Conformational identification of individual adsorbed molecules with the STM

Jung, Thomas A.; Schlittler, R. R.; Gimzewski, J. K.

doi:10.1038/386696a0

Cited by 385 publications

(336 citation statements)

References 24 publications

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“…The metalation state and type of metal ion in the porphyrin are powerful means to modulate the photophysical properties and the chemical reactivity of the nonamers and the nanoscale aggregates. This work dovetails well with other recent work on nanoscaled materials based in inorganic, organic, and organometallic systems (27)(28)(29)(30)(31)(32)(33).…”

Section: Discussionsupporting

confidence: 63%

Designing supramolecular porphyrin arrays that self-organize into nanoscale optical and magnetic materials

Drain

Batteas

Flynn

et al. 2002

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

132

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Tessellation of nine free-base porphyrins into a 3 ؋ 3 array is accomplished by the self-assembly of 21 molecular entities of four different kinds, one central, four corner, and four side porphyrins with 12 trans Pd(II) complexes, by specifically designed and targeted intermolecular interactions. Strikingly, the self-assembly of 30 components into a metalloporphyrin nonamer results from the addition of nine equivalents of a first-row transition metal to the above milieu. In this case each porphyrin in the nonameric array coordinates the same metal such as Mn(II), Ni(II), Co(II), or Zn(II). This feat is accomplished by taking advantage of the highly selective porphyrin complexation kinetics and thermodynamics for different metals. In a second, hierarchical self-assembly process, nonspecific intermolecular interactions can be exploited to form nanoscaled three-dimensional aggregates of the supramolecular porphyrin arrays. In solution, the size of the nanoscaled aggregate can be directed by fine-tuning the properties of the component macrocycles, by choice of metalloporphyrin, and the kinetics of the secondary self-assembly process. As precursors to device formation, nanoscale structures of the porphyrin arrays and aggregates of controlled size may be deposited on surfaces. Atomic force microscopy and scanning tunneling microscopy of these materials show that the choice of surface (gold, mica, glass, etc.) may be used to modulate the aggregate size and thus its photophysical properties. Once on the surface the materials are extremely robust.

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Section: Discussionsupporting

confidence: 63%

Designing supramolecular porphyrin arrays that self-organize into nanoscale optical and magnetic materials

Drain

Batteas

Flynn

et al. 2002

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

132

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“…[10][11][12][13][14][15] The enormous potential of porphyrins for the fabrication of tailor-made functional molecular architectures on well-defined substrates has stimulated significant activities in fundamental research. 4,[16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] In this contribution, we review recent advances in the understanding of the dynamic behaviour of porphyrins, as representatives of organic molecules, adsorbed on a Cu(111) single crystal surface in ultra-high vacuum (UHV). Based on temperaturedependent measurements of individual molecules, the kinetics and energetics of diffusion 33,34 and rotation, 34 of the so-called self-metalation reaction 35,36 and finally of conformational switching of particular free base porphyrins 37 can be determined.…”

Section: Introductionmentioning

confidence: 99%

Studying the dynamic behaviour of porphyrins as prototype functional molecules by scanning tunnelling microscopy close to room temperature

Marbach

Steinrück

2014

Chem. Commun.

