Markus Lackinger

Publications (33)150.07 Total impact

• Article: Solution Preparation of Two Dimensional Covalently Linked Networks by Polymerization of 1,3,5-Tri(4-iodophenyl)benzene on Au(111).

  Georg Eder, Emily F Smith, Izabela Cebula, Wolfgang M Heckl, Peter Beton, Markus Lackinger
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  ABSTRACT: The polymerization of 1,3,5-tri(4-iodophenyl)benzene (TIPB) on Au(111) through covalent aryl-aryl coupling is accomplished using a solution-based approach and investigated by scanning tunneling microscopy. Drop-casting of the TIPB monomer onto Au(111) at room temperature results in poorly ordered non-covalent arrangements of molecules and partial de-halogenation. However, drop-casting on a pre-heated Au(111) substrate yields various topologically distinct covalent aggregates and networks. Interestingly, some of these covalent nanostructures do not adsorb directly on the Au(111) surface, but are loosely bound to a disordered layer of a mixture of chemisorbed iodine and molecules, a conclusion which is drawn from STM data and supported by X-ray photoelectron spectroscopy. We argue that the gold surface becomes covered by a strongly chemisorbed iodine monolayer which eventually inhibits further polymerization.
  ACS Nano 03/2013; · 10.77 Impact Factor
• Article: On-surface polymerization of 1,4-diethynylbenzene on Cu(111).

  Johanna Eichhorn, Wolfgang M Heckl, Markus Lackinger
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  ABSTRACT: The polymerization of 1,4-diethynylbenzene was studied on a Cu(111) surface using scanning tunneling microscopy (STM) under ultra-high vacuum conditions. Thermal activation yielded disordered covalent networks, where distinct basic structural motifs indicate different coupling reactions.
  Chemical Communications 03/2013; · 6.17 Impact Factor
• Source

  Available from: Subhadip Neogi

  Article: Control of Intermolecular Bonds by Deposition Rates at Room Temperature: Hydrogen Bonds vs. Metal-Coordination in Trinitrile Monolayers.

  Thomas Sirtl, Stefan Schlögl, Atena Rastgoo-Lahrood, Jelina Jelic, Subhadip Neogi, Michael Schmittel, Wolfgang M Heckl, Karsten Reuter, Markus Lackinger
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  ABSTRACT: Self-assembled monolayers of 1,3,5-tris(4'-biphenyl-4''-carbonitrile)-benzene - a large functional trinitrile molecule - are studied on the (111) surfaces of copper and silver under ultra-high vacuum conditions by scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). A densely packed hydrogen bonded polymorph was equally observed on both surfaces. Addi-tionally, deposition onto Cu(111) yielded a well-ordered metal-coordinated porous polymorph that coexisted with the hydrogen bonded structure. The required coordination centers are supplied by the adatom gas of the Cu(111) surface. On Ag(111), however, the well-ordered metal-coordinated network was never observed. Differences in the adatom reactivity between copper and silver and the resulting bond strength of the respective coordination bond are held responsible for this substrate dependence. By utilizing ultra-low deposition rates, we demonstrate that on Cu(111) adatom kinetics plays a decisive role in the expression of intermolecular bonds - and hence for structure selection.
  Journal of the American Chemical Society 12/2012; · 9.91 Impact Factor
• Article: Isoreticular two-dimensional covalent organic frameworks synthesized by on-surface condensation of diboronic acids.

  Jürgen F Dienstmaier, Dana D Medina, Mirjam Dogru, Paul Knochel, Thomas Bein, Wolfgang M Heckl, Markus Lackinger
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  ABSTRACT: On-surface self-condensation of 1,4-benzenediboronic acid was previously shown to yield extended surface-supported, long-range-ordered two-dimensional covalent organic frameworks (2D COFs). The most important prerequisite for obtaining high structural quality is that the polycondensation (dehydration) reaction is carried out under slightly reversible reaction conditions, i.e., in the presence of water. Only then can the subtle balance between kinetic and thermodynamic control of the polycondensation be favorably influenced, and defects that are unavoidable during growth can be corrected. In the present study we extend the previously developed straightforward preparation protocol to a variety of para-diboronic acid building blocks with the aim to tune lattice parameters and pore sizes of 2D COFs. Scanning tunneling microscopy is employed for structural characterization of the covalent networks and of noncovalently self-assembled structures that form on the surface prior to the thermally activated polycondensation reaction.
  ACS Nano 07/2012; 6(8):7234-42. · 10.77 Impact Factor
• Article: Synthesis of well-ordered COF monolayers: surface growth of nanocrystalline precursors versus direct on-surface polycondensation.

