101
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Wiengarten A, Lloyd JA, Seufert K, Reichert J, Auwärter W, Han R, Duncan DA, Allegretti F, Fischer S, Oh SC, Sağlam Ö, Jiang L, Vijayaraghavan S, Écija D, Papageorgiou AC, Barth JV. Surface-Assisted Cyclodehydrogenation; Break the Symmetry, Enhance the Selectivity. Chemistry 2015. [PMID: 26211450 DOI: 10.1002/chem.201502001] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Selectivity in chemical reactions is a major objective in industrial processes to minimize spurious byproducts and to save scarce resources. In homogeneous catalysis the most important factor which determines selectivity is structural symmetry. However, a transfer of the symmetry concept to heterogeneous catalysis still requires a detailed comprehension of the underlying processes. Here, we investigate a ring-closing reaction in surface-confined meso-substituted porphyrin molecules by scanning tunneling microscopy, temperature-programmed desorption, and computational modeling. The identification of reaction intermediates enables us to analyze the reaction pathway and to conclude that the symmetry of the porphyrin core is of pivotal importance regarding product yields.
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102
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Krenner W, Kühne D, Klappenberger F, Barth JV. Erratum: CORRIGENDUM: Assessment of Scanning Tunneling Spectroscopy Modes Inspecting Electron Confinement in Surface-Confined Supramolecular Networks. Sci Rep 2015. [PMCID: PMC3899749 DOI: 10.1038/srep03772] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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103
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Vijayaraghavan S, Auwärter W, Ecija D, Seufert K, Rusponi S, Houwaart T, Sautet P, Bocquet ML, Thakur P, Stepanow S, Schlickum U, Etzkorn M, Brune H, Barth JV. Restoring the Co magnetic moments at interfacial Co-porphyrin arrays by site-selective uptake of iron. ACS NANO 2015; 9:3605-3616. [PMID: 25856066 DOI: 10.1021/nn507346x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Magnetochemistry recently emerged as a promising approach to control addressable spin arrays on surfaces. Here we report on the binding, spatial ordering, and magnetic properties of Fe on a highly regular Co-tetraphenylporphyrin (Co-TPP) template and highlight how the Fe controls the magnetism of the Co centers. As evidenced by scanning tunneling microscopy (STM) single Fe atoms attach to the saddle-shape conformers site-selectively in a unique coordination environment offered through a heptamer defined by the Co-N-C-C-C-N cyclic subunit. While the magnetic moment of Co is quenched for bare Co-TPP/Ag(111), the Fe presence revives it. Our X-ray magnetic circular dichroism (XMCD) experiments, complemented by density functional theory (DFT) calculations, evidence a ferromagnetic coupling between the Fe and the Co center concomitant with a complex charge redistribution involving the porphyrin ligand. Thus, we demonstrate an unusual metalloporphyrin coordination geometry that opens pathways to spatially order and engineer magnetic moments in surface-based nanostructures.
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104
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Palma CA, Joshi S, Hoh T, Ecija D, Barth JV, Auwärter W. Two-level spatial modulation of vibronic conductance in conjugated oligophenylenes on boron nitride. NANO LETTERS 2015; 15:2242-8. [PMID: 25756645 DOI: 10.1021/nl503956p] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Intramolecular current-induced vibronic excitations are reported in highly ordered monolayers of quaterphenylene dicarbonitriles at an electronically patterned boron nitride on copper platform (BN/Cu(111)). A first level of spatially modulated conductance at the nanometer-scale is induced by the substrate. Moreover, a second level of conductance variations at the molecular level is found. Low temperature scanning tunneling microscopy studies in conjunction with molecular dynamics calculations reveal collective amplification of the molecule's interphenylene torsion angles in the monolayer. Librational modes influencing these torsion angles are identified as initial excitations during vibronic conductance. Density functional theory is used to map phenylene breathing modes and other vibrational excitations that are suggested to be at the origin of the submolecular features during vibronic conductance.
