Scanning Tunneling Microscopy, Orbital-Mediated Tunneling Spectroscopy, and Ultraviolet Photoelectron Spectroscopy of Metal(II) Tetraphenylporphyrins Deposited from Vapor

Scudiero, Louis; Barlow, Daniel E.; Mazur, Ursula; Hipps, K. W.

doi:10.1021/ja0100726

Cited by 248 publications

(357 citation statements)

References 40 publications

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“…The UPS spectrum corresponding to the bare Au substrate shows the same pattern and peak positions (2.7 and 4.3 eV vs EF) to that previously reported for clean Au surfaces and corresponds to the 5d bands. 38 At this point it is important to note that the escape depth (or attenuation length) λ of photoelectrons with 15 eV kinetic energy, i.e., below the Fermi edge photoemission for Au in a He(I) experiment, is approximately 8 Å for a compact hydrocarbon film. 39 Therefore, the sampling depth in the photoemission experiment at zero degrees take-off angle is approximately 24 Å (3 λ) hence this experiment samples the entire SAM layer and the SAM/Au interface.…”

Section: Electrochemical Measurementsmentioning

confidence: 99%

Molecular and electronic structure of electroactive self-assembled monolayers

Leo

Llave

Scherlis

et al. 2013

The Journal of Chemical Physics

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Self-assembled monolayers (SAMs) containing electroactive functional groups are excellent model systems for the formation of electronic devices by self-assembly. In particular ferrocene-terminated alkanethiol SAMs have been extensively studied in the past. However, there are still open questions related with their electronic structure including the influence of the ferrocene group in the SAMinduced work function changes of the underlying metal. We have thus carried out a thorough experimental and theoretical investigation in order to determine the molecular and electronic structure of ferrocene-terminated alkanethiol SAMs on Au surfaces. In agreement with previous studies we found that the Fc-containing alkanethiol molecules adsorb forming a thiolate bond with the Au surface with a molecular geometry 30• tilted with respect to the surface normal. Measured surface coverages indicate the formation of a compact monolayer. We found for the first time that the ferrocene group has little influence on the observed work function decrease which is largely determined by the alkanethiol. Furthermore, the ferrocene moiety lies 14 Å above the metal surface covalently bonded to the alkanethiol SAM and its HOMO is located at −1.6 eV below the Fermi level. Our results provide new valuable insight into the molecular and electronic structure of electroactive SAMs which are of fundamental importance in the field of molecular electronics.

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Section: Electrochemical Measurementsmentioning

confidence: 99%

Molecular and electronic structure of electroactive self-assembled monolayers

Leo

Llave

Scherlis

et al. 2013

The Journal of Chemical Physics

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“…[1][2][3] Many of these applications rely on the formation of thin films of ordered structures of porphyrins and related compounds. [4][5][6][7] Intermolecular interactions such as dipole-dipole, 8 hydrogen bonding, 8 and coordination 9 in porphyrin building blocks are being used to create selfassembled structures on surfaces with increasing sophistication. Itaya et al demonstrated that the ordering of porphyrin molecules on metal surfaces can be promoted by a passivating layer of iodine, which reduces the adsorbate-substrate interaction and facilitates surface diffusion.…”

Section: Introductionmentioning

confidence: 99%

Adsorption and Electrochemical Activity: An In Situ Electrochemical Scanning Tunneling Microscopy Study of Electrode Reactions and Potential-Induced Adsorption of Porphyrins

Borguet

2006

J. Phys. Chem. B

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The effect of adsorption on molecular properties and reactivity is a central topic in interfacial physical chemistry. At electrochemical interfaces, adsorbed molecules may lose their electrochemical activity. The absence of in situ probes has hindered our understanding of this phenomenon and electrode reactions in general. In this work, classical electrochemistry and electrochemical scanning tunneling microscopy (EC-STM) were combined to provide molecular level insight into electrochemical reactions and the molecular adsorption state at the electrolyte-electrode interface. The metal-free porphyrin 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (TPyP) adsorbed on Au(111) in 0.1 M H 2 SO 4 solution was chosen as a model system. TPyP is found to irreversibly adsorb on Au(111) over a wide range of potentials, from -0.25 to 0.6 V SCE . The adsorption state of TPyP has a dramatic effect on its electrochemistry. Preadsorbed, oxidized TPyP displays no well-defined cathodic peaks in cyclic voltammograms in sharp contrast to solution-phase TPyP. Our present work provides direct, molecular level evidence of the electrochemically "invisible" species. Electrochemical activity of absorbed species is recovered by allowing the oxidized molecule sufficient time (tens of minutes) to reduce. The redox state of adsorbed TPyP also affects the nature of the adsorption. Oxidized species can apparently only form monolayers. However, multilayers, stable enough to be imaged by STM, can form when the adsorbed TPyP is in the reduced state. This suggests that by controlling the electrochemistry one can either promote or suppress the formation of multilayers.