  Jürgen F Dienstmaier, Alexander M Gigler, Andreas J Goetz, Paul Knochel, Thomas Bein, Andrey Lyapin, Stefan Reichlmaier, Wolfgang M Heckl, Markus Lackinger
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  ABSTRACT: Two different straightforward synthetic approaches are presented to fabricate long-range-ordered monolayers of a covalent organic framework (COF) on an inert, catalytically inactive graphite surface. Boronic acid condensation (dehydration) is employed as the polymerization reaction. In the first approach, the monomer is prepolymerized by a mere thermal treatment into nanocrystalline precursor COFs. The precursors are then deposited by drop-casting onto a graphite substrate and characterized by scanning tunneling microscopy (STM). While in the precursors monomers are already covalently interlinked into the final COF structure, the resulting domain size is still rather small. We show that a thermal treatment under reversible reaction conditions facilitates on-surface ripening associated with a striking increase of the domain size. Although this first approach allows studying different stages of the polymerization, the direct polymerization, that is, without the necessity of preceding reaction steps, is desirable. We demonstrate that even for a comparatively small diboronic acid monomer a direct thermally activated polymerization into extended COF monolayers is achievable.
  ACS Nano 12/2011; 5(12):9737-45. · 10.77 Impact Factor
• Article: Synthesis of two-dimensional phenylene-boroxine networks through in vacuo condensation and on-surface radical addition.

  Stefan Schlögl, Thomas Sirtl, Johanna Eichhorn, Wolfgang M Heckl, Markus Lackinger
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  ABSTRACT: We report on covalent two-dimensional phenylene-boroxine hybrid-networks that were synthesized under ultra-high vacuum conditions from doubly functionalized monomers through thermally activated condensation prior to deposition and successive heterogeneously catalyzed radical addition on Ag(111). Structural properties were characterized in situ by high resolution Scanning-Tunneling-Microscopy (STM).
  Chemical Communications 12/2011; 47(45):12355-7. · 6.17 Impact Factor
• Article: Incorporation dynamics of molecular guests into two-dimensional supramolecular host networks at the liquid-solid interface.

  Georg Eder, Stephan Kloft, Natalia Martsinovich, Kingsuk Mahata, Michael Schmittel, Wolfgang M Heckl, Markus Lackinger
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  ABSTRACT: The objective of this work is to study both the dynamics and mechanisms of guest incorporation into the pores of 2D supramolecular host networks at the liquid-solid interface. This was accomplished by adding molecular guests to prefabricated self-assembled porous monolayers and the simultaneous acquisition of scanning tunneling microscopy (STM) topographs. The incorporation of the same guest molecule (coronene) into two different host networks was compared, where the pores of the networks either featured a perfect geometric match with the guest (for trimesic acid host networks) or were substantially larger than the guest species (for benzenetribenzoic acid host networks). Even the moderate temporal resolution of standard STM experiments in combination with a novel injection system was sufficient to reveal clear differences in the incorporation dynamics in the two different host networks. Further experiments were aimed at identifying a possible solvent influence. The interpretation of the results is aided by molecular mechanics (MM) and molecular dynamics (MD) simulations.
  Langmuir 09/2011; 27(22):13563-71. · 4.19 Impact Factor
• Article: Extended two-dimensional metal-organic frameworks based on thiolate-copper coordination bonds.

  Hermann Walch, Jürgen Dienstmaier, Georg Eder, Rico Gutzler, Stefan Schlögl, Thomas Sirtl, Kalpataru Das, Michael Schmittel, Markus Lackinger
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  ABSTRACT: Self-assembly and surface-mediated reactions of 1,3,5-tris(4-mercaptophenyl)benzene--a three-fold symmetric aromatic trithiol--are studied on Cu(111) by means of scanning tunneling microscopy (STM) under ultrahigh-vacuum (UHV) conditions. In order to reveal the nature of intermolecular bonds and to understand the specific role of the substrate for their formation, these studies were extended to Ag(111). Room-temperature deposition onto either substrate yields densely packed trigonal structures with similar appearance and lattice parameters. Yet, thermal annealing reveals distinct differences between both substrates: on Cu(111) moderate annealing temperatures (~150 °C) already drive the emergence of two different porous networks, whereas on Ag(111) higher annealing temperatures (up to ~300 °C) were required to induce structural changes. In the latter case only disordered structures with characteristic dimers were observed. These differences are rationalized by the contribution of the adatom gas on Cu(111) to the formation of metal-coordination bonds. Density functional theory (DFT) methods were applied to identify intermolecular bonds in both cases by means of their bond distances and geometries.
  Journal of the American Chemical Society 05/2011; 133(20):7909-15. · 9.91 Impact Factor
• Article: A combined ion-sputtering and electron-beam annealing device for the in vacuo postpreparation of scanning probes

