Markus Lackinger

Technische Universität München, München, Bavaria, Germany

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Publications (54)304.68 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Ullmann coupling of 1,3-diiodobenzene is studied on Cu(111) surfaces in ultra-high vacuum (UHV). In situ Scanning Tunneling Microscopy (STM) at room temperature revealed an unexpected ordered arrangement of highly uniform reaction products adsorbed atop a closed iodine monolayer.
    Chemical Communications 07/2015; 51:13301. DOI:10.1039/c5cc04453g · 6.83 Impact Factor
  • Markus Lackinger
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    ABSTRACT: Two-dimensional (2D) polymers are novel covalent sheet materials with promising properties, but also great synthetic challenges. The inadequacy of traditional wet chemical synthesis calls for new synthetic paradigms. In this respect, employing surfaces as inherently two-dimensional reaction venues appears as adequate choice and has recently already yielded encouraging results. Polymerization at air-liquid and liquid-liquid interfaces has been reported from time to time over the last decades, whereas recent efforts on solid surfaces are less traditional. In either case, both movement and coupling of monomers at interfaces or on surfaces are already confined in two dimensions. Accordingly, this approach naturally affords low-dimensional reaction products. To achieve two-dimensional reticulation, monomers are functionalized with multiple reactive groups of the same or different kind, whereby their number and stereochemical arrangement predefines the ideal structure of the resulting 2D polymer. This perspective article exemplifies different approaches, i.e. types of surfaces, coupling chemistry, and activation schemes to employ surfaces for novel synthetic routes for the bottom-up synthesis of 2D polymers.
    Polymer International 05/2015; 64(9). DOI:10.1002/pi.4943 · 2.41 Impact Factor
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    ABSTRACT: We present the synthesis of a two-dimensional polymer at the air/water interface and its nm-resolution imaging. Trigonal star, amphiphilic monomers bearing three anthraceno groups on a central triptycene core are confined at the air/water interface. Compression followed by photopolymerization on the interface provides the two-dimensional polymer. Analysis by scanning tunneling microscopy suggests that the polymer is periodic with ultra-high pore density.
    Journal of the American Chemical Society 02/2015; 137(10). DOI:10.1021/ja512018j · 12.11 Impact Factor
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    ABSTRACT: We demonstrate here that supramolecular interactions enhance the sensitivity towards detection of electron-deficient nitro-aromatic compounds (NACs) over discrete analogues. NACs are the most commonly used explosive ingredients and are common constituents of many unexploded landmines used during World War II. In this study, we have synthesised a series of pyrene-based polycarboxylic acids along with their corresponding discrete esters. Due to the electron richness and the fluorescent behaviour of the pyrene moiety, all the compounds act as sensors for electron-deficient NACs through a fluorescence quenching mechanism. A Stern–Volmer quenching constant determination revealed that the carboxylic acids are more sensitive than the corresponding esters towards NACs in solution. The high sensitivity of the acids was attributed to supramolecular polymer formation through hydrogen bonding in the case of the acids, and the enhancement mechanism is based on an exciton energy migration upon excitation along the hydrogen-bond backbone. The presence of intermolecular hydrogen bonding in the acids in solution was established by solvent-dependent fluorescence studies and dynamic light scattering (DLS) experiments. In addition, the importance of intermolecular hydrogen bonds in solid-state sensing was further explored by scanning tunnelling microscopy (STM) experiments at the liquid–solid interface, in which structures of self-assembled monolayer of the acids and the corresponding esters were compared. The sensitivity tests revealed that these supramolecular sensors can even detect picric acid and trinitrotoluene in solution at levels as low as parts per trillion (ppt), which is much below the recommended permissible level of these constituents in drinking water.
    Chemistry - A European Journal 10/2014; 20(42). DOI:10.1002/chem.201403345 · 5.73 Impact Factor
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    ABSTRACT: Monolayer self-assembly of a hexabrominated, three-fold symmetric aromatic molecule is studied at the heptanoic acid – graphite interface. Thermodynamical insights are obtained from an adapted Born-Haber cycle that is utilized to derive the overall enthalpy change including solvent effects. Comparison with theoretical entropy estimates suggests a minor influence of solvation.
    Chemical Communications 09/2014; 50(88). DOI:10.1039/C4CC06251E · 6.83 Impact Factor
