Rearrangements in the Scholl oxidation: implications for molecular architectures

Ormsby, Jason L.; Black, Tessa D.; Hilton, Cameron L.; Bharat,; King, Benjamin T.

doi:10.1016/j.tet.2008.09.105

Cited by 88 publications

(63 citation statements)

References 47 publications

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“…3). As this value is much smaller than the apparent height of the monolayer of the OP 8 Br lm (0.15 nm) in the STM imaging, and considering the highly complex stereochemistry of OP 8 s, including perfectly and partially folded helical conformers, it is reasonable to assume that the local deviation of the apparent height in the OP 8 Br lm may originate from the coexistence of different molecular conformers. Notably, there are a number of randomly scattered bright spots that are higher than the surrounding area distributed over the entire observation area.…”

Section: Resultsmentioning

confidence: 85%

“…Based on these considerations, we propose a schematic structure for a few-layer lm of OP 8 Br on Au(111) in Fig. 4a.…”

Section: Resultsmentioning

confidence: 99%

“…Au(111) substrates, obtained by thermal evaporation of Au onto a freshly cleaved mica substrate, were ame-annealed and quenched in ethanol prior to use. High-resolution STM images of an OP 8 Br lm on a single terrace of Au(111) conrmed that the observed bright spots are not due to pollution, but arise from adsorbed individual OP 8 Br molecules (Fig. S4 †).…”

Section: Methodsmentioning

confidence: 99%

“…[5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Due to their heavily angled aromatic connection, oligomeric o-phenylenes are able to adopt a closely packed helical conformation featuring axial chirality. Oligomeric and polymeric o-phenylenes, consisting of multiple phenylene units linked together at their ortho-positions, are an emerging class of such helical molecules.…”

Section: Introductionmentioning

confidence: 99%

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Scanning tunnelling microscopy analysis of octameric o-phenylenes on Au(111)

et al. 2016

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Oligomeric o-phenylenes are an emerging class of helical molecules that exhibit complex conformational behaviour, which is determined by their terminal groups and the solvent environment. Using scanning tunnelling microscopy (STM), we investigated the conformational behaviour of octameric o-phenylenes (OP 8 s) featuring Br or NO 2 terminal groups (OP 8 Br and OP 8 NO 2 ). These o-phenylene oligomers are known to adopt a well-defined helical conformation in the solid state, but undergo a rapid helical inversion in solution at ambient temperature. We show that STM microscopy allows the direct observation of perfectly and partially folded helical conformers of OP 8 Br and OP 8 NO 2 , both of which are simultaneously present in their respective molecular films on Au(111). Possible electronic interactions between the Au(111) surface and the exposed p-system of the OP 8 derivatives might result in a thermodynamic bias able to stabilize the metastable, partially folded conformation. Recent studies have revealed that the helical inversion rate of OP 8 NO 2 in solution decreases substantially upon oxidation to the corresponding radical cation (OP 8 NO 2 c + ). The OP 8 NO 2 and OP 8 NO 2 c + film morphologies on Au (111) observed by STM differed substantially with respect to each other, most likely reflecting differences arising from the conformational states of OP 8 NO 2 and OP 8 NO 2 c + at the molecular level, as well as improved charge-transport properties of the oxidized state. † Electronic supplementary information (ESI) available: STM images of a clean Au substrate and OP 8 Br and OP 8 NO 2 lms on Au(111), analytical data for an STM image of an OP 8 Br lm on Au(111), as well as Cartesian coordinates and energies of the theoretically optimized structures of the perfectly and partially folded conformers. See

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Section: Resultsmentioning

confidence: 85%

“…Based on these considerations, we propose a schematic structure for a few-layer lm of OP 8 Br on Au(111) in Fig. 4a.…”

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Scanning tunnelling microscopy analysis of octameric o-phenylenes on Au(111)

et al. 2016

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“…110,126,128 Previous work has also shown that in the synthesis of PAHs with the Scholl reaction, rearrangement of phenyl groups often occurs, making the structures of the final products sometimes unpredictable and requiring a better understanding of the reaction mechanisms. 130,141,148,149 Even with highly effective solubilization methods, the large size of the graphene nanostructures could invalidate some of the well-established purification and characterization techniques in organic chemistry. More specifically, extension of widely successful chromatography techniques for organic purification to graphene QDs has not been straightforward due to the large conjugation.…”

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confidence: 99%

Solution-chemistry approach to graphene nanostructures

Yan

2011

J. Mater. Chem.

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Graphene has many novel optical and electrical properties desirable for applications in future electrooptical devices. Graphene nanostructures are especially attractive for their wide range of tunable properties. Here we describe the recent progress and challenges in the solution-chemistry approach to graphene nanostructures. This approach could not only lead to new materials with various well-defined properties, but also enable their production in large quantities.Graphene, containing a single layer of sp 2 -hybridized carbon atoms, has become an intensively studied topic because of its unique two-dimensional (2D) crystalline structure, extraordinary physical properties, 1-3 and potential applications in future optics and electronics. Even though graphene is the basic building block for graphite, carbon nanotubes, and fullerenes which have been studied for decades, not a lot of attention was paid to graphene until the first isolation of single-layer graphene from graphite by Geim and his co-workers 4 with a ''Scotch tape'' approach in 2004. Numerous follow-up investigations subsequently revealed a wide range of very attractive properties, such as extremely high carrier mobilities, 5-9 quantum hall effect, 10-16 and ambipolar field effect, 4,17 etc. These properties make graphene a very promising material for future devices, such as high-speed, high-frequency electronic devices, 6,7,18-21 single molecule sensors, 22,23 and ultrathin transparent electrodes. [24][25][26][27][28][29][30][31] Reliable production of graphene with high quality and in large quantities is still a challenge. 32 Although some proof-of-concept devices have been made from mechanically exfoliated graphene, the original layer-by-layer peel-off method cannot be used for large-scale production. In order to overcome this challenge, two distinct approaches have been taken by scientists: breaking down graphite into graphene (''top-down'' approach) and building up graphene from atomic or molecular building blocks (''bottom-up'' approach). The top-down approaches include mechanical exfoliation, 1,4,18 intercalation followed by solution-based exfoliation, 28,30,33-45 reduction of graphene oxide, 46-56 etc, (Fig. 1). The bottom-up approaches mostly include chemical vapor deposition (CVD) 31,57-66 and a solution-chemistry approach. 67,68 In this review we discuss the latest development in the emerging solution-chemistry approach to graphene nanostructures, especially quantum dots (QDs). 69 We refer readers to some recent reviews 70-72 for detailed descriptions of top-down approaches and CVD methods to make graphene.To make stable single-layer graphene it is essential to overcome inter-layer van der Waals attraction that favors formation of graphite. It is achieved in mechanical exfoliation with external forces, and in CVD methods with introduction of substrates to simultaneously immobilize graphene when they form.

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Six‐Membered Carbocycles

2010

Name Reactions for Carbocyclic Ring Formations

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Rearrangements in the Scholl oxidation: implications for molecular architectures

Cited by 88 publications

References 47 publications

Scanning tunnelling microscopy analysis of octameric o-phenylenes on Au(111)

Scanning tunnelling microscopy analysis of octameric o-phenylenes on Au(111)

Solution-chemistry approach to graphene nanostructures

Six‐Membered Carbocycles

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