  Georg Eder, Stefan Schlogl, Klaus Macknapp, Wolfgang M. Heckl, Markus Lackinger
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  ABSTRACT: We describe the setup, characteristics, and application of an in vacuo ion-sputtering and electron-beam annealing device for the postpreparation of scanning probes (e.g., scanning tunneling microscopy (STM) tips) under ultrahigh vacuum (UHV) conditions. The proposed device facilitates the straightforward implementation of a common two-step cleaning procedure, where the first step consists of ion-sputtering, while the second step heals out sputtering-induced defects by thermal annealing. In contrast to the standard way, no dedicated external ion-sputtering gun is required with the proposed device. The performance of the described device is demonstrated by SEM micrographs and energy dispersive x-ray characterization of electrochemically etched tungsten tips prior and after postprocessing.
  Review of Scientific Instruments 04/2011; · 1.37 Impact Factor
• Article: Material- and Orientation-Dependent Reactivity for Heterogeneously Catalyzed Carbon−Bromine Bond Homolysis

  Hermann Walch, Rico Gutzler, Thomas Sirtl, Georg Eder, Markus Lackinger
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  ABSTRACT: Adsorption of the brominated aromatic molecule 1,3,5-tris(4-bromophenyl)benzene on different metallic substrates, namely Cu(111), Ag(111), and Ag(110), has been studied by variable-temperature scanning tunneling microscopy (STM). Depending on substrate temperature, material, and crystallographic orientation, a surface-catalyzed dehalogenation reaction is observed. Deposition onto the catalytically more active substrates Cu(111) and Ag(110) held at room temperature leads to cleavage of carbon−bromine bonds and subsequent formation of protopolymers, i.e., radical metal coordination complexes and networks. However, upon deposition on Ag(111) no such reaction has been observed. Instead, various self-assembled ordered structures emerged, all based on intact molecules. Also sublimation onto either substrate held at 80 K did not result in any dehalogenation, thereby exemplifying the necessity of thermal activation. The observed differences in catalytic activity are explained by a combination of electronic and geometric effects. A mechanism is proposed, where initial charge transfer from substrate to adsorbate, followed by subsequent intramolecular charge transfer, facilitates C−Br bond homolysis.
  07/2010;
• Article: On the scalability of supramolecular networks--high packing density vs optimized hydrogen bonds in tricarboxylic acid monolayers.

  Jürgen F Dienstmaier, Kingsuk Mahata, Hermann Walch, Wolfgang M Heckl, Michael Schmittel, Markus Lackinger
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  ABSTRACT: We present a scanning tunneling microscopy (STM) based study of 1,3,5-tris[4'-carboxy(1,1'-biphenyl-4-yl)]benzene (TCBPB) monolayers at the liquid-solid interface. In analogy to smaller aromatic 3-fold symmetric tricarboxylic acids, this compound was aimed to yield two-dimensional nanoporous networks with large cavities. Depending on the solute concentration, three crystallographically distinct phases with pores of different size and shape were observed on graphite (001) with heptanoic acid as solvent. All three phases have the same dimer motif as basic building block in common. Yet, as opposed to other carboxylic acid assemblies, these dimers are not interconnected by 2-fold O-H...O hydrogen bonds as anticipated, but by two energetically inferior C-H...O hydrogen bonds. Instead of the common head-to-head arrangement, this bonding pattern results in displaced dimers, which allow for higher packing density, and due to their lower symmetry give rise to chiral polymorphs. In accordance with studies of comparable systems, a positive correlation between solute concentration and average surface packing density is identified and rationalized by thermodynamic arguments.
  Langmuir 07/2010; 26(13):10708-16. · 4.19 Impact Factor
• Article: Reversible phase transitions in self-assembled monolayers at the liquid-solid interface: temperature-controlled opening and closing of nanopores.