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Scanning tunnelling microscopy (STM) enables us to directly observe the dynamic behaviour of organic molecules on surfaces. While imaging atoms and molecules using STM is certainly fascinating by itself, corresponding temperature-dependent measurements allow for the quantitative determination of the energetics and kinetics of the underlying molecular surface processes. Herein, we review recent advances in the STM investigation of the dynamic behaviour of adsorbed porphyrins at and close to room temperature.Three different case studies are discussed, providing insight into the dynamics of diffusion, rotation, reaction, and molecular switching at surfaces, based on isothermal STM measurements. The reviewed examples demonstrate that variable temperature STM can be a suitable tool to directly monitor the dynamic behaviour of individual adsorbed molecules, at and close to room temperature. Free base porphyrins on Cu(111) proved to be particularly suitable for these studies due to the strong bonding interaction between the iminic nitrogen atoms in the porphyrin macrocycle and the Cu substrate atoms. As a consequence, the corresponding activation energies for surface diffusion, self-metalation reaction and conformational switching are of a magnitude that allows for monitoring the processes at and around room temperature, in contrast to most previous studies, which were performed at cryogenic temperatures. The kinetic analysis of the surface diffusion and self-metalation was performed using an Arrhenius approach, yielding the corresponding activation energies and preexponential factors. In contrast, the conformational switching process was analysed in the framework of transition state theory, based on the Eyring equation. This approach provides a more detailed insight into interpretable thermodynamic potentials, i.e., the enthalpic and entropic contributions to the activation barrier. The analysis shows that at room temperature the adsorption and switching behaviour of the investigated free base porphyrin on Cu(111) is dominated by entropic effects. Since the entropic energy contribution vanishes at low temperatures, the importance of experiments conducted at temperatures close to room temperature is emphasized.

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“…The conformational flexibility of TTBPP species on different substrates is well known and was reported before. [16][17][18][19][20] From the inspection of Fig. 3, it becomes immediately apparent that the different supramolecular arrangements go along with different intramolecular conformations.…”

mentioning

confidence: 99%

Massive conformational changes during thermally induced self-metalation of 2H-tetrakis-(3,5-di-tert-butyl)-phenylporphyrin on Cu(111)

et al. 2014

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Based on a combined scanning tunnelling microscopy and X-ray photoelectron spectroscopy study we present detailed insights into pronounced changes of long-range order and intramolecular conformation during the self-metalation of 10,15, to CuTTBPP on Cu(111).Upon metalation, the porphyrin literally ''pops up'' from the surface, due to a drastically reduced molecule-substrate interaction.A detailed understanding of the adsorption behaviour of molecular building blocks on solid surfaces is a crucial step towards the bottom-up fabrication of functional devices.1,2 Scanning tunnelling microscopy (STM) is an especially suitable method to study the relevant elementary processes. Porphyrins are regarded as prototype functional molecular building blocks for nanotechnology applications. Recent surface science studies of porphyrins addressed their switching capabilities 3-5 and adsorption behaviour as well as surface-mediated metalation of free base porphyrins. 6 The metalation can occur with predeposited and postdeposited metal atoms, or via the so-called self-metalation with atoms from an underlying metal substrate. 7-10 Thereby, the free base porphyrin picks up a substrate atom and reacts to the corresponding metalloporphyrin with the release of hydrogen. Herein, we report on the self-metalation of 2HTTBPP on Cu(111), which goes along with a massive intramolecular conformational change due to reduced molecule-substrate interactions. In a vivid image, this process can be summarized as a popping up of the molecular centre from the surface. The investigation of free base porphyrins on single crystal Cu surfaces recently received great interest, mainly due to the very strong attractive interactions of the iminic nitrogen atoms of the porphyrin macrocycle with Cu atoms from the substrate. 11-15This interactions can give rise to very peculiar adsorption behaviours like the one observed by STM for 2HTTBPP on Cu(111), see Fig. 1a. The corresponding supramolecular structure exhibits a bimodal appearance, i.e. alternating bright and dark rows, which (predominantly) consist of convex and concave intramolecular conformations, respectively (see also Fig. 3a-h and discussion below).

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Conformational identification of individual adsorbed molecules with the STM

Cited by 385 publications

References 24 publications

Designing supramolecular porphyrin arrays that self-organize into nanoscale optical and magnetic materials

Designing supramolecular porphyrin arrays that self-organize into nanoscale optical and magnetic materials

Studying the dynamic behaviour of porphyrins as prototype functional molecules by scanning tunnelling microscopy close to room temperature

Massive conformational changes during thermally induced self-metalation of 2H-tetrakis-(3,5-di-tert-butyl)-phenylporphyrin on Cu(111)

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