The Synthesis and STM/AFM Imaging of ‘Olympicene’ Benzo[<i>cd</i>]pyrenes

Mistry, Anish; Moreton, Ben; Schuler, Bruno; Mohn, Fabian; Meyer, Gerhard; Groß, Leo; Williams, Antony J.; Scott, Peter; Costantini, Giovanni; Fox, David J.

doi:10.1002/chem.201404877

Cited by 40 publications

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“…Furthermore, the resonance energy of an aromatic pyrene core for structures 2c or 2d (not observed in the experiment) is appreciably lower. These considerations are consistent with similar observations for benzo[cd]pyrenes 17 and are also confirmed by DFT calculations favouring 2a by 21 meV over 2b, but by 207 meV over 2c isomers (see Supplementary Table 1). Thus, we anticipate that we measured an ensemble of molecules representative of compound 2.…”

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confidence: 91%

“…The atomic positions were taken from the DFT-calculated geometries. The lateral stiffness of the CO molecule was set to 0.29 N/m, a value that was determined independently for similarly sized molecules 16,17 .…”

Section: Supplementary Note 2: Comparison Of Afm Data To Simulated Afmentioning

confidence: 99%

“…A ketone group can be identified by its dark (more attractive) appearance in the AFM images as known from studies on 6-oxo-6H-benzo[cd]pyrene 17,18 .…”

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Synthesis and characterization of triangulene

et al. 2017

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* These authors contributed equally to this workTriangulene, the smallest triplet ground state polybenzenoid (also known as Clar's hydrocarbon), has been an enigmatic molecule ever since its existence was first hypothesized isomers (2, also denoted as dihydrotriangulenes) as precursor molecules. Compound 2 was deposited on Cu(111), NaCl(100), and Xe(111) surfaces to generate triangulene (1) by means of atomic manipulation. STM/AFM is an ideal combination to study on-surface synthesis ranging from individual molecules 9, 10 to graphene nanoribbons 11,12 . The chemical structure of reactants and products can be resolved by means of AFM with functionalized tips 13 . Even molecules too elusive to be studied by other means 14,15 can be stabilized by using an ultrathin insulating film as a decoupling 2 layer. A decoupling layer also facilitates studying the frontier molecular orbitals of the free molecule by means of STM and scanning tunnelling spectroscopy (STS) 16 .Figure 2 presents STM and AFM images of four different molecular species of compound 2 adsorbed on NaCl. As expected, different isomers of dihydrotriangulene are observed. This observation can be discussed by a comparison of Fig. 2e and Fig. 2f, showing the non-equivalent isomers 2a and 2b which we found on the surface, respectively. Because the former isomer is prochiral with respect to adsorption, we also observed its surface enantiomer (see Supplementary Fig. 5). Note that 2a is about three times more abundant than the highly symmetric 2b, although two Clar sextets can be drawn for both species. This difference can be rationalized by the resonance energy of its aromatic Remarkably, the ketone 3 in Fig. 2g represents an oxidized structure of 2 that was already reported by Clar and Stewart 1. A comparison of STM and AFM data reveals that in the STM images a tiny sharp kink arises at the position of a single CH 2 group. In contrast, a ketone group leads to a fainter bulge in STM images (Figs. 2c, d) and a lower contrast of the hexagon involved. The central carbon of the three adjacent CH 2 group in 3 adopts the expected tetrahedral bond angle for sp 3 carbon leading to sharp ridges in both STM and AFM mode (Figs. 2c, g) because of strong tilting of the CO molecule at the tip apex.We dehydrogenated promising candidates (2a and 2b molecules) to obtain triangulene by means of atomic manipulation 14,15,19 . To this end, we first positioned the tip above a molecule. Then, we opened the feedback loop and retracted the tip by 0.5 to 0.7 nm to limit the tunnelling current to a few picoamperes. Finally, we increased the voltage to values ranging from 3.5 to 4.1 V for several seconds. In many cases, this procedure also resulted in a lateral displacement of the molecule. When a subsequent STM image indicated a change in the appearance of the molecule, we recorded AFM 3 images to obtain its structure. Using this procedure, we did not observe any changes in the molecular structure other than the removal of single hydrogens from a CH 2 groups throughout our experiment...

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confidence: 91%

Section: Supplementary Note 2: Comparison Of Afm Data To Simulated Afmentioning

confidence: 99%

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Synthesis and characterization of triangulene

et al. 2017

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“…Thethree components were separable by flash chromatography,p roviding pure samples of each hydrocarbon. [11,12] Our spectral data match those reported earlier.1 ,2,3,8-Te trahydrotriangulene (11)i sanew derivative of olympicene, [36] possessing one additional saturated ring. [11,12] Our spectral data match those reported earlier.1 ,2,3,8-Te trahydrotriangulene (11)i sanew derivative of olympicene, [36] possessing one additional saturated ring.…”

Section: Angewandte Chemiesupporting

confidence: 87%

A Short and Efficient Synthesis of the [3]Triangulene Ring System

2019

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Triangulenes are of current interest for potential applications in molecular electronics.W edescribe here athree step synthesis of the 4,8,12-trihydro[3]triangulenium cation by cascade cyclization of atetra-benzyl alcohol precursor in triflic acid solution. This stable carbocation is easily observed by NMR and optical spectroscopya nd is highly fluorescent. Quenching of the cation into basic solutions or by hydride transfer from triethylsilane provides access to stable dihydro and tetrahydro[3]triangulenes.T hese neutral species interconvert with cations in ac omplex series of proton and hydride transfers.This route provides several important [3]triangulene precursors.P reliminary experiments designed to generate [3]triangulene in the solution phase provide evidence for its formation and rapid oligomerization.

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“…8,9 If enough molecules are imaged, a statistically significant analysis is possible 13 and even rare side products can be identified. 3,19 Moreover, AFM analysis requires only a small amount of material (about 0.1–1 mg) 20 and does not demand the compound to be soluble. Especially the single molecule sensitivity renders AFM an interesting tool for the investigation of complex molecular mixtures like petroleum, which contains a tremendous diversity and number of molecular species, 21,22 of which asphaltenes are one fraction.…”

Section: Introductionmentioning

confidence: 99%