Investigation of Intramolecular Through-Space Charge-Transfer States in Donor–Acceptor Charge-Transfer Systems

Abstract

Commonly, thermally activated delayed fluorescence (TADF) emitters present a twisted donor–acceptor structure. Here, electronic communication is mediated through-bond via π-conjugation between donor and acceptor groups. A second class of TADF emitters are those where electronic communication between donor and acceptor moieties is mediated through-space. In these through-space charge-transfer (TSCT) architectures, the donor and acceptor groups are disposed in a pseudocofacial orientation and linked via a bridging group that is typically an arene (or heteroarene). In most of these systems, there is no direct evidence that the TSCT is the dominant contributor to the communication between the donor and acceptor. Herein we investigate the interplay between through-bond localized excited (LE) and charge-transfer (CT) states and the TSCT in a rationally designed emitter, TPA-ace-TRZ , and a family of model compounds. From our photophysical studies, TSCT TADF in TPA-ace-TRZ is unambiguously confirmed and supported by theoretical modeling.

Not the sum of their parts: understanding multi-donor interactions in symmetric and asymmetric TADF emitters

“…[18][19][20] In recent years through-space (exciplex-like) D-A interactions and non-overlapping single-molecule multiresonant electronic structures have also been shown to deliver unexpected and outstanding TADF performance. [21][22][23][24][25][26] The choice of specific D and A chromophores and any structural modulation of the dihedral angle between them is often the foremost tool for tuning of the CT character, emission energy, and reduction of DE ST towards engineering efficient rISC and TADF. However, additional undesirable effects such as red-shifting and broadening of the emission as well as severe reduction of the oscillator strength 27 can also occur somewhat unpredictably.…”

“…18–20 In recent years through-space (exciplex-like) D–A interactions and non-overlapping single-molecule multi-resonant electronic structures have also been shown to deliver unexpected and outstanding TADF performance. 21–26…”

An unexpected non-conjugated AIEgen with a discrete dimer for pure intermolecular through-space charge transfer emission

“… 28–30 The currently studied TSCT system mainly relies on the intramolecular through-space interaction between the donor and acceptor. 31 However, this type of material extremely relies on a tailored structure design, especially the spatial distance of the donor and acceptor, which has a great influence on the photophysics. 32 This also brings multiple synthetic steps, which not only leads to sophisticated and tedious purification but is also time-consuming and economically unfriendly.…”

Symmetrically Tetra‐functionalized Pillar[6]arenes Prepared by Fragment Coupling

“…The strategy of TSCT was widely employed in thermally activated delayed fluorescence materials. [84][85][86][87][88][89] All the Xpillar [6]arenes reported in this article could be regarded as combinations of p-diethoxybenzene moieties as the electron-rich components and functionalized benzene rings as the electron-deficient components. Due to the unconjugated nature of the methylene group as the connecting node, the charge transfer between the electron-rich component and the electron-deficient component on the X-pillar [6]arenes can be presumed to be a through-space charge transfer.…”