Radiaannulenes: synthesis, electrochemistry, and solid-state structure

Gholami, Mojtaba; Chaur, Manuel N.; Wilde, Myron M. D.; Ferguson, Michael J.; McDonald, Robert; Echegoyen, Luís; Tykwinski, Rik R.

doi:10.1039/b904762j

Cited by 27 publications

(16 citation statements)

References 25 publications

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“…Beyond the quinone-hydroquinone system, it was thus illustrated for difluorenylidene-carbo-quinoid hydrocarbons 22. 80 The synthesis of the fully expanded C 18 macrocyclic bis-fluorenylidene-carbo-quinoid 22 was performed from the [6]pericyclynedione 12. 5).…”

Section: Proaromatic Carbo-quinoidsmentioning

confidence: 99%

“Carbo-aromaticity” and novel carbo-aromatic compounds

et al. 2015

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While the concept of aromaticity is being more and more precisely delineated, the category of "aromatic compounds" is being more and more expanded. This is illustrated by an introductory highlight of the various types of "aromaticity" previously invoked, and by a focus on the recently proposed "aromatic character" of the "two-membered rings" of the acetylene and butatriene molecules. This serves as a general foundation for the definition of "carbo-aromaticity", the relevance of which is surveyed through recent results in the synthetic, physical, and theoretical chemistry of carbo-mers and in particular macrocyclic-polycyclic representatives constituting a natural family of "novel aromatic compounds". With respect to their parent molecules, carbo-mers are constitutionally defined as "carbon-enriched", and can also be functionally regarded as "π-electron-enriched". This is exemplified by recent experimental and theoretical results on functional, aromatic, rigid, σ,π-macrocyclic carbo-benzene archetypes of various substitution patterns, with emphasis on the quadrupolar pattern. For the purpose of comparison, several types of non-aromatic references of carbo-benzenes are then considered, i.e. freely rotating σ,π-acyclic carbo-n-butadienes and flexible σ-cyclic, π-acyclic carbo-cyclohexadienes, and to "pro-aromatic" congeners, i.e. rigid σ,π-macrocyclic carbo-quinoids. It is shown that functional carbo-mers are entering the field of "molecular materials" for properties such as linear or nonlinear optical properties (e.g. dichromism and two-photon absorption) and single molecule conductivity. Since total or partial carbo-mers of aromatic carbon-allotropes of infinite size such as graphene (graphynes and graphdiynes) and graphite ("graphitynes") have long been addressed at the theoretical or conceptual level, recent predictive advances on the electrical, optical and mechanical properties of such carbo-materials are surveyed. Very preliminary experimental results on a carbo-benzenoid fragment are finally disclosed.

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Section: Proaromatic Carbo-quinoidsmentioning

confidence: 99%

“Carbo-aromaticity” and novel carbo-aromatic compounds

et al. 2015

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“…169 On the contrary, sp-sp 2 -carbon molecular building blocks for extended graphyne and graphdiynes have been produced by Diederich and co-workers, 170,171 by Haley and coworkers 162,[172][173][174] and by other groups. 175 Very recently conductivity measurements have been performed on model sp-sp 2 -molecules (i.e., carbo-benzene and carbo-n-butadiene) at the single molecule level by means of the scanning tunnelling microscopy break junction method. 176 Such systems can be considered as fundamental building blocks of extended α-graphyne systems even though they have been endcapped with suitable anchoring groups to be connected with metal electrodes (i.e., the tip and the substrate).…”

Section: Caws Integrated With Sp 2 -Carbonmentioning

confidence: 99%

Carbon-atom wires: 1-D systems with tunable properties

et al. 2016

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This review provides a discussion of the current state of research on linear carbon structures and related materials based on sp-hybridization of carbon atoms ( polyynes and cumulenes). We show that such systems have widely tunable properties and thus represent an intriguing and mostly unexplored field for both fundamental and applied sciences. We discuss the rich interplay between the structural, vibrational, and electronic properties focusing on recent advances and the future perspectives of carbon-atom wires and novel hybrid sp-sp 2 -carbon architectures.

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“…[38,39] In this paper, we scrutinize the viability of this concept and present an in-depth investigation of C,C-A 2 PAs that engage in oxidative acetylene homo-and heterocoupling reactions. The synthesis, crystallographic, spectroscopic, and electrochemical characterization of the first acetylene-expanded dendralene fragments in which the exotopic C=C double bonds have been replaced by P=C units is presented.…”

Section: Introductionmentioning

confidence: 99%

Acetylene‐Expanded Dendralene Segments with Exotopic Phosphaalkene Units

Geng

Ott

2011

Chemistry A European J

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Bis-TMS protected C,C-diacetylenic phosphaalkene (A(2)PA) 1 (Mes*P=C(C≡CTMS)(2); Mes* = 2,4,6-tBu(3)Ph) has been used as a building block for the construction of butadiyne-expanded dendralene fragments in which phosphaalkenes feature as exotopic double bonds. Treatment of 1 with CuCl gives rise to a Cu(I) acetylide that is selectively formed at the acetylene trans to the Mes* group. The cis-TMS-acetylene engages in similar chemistry, albeit at higher temperatures and longer reaction times. The differentiation between the two acetylene termini of 1 allows for the controlled synthesis of the title compounds by a variety of different Cu- and Pd-catalyzed oxidative acetylene homo- and heterocoupling protocols. Crystallographic characterization of A(2)PA 1 and dimeric Mes*P=C(C≡CR(1))C(4)(R(2) C≡C)C=PMes* (3b, R(1) = R(2) = Ph; 6, R(1) = R(2) = TMS), and 10 (R(1) = R(2) = C≡CPh) verifies that the stereochemistry across the P=C bond is conserved during the coupling reactions, whereas spectroscopic evidence reveals cis/trans isomerization in an iodo-substituted A(2)PA intermediate 4 (Mes*P=C(C≡CTMS)(C≡CI). UV/Vis spectroscopic and electrochemical studies reveal that efficient π conjugation operates through the entire acetylenic phosphaalkene framework, even in the cross-conjugated dimeric structures. The P centers contribute considerably to the frontier molecular orbitals of the compounds, thereby leading to smaller HOMO-LUMO gaps than in all-carbon-based congeners. Phenyl- and/or ethynylphenyl substituents at the A(2)PA framework influence the HOMO and LUMO to a varying degree depending on their relationship to the Mes* group, thus enabling a fine-tuning of the frontier molecular orbitals of the compounds.

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Radiaannulenes: synthesis, electrochemistry, and solid-state structure

Abstract: Two new carbon-rich macrocycles (radiaannulenes) have been synthesized, and they possess an unsaturated carbon framework that is intermediate between that of linearly-conjugated dehydrobenzannulenes and cross-conjugated expanded radialenes.

Cited by 27 publications

References 25 publications

“Carbo-aromaticity” and novel carbo-aromatic compounds

“Carbo-aromaticity” and novel carbo-aromatic compounds

Carbon-atom wires: 1-D systems with tunable properties

Acetylene‐Expanded Dendralene Segments with Exotopic Phosphaalkene Units

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