title: Forward molecular design for highly efficient OLED emitters: a theoretical analysis of photophysical properties of platinum(II) complexes with N-heterocyclic carbene ligands.
abstract: The electronic structures and photophysical properties of eight Pt-complexes with different N-heterocyclic carbene ligands and potential to serve as light emitting diode materials were investigated by density functional theory and time-dependent density functional theory, employing the BP86 functional for geometry optimisations, SAOP potential for excited state calculations and all-electron TZ2P basis set throughout. Non-radiative and radiative decay rate constants were determined for each system through analyses of the geometric relaxations, d-orbital splitting and spin-orbit couplings at the optimised S(0) and T(1) geometries. Three Pt-systems bound to two N-heterocyclic carbenes were shown to be nonemissive, while a fourth was shown to be emissive from the T(1) excited state. Similar T(1)-initated emission was observed for three other Pt-systems investigated, each bound to four N-heterocyclic carbenes, while a fourth similarly tetra-ligated system showed T(2)-initation of emission. The results highlight the coupling of ligand-identity to photophysical properties and more importantly, the potential for rational optimisation and tuning of emission wavelengths and phosphorescent efficiencies. Encouragingly, two of the tetra-N-heterocyclic carbene ligated systems show strong potential to serve as highly-efficient blue and green light emitting materials, respectively.
authors.affiliation: Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun, 130024, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Wu
authors.forename: Shui-Xing
authors.initials: SX
authors.lastname: Wu
authors.forename: Hai-Bin
authors.initials: HB
authors.lastname: Li
authors.forename: Yun
authors.initials: Y
authors.lastname: Geng
authors.forename: Zhong-Min
authors.initials: ZM
authors.lastname: Su