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“…These processes will play a critical role in the so-called ''bottom-up'' strategy of nanofabrication. Therefore, understanding the organization of molecules on solid surfaces is important, both from a fundamental and applied perspective, for the construction of surface molecular nanostructures and nanodevices (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13). A self-organized molecular pattern with control of structure and derived concomitant function could provide promising materials for the construction of nanodevices that cannot be prepared by conventional microfabrication.…”

mentioning

confidence: 99%

Mesoscopic self-organization of a self-assembled supramolecular rectangle on highly oriented pyrolytic graphite and Au(111) surfaces

Gong

Wan

Yuan

et al. 2005

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

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A self-assembled supramolecular metallacyclic rectangle was investigated with scanning tunneling microscopy on highly oriented pyrolytic graphite and Au(111) surfaces. The rectangles spontaneously adsorb on both surfaces and self-organize into well ordered adlayers. On highly oriented pyrolytic graphite, the long edge of the rectangle stands on the surface, forming a 2D molecular network. In contrast, the face of the rectangle lays flat on the Au(111) surface, forming linear chains. The structures and intramolecular features obtained through high-resolution scanning tunneling microscopy imaging are discussed.metallacyclic macrocycle ͉ scanning tunneling microscopy ͉ molecular adlayer ͉ molecular orientation S elf-organization (1) and self-assembly (2) are critical and necessary processes in all living organisms and are of ever increasing importance in chemistry and material science. These processes will play a critical role in the so-called ''bottom-up'' strategy of nanofabrication. Therefore, understanding the organization of molecules on solid surfaces is important, both from a fundamental and applied perspective, for the construction of surface molecular nanostructures and nanodevices (3-13). A self-organized molecular pattern with control of structure and derived concomitant function could provide promising materials for the construction of nanodevices that cannot be prepared by conventional microfabrication. The arrangement of adsorbed molecules onto a surface depends on both intermolecular and molecule-surface interactions. For example, Hipps and colleagues (3, 4) prepared a self-organized 2D bifunctional structure on a Au (111) Metal-containing macrocycles with high symmetry and precise architecture are a new class of promising supramolecules for future application in nanotechnology because of their exact shape and size, as well as magnetic, photophysical, and electrostatic properties (14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27). In this article, we describe scanning tunneling microscopy (STM) studies of the self-assembled supramolecular metallacyclic rectangle, cyclobis [(1, ) 2 )anthracene)(1,4Ј-bis(4-ethynylpyridyl)benzene](PF 6 ) 4 , (Fig. 1) (28). The dimensions of a single rectangle molecule were independently determined to be 3.1 nm long by 1.2 nm wide, from the previously reported x-ray crystallographic data (28). The molecular adlayers were prepared on highly oriented pyrolytic graphite (HOPG) and Au(111) surfaces to investigate the effect of substrate on adlayer formation. The molecules self-organize into well ordered 2D adlayers on both surfaces, and high-resolution STM results clearly reveal an intact rectangle on both HOPG and Au (111) surfaces, but the symmetry and molecular orientation the molecules adopt depends on the substrate. Materials and MethodsChemicals. The PF 6 Ϫ salt of the rectangle was prepared analogously to the ClO 4 Ϫ salt previously reported (28), substituting KPF 6 for NaClO 4 .Substrates. HOPG (quality ZYB) was purchased from Digital Instruments (Santa Barbar...

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Scanning Tunneling Microscopy, Orbital-Mediated Tunneling Spectroscopy, and Ultraviolet Photoelectron Spectroscopy of Metal(II) Tetraphenylporphyrins Deposited from Vapor

Cited by 248 publications

References 40 publications

Molecular and electronic structure of electroactive self-assembled monolayers

Molecular and electronic structure of electroactive self-assembled monolayers

Adsorption and Electrochemical Activity: An In Situ Electrochemical Scanning Tunneling Microscopy Study of Electrode Reactions and Potential-Induced Adsorption of Porphyrins

Mesoscopic self-organization of a self-assembled supramolecular rectangle on highly oriented pyrolytic graphite and Au(111) surfaces

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