Theoretical study of the substituent effect controlling the radiative and non-radiative decay processes of platinum(ii) complexes

Wei Shen; Wenting Zhang; Chaoyuan Zhu

doi:10.1039/c7cp04376g

Theoretical study of the substituent effect controlling the radiative and non-radiative decay processes of platinum(ii) complexes

Phys Chem Chem Phys. 2017 Aug 30;19(34):23532-23540. doi: 10.1039/c7cp04376g.

Authors

Wei Shen¹, Wenting Zhang², Chaoyuan Zhu³

Affiliations

¹ Department of Applied Chemistry, Institute of Molecular Science and Center for Interdisciplinary Molecular Science, National Chiao-Tung University, Hsinchu 30010, Taiwan. [email protected] and School of Chemistry and Chemical Engineering, Southwest University, Chongqing, P. R. China.
² School of Chemistry and Chemical Engineering, Southwest University, Chongqing, P. R. China.
³ Department of Applied Chemistry, Institute of Molecular Science and Center for Interdisciplinary Molecular Science, National Chiao-Tung University, Hsinchu 30010, Taiwan. [email protected].

PMID: 28829465
DOI: 10.1039/c7cp04376g

Abstract

Six platinum complexes bearing different electron-withdrawing groups (-CN, -NO₂, -o-carborane, -SF₅ and -CF₂CF₂CF₃) have been designed to explore the electron-withdrawing capability and the conjugative effect of the substituents, and density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations have been performed to determine their electronic structures and phosphorescent properties. Three factors, including the oscillator strength μ(S_n) for S₀-S_n excitations, the energy gap between the triplet and singlet states ΔE(S_n-T₁) and the spin-orbital coupling 〈T₁|Ĥ_SOC|S_n〉, have been calculated to analyze the radiative processes. In addition, temperature-independent, temperature-dependent and triplet-triplet annihilation (TTA) have been analyzed to determine the non-radiative decay processes. Introducing strong electron-withdrawing groups into phosphorescent transition-metal complexes has a significant impact on the phosphorescent properties and some regularity besides the inductive effect (the electron-withdrawing capability) and the conjugative effect of the substituents. The stronger electron-withdrawing capability and smaller conjugative effect can give rise to blue-shifted emission behavior and give larger radiative decay rate constants. The results demonstrate that complex 4 (-NO₂ substituted) and complex 2 (-o-carborane) are possible candidates for blue-emitting materials.