Željko Tomović

Publications (6)12.34 Total impact

• Article: On the transfer of cooperative self-assembled π-conjugated fibrils to a gold substrate.

  Martin Wolffs, Mantas Malisauskas, Inge De Cat, Željko Tomović, Jeroen van Herrikhuyzen, Christianus M A Leenders, Evan J Spadafora, Benjamin Grévin, Steven De Feyter, E W Meijer, Albertus P H J Schenning, Philippe Leclère
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  ABSTRACT: The transfer of the cooperative self-assembled fibrils to a gold substrate has been studied by means of scanning probe microscopy techniques revealing the crucial role of the early formation of a monolayer.
  Chemical Communications 09/2011; 47(33):9333-5. · 6.17 Impact Factor
• Article: Insight into the chiral induction in supramolecular stacks through preferential chiral solvation.

  Subi J George, Željko Tomović, Albertus P H J Schenning, E W Meijer
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  ABSTRACT: Preferred handedness in the supramolecular chirality of self-assembled achiral oligo(p-phenylenevinylene) (OPV) derivatives is induced by chiral solvents and spectroscopic probing provides insight into the mechanistic aspects of this chiral induction through chiral solvation.
  Chemical Communications 02/2011; 47(12):3451-3. · 6.17 Impact Factor
• Article: Star-Shaped Oligo(p-phenylenevinylene) Substituted Hexaarylbenzene:  Purity, Stability, and Chiral Self-assembly†

  Željko Tomović, Joost van Dongen, Subi J. George, Hong Xu, Wojciech Pisula, Philippe Leclère, Maarten M. J. Smulders, Steven De Feyter, E. W. Meijer, Albertus P. H. J. Schenning
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  ABSTRACT: An oligo(p-phenylenevinylene) (OPV)-substituted hexaarylbenzene has been synthesized and fully characterized. Recycling gel permeation chromatography appeared to be a powerful technique to obtain the OPV molecules in a very pure form. X-ray analysis and polarization optical microscopy revealed that