Azobenzene-Containing Triazatriangulenium Adlayers on Au(111): Structural and Spectroscopic Characterization

Jung, Ulrich; Kühn, Sonja; Cornelissen, Ursula; Tuczek, Felix; Strunskus, Thomas; Zaporojtchenko, V.; Kubitschke, Jens; Herges, Rainer; Magnussen, Olaf M.

doi:10.1021/la104654p

Cited by 57 publications

(88 citation statements)

References 76 publications

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“…2a and b, inset) reveal the triangular shape of the molecules, indicating a planar adsorption of the bare and vertically functionalized platforms and a uniform orientation of the molecules. As in our previous studies of TATA adlayers, 3,5 no indications for the BF 4 À counter ions were found. Most probably, these are not coadsorbed on the surface, which can be explained by charge transfer from the substrate to the adsorbate molecules.…”

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confidence: 64%

“…1 We recently introduced the platform approach for preparation of wellordered adlayers with freestanding functional groups on metal surfaces and illustrated its feasibility by employing derivatives of the triazatriangulenium (TATA) ion. [2][3][4][5] The triangularshaped TATA platform can be functionalized either vertically at the central carbon or laterally at the outer nitrogen atoms and thus serves as a chemically very modular and versatile template. Up to now, more than 30 TATA derivatives with different functional groups have been synthesized.…”

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Adlayers based on molecular platforms of trioxatriangulenium

et al. 2011

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The platform approach for preparation of molecular adlayers with freestanding functional groups was extended to systems on the basis of the trioxatriangulenium ion. Self-assembled monolayers of these compounds were prepared on Au(111) surfaces and characterized by scanning tunneling microscopy, revealing highly-ordered structures.Organic surface functionalization with defined vertical architecture is of considerable current interest. 1 We recently introduced the platform approach for preparation of wellordered adlayers with freestanding functional groups on metal surfaces and illustrated its feasibility by employing derivatives of the triazatriangulenium (TATA) ion.2-5 The triangularshaped TATA platform can be functionalized either vertically at the central carbon or laterally at the outer nitrogen atoms and thus serves as a chemically very modular and versatile template. Up to now, more than 30 TATA derivatives with different functional groups have been synthesized. 4 Adlayers of these compounds have been studied by STM, 2,3,5 different spectroscopies, 5 and electrochemical methods. 5,3 Using these techniques the TATA derivatives were shown to form hexagonally-ordered adlayers where the platforms adsorb flat on the metal substrate, the intermolecular distances can be varied by the attached side groups, and the central functional groups are oriented perpendicularly to the surface. Although this approach turned out to be an excellent method for preparation of highly-ordered functional adlayers, the employed TATA platforms have some disadvantages. First, it is not possible to prepare functional TATA adlayers by vacuum deposition, because they decompose below their sublimation point. This limits their applicability for studies under ultrahigh vacuum conditions. Second, the inevitably present side groups attached to the nitrogen atoms partially reside above the TATA layer and (for the employed alkane chains) do not seem to exhibit well-defined positions, which reduces the structural order in the adlayers.In this work we use an alternative molecular platform system, derivatives of the trioxatriangulenium (TOTA) ion (Fig. 1), which does not have these disadvantages. TOTA is structurally closely related to TATA, but exhibits three oxygen atoms in the platform instead of nitrogen atoms with attached side groups and thus a significantly reduced molecular mass. Similarly as for TATA perpendicular as well as lateral functionalization is possible, although the latter only at para or meta positions of the benzene rings in the platform. The bond strength of vertically attached functional groups to the central carbon atom of the TOTA platform should be increased as compared to TATA, making these molecules better suited for adlayer preparation via vacuum deposition. The TOTA derivatives have been extensively studied since the 1960s, [6][7][8] but up to now not in context of surface functionalization. As we will show in the following STM studies, highly-ordered adlayers of TOTA and functional TOTA derivatives can be prepared on ...

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Adlayers based on molecular platforms of trioxatriangulenium

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“…Although these arguments, supported by literature data that confirm the Ag-supported photocatalyzed formation of azo bonds from primary amines, [64][65][66][67][68] would suggest a straightforward association of this new component to the azo nitrogen, we note that the expected BE for a simply physisorbed azo group should be higher than the observed one. [69][70][71][72] Chemisorption on metal surfaces generally induces a BE redshift [73] as consequence of the electron donation from the surface. [74] In particular, chemisorption through the central azo bridge at the metal surface [75] can reduce the observed binding energy to 398 eV.…”

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Stereoselective Photopolymerization of Tetraphenylporphyrin Derivatives on Ag(110) at the Sub‐Monolayer Level

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Colazzo

Sedona

et al. 2014

Chemistry A European J

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We explore a photochemical approach to achieve an ordered polymeric structure at the sub-monolayer level on a metal substrate. In particular, a tetraphenylporphyrin derivative carrying para-amino-phenyl functional groups is used to obtain extended and highly ordered molecular wires on Ag(110). Scanning tunneling microscopy and density functional theory calculations reveal that porphyrin building blocks are joined through azo bridges, mainly as cis isomers. The observed highly stereoselective growth is the result of adsorbate/surface interactions, as indicated by X-ray photoelectron spectroscopy. At variance with previous studies, we tailor the formation of long-range ordered structures by the separate control of the surface molecular diffusion through sample heating, and of the reaction initiation through light absorption. This previously unreported approach shows that the photo-induced covalent stabilization of self-assembled molecular monolayers to obtain highly ordered surface covalent organic frameworks is viable by a careful choice of the precursors and reaction conditions.

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“…The bands at 1,600 and 1,510 cm −1 are assigned to ring breathing of aromatic ring and appears in the spectra of modified materials. While the bands at 1,410 and 1,440 cm −1 are assigned to –N=N‐ bonds and also occur only in the modified zeolite .…”

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Mechanically robust and thermally stable abrasive tools from phenolic resins reinforced with diazonium‐modified zeolites

et al. 2018

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The contact area between the filler and the polymer is a critical region that influences to a great extent the filler–matrix adhesion and therefore the mechanical properties of the composite. Controlling the type of interactions at this interface has a significant effect on the properties of the composite materials. In this context, we prepared composites by covalent reaction of diazonium‐functionalized zeolite with phenol‐formaldehyde resin. Introducing the hydroxymethyl groups onto the surface of the filler via diazonium chemistry allows for covalent bonds between the resin and the modified filler. Such a modification resulted in higher flexural strength of the composites, better ability to dissipate mechanical energy during load and also better damping properties (which are strongly linked to the final product durability) compared with the composites bearing pristine zeolite filler. Moreover, application of modified filler accelerates the crosslinking of novolac resin used as a binder in abrasive tools. One key feature of the work was brought by thermogravimetric analysis–mass spectrometry results which indicate no release of toxic urotropine degradation products for composites containing modified fillers. This work demonstrates conclusively that diazonium‐functionalized zeolite filler particles improve remarkably the thermal and mechanical properties of novolac‐based composites. Such robust composites have high potential in the production of novel abrasive tools. POLYM. COMPOS., 40:3209–3219, 2019. © 2018 Society of Plastics Engineers

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Azobenzene-Containing Triazatriangulenium Adlayers on Au(111): Structural and Spectroscopic Characterization

Cited by 57 publications

References 76 publications

Adlayers based on molecular platforms of trioxatriangulenium

Adlayers based on molecular platforms of trioxatriangulenium

Stereoselective Photopolymerization of Tetraphenylporphyrin Derivatives on Ag(110) at the Sub‐Monolayer Level

Mechanically robust and thermally stable abrasive tools from phenolic resins reinforced with diazonium‐modified zeolites

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