Electronic structures and photophysical properties of phosphorescent platinum (II) complexes with tridentate C^N*N cyclometalated ligands

Abstract

To get an insight into the structure–property relationships in a series of strongly phosphorescent platinum(II) complexes with tridentate C^N*N cyclometalated ligands, their electronic structures and electroluminescence properties were systematically investigated via density functional theory and time‐dependent density functional theory. Moreover, the factors related to the radiative and non‐radiative decay process, including the transition electric dipole moment μ(Sn), the energy difference between singlet and lowest triplet excited states ΔE(Sn–T1) and the spin–orbital coupling matrix elements , as well as the energy gap between T1 and S0 states ΔE(T1–S0) and absorption–emission Stokes shifts have been calculated. Fine emission color tuning and high phosphorescence quantum yield of phosphorescent complexes may be achieved through introducing five–six‐membered metallacycle geometries and linking a substituent (such as phenyl) at bridge atoms. Additionally, phosphorescent properties of these complexes show a clear dependence on the electronegativity of bridge atoms.