes were applied as color down-converting filters for the fabrication of deep-red hybrid light-emitting diodes (HLEDs).