Diradical B/N‐Doped Polycyclic Hydrocarbons

Abstract

Heterocyclic diradicaloids with atom‐precise control over open‐shell nature are promising materials for organic electronics and spintronics. Herein, we disclose quinoidal π‐extension of a B/N‐heterocycle for generating B/N‐type organic diradicaloids. Two quinoidal π‐extended B/N‐doped polycyclic hydrocarbons that feature fusion of the B/N‐heterocycle motif with the antiaromatic s‐indacene or dicyclopenta[b,g]naphthalene core were synthesized. This quinoidal π‐extension and B/N‐heterocycle leads to their open‐shell electronic nature, which stands in contrast to the multiple‐resonance effect of conventional B/N‐type emitters. These B/N‐type diradicaloids have modulated (anti)aromaticity and enhanced diradical characters comparing with the all‐carbon analogues, as well as intriguing properties, such as magnetic activities, narrow energy gaps and highly red‐shifted absorptions. This study thus opens the new space for both of B/N‐doped polycyclic π‐systems and heterocyclic diradicaloids.

Ladder-type boron-containing π-systems with enhanced open-shell characteristics and photothermal conversion properties

“…Lewis acidity is an intriguing feature of this kind of B-containing organic radical, because it provides a new scaffold to achieve modulation of the radical characteristic and (anti)aromaticity by intermolecular Lewis acid-base coordination. 29,30,45 These molecular ladders composed of two distant and well-separated triphenylborane groups offer the possibility of gaining insight into the electronic effects of aromatic rings on the antiaromatic π-skeleton and Lewis coordination. Titration experiments were performed on BML1 and BML2 and monitored by UV/Vis absorption spectroscopy (Fig.…”

“…1a, including neutral boron-containing π-monoradicals (I-III) and π-diradicaloids (IV-VII). [23][24][25][26][27][28][29][30][31] For instance, Yamaguchi et al elegantly developed the highly stable π-radical I that contains a boron atom in a planarized triphenylmethyl radical framework, and demonstrated its potential utility as an ambipolar semiconductor in singlecrystal field-effect transistors and as an emitting material in organic light-emitting diodes. 23,24 Wang et al reported dioxoborocyclic monoradical III and diradical VII as new kinds of boron-containing π-radicals, which feature an intramolecular ion pairing state via Lewis acid-induced single electron transfer.…”

Design Strategies for Diradical Boron/Nitrogen Doped Carbon‐Based Materials

“…The theoretical ΔE SÀ T were À 12.68 and À 6.42 kcal mol À 1 for compounds 1 and 2, respectively, agreeing with the experimental trend. Interestingly, the DFT calculations (see reference [10] and its Supporting Information) disclosed that the substitution of the antiaromatic sindacene and dicyclopenta[b,g]naphthalene core (compounds 3 and 4, respectively) results in a decrease of the ΔE SÀ T with respect to their B/N doped analogues. The decrease in the gap between the singlet and triplet diradicaloid states is readily explained by the expansion of the π-conjugation going from compound 1 to 2, and going from compounds 3 and 4 to 1 and 2, respectively, which decreases the exchange interaction energy largely determining the ΔE SÀ T .…”

“…[9] In a recent research article, Guo et al synthesized two B/N-doped quinoidal PAHs, compounds 1 and 2 (Figure 1a), that can be seen as the fusion of B/N doped PAHs with the antiaromatic s-indacene or dicyclopenta[b,g]naphthalene core, respectively. [10] This new strategy to design diradicaloids is essentially playing on the cooperative effect of the boron and nitrogen atoms to perturb the electronic structure of the PAHs and to tune its diradical character. Single crystals of compound 2 were grown and revealed that bond [10] ) and 2 (5 in [10] )) and their all-carbon (heterocyclic-free) analogues (3 (6 in [10] ) and 4 (7 in [10] )); b) X-ray crystal structure of 2 with thermal ellipsoids shown at 50 % probability; c) Resonance structures in closedshell and open-shell forms for the unsubstituted compound 1.…”

Linear and macrocyclic oligo(p-phenylene iminoboranes) with ferrocenyl side groups – observation of selective, non-templated macrocyclization

“…The doping of organic compounds with B and N atoms, the combination of which being isoelectronic and isosteric with CC couples, has evolved into a powerful approach for accessing novel materials with modified, often intriguing properties. 4,5 Application of this BN/CC isosterism concept to conjugated polymers, however, is still in its infancy. 6–8 Our group has developed a series of BN-doped polymers with direct BN bonds, including a BN analogue of poly( p -phenylene vinylene) (PPV) B 6 b and the first examples of the poly(iminoboranes) C , which are polyacetylene isosteres.…”