Boosting Circularly Polarized Luminescence of Organic Conjugated Systems via Twisted Intramolecular Charge Transfer.

Junfeng Li,Shanqi Xu,Xuelei Peng,Chao Huang,Wei Huang,Wen-Yong Lai,Chenxi Hou,Qi Qi

doi:10.34133/2020/3839160

Abstract

Realizing a high luminescence dissymmetry factor (glum) is a paramount yet challenging issue in the research field of circularly polarized luminescence (CPL). Here, we reported a novel set of organic conjugated systems with twisted intramolecular charge transfer (TICT) characteristics based on conjugated o-carborane-binaphthyl dyads composing of binaphthyl units as chiral electron donors and o-carborane units as achiral electron acceptors, demonstrating intense CPL with large glum values. Interestingly, single-crystalline o-1 exhibited a high-level brightness and a large glum factor as high as +0.13, whereas single-crystalline o-2 processed a relatively low brightness with a decreased glum value to -0.04. The significant diversity of CPL-active properties was triggered by the selective introduction of o-carborane units onto the binaphthyl units. Benefiting from the large magnetic dipole transition moments in TICT states, the CPL activity of TICT o-carborane-based materials exhibited amplified circular polarization. This study provides an efficient molecular engineering strategy for the rational design and development of highly efficient CPL-active materials.

Highlights

The synthetic routes to o-1 and o-2 are depicted in Supplementary Materials. o-1 and o-2 were synthesized in an average yield about 53% by Diels-Alder cross-coupling reaction of decaborane with (R)-2,2′-diethoxy-6,6′-bis(phenylethynyl)-1,1′-binaphthyl and (R)-2,2′-diethoxy-3,3′-bis(phenylethynyl)-1,1′-binaphthyl using N, N-dimethylaniline as a Lewis base
A set of circularly polarized luminescence (CPL)-active organic conjugated systems based on chiral o-carborane-binaphthyl dyads have been designed, synthesized, and systematically investigated
In the crystalline states, exhibited twisted intramolecular charge transfer (TICT) emissions owing to the dynamic rotational movement of o-carborane units, which represents the first example of CPL-active organic material system with TICT characteristics

Summary

Introduction

Organic π-conjugated functional materials [1,2,3], especially chiroptical materials featuring with circularly polarized luminescence (CPL), have attracted growing interest for their wide potential applications in threedimensional (3D) optical displays [4], optical storage and processing systems [5], color-image projection [6], liquid crystal lasers [7], biological probes and signatures [8], security tags [9], light-emitting diodes [10,11,12], and, especially, backlighting liquid crystal displays [13]. It is surmised that intense CPL with large glum could be achieved for the CT-active materials that are emissive with inherent chirality, which remains yet to be attempted by far. In this contribution, to verify the above hypothesis, a novel set of organic conjugated systems based on isomeric o-carborane-functionalized binaphthyl (BINOL) dyads with the same (R)-axial chirality have been designed, synthesized, and investigated, in which o-carborane units act as achiral electron acceptors and BINOL units as chiral electron donors. The TICT process of o-carborane-based BINOL molecule is beneficial to regulate its dynamic conformations for enhancing magnetic transition dipole moments and forbidding electric transition dipole moments, boosting glum values

Results and Discussion

A A : Accepter

Conclusions

Conflicts of Interest