An isomeric strategy for enhancing phosphorescence efficiency of iridium(III) complexes with N-heterocyclic naphthyridine ligands: A theoretical study

作者：Ma Ming Shuo; Zou Lu Yi; Li Yan; Ren Ai Min^*; Feng Ji Kang

来源：Organic Electronics, 2015, 22: 180-190.

DOI：10.1016/j.orgel.2015.03.037

• Naphthyridine
• Spin-orbit coupling
• Phosphorescence quantum efficiency

The electronic structures and photophysical properties of six isomeric Ir(III) complexes with different N-heterocyclic naphthyridine ligands were investigated by density functional theory (DFT) and time dependent DFT (TD-DFT) approach. The radiative transition rates (k(r)) were determined through calculated the spin-orbital coupling (SOC) matrix elementsh < T-m vertical bar H-SOC vertical bar S-n > and the energy levels (E-Sn and E-Tm). The non-radiative transition rates (k(nr)) were estimated through analysis of the structural distortions, the d-orbital splittings and the energy differences between the S-0 and T-1 states Delta E(T-1 - S-0). As the results, the E-Sn, the E-Tm and the energy splittings (Delta ES1-Tm and Delta ETm-Tm-1) can be regulated by the position of two nitrogen atoms in naphthyridine ring for studied complexes. Moreover, Ir(III) complex inclusive of quinoxaline heterocyclic ring presents large k(r) and k(nr), so its phosphorescence quantum efficiency is difficult up to be 100%. While two Ir(III) complexes bound to quinazoline heterocyclic ring show weakly emissive because of large k(nr). Notably, the presence of the cinnoline heterocyclic ring in the Ir(III) complex makes singlet-triplet intersystem (ISC) rate and k(r) fast but k(nr) slow, then leads to its high phosphorescence quantum efficiency.

• 出版日期2015-7
• 单位吉林化工学院; 吉林大学