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105
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Urgel JI, Ecija D, Auwärter W, Stassen D, Bonifazi D, Barth JV. Orthogonal insertion of lanthanide and transition-metal atoms in metal-organic networks on surfaces. Angew Chem Int Ed Engl 2015; 54:6163-7. [PMID: 25832804 DOI: 10.1002/anie.201410802] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Revised: 03/02/2015] [Indexed: 11/07/2022]
Abstract
The orthogonal coordinative properties of tetrapyrrole macrocycles and nitrile ligands have been used in a multistep procedure towards interfacial d-f hetero-bimetallic nanoarchitectures based on a free-base porphyrin derivative functionalized with meso-cyanobiphenylene substituents. Molecular-level scanning tunneling microscopy studies reveal that the porphyrin module alone self-assembles on Ag(111) in a close-packed layer with a square unit cell. Upon co-deposition of Gd atoms, a square-planar motif is formed that reflects the fourfold coordination of CN ligands to the rare-earth centers. The resulting nanoporous network morphology is retained following exposure to a beam of Co atoms, which induces selective porphyrin metalation and ultimately yields a gridlike 2D metallosupramolecular architecture.
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106
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Urgel JI, Ecija D, Auwärter W, Stassen D, Bonifazi D, Barth JV. Orthogonal Insertion of Lanthanide and Transition-Metal Atoms in Metal-Organic Networks on Surfaces. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201410802] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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107
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Kepčija N, Huang TJ, Klappenberger F, Barth JV. Quantum confinement in self-assembled two-dimensional nanoporous honeycomb networks at close-packed metal surfaces. J Chem Phys 2015; 142:101931. [PMID: 25770520 DOI: 10.1063/1.4913244] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Quantum confinement of a two-dimensional electron gas by supramolecular nanoporous networks is investigated using the boundary elements method based on Green's functions for finite geometries and electron plane wave expansion for periodic systems. The "particle in a box" picture was analyzed for cases with selected symmetries that model previously reported architectures constructed from organic and metal-organic scattering centers confining surface state electrons of Ag(111) and Cu(111). First, by analyzing a series of cases with systematically defined parameters (scattering geometry, potentials, and effective broadening), we demonstrate how the scattering processes affect the properties of the confined electrons. For the features of the local density of states reported by scanning tunneling spectroscopy (STS), we disentangle the contributions of lifetime broadening and splitting of quantum well states due to coupling of neighboring quantum dots. For each system, we analyze the local electron density distribution and relate it to the corresponding band structure as calculated within the plane-wave expansion framework. Then, we address two experimental investigations, where in one case only STS data and in the other case mainly angle-resolved photoemission spectroscopy (ARPES) data were reported. In both cases, the experimental findings can be successfully simulated. Furthermore, the missing information can be complemented because our approach allows to correlate the information obtained by STS with that of ARPES. The combined analysis of several observations suggests that the scattering potentials created by the network originate primarily from the adsorbate-induced changes of the local surface dipole barrier.
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108
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Margapoti E, Li J, Ceylan Ö, Seifert M, Nisic F, Anh TL, Meggendorfer F, Dragonetti C, Palma CA, Barth JV, Finley JJ. A 2D semiconductor-self-assembled monolayer photoswitchable diode. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2015; 27:1426-1431. [PMID: 25641369 DOI: 10.1002/adma.201405110] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Revised: 12/15/2014] [Indexed: 06/04/2023]
Abstract
A switchable diode in a 2D semiconductor-molecular junction heterostructure is reported. MoS2 is exfoliated on top of a monolayer of azobenzene-substituted thiols on gold. Photoisomerization of the azobenzenes results in switching between a rectifier with rectifying ratios of 10(4) and a conductive state, as revealed by conducting atomic force microscopy.