  Rico Gutzler, Thomas Sirtl, Jürgen F Dienstmaier, Kingsuk Mahata, Wolfgang M Heckl, Michael Schmittel, Markus Lackinger
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  ABSTRACT: We present a variable-temperature study of monolayer self-assembly at the liquid-solid interface. By means of in situ scanning tunneling microscopy (STM), reversible phase transitions from a nanoporous low-temperature phase to a more densely packed high-temperature phase are observed. The occurrence of the phase transition and the respective transition temperature were found to depend on the type of solvent and solute concentration. Estimates of the entropic cost and enthalpic gain upon monolayer self-assembly suggest that coadsorption of solvent molecules within the cavities of the nanoporous structure renders this polymorph thermodynamically stable at low temperatures. At elevated temperatures, however, desorption of these relatively weakly bound solvent molecules destabilizes the nanoporous polymorph, and the densely packed polymorph becomes thermodynamically favored. Interestingly, the structural phase transition provides external control over the monolayer morphology and, for the system under discussion, results in an effective opening and closing of supramolecular nanopores in a two-dimensional molecular monolayer.
  Journal of the American Chemical Society 03/2010; 132(14):5084-90. · 9.91 Impact Factor
• Article: Influence of Solvophobic Effects on Self-Assembly of Trimesic Acid at the Liquid−Solid Interface

  Nguyen T. N. Ha, Thiruvancheril G. Gopakumar, Rico Gutzler, Markus Lackinger, Hao Tang, Michael Hietschold
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  ABSTRACT: Despite the multitude of surface supported monolayer structures already reported for trimesic acid (TMA), new self-assembled structures are still discovered, depending on conditions and environment. This exemplifies the versatility of this archetypical supramolecular building block and justifies its role as a model system. At the interface between 1-phenyloctane (PO), a highly nonpolar solvent, and graphite, a new densely packed and partly hydrogen-bonded TMA structure is observed by means of scanning tunneling microscopy (STM). Normally, the TMA solubility in PO is too low to allow for self-assembly of interfacial monolayers. However, as verified by UV−vis spectroscopy, sonication of solutions with TMA sediment increases the amount of dissolved solute molecules. Consequently, the self-assembly of interfacial monolayers can be observed with these enriched solutions. In contrast to many other structures reported, the observed monolayers are densely packed and composed of partly hydrogen-bonded TMA molecules that form zigzag chains. The proposed structural model is derived from semiempirical quantum chemistry methods, which also provide the basis for STM image simulations by means of a scattering formalism. Solvophobic effects are likely to account for both, low TMA solubility in PO and the high packing density of the interfacial monolayer.
  02/2010;
• Article: Combination of a Knudsen effusion cell with a quartz crystal microbalance: in situ measurement of molecular evaporation rates with a fully functional deposition source.

  Rico Gutzler, Wolfgang M Heckl, Markus Lackinger
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  ABSTRACT: We describe a straightforward, reliable, and inexpensive design of a Knudsen type molecular effusion cell capable of measuring molecular evaporation rates in situ. This is accomplished by means of a quartz crystal microbalance integrated into the shutter of the effusion cell. The presented layout facilitates both the measurement of effusion rates under ultrahigh vacuum conditions without the need for a separate experimental setup and the growth of surface supported molecular layers and nanostructures. As an important prerequisite for reproducible deposition of molecular films with defined coverages ranging from submonolayers up to multilayers, the Knudsen cell features a stable deposition rate for crucible temperatures between 50 and 500 degrees C. Experimental determination of deposition rates for different crucible temperatures allows to approximate sublimation enthalpies of the evaporant based on the Clausius-Clapeyron equation.
  The Review of scientific instruments 01/2010; 81(1):015108. · 1.52 Impact Factor
• Article: Surface mediated synthesis of 2D covalent organic frameworks: 1,3,5-tris(4-bromophenyl)benzene on graphite(001), Cu(111), and Ag(110).

  Rico Gutzler, Hermann Walch, Georg Eder, Stephan Kloft, Wolfgang M Heckl, Markus Lackinger
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  ABSTRACT: The on surface synthesis of a two-dimensional (2D) covalent organic framework from a halogenated aromatic monomer under ultra-high vacuum conditions is shown to be dependent on the choice of substrate.
  Chemical Communications 09/2009; · 6.17 Impact Factor
• Article: Carboxylic acids: versatile building blocks and mediators for two-dimensional supramolecular self-assembly.

  Markus Lackinger, Wolfgang M Heckl
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  ABSTRACT: Two-dimensional (2D) supramolecular self-assembly of various organic molecules at the liquid-solid interface is presented and discussed with a focus on compounds that are primarily functionalized by carboxylic groups. The main analytical tool utilized is scanning tunneling microscopy (STM), a high-resolution real-space technique capable of readily providing full crystallographic information (i.e., not only lattice parameters but also number, type, and orientation of molecules within the unit cell). Carboxylic groups are of particular interest because their combined donor and acceptor character with regard to hydrogen bonds provides reliable intermolecular cross-linking, thereby facilitating the self-assembly of well-ordered, stable monolayers. By means of various homomeric (monomolecular) and heteromeric (here, bimolecular) examples, this feature article illustrates the influence of both molecular structure and external conditions (type of solvent, concentration, etc.) on monolayer self-assembly at the liquid-solid interface. A very intriguing aspect of interfacial self-assembly is that many systems are thermodynamically controlled (i.e., adsorbed molecules at the surface are in equilibrium with molecules dissolved in the supernatant liquid phase). This offers the unique possibility not only to steer the system reliably by intensive thermodynamic parameters such as temperature and concentration but also to gain fundamental knowledge about decisive processes and steps in supramolecular self-assembly.
  Langmuir 06/2009; 25(19):11307-21. · 4.19 Impact Factor
• Article: Aromatic interaction vs. hydrogen bonding in self-assembly at the liquid-solid interface.

