carbo‐Naphthalene: A Polycyclic carbo‐Benzenoid Fragment of α‐Graphyne

Abstract

A ring carbo-mer of naphthalene, C Ar (Ar=p-n-pentylphenyl), has been obtained as a stable blue chromophore, after a 19-step synthetic route involving methods inspired from those used in the synthesis of carbo-benzenes, or specifically devised for the present target, like a double Sonogashira-type coupling reaction. The last step is a SnCl /HCl-mediated reduction of a decaoxy-carbo-decalin, which is prepared through successive [8+10] macrocyclization steps. Two carbo-benzene references are also described, C Ar and o-C Ar (C≡C-SiiPr ) . The carbo-naphthalene bicycle is locally aromatic according to structural and magnetic criteria, as revealed by strong diatropic ring current effects on the deshielding of H nuclei of the Ar groups and on the negative value of the DFT-calculated NICS at the center of the C rings (-12.8 ppm). The stability and aromaticity of this smallest fused molecular fragment of α-graphyne allows prediction of the same properties for the carbon allotrope itself.

Carbo‐biphenyls and Carbo‐terphenyls: Oligo(phenylene ethynylene) Ring Carbo‐mers

“…three times weaker energetic aromaticity of the C 18 ring as compared to the C 6 parent. After ar ecent report of the first molecule containing two carbo-benzene rings in the fused mode, a carbo-naphthalene, [7] counterparts in the catenated mode through acetylene linkers are thus devised from the known carbo-benzene 1, [8] as the carbo-biphenyl and carbo-terphenyl targets 2 and 3 (the carbo descriptor referring to the whole carbon skeleton). After ar ecent report of the first molecule containing two carbo-benzene rings in the fused mode, a carbo-naphthalene, [7] counterparts in the catenated mode through acetylene linkers are thus devised from the known carbo-benzene 1, [8] as the carbo-biphenyl and carbo-terphenyl targets 2 and 3 (the carbo descriptor referring to the whole carbon skeleton).…”

“…Them ost efficient method implemented for the preparation of 10 a (Supporting Information) was resumed for the preparation of 10 b.T he pentylphenyl [6]pericyclynedione 11 was first obtained from the known triyne 12 and dialdehyde 13 by at wo-step procedure adapted from the one used for the phenyl congener 4. [7] In the presence of LiHMDS,a ddition of two equivalents of 8 to 4 and 11 thus afforded the respective primary targets 10 a and 10 b.T he latter could not be isolated in pure form, but direct treatment with SnCl 2 /HCl, gave 3a and 3b with 20 %and 9% yield over two steps,r espectively.J ust as 2,t he obtained black solids 3a,b gave red solutions turning to red-violet upon increase of concentration in chlorinated solvents (e.g.,c hloroform). The poor solubility in other solvents (THF,t oluene) makes the corresponding colors remain red or light red, without indication of solvatochromism.…”

“…[6] Beyond this,the access to OPP skeleton carbo-mers, or OPE ring carbo-mers,a ppears as an atural challenge ( Figure 1). After ar ecent report of the first molecule containing two carbo-benzene rings in the fused mode, a carbo-naphthalene, [7] counterparts in the catenated mode through acetylene linkers are thus devised from the known carbo-benzene 1, [8] as the carbo-biphenyl and carbo-terphenyl targets 2 and 3 (the carbo descriptor referring to the whole carbon skeleton). The n-octyl ends,and n-pentyl lateral chains of 3b,were selected with the view to enhancing solubility and processability.F or the sake of reference to parent OPPs and OPEs,b eyond known dioctyl-OPPn, [9,10] dioctyl-OPE2 was employed for the syntheses of substituted acenes and blueemitting conjugated polymers applicable in organic semiconducting materials.…”

Selective access to p-dialkyl-carbo-benzenes from a [6]pericyclynedione: the n-butyl nucleophile model for a metal switch study

“…This can be illustrated by the recent report of a ring carbo-mer of naphthalene, 5 eight ppentylphenyl substituents of the C 32 core having allowed full characterization of this first example of fused polycyclic α-graphyne fragment, in or from solutions in CHCl 3 . 4 The solubilizing effect of the p-pentylphenyl groups appeared however limited, even on the smaller carbo-benzene congener C 18 (4-n-C 5 H 11 -C 6 H 4 ) 6 . The carbo-benzene C 18 ring is actually the smallest cyclic primitive motif of α-graphyne, and most of the derivatives reported hitherto bear only H, aryl, or alkynyl substituents.…”

“…Among π-conjugated carbon allotropes and beyond the foremost graphene type, graphynic materials, composed of both sp 2 -C and sp-C atoms, have been considered at the theoretical level, 1 but more sparingly studied experimentally. Nevertheless, several molecular fragments of γ-graphyne, 2 γ-graphdiyne, 3 and even α-graphyne, 4 have been described. A key issue in the synthesis and study of such carbon-rich compounds is their limiting solubility, approaching that of graphite upon increase of the size of the carbon core within a C-H bond periphery.…”