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109
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Palma CA, Björk J, Klappenberger F, Arras E, Kühne D, Stafström S, Barth JV. Visualization and thermodynamic encoding of single-molecule partition function projections. Nat Commun 2015; 6:6210. [PMID: 25703681 DOI: 10.1038/ncomms7210] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Accepted: 01/06/2015] [Indexed: 12/28/2022] Open
Abstract
Ensemble averaging of molecular states is fundamental for the experimental determination of thermodynamic quantities. A special case occurs for single-molecule investigations under equilibrium conditions, for which free energy, entropy and enthalpy at finite temperatures are challenging to determine with ensemble averaging alone. Here we report a method to directly record time-averaged equilibrium probability distributions by confining an individual molecule to a nanoscopic pore of a two-dimensional metal-organic nanomesh, using temperature-controlled scanning tunnelling microscopy. We associate these distributions with partition function projections to assess real-space-projected thermodynamic quantities, aided by computational modelling. The presented molecular dynamics-based analysis is able to reproduce experimentally observed projected microstates with high accuracy. By an in silico customized energy landscape, we demonstrate that distinct probability distributions can be encrypted at different temperatures. Such modulation provides means to encode and decode information into position-temperature space.
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110
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Urgel JI, Schwarz M, Garnica M, Stassen D, Bonifazi D, Ecija D, Barth JV, Auwärter W. Controlling Coordination Reactions and Assembly on a Cu(111) Supported Boron Nitride Monolayer. J Am Chem Soc 2015; 137:2420-3. [DOI: 10.1021/ja511611r] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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111
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Chen Z, Klyatskaya S, Urgel JI, Écija D, Fuhr O, Auwärter W, Barth JV, Ruben M. Synthesis, characterization, monolayer assembly and 2D lanthanide coordination of a linear terphenyl-di(propiolonitrile) linker on Ag(111). BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2015; 6:327-335. [PMID: 25821671 PMCID: PMC4362489 DOI: 10.3762/bjnano.6.31] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Accepted: 12/19/2014] [Indexed: 06/04/2023]
Abstract
As a continuation of our work employing polyphenylene-dicarbonitrile molecules and in particular the terphenyl derivative 1 (TDCN), we have synthesized a novel ditopic terphenyl-4,4"-di(propiolonitrile) (2) linker for the self-assembly of organic monolayers and metal coordination at interfaces. The structure of the organic linker 2 was confirmed by single crystal X-ray diffraction analysis (XRD). On the densely packed Ag(111) surface, the terphenyl-4,4"-di(propiolonitrile) linkers self-assemble in a regular, molecular chevron arrangement exhibiting a Moiré pattern. After the exposure of the molecular monolayer to a beam of Gd atoms, the propiolonitrile groups get readily involved in metal-ligand coordination interactions. Distinct coordination motifs evolve with coordination numbers varying between three and six for the laterally-bound Gd centers. The linker molecules retain an overall flat adsorption geometry. However, only networks with restricted local order were obtained, in marked contrast to previously employed, simpler polyphenylene-dicarbonitrile 1 linkers.
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112
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Palma CA, Ciesielski A, Öner MA, Schaeffer G, Lehn JM, Barth JV, Samorì P. Two-dimensional soft supramolecular networks. Chem Commun (Camb) 2015; 51:17297-300. [DOI: 10.1039/c5cc07204b] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Soft networks are self-assembled at the solid/liquid interface and characterized by local disorder arising from multivalent flexible intermolecular interactions.
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113
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Margapoti E, Strobel P, Asmar MM, Seifert M, Li J, Sachsenhauser M, Ceylan O, Palma CA, Barth JV, Garrido JA, Cattani-Scholz A, Ulloa SE, Finley JJ. Emergence of photoswitchable states in a graphene-azobenzene-Au platform. NANO LETTERS 2014; 14:6823-6827. [PMID: 25414977 DOI: 10.1021/nl503681z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The perfect transmission of charge carriers through potential barriers in graphene (Klein tunneling) is a direct consequence of the Dirac equation that governs the low-energy carrier dynamics. As a result, localized states do not exist in unpatterned graphene, but quasibound states can occur for potentials with closed integrable dynamics. Here, we report the observation of resonance states in photoswitchable self-assembled molecular(SAM)-graphene hybrid. Conductive AFM measurements performed at room temperature reveal strong current resonances, the strength of which can be reversibly gated on- and off- by optically switching the molecular conformation of the mSAM. Comparisons of the voltage separation between current resonances (∼ 70-120 mV) with solutions of the Dirac equation indicate that the radius of the gating potential is ∼ 7 ± 2 nm with a strength ≥ 0.5 eV. Our results and methods might provide a route toward optically programmable carrier dynamics and transport in graphene nanomaterials.