  Rico Gutzler, Sophie Lappe, Kingsuk Mahata, Michael Schmittel, Wolfgang M Heckl, Markus Lackinger
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  ABSTRACT: Interfacial self-assembly of specific monolayer structures from solution on a graphite surface can be steered by tuning the interplay between solute-solute and solute-solvent interactions.
  Chemical Communications 03/2009; · 6.17 Impact Factor
• Source

  Available from: nano-science.de

  Article: Distinct differences in self-assembly of aromatic linear dicarboxylic acids.

  Christoph Heininger, Lorenz Kampschulte, Wolfgang M Heckl, Markus Lackinger
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  ABSTRACT: Self-assembly into two-dimensionally ordered supramolecular structures of three aromatic dicarboxylic acids-2,6-naphthalenedicarboxylic acid (NDA), 4,4'-biphenyldicarboxylic acid (BPDA), and 4,4'-stilbenedicarboxylic acid (SDA)-is studied at the liquid-solid interface by scanning tunneling microscopy. All compounds possess structural similarities, namely, two interconnected aromatic moieties and functionalization through two carboxylic groups in linear configuration. For all molecules, ordered monolayers were observed on a graphite substrate, and the resulting structures can be described as a dense packing of one-dimensionally hydrogen-bonded rows. However, concerning the stability of the adsorbate layers, the average domain size, and the degree of order, distinct differences were noticed. Supported by density functional theory (DFT) calculations, these differences are analyzed and explained as a consequence of molecular structure, adsorption geometry, and adsorption energy.
  Langmuir 01/2009; 25(2):968-72. · 4.19 Impact Factor
• Article: Isotopological Supramolecular Networks from Melamine and Fatty Acids

  Hermann Walch, Anne-Kathrin Maier, Wolfgang M. Heckl, Markus Lackinger
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  ABSTRACT: The formation of bimolecular isotopological monolayers comprised of melamine and members of the homologous series of fatty acids extending from pentanoic through tridecanoic acid was studied at the liquid−graphite interface by scanning tunneling microscopy. In these systems, the fatty acids not only serve as solvents, i.e., provider and transport medium for solute molecules, but are also a structure determining part of the self-assembled monolayers. For all solvents, hexagonal structures were observed where the lattice parameter increases linearly with the chain length of the fatty acid from 2.8 nm for pentanoic acid to 4.1 nm for tridecanoic acid. All bimolecular networks exhibit the same topology: the basic unit consists of a melamine hexamer which is stabilized by internal N···H−N hydrogen bonds and surrounded by 12 radially arranged fatty acid molecules. The p6 symmetry of the monolayer originates from the melamine core, whereas the lattice parameter is determined by the aliphatic chain length of the fatty acid. For a deeper insight into the relative energetics, all experimentally observed structures were simulated by force-field calculations
  12/2008;
• Source

  Available from: nano-science.de

  Article: Thermodynamical equilibrium of binary supramolecular networks at the liquid-solid interface.

  Lorenz Kampschulte, Tova L Werblowsky, Ravuri S K Kishore, Michael Schmittel, Wolfgang M Heckl, Markus Lackinger
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  ABSTRACT: Coadsorption of two different carboxylic acids, benzenetribenzoic acid and trimesic acid, was studied at the liquid-solid interface in two different solvents (heptanoic and nonanoic acid). Independent alteration of both concentrations in binary solutions resulted in six nondensely packed monolayer phases with different structures and stoichiometries, as revealed by means of scanning tunneling microscopy (STM). All of these structures are stabilized by intermolecular hydrogen bonding between the carboxylic acid functional groups. Moreover, phase transitions of the monolayer structures, accompanied by an alteration of the size and shape of cavity voids in the 2D molecular assembly, could be achieved by in situ dilution. The emergence of the various phases could be described by a simple thermodynamic model.
  Journal of the American Chemical Society 08/2008; 130(26):8502-7. · 9.91 Impact Factor