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    ABSTRACT: On-surface Ullmann coupling is a versatile and appropriate approach for the bottom-up fabrication of covalent organic nanostructures. In two-dimensional networks, however, the kinetically controlled and irreversible coupling leads to high defect densities and a lack of long-range order. To derive general guidelines for optimizing reaction parameters, the structural quality of 2D porous covalent networks was evaluated for different preparation protocols. For this purpose, polymerization of an iodine and bromine functionalized monomer was studied on Au(111) by Scanning Tunneling Microscopy under ultra-high vacuum conditions. By taking advantage of the vastly different temperature thresholds for C-Br and C-I cleavage two different polymerization routes were compared - hierarchical and direct polymerization. The structural quality of the covalent networks was evaluated for different reaction parameters, such as surface temperatures, heating rates, and deposition rates by statistical analysis of STM data. Experimental results are compared to Monte Carlo simulations.
    ACS Nano 07/2014; 8(8). DOI:10.1021/nn501567p · 12.88 Impact Factor
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    ABSTRACT: The role of organometallic intermediates during on-surface polymerization via Ullmann coupling was studied on Ag(111). The polymerization progress was monitored by X-ray photoelectron spectroscopy (XPS). Scanning Tunneling Microscopy (STM) was used to characterize organometallic and covalent networks and to identify the temperature regimes for organometallic and covalent bond formation.
    Chemical Communications 06/2014; 50(57). DOI:10.1039/c4cc02757d · 6.83 Impact Factor
  • W Song · N Martsinovich · W M Heckl · M Lackinger
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    ABSTRACT: A direct calorimetric measurement of the overall enthalpy change associated with self-assembly of organic monolayers at the liquid-solid interface is for most systems of interest practically impossible. In previous work we proposed an adapted Born-Haber cycle for an indirect assessment of the overall enthalpy change by using terephthalic acid monolayers at the nonanoic acid-graphite interface as a model system. To this end, the sublimation enthalpy, dissolution enthalpy, the monolayer binding enthalpy in vacuum, and a dewetting enthalpy are combined to yield the total enthalpy change. In the present study the Born-Haber cycle is applied to 4,4'-stilbenedicarboxylic acid monolayers. A detailed comparison of these two aromatic dicarboxylic acids is used to evaluate and quantify the contribution of the organic backbone for stabilization of the monolayer at the nonanoic acid-graphite interface.
    Physical Chemistry Chemical Physics 05/2014; 16(26). DOI:10.1039/c4cp01147c · 4.49 Impact Factor
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    ABSTRACT: Self-assembly and thermally activated surface chemistry of 1,3,5-benzenetrithiol (BTT) on Cu(111) are studied under ultrahigh vacuum (UHV) conditions by different complementary surface sensitive techniques. Low-energy electron diffraction (LEED) patterns acquired at room temperature and during subsequent heating reveal irreversible phase transitions between in total four different long-range-ordered phases termed α-phase to δ-phase. X-ray photoelectron spectroscopy (XPS) of the different phases facilitates the identification of major chemical changes for the first phase transition from α- to β-phase, whereas in the succeeding phase transitions, no significant chemical shifts are observed anymore. The structural characterization of each phase is carried out by high-resolution scanning tunneling microscopy (STM), and adsorption geometries of the phenyl rings are derived from C 1s near-edge X-ray absorption fine structure (NEXAFS). The combination of the results from this array of experimental techniques leads to a consistent picture of the various phases and underlying processes. Upon room-temperature deposition, BTT fully deprotonates and planar-adsorbed molecules self-assemble into an ordered monolayer. With a temperature onset of 300 K, the carbon–sulfur bonds start dissociating. Sulfur forms a copper sulfide superstructure, whereas the organic remainders form disordered structures. Further heating converts an initial metastable and rarely observed (√3 × √3)R ± 30° copper sulfide superstructure into the more stable and well-known (√7 × √7)R ± 19.1° polymorph.
    The Journal of Physical Chemistry C 02/2014; 118(7):3590–3598. DOI:10.1021/jp411084k · 4.77 Impact Factor
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    ABSTRACT: The driving force for self-assembly is the associated gain in free energy with decisive contributions from both enthalpy and entropy differences between final and initial state. For monolayer self-assembly at the liquid-solid interface, solute molecules are initially dissolved in the liquid phase and become then incorporated into an adsorbed monolayer. In this work we present an adapted Born-Haber cycle for obtaining precise enthalpy values for self-assembly at the liquid-solid interface, a key ingredient for a profound thermodynamic understanding of this process. By choosing terephthalic acid as a model system, it is demonstrated that all required enthalpy differences between well-defined reference states can be independently and consistently assessed by both experimental and theoretical methods, giving in the end a reliable value of the overall enthalpy gain for self-assembly of interfacial monolayers. A quantitative comparison of enthalpy gain and entropy cost reveals essential contributions from solvation and dewetting, which lowers the entropic cost and render monolayer self-assembly a thermodynamically favored process.
