Synthesis of a Doubly Boron‐Doped Perylene through NHC‐Borenium Hydroboration/C−H Borylation/Dehydrogenation

Abstract

Reaction of an N-heterocyclic carbene (NHC)borenium ion with 9,10-distyrylanthracenef orms four B À C bonds through two selective,t andem hydroboration-electrophilic CÀHb orylations to yield an isolable,c rystallographically characterizable polycyclic diborenium ion as its [NTf 2 ] À salt (1). Dehydrogenation of 1 with TEMPO radical followed by acidic workup yields a3 ,9-diboraperylene as its corresponding borinic acid (2). This sequence can be performed in one pot to allowthe facile,metal-free conversion of an alkene into as mall molecule containing ab oron-doped graphene substructure.D oubly boron-doped perylene 2 exhibits visible range absorbance and fluorescence in chloroform solution (F = 0.63) and undergoes two reversible one-electron reductions at moderate potentials of À1.30 and À1.64 eV vs. ferrocenium/ferrocene in DMSO.D espite sterically accessible boron centers and facile electrochemical reductions,c ompound 2 is air-, moisture-, and silica gel-stable.

Diboraperylene Diborinic Acid Self‐Assembly on Ag(111)—Kagome Flat Band Localized States Imaged by Scanning Tunneling Microscopy and Spectroscopy

“…A contour map of the tunneling current measured in the constant‐height mode is displayed in Figure 3c. The molecular skeletons of B 2 −Per with an intramolecular B−C distance of ~0.72 nm (as calculated by DFT in the gas phase, see top left inset of Figure 3c, and in excellent agreement with the value of 0.718 nm observed in the crystal structure of a related previously reported derivative of Br 2 −Per ) [22] are superimposed to the BR‐STM image for guidance of the eyes. This superposition results in a distance of the intramolecular benzenoid rings in STM data of (521.8±9.4) pm, in good agreement with the theoretically expected value of 517.8 pm.…”

“…Here, following a previously introduced consecutive hydroboration/electrophilic borylation/dehydrogenation protocol, [22] we accomplished the first fully planar 3,9‐diboraperylene diborinic acid derivative B 2 −Per and demonstrate its suitability for the formation of well‐organized self‐assembled adlayers by vacuum‐deposition on metallic surfaces. Using a low‐temperature scanning tunneling microscope (LT‐STM) and high‐resolution bond‐resolving imaging with carbon monoxide (CO) functionalized tips, [23] we reveal that B 2 −Per on Ag(111) self‐assembles by hydrogen bonds between the BOH subunits in a kagome lattice.…”

Synthesis of a helical boron-doped PAH by post-functionalization of 3,9-diboraperylene

“…We have recently reported the synthesis of parent borinic acid 2 by a hydroboration/borylation cascade followed by oxidative and hydrolytic workup (see Scheme 1 and Scheme S1, ESI †). 44,46 Its tert-butylphenyl-substituted derivative 2,8-bis(4tert-butylphenyl)-3,9-hydroxy-3,9-diboraperylene (tBuPh-2), bearing additional solubilizing groups, was furnished in the same manner as the previously reported 2,8-diphenyl-3,9hydroxy-3,9-diboraperylene 44 (Ph-2, see Scheme S1, ESI †). Next, we selected various aromatic groups for the substitution reaction of borinic acids.…”

“…To our surprise, only one boron substituent, namely 2,6-diisopropenylphenyl, has been used for this Friedel-Crafts strategy and no further attempts to expand the substrate scope of this strategy have been performed so far. With our successful synthesis of a series of boron-doped PAHs using diboraperylene as the starting material, 9,[44][45][46] we conjectured that an extension of available boron substituents for such a π-scaffold would open up possibilities for producing boron-doped PAHs with interesting functional features such as long-wavelength absorption, high electron affinity, charge-transfer character, and even novel contorted π-scaffolds.…”

Cationic Complexes of Boron and Aluminum: An Early 21st Century Viewpoint

“…Notably,arelated dehydrogenative borylationv ia NHC-stabilized borenium ion was implemented to furnishadoubly boron-dopedp eryleneb yt he group of Würthner. [45] The borenium ions (24 + , 25 + )e xhibited 11 Bs ignals at 48.6 ppm and 42.4 ppm, respectively,i nt he NMR spectroscopic analyses (both in CD 2 Cl 2 )w hich is diagnostic for three-coordinate boron centers. Of course, 25 + stands out with its structure motivem arked by planarity extended over the entirep entacyclic molecule.…”