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114
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Diller K, Klappenberger F, Allegretti F, Papageorgiou AC, Fischer S, Duncan DA, Maurer RJ, Lloyd JA, Oh SC, Reuter K, Barth JV. Temperature-dependent templated growth of porphine thin films on the (111) facets of copper and silver. J Chem Phys 2014; 141:144703. [DOI: 10.1063/1.4896605] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
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115
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Palma CA, Björk J, Rao F, Kühne D, Klappenberger F, Barth JV. Topological dynamics in supramolecular rotors. NANO LETTERS 2014; 14:4461-4468. [PMID: 25078022 DOI: 10.1021/nl5014162] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Artificial molecular switches, rotors, and machines are set to establish design rules and applications beyond their biological counterparts. Herein we exemplify the role of noncovalent interactions and transient rearrangements in the complex behavior of supramolecular rotors caged in a 2D metal-organic coordination network. Combined scanning tunneling microscopy experiments and molecular dynamics modeling of a supramolecular rotor with respective rotation rates matching with 0.2 kcal mol(-1) (9 meV) precision, identify key steps in collective rotation events and reconfigurations. We notably reveal that stereoisomerization of the chiral trimeric units entails topological isomerization whereas rotation occurs in a topology conserving, two-step asynchronous process. In supramolecular constructs, distinct displacements of subunits occur inducing a markedly lower rotation barrier as compared to synchronous mechanisms of rigid rotors. Moreover, the chemical environment can be instructed to control the system dynamics. Our observations allow for a definition of mechanical cooperativity based on a significant reduction of free energy barriers in supramolecules compared to rigid molecules.
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116
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Li J, Wieghold S, Öner MA, Simon P, Hauf MV, Margapoti E, Garrido JA, Esch F, Palma CA, Barth JV. Three-dimensional bicomponent supramolecular nanoporous self-assembly on a hybrid all-carbon atomically flat and transparent platform. NANO LETTERS 2014; 14:4486-4492. [PMID: 25115337 DOI: 10.1021/nl501452s] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Molecular self-assembly is a versatile nanofabrication technique with atomic precision en route to molecule-based electronic components and devices. Here, we demonstrate a three-dimensional, bicomponent supramolecular network architecture on an all-carbon sp(2)-sp(3) transparent platform. The substrate consists of hydrogenated diamond decorated with a monolayer graphene sheet. The pertaining bilayer assembly of a melamine-naphthalenetetracarboxylic diimide supramolecular network exhibiting a nanoporous honeycomb structure is explored via scanning tunneling microscopy initially at the solution-highly oriented pyrolytic graphite interface. On both graphene-terminated copper and an atomically flat graphene/diamond hybrid substrate, an assembly protocol is demonstrated yielding similar supramolecular networks with long-range order. Our results suggest that hybrid platforms, (supramolecular) chemistry and thermodynamic growth protocols can be merged for in situ molecular device fabrication.
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117
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Wiengarten A, Seufert K, Auwärter W, Ecija D, Diller K, Allegretti F, Bischoff F, Fischer S, Duncan DA, Papageorgiou AC, Klappenberger F, Acres RG, Ngo TH, Barth JV. Surface-assisted Dehydrogenative Homocoupling of Porphine Molecules. J Am Chem Soc 2014; 136:9346-54. [DOI: 10.1021/ja501680n] [Citation(s) in RCA: 128] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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118
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Arras E, Seitsonen AP, Klappenberger F, Barth JV. Nature of the attractive interaction between proton acceptors and organic ring systems. Phys Chem Chem Phys 2014; 14:15995-6001. [PMID: 23089650 DOI: 10.1039/c2cp42293j] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Systematic ab initio calculations are combined with a deconvolution of electrostatic contributions to analyze the interplay between potential hydrogen bond acceptors and organic rings with C(sp(2))-H groups (benzene, pyridine and cyclopentadiene). A distinct anisotropic interaction between the ring systems and the electron lone pairs of cyanide, water and other acceptor species is revealed that favors the in-plane orientation of the proton acceptor group. In the attractive regime this interaction carries a pronounced electrostatic signature. By decomposing the electrostatic contribution into parts attributed to different subunits of the ring systems we demonstrate that a major proportion of the interaction energy gain is originating from the non-adjacent moieties, that are not in close contact with. This behavior holds equally for homocyclic, heterocyclic and non-aromatic rings but contrasts that of the ethyne molecule, taken as reference for a weak hydrogen bond donor clearly exhibiting the expected localized character. The ring interaction requires the presence of π-electron clouds and typically results in an interaction energy gain of 40 to 80 meV. Our findings suggest the proton acceptor-ring interaction as a new category of intermolecular non-covalent interactions.
