Benzo[4,5]cyclohepta[1,2-b]fluorene: an isomeric motif for pentacene containing linearly fused five-, six- and seven-membered rings

Abstract

A new class of conjugated polycyclic molecules containing a C6–C5–C6–C7–C6 polycylic framework was synthesized. Both experiments and calculations show different electron structures in comparison to their pentacene isomers.

Reductive Aromatization/Dearomatization and Elimination Reactions to Access Conjugated Polycyclic Hydrocarbons, Heteroacenes, and Cumulenes

“…Yamashita demonstrated that one could proceed directly from lithium alkoxides 75a–d to IFs 76 a – d , albeit in low yield (Scheme ) . Miao and co‐workers used an analogous method to synthesize CPM 77 containing an imbedded cycloheptatriene moiety, and a constitutional isomer of TIPS‐pen containing a 6‐7‐6‐5‐6 fused ring system ( 78 , Scheme ); thin‐film transistors formed with 77 showed hole mobilities up to 0.76 cm 2 V −1 s −1 . Chi and co‐workers used SnCl 2 with excess HCl in THF to form quinoidal CPM 79 …”

Aromatic polymers made by reductive polydehalogenation of oligocyclic monomers as conjugated polymers of intrinsic microporosity (C-PIMs)

“…The non-alkylated analogues of the diketone model compounds DK77 and DK57 were already described in the literature. 16,17 Instead of following the published route for non-alkylated DK77, we adapted a more recent route published by Yang et al 15 for DK57, starting for both monomers from 2,5dibromoterephthalic acid, which is a frequently used starting material for ladder-type polyarylenes made by us previously. 18,19 For the synthesis of M57 and M77, we used an elegant procedure by Ciganek et al involving a one-pot dehydrogenation/ chlorination of the corresponding, single-or double-ethanebridged diketones 5.…”

“…42°twisted exocyclic double bond that connects two, almost planar fluorenylidene units. 13,14 Next, we tested the polycondensation of the "mixed" monomer M57 that contains one 5-and 7-membered ring each 15 and, for comparison, of a 1 : 1 M55/M77 monomer mixture. Since we expect a quite different reactivity of both geminal >CCl 2 -functions in the reductive polyolefination when incorporated into 5-or 7-membered rings, we investigated the incorporation pattern of the monomeric subunits into the resulting fulvalene linkages in more detail.…”

Antiaromatic character of cycloheptatriene-bis-annelated indenofluorene framework mainly originated from heptafulvene segment

“…An alternative approach to access antiaromatic frameworks relies on the use of methylenecycloheptatriene (heptafulvene) segments to form tricyclic 16π-electron benzo[1, 2:4, 5]di[7]annulene (BDA), whereas pristine heptalene exhibits nonaromatic character due to its twisted non-planar geometry 40 . Although several polycyclic hydrocarbons containing a BDA framework have been synthesized 41–47 , the development of BDA-based antiaromatic compounds is still limited due to the difficulty of (1) the molecular design to incorporate heptafulvene units into the π-conjugated systems and (2) the synthetic method for the construction of seven-membered rings 41,42,44–46 . In contrast to the fulvene unit, the formation of cycloheptatrienyl cation by one-electron oxidation of heptafulvene leads to aromatic stabilization.…”

“…In contrast to the fulvene unit, the formation of cycloheptatrienyl cation by one-electron oxidation of heptafulvene leads to aromatic stabilization. Thus, the thin-film of 1 showed hole-transporting characteristics in organic field-effect transistor (OFET) devices 44–46 . However, irrespective of these electronically complemental properties, fundamental studies to directly investigate the antiaromatic character between the ID and BDA frameworks have not been carried out so far.…”