Directed Rotations of Single Porphyrin Molecules Controlled by Localized Force Spectroscopy

Pawlak, Rémy; Fremy, Sweetlana; Kawai, Shigeki; Glatzel, Thilo; Fang, Han; Fendt, Leslie-Anne; Diederich, François; Meyer, Ernst

doi:10.1021/nn301774d

Cited by 46 publications

(54 citation statements)

References 44 publications

(70 reference statements)

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“…At positions where dissipation is observed, the molecule presumably changes its adsorption site as a function of tip height during the cantilever's oscillation, with a hysteresis giving rise to dissipation. The effect can be compared to the similar molecular rotations described by Pawlak and co-workers 61 .…”

Section: Supplementary Note 4: Stm and Afm Data Of Triangulene On Naclmentioning

confidence: 77%

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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Section: Supplementary Note 4: Stm and Afm Data Of Triangulene On Naclmentioning

confidence: 77%

Synthesis and characterization of triangulene

et al. 2017

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“…The tip apex (likely decorated by gold atoms picked up from the sample) was positioned precisely at the end of the molecular chain, indicated by the arrow, close enough to connect to the chain, as approaching the terminus increases the pulling efficiency (15). Whenever a strong bond to the tip is established, the sudden variation of the tip-sample interaction causes an abrupt Δf change in the AFM (26,27). Then, the tip was retracted in the vertical z-direction while recording Δf .…”

Section: Pulling Measurementsmentioning

confidence: 99%

Quantifying the atomic-level mechanics of single long physisorbed molecular chains

Kawai

Koch

Gnecco

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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Individual in situ polymerized fluorene chains 10-100 nm long linked by C-C bonds are pulled vertically from an Au(111) substrate by the tip of a low-temperature atomic force microscope. The conformation of the selected chains is imaged before and after manipulation using scanning tunneling microscopy. The measured force gradient shows strong and periodic variations that correspond to the step-by-step detachment of individual fluorene repeat units. These variations persist at constant intensity until the entire polymer is completely removed from the surface. Calculations based on an extended Frenkel-Kontorova model reproduce the periodicity and magnitude of these features and allow us to relate them to the detachment force and desorption energy of the repeat units. The adsorbed part of the polymer slides easily along the surface during the pulling process, leading to only small oscillations as a result of the high stiffness of the fluorenes and of their length mismatch with respect to the substrate surface structure. A significant lateral force also is caused by the sequential detachment of individual units. The gained insight into the moleculesurface interactions during sliding and pulling should aid the design of mechanoresponsive nanosystems and devices.force spectroscopy | conjugated polymers | adhesion | friction | nanomanipulation

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“…Another example of the local deformation of a single molecule on a surface is the study presented by Pawlak et al [39]. H 2 TBCPP porphyrin molecules (chemical structure in inset of Fig.…”

Section: Elasticity Of Single Moleculesmentioning

confidence: 97%

“…b Schematic view of the saddle conformation and STM images of the two enantiomers [56]. c Individual approach-retract curves taken above a single nitrogen atom and the determined vertical extension as well as the tip-sample stiffness during the switching process [39] The oscillation amplitude used in this studies was A = 40-60 pm and the hysteretic behavior was attributed to the formation of a junction between the Cu-terminated tip and the N atom of the targeted carbonitrile group. Upon retraction, the bond formation is strong enough to lift the carbonitrile group (transition 2-3).…”

Section: Elasticity Of Single Moleculesmentioning

confidence: 99%

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Mechanical and Electrical Properties of Single Molecules

Glatzel

2015

Imaging and Manipulation of Adsorbates Using Dynamic Force Microscopy

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Molecular systems and devices are an strongly emerging technology. Various devices are already available, while others are still under development. The usage of molecules offers a great advantage to Si-based electronics, the functional groups of the molecules are adoptable allowing to artificially generate a huge variety of different properties and functionalities. However, the fundamental requirements of molecular engineering are not fully developed yet, mainly wellknown molecules with limited functionality are used nowadays. To analyze and create new molecular structures providing, for example, a very high extinction coefficient while maintaining the chemical structure under environmental conditions would allow to create new types of solar cell conversion devices. This chapter introduces and reviews the research activities of the Nanolino-group at the University of Basel in the active field of the usage of scanning probe microscopy techniques to characterize the mechanical and electrical properties of molecular assemblies down to single molecules.

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Directed Rotations of Single Porphyrin Molecules Controlled by Localized Force Spectroscopy

Cited by 46 publications

References 44 publications

Synthesis and characterization of triangulene

Synthesis and characterization of triangulene

Quantifying the atomic-level mechanics of single long physisorbed molecular chains

Mechanical and Electrical Properties of Single Molecules

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