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119
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Urgel JI, Ecija D, Auwärter W, Barth JV. Controlled manipulation of gadolinium-coordinated supramolecules by low-temperature scanning tunneling microscopy. NANO LETTERS 2014; 14:1369-1373. [PMID: 24456175 DOI: 10.1021/nl4044339] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Coordination bonding between para-quarterphenyl-dicarbonitrile linkers and gadolinium on Ag(111) has been exploited to construct pentameric mononuclear supramolecules, consisting of a rare-earth center surrounded by five molecular linkers. By employing a scanning tunneling microscope tip, a manipulation protocol was developed to position individual pentamers on the surface. In addition, the tip was used to extract and replace individual linkers yielding tetrameric, pentameric, nonameric, and dodecameric metallosupramolecular arrangements. These results open new avenues toward advanced nanofabrication methods and rare-earth nanochemistry by combining the versatility of metal-ligand interactions and atomistic manipulation capabilities.
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120
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Palma CA, Diller K, Berger R, Welle A, Björk J, Cabellos JL, Mowbray DJ, Papageorgiou AC, Ivleva NP, Matich S, Margapoti E, Niessner R, Menges B, Reichert J, Feng X, Räder HJ, Klappenberger F, Rubio A, Müllen K, Barth JV. Photoinduced C–C Reactions on Insulators toward Photolithography of Graphene Nanoarchitectures. J Am Chem Soc 2014; 136:4651-8. [DOI: 10.1021/ja412868w] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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121
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Fischer S, Papageorgiou AC, Lloyd JA, Oh SC, Diller K, Allegretti F, Klappenberger F, Seitsonen AP, Reichert J, Barth JV. Self-assembly and chemical modifications of bisphenol a on Cu(111): interplay between ordering and thermally activated stepwise deprotonation. ACS NANO 2014; 8:207-215. [PMID: 24341488 DOI: 10.1021/nn4030493] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Bisphenol A (BPA) is a chemical widely used in the synthesis pathway of polycarbonates for the production of many daily used products. Besides other adverse health effects, medical studies have shown that BPA can cause DNA hypomethylation and therefore alters the epigenetic code. In the present work, the reactivity and self-assembly of the molecule was investigated under ultra-high-vacuum conditions on a Cu(111) surface. We show that the surface-confined molecule goes through a series of thermally activated chemical transitions. Scanning tunneling microscopy investigations showed multiple distinct molecular arrangements dependent on the temperature treatment and the formation of polymer-like molecular strings for temperatures above 470 K. X-ray photoelectron spectroscopy measurements revealed the stepwise deprotonation of the hydroxy groups, which allows the molecules to interact strongly with the underlying substrate as well as their neighboring molecules and therefore drive the organization into distinct structural arrangements. On the basis of the combined experimental evidence in conjunction with density functional theory calculations, structural models for the self-assemblies after the thermal treatment were elaborated.
