Introducing Perylene as a New Member to the Azaborine Family

Abstract

Substitutional doping of perylene with two boron atoms at the 6b/12b positions and two oxygen or nitrogen atoms at the 1/7 positions has been achieved. The modular synthesis route developed for these bis‐BO‐ (3) and bis‐BN‐perylenes (5) starts from the readily accessible borinic acid derivative of the doubly brominated 9,10‐dihydro‐9,10‐diboraanthracene (DBA), 1,5‐Br2DBA(OH)2. A Stille‐type reaction first furnishes the alkynyl‐substituted species 1,5‐(RCC)2DBA(OH)2 (2), which undergo double ring closure to afford 3 via the gold‐catalyzed addition of the O−H bonds to the C≡C bonds. Treatment of 2 with MeN(SiMe3)2 leads to aminoborane intermediates 1,5‐(RCC)2DBA(N(H)Me)2, which can be ring‐closed to give 5 in a similar manner as in the case of 3. Different substituents R (such as Me, tBuPh) can be introduced at the 2/8 positions of the perylene core. The products obtained undergo reversible reduction and are efficient blue/turquoise emitters.

Intramolecular Borylation via Sequential B−Mes Bond Cleavage for the Divergent Synthesis of B,N,B‐Doped Benzo[4]helicenes

“…Despite their great application potential, for example, in organic optoelectronics, chemical sensing, and organocatalysis, systematic investigation of B‐PAHs is hampered by complex synthetic methods, especially for implementation of multiple boron centers into one molecule . Synthesis of B‐PAHs typically relies on transmetallation and/or electrophilic aromatic substitution involving a strong electrophile (BCl 3 , BBr 3 ), also referred to as Friedel–Crafts (FC) borylation . Lewis acids, for example, AlCl 3 , in combination with a bulky amine NR 3 can activate the electrophile by formation of borenium ions [R 3 N‐BX 2 ] + .…”

“…Removal of the HX produced can occur through NR 3 or, most recently, through addition of triarylboranes BAr 3 . Other methods include Wacker type cyclisations, hydroboration with NHC borenium ions, and construction of the targeted PAH framework around a pre‐installed boron center via Yamamoto coupling or Scholl reactions . Pioneering work by Kawashima et al on the synthesis of 1,4‐B,N‐doped linear acenes for applications in OLEDs established the growing class of 1,4‐azaborines .…”

“…Abstract: New symmetric and unsymmetric B,N,B-doped benzo [4]helicenes 3-6a/b have been achieved in good yields, using at hree-step process,s tarting from N(tolyl) 3 in ah ighly divergent manner (7 examples). Aborinic acid functionalized 1,4-B,N-anthracene 1 was found to displayu nprecedented reactivity,acting as aconvenient and highly effective precursor for selective formation of bromo-substituted B,N,B-benzo- [4]helicenes 2a/2b via intramolecular borylation and sequential BÀMes bond cleavage in the presence of BBr 3 .Subsequent reaction of 2a/2b with Ar-Li provided ah ighly effective toolbox for the preparation of symmetrically/unsymmetrically functionalizedB,N,B-helicenes.Their high photoluminescence quantum yields along with the small DE ST suggest their potential as thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diodes (OLEDs).…”

“…[6b,c] Pioneering work by Kawashima et al on the synthesis of 1,4-B,N-doped linear acenes [2d,e,7h,i] for applications in OLEDs established the growing class of 1,4-azaborines. [7] Embedding 1,4-azaborine units into the scaffold of benzo [4]helicene (DABNAa nd vDABNAi nS cheme 1) by Hatakeyama et al led to the discovery of multi-resonance TADF (MR-TADF) in 2016. [3h] In contrast to their charge transfer (CT) governed, donoracceptor analogues, [8] MR-TADF molecules exhibit anarrow p!p*e mission band, [3h] improving the color purity of the corresponding OLEDs significantly.Notably,only afew MR-TADF emitters are known so far and optimization of their photophysical properties relies on early-stage introduction of donor units,which greatly hinders asystematic exploration of this new class of emitters.…”

“…[3h] In contrast to their charge transfer (CT) governed, donoracceptor analogues, [8] MR-TADF molecules exhibit anarrow p!p*e mission band, [3h] improving the color purity of the corresponding OLEDs significantly.Notably,only afew MR-TADF emitters are known so far and optimization of their photophysical properties relies on early-stage introduction of donor units,which greatly hinders asystematic exploration of this new class of emitters. [3a,d,e,h] With the aim of achieving new B,N,B-doped helicenes such as 3-an inverted DABNAwith respect to Ba nd Np ositions (Scheme 1)-we discovered an ew and highly effective borylation method using 1,4-B,Nanthracene borinic acid 1 as the precursor,which enabled the synthesis of as eries of symmetric and unsymmetric B,N,Bbenzo [4]helicenes.T he details are presented herein.…”