Strategically Formulating Aggregation‐Induced Emission‐Active Phosphorescent Emitters by Restricting the Coordination Skeletal Deformation of Pt(II) Complexes Containing Two Independent Monodentate Ligands

Abstract

Aggregation‐induced emission (AIE)‐active phosphorescent emitters have intrinsic advantages in time‐gated imaging/sensing and improving the electroluminescent efficiencies of organic light‐emitting devices (OLEDs). However, compared with the very prosperous and fruitful developments of AIE‐active fluorescent emitters and related working mechanisms, the progresses on AIE‐active phosphorescent emitters and associated AIE mechanisms are still relatively slow. Herein, the AIE properties of a series of phosphorescent Pt(II) complexes with two monodentate ligands are reported. Compared with the conventional rigid Pt(II) complexes bearing two bidentate ligands or one tri‐/tetradentate ligand, the incorporation of two monodentate ligands provides the resulting Pt(II) complexes with more room to deform their coordination skeletons from the square‐planar geometry in the ground state to the quasi‐tetrahedral configuration in the excited state, causing poor solution emissions. In doped films and aggregate states, intense emissions are observed for these Pt(II) complexes. The as‐fabricated solution‐processed OLED exhibits an impressively high external quantum efficiency of 21.7%. This study provides an effective way to develop excellent AIE‐active phosphorescent emitters.

Realization of Distinct Mechano- and Piezochromic Behaviors via Alkoxy Chain Length-Modulated Phosphorescent Properties and Multidimensional Self-Assembly Structures of Dinuclear Platinum(II) Complexes

“…Chromophoric and luminescent materials based on transition-metal coordination complexes have shown attractive features that are relevant to various fields, such as in OLEDs, − chemsensing, bioimaging, , nonlinear optics, and catalysis . Among them, platinum­(II) complexes adopting a square-planar geometry exhibit intriguing luminescence properties. − The introduction of π-conjugated organic ligands has led to intra- or intermolecular π–π stacking and metal–metal interactions, accompanied by obvious changes in the spectroscopic and optical properties, that may be utilized for the construction and potential development of functional materials. ,,, Through the rational design of organic ligands, the tuning of the photophysical properties of the metal complexes can be realized. ,, …”

Ligand Engineering toward Deep Blue Emission in Nonplanar Terdentate Platinum(II) Complexes

“…Luminescent transition-metal complexes have attracted considerable research attention in the past few decades . Among them, the luminescent platinum complexes have been widely studied, due to their potential applications in biomedicine, organic light-emitting devices (OLEDs), light to chemical energy conversion, chemsensors, and bioimaging . Most of the reported platinum complexes possess a square-planar geometry with a bidentate, terdentate, or tetradentate chelate ligand .…”

Ligand-Mediated Photophysics Adjustability in Bis-tridentate Ir(III) Complexes and Their Application in Efficient Optical Limiting Materials

“…This indicates that the TD-DFT methodology in this work is suitable for predicting the lowest Franck–Condon transition based on the optimized geometry structures of desired complexes Ir1 – Ir5 in the S 0 and T 1 states. ,, What should be paid attention to is that the excitation energy’s unique localization/delocalization properties of the exciting wave function will affect the measuring precision . The dramatic difference of the absorption wavelength might be related to the π-electron-accepting ability of the modified groups at the fourth and sixth positions of the central ring in N ∧ C ∧ N-type ligand, thereby leading to the unique absorption behavior of the above-mentioned Ir­(III) complex . Given the electron cloud distributions of the HOMOs and LUMOs for these complexes, the electronic excitation between the S 0 and T 1 states is primarily from HOMO to LUMO.…”

“…14 The dramatic difference of the absorption wavelength might be related to the π-electronaccepting ability of the modified groups at the fourth and sixth positions of the central ring in N ∧ C ∧ N-type ligand, thereby leading to the unique absorption behavior of the abovementioned Ir(III) complex. 60 Given the electron cloud distributions of the HOMOs and LUMOs for these complexes, the electronic excitation between the S 0 and T 1 states is primarily from HOMO to LUMO. All the complexes in the T 1 state presented a mixed MLCT (dπ(Ir)…”