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122
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Joshi S, Bischoff F, Koitz R, Ecija D, Seufert K, Seitsonen AP, Hutter J, Diller K, Urgel JI, Sachdev H, Barth JV, Auwärter W. Control of molecular organization and energy level alignment by an electronically nanopatterned boron nitride template. ACS NANO 2014; 8:430-42. [PMID: 24328081 DOI: 10.1021/nn406024m] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Suitable templates to steer the formation of nanostructure arrays on surfaces are indispensable in nanoscience. Recently, atomically thin sp(2)-bonded layers such as graphene or boron nitride (BN) grown on metal supports have attracted considerable interest due to their potential geometric corrugation guiding the positioning of atoms, metallic clusters or molecules. Here, we demonstrate three specific functions of a geometrically smooth, but electronically corrugated, sp(2)/metal interface, namely, BN/Cu(111), qualifying it as a unique nanoscale template. As functional adsorbates we employed free-base porphine (2H-P), a prototype tetrapyrrole compound, and tetracyanoquinodimethane (TCNQ), a well-known electron acceptor. (i) The electronic moirons of the BN/Cu(111) interface trap both 2H-P and TCNQ, steering self-organized growth of arrays with extended molecular assemblies. (ii) We report an effective decoupling of the trapped molecules from the underlying metal support by the BN, which allows for a direct visualization of frontier orbitals by scanning tunneling microscopy (STM). (iii) The lateral molecular positioning in the superstructured surface determines the energetic level alignment; i.e., the energy of the frontier orbitals, and the electronic gap are tunable.
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123
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Cirera B, Zhang YQ, Björk J, Klyatskaya S, Chen Z, Ruben M, Barth JV, Klappenberger F. Synthesis of extended graphdiyne wires by vicinal surface templating. NANO LETTERS 2014; 14:1891-7. [PMID: 24564910 DOI: 10.1021/nl4046747] [Citation(s) in RCA: 118] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Surface-assisted covalent synthesis currently evolves into an important approach for the fabrication of functional nanostructures at interfaces. Here, we employ scanning tunneling microscopy to investigate the homocoupling reaction of linear, terminal alkyne-functionalized polyphenylene building-blocks on noble metal surfaces under ultrahigh vacuum. On the flat Ag(111) surface, thermal activation triggers a variety of side-reactions resulting in irregularly branched polymeric networks. Upon alignment along the step-edges of the Ag(877) vicinal surface drastically improves the chemoselectivity of the linking process permitting the controlled synthesis of extended-graphdiyne wires with lengths reaching 30 nm. The ideal hydrocarbon scaffold is characterized by density functional theory as a 1D, direct band gap semiconductor material with both HOMO and LUMO-derived bands promisingly isolated within the electronic structure. The templating approach should be applicable to related organic precursors and different reaction schemes thus bears general promise for the engineering of novel low-dimensional carbon-based materials.
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124
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Zhang YQ, Öner MA, Lahoz IR, Cirera B, Palma CA, Castro-Fernández S, Míguez-Lago S, Cid MM, Barth JV, Alonso-Gómez JL, Klappenberger F. Morphological self-assembly of enantiopure allenes for upstanding chiral architectures at interfaces. Chem Commun (Camb) 2014; 50:15022-5. [DOI: 10.1039/c4cc06398h] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Upstanding chiral architectures (UCAs) were fabricated from chiroptically active allenes under surface-confined conditions with morphological complementarity being central to the self-assembly process.
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125
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Seufert K, Auwärter W, García de Abajo FJ, Ecija D, Vijayaraghavan S, Joshi S, Barth JV. Controlled interaction of surface quantum-well electronic states. NANO LETTERS 2013; 13:6130-6135. [PMID: 24245663 DOI: 10.1021/nl403459m] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We report on the construction of well-defined surface quantum well arrangements by combining self-assembly protocols and molecular manipulation procedures. After the controlled removal of individual porphyrin molecules from dense-packed arrays on Ag(111), the surface state electrons are confined at the bare silver patches. These act as quantum wells that show well-defined unoccupied bound surface states. Scanning tunneling spectroscopy and complementary boundary element method calculations are performed to characterize the interaction between the bound states of adjacent quantum wells and reveal a hybridization of wave functions resulting in bonding and antibonding states. The interwell coupling can be tuned by the deliberate choice of the molecules acting as potential barriers. The fabrication method is shown to be ideally suited to engineer specific configurations as one-dimensional chains or two-dimensional artificial molecules.
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