    Journal of the American Chemical Society 09/2013; 135(39). DOI:10.1021/ja407698t · 12.11 Impact Factor
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    ABSTRACT: Self-assembly of 1,3,5-tris(4'-biphenyl-4''-carbonitrile)benzene monolayers was studied at the liquid-solid interface by scanning tunneling microscopy. Application of different fatty acid homologues as solvents revealed a solvent-induced polymorphism. Yet, tempering triggered irreversible phase transitions of the initially self-assembled monolayers, thereby indicating their metastability. Interestingly, in either case the same, thermodynamically more stable and more densely packed monolayer polymorph is obtained after the thermal treatment, irrespective of the initial structure. Again the same densely packed structure was obtained in complementary solvent-free experiments conducted under ultra-high vacuum conditions. Thus, self-assembly of metastable polymorphs at room temperature is explained by adsorption of partially solvated species under kinetic control. The irreversible phase transitions are induced by thermal desolvation, i.e. desorption of co-adsorbed solvent molecules.
    ACS Nano 07/2013; 7(8). DOI:10.1021/nn4014577 · 12.88 Impact Factor
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    ABSTRACT: The adsorption geometry of 1,3,5-tris(4-mercaptophenyl)benzene (TMB) on Cu(111) is determined with high precision using two independent methods, experimentally by quantitative low energy electron diffraction (LEED-I(V)) and theoretically by dispersion corrected density functional theory (DFT-vdW). Structural refinement using both methods consistently results in similar adsorption sites and geometries. Thereby a level of confidence is reached that allows deduction of subtle structural details such as molecular deformations or relaxations of copper substrate atoms.
    Physical Chemistry Chemical Physics 05/2013; 15(26). DOI:10.1039/c3cp50752a · 4.49 Impact Factor
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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; 7(4). DOI:10.1021/nn400337v · 12.88 Impact Factor
  • 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; 49(28). DOI:10.1039/c3cc40444g · 6.83 Impact Factor
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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; 135(2). DOI:10.1021/ja306834a · 12.11 Impact Factor
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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. DOI:10.1021/nn302363d · 12.88 Impact Factor
  • Stefan Schlögl · Wolfgang M. Heckl · Markus Lackinger
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    ABSTRACT: In the present study on-surface polymerisation of aromatic iodinated precursor molecules through radical addition is studied by scanning tunneling microscopy (STM) on Au(111) under ultra-high vacuum (UHV) conditions. Comparison of the two analogous monomers s-triiodobenzene and s-triiodophenylbenzene with similar symmetry and functionalization but differently sized organic backbones aimed to study the influence of monomer size on the morphology of resulting covalent networks. In contrast to previous studies on brominated monomers, here the reaction by-product, i.e., the split-off iodine atoms, was found to adsorb stably on Au(111) in ordered structures. The influence of post-processing by thermal annealing on both the covalent networks and the iodine structures was studied for different temperatures. DFT calculations were applied to evaluate formation energies of commonly observed topological defects and related to their experimental probability of occurrence.
    Surface Science 07/2012; 606(s 13–14):999–1004. DOI:10.1016/j.susc.2012.02.011 · 1.93 Impact Factor
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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. DOI:10.1021/nn2032616 · 12.88 Impact Factor
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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. DOI:10.1039/c1cc13896k · 6.83 Impact Factor

Publication Stats

2k Citations
304.68 Total Impact Points


  • 2008–2015
    • Technische Universität München
      München, Bavaria, Germany
  • 2012–2013
    • Deutsches Museum
      München, Bavaria, Germany
  • 2004–2013
    • Ludwig-Maximilian-University of Munich
      • Department of Earth and Environmental Sciences (Geophysics)
      München, Bavaria, Germany
  • 2002–2006
    • Technische Universität Chemnitz
      • Institute of Physics
      Karl-Marx-Stadt, Saxony, Germany
  • 2005
    • University of California, Irvine
      Irvine, California, United States
    • Columbia University
      • Department of Chemistry
      New York, New York, United States