Charge-Transfer Emitting Triarylborane π-Electron Systems

Abstract

Triarylboranes have attracted significantly increasing research interest as a remarkable class of photoelectronic π-electron materials. Because of the presence of vacant p orbital on the B center, the boryl group is a very unique electron acceptor that exhibits not only electron-accepting ability through p-π* conjugation but also high Lewis acidity to coordinate with Lewis bases and steric bulk arising from the aryl substituent on the B center to get enough kinetic stability. Thus, the incorporation of a trivalent B element into π-conjugated systems is an efficient strategy to tune the electronic and stereo structures and thus the photoelectronic properties of π-electron systems. When an electron-donating group, such as amino, is present, triarylboranes would likely display intramolecular charge-transfer transitions. These kinds of molecules are often highly emissive. In addition, the geometry of the molecules has a great impact on the emission properties. In this Forum Article, we herein describe our recent progress on the charge-transfer emitting triarylborane π-electron systems with novel geometries, which include the lateral boryl-substituted π-system with amino groups at the terminal positions, the o,o'-substituted biaryl π-system with boryl and amino groups at the o,o'-positions, a triarylborane-based BODIPY system, and a B,N/S-bridged ladder-type π-system. We mainly put the emphasis on the molecular design concept, structure-property relationships, intriguing emission properties and great applications of the corresponding triarylborane π-systems.

Synthesis, Photophysical, and Electrochemical Properties of Pyrenes Substituted with Donors or Acceptors at the 4- or 4,9-Positions

“…In this paper, we provide examples of the synthesis of 4-, 4,9-and 4,10-substituted pyrenes. As exemplifying examples (Scheme 2), the electron donor-(NPh2) and acceptor-(BMes2) [24][25][26][27][28][29] substituted compounds 1-3 have been synthesized, and their electrochemical and photophysical properties have been studied. We also note that the substituent at the 4-position does not communicate strongly with that at the 9position.…”

Synthesis, photophysical and electronic properties of tetra-donor- or acceptor-substitutedortho-perylenes displaying four reversible oxidations or reductions

“…77,78 Diarylboryl groups have attracted much interest for use in optoelectronic materials, as the vacant p z -orbital of the three-coordinate boron serves as a strong p-acceptor, interacting with an adjacent p-system. [79][80][81][82][83][84][85][86][87][88][89][90][91] This conjugation provides the electron-decient character that gives rise to useful photophysical properties. [92][93][94] For example, attaching a Bmes 2 moiety to the 2-and 2,7-positions of pyrene leads to a switch of the energetic order of the LUMO+1 and LUMO, which is a consequence of the mixing of the empty p z -orbital with the pyrene B 3u LUMO+1.…”

Insights into the Optical Properties of Triarylboranes with Strongly Electron‐Accepting Bis(fluoromesityl)boryl Groups: when Theory Meets Experiment

“…A large number of air-stable conjugated three-coordinate organoboron compounds have been synthesized over the last few decades [1][2][3][4][5][6][7][8] for various applications, particularly in linear [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] and nonlinear [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] optics, electro-optic devices, [40][41][42] anion sensors, [43,44] cell imaging, [45][46][47][48] etc. The boron center in these species possesses an empty p-orbital and can thus serve as a strong π-acceptor following photo-excitation, or as a readily reducible center.…”