Boron-Doped Pentacenes: Isolation of Crystalline 5,12- and 5,7-Diboratapentacene Dianions

Abstract

The syntheses, molecular structures, reactivities, and computational assessment of dipotassium diboratapentacene isomers are described (1 and 2). These compounds represent the first examples of aromatized diboraacenes where the boron atoms are spatially separated in different rings of the acene framework. Both 1 and 2 react with carbon dioxide (CO2) via diastereoselective carboxylation of the pentacene backbone that likely proceeds by a frustrated Lewis pair-like mechanism. The placement of the boron atoms and the reactivity studies provide a platform for later stage functionalization of diboraacenes beyond the central ring of the polycyclic aromatic hydrocarbon core.

Structure and Electronics of a Series of CAAC-Stabilized Diboron-Doped Acenes from 1,4-Diboranaphthalene to 6,13-Diborapentacene

“…Boron doping of PAHs has been shown to decrease their HOMO–LUMO (H–L) gap significantly, mainly through the participation of the empty boron p z orbital in the LUMO and often more efficiently than the extension of the PAH framework itself. , Stable dihydrodiboraacenes, i.e., n -acenes in which two CR units (R = anionic substituent) have been replaced by isosteric (but not isoelectronic) BR units, have been prepared up to n = 9 from simple precursors through Si–B metathesis and/or C–H borylation reactions and show strong luminescence or emission in the near-IR region. − Air-stable 9,10-dihydro-9,10-diboraanthracene (9,10-R 2 -DHDBA) derivatives, in particular, have shown great promise in OLED applications. − …”

A theoretical study of the reaction of borata derivatives of benzene, anthracene and pentacene with CO2

“…5,12-Dimethyl-5,12-diboratapentacene ( trans - DBP ) and 5,7-dimethyl-5,7-diboratapentacene ( cis - DBP ) potassium salts (Refcode: NEWBAW, NEWBEA, NEWBIE, NEWBOK) 39 and the corresponding CO 2 adducts are available in the CSD database (Refcode: NEWCOL, NEWCUR, and NEWDAY). 39 Superpositions of experimental and optimized structures are available in Fig. S5 (ESI†).…”

“…This is in agreement with the experimental observation that the central rings are more aromatic than the lateral ones. 39…”

“…The effect of the solvent in the reactions has been addressed with the SMD model 42 and tetrahydrofuran (THF) parameters; THF is the solvent used in the experimental study of the reactions of 5,12- and 5,7-diboratapentacene dianions with CO 2 . 39 Since the X-ray structures of the 5,12- and 5,7-diboratapentacene monomers and adducts show 1.5 molecules of THF per diboratapentacene molecule, in some cases, systems with two molecules of THF interacting with the potassium cation on top of the SMD model have been calculated. The results of the combination of explicit and implicit solvent models are very similar to those obtained only with the implicit SMD one (Table S3, ESI†).…”

Triple-Decker Iron and Cobalt Complexes Featuring a Bridging 1,2-Diboratabenzene Ligand

“…In six membered systems, a boron atom can be substituted into benzene resulting in anionic boratabenzene ligands that are stronger donors than benzene and comparable to Cp . Incorporating a second boron atom into benzene, a diboratabenzene, increases the charge to dianionic, which has not been widely explored . Three possible isomers of diboratabenzene exist, with boron atoms in the 1,2-, the 1,3-, or the 1,4-positions.…”