Tuning Diradical Properties of Boron‐Containing π‐Systems by Structural Isomerism

Abstract

Tuning diradical character is an important topic for organic diradicaloids. Herein, we report the precise borylation enabling structural isomerism as an effective strategy to modulate diradical character and thereby properties of organic diradicaloids. We synthesized a new B‐containing polycyclic hydrocarbon that has the indeno[1,2‐b]fluorene π‐skeleton with the β‐carbons bonding to two boron atoms. Detailed theoretical and experimental results show that this bonding pattern leads to its distinctive electronic structures and properties in comparison to that of its isomeric molecule. This molecule has the efficient conjugation between boron atoms and π‐skeleton, resulting in downshifted LUMO and HOMO levels. Moreover, it exhibits smaller diradical character and thereby inhibited diradical properties, such as significantly blue‐shifted light absorption, larger energy bandgap and weak para‐magnetic resonance. Notably, this B‐containing polycyclic hydrocarbon possesses much stronger Lewis acidity and its Lewis acid‐base adducts display enhanced diradical character, demonstrating the positive effects of Lewis coordination on modulating diradical performance.

Expanding new chemistry of aza-boracyclophanes with unique dipolar structures, AIE and redox-active open-shell characteristics

“…6 k ,7 The electron-deficient triarylboron exhibits a remarkable electronic polarization and intramolecular charge transfer (ICT) in the presence of electron donors, leading to tunable emissions, enhanced charge-transport characteristics and unusual redox properties. 8 The Jäkle group pioneered boracyclophane chemistry by developing a fluoreneborane cycle ( MC-B6-Flu ), 6 a followed by an ambipolar macrocycle M2 with alternating arylamines and arylboranes. 6 b They have recently designed a considerably electron-deficient M3 with a low-lying LUMO and strong electronic affinity regardless of the synthetic challenge associated with the enhanced electron deficiency.…”

A multi-responsive system based on intramolecular B ← OP Lewis acid–base pairs

“…16 Recently, Dou group reported boron-containing organic diradicaloids and the corresponding Lewis acid-base adducts, thus unprecedentedly achieving dynamic modulations of (anti)aromaticity and diradical character of organic diradicaloids and the construction of supramolecular diradicaloids. [27][28][29] In 2018, our group reported a simple aldehyde functionalized amino-triarylborane donor-acceptor (D-A) system, which shows distinct responses toward multiple external stimuli with emission colours changing from blue to red. 22 In this work, we further the scope of these simple boryl based D-A compounds as smart luminescent materials with changing substituents.…”

“…16 Recently, Dou group reported boron-containing organic diradicaloids and the corresponding Lewis acid–base adducts, thus unprecedentedly achieving dynamic modulations of (anti)aromaticity and diradical character of organic diradicaloids and the construction of supramolecular diradicaloids. 27–29…”

PO-containing dibenzopentaarenes: facile synthesis, structures and optoelectronic properties

“…[5][6][7][8][9][10][11][12] For example, azaacenes containing N atoms have been reported as excellent organic semiconductors with intriguing low-lying energy levels and good stability; [13][14][15] P-embedded polyacenes have been developed for supramolecular chemistry and materials; [16][17][18] B-doped polyarenes with amazing structures have been constructed for organocatalysts and optoelectronic materials, [19][20][21][22][23] as well as supramolecular diradicaloids. 24,25 Therefore, heterocyclic polyarenes remain a highly important topic in organic chemistry and materials science.…”