Theoretical Exploration on Phosphorescent Pt(II) Complexes with
2,2’-bipyridine Ligand: Influence of Isotope Effect and Ligand
Modification on OLED Quantum Yield
Abstract
In order to explore the influence of isotope effect and ligand
modification on the quantum yield of OLED, three classes Pt(II)
complexes with 2,2’-bipyridine ligand have been investigated by using
density functional theory (DFT) and time-dependent density functional
theory (TD-DFT). The explored Pt(II) complexes, class 1 included
Pt(RC≡CBpyC≡CR)(C≡CBpy)2, (R = trimethylsilyl,1a or H, 1b, C≡CBpyC≡C =
5,5-bis(ethynyl)-2,2-bipyridine, C≡CBpy corresponds to
bipyridineacetylene) and Pt(Bpy)(C≡CBpy)2 (Bpy = bipyridine, 1c); class
2, Pt(Bpy)(C≡CPy)2 (C≡CPy = pyridineacetylene, 2a) , Pt(Bpy)(C≡CPh)2
(C≡CPh =phenylethynyl, 2b), Pt(dbBpy)(C≡CPh)2(dbBpy =
4,4’-di-tert-butyl-2,2’-bipyridine, 2c); and class 3, Pt(Bpy)(Tda) (Tda
= tolan-2,2’-diacetylide, 3a), Pt(dbBpy)(Tda) (3b),
Pt(3,3’,4,4’-OH-Bpy)(Tda) (3c). The calculation results reveal that the
heavy isotope effect effectively reduces the overall vibration frequency
of these complexes, and in turn decreases the non-radiative decay rate
κnr, which lead to the promotion of phosphorescent quantum yield ϕem.
Theoretical studies also reveal the influence of ligand modification on
the phosphorescence quantum yields of OLED, and a new Pt(II) complex 3c
was designed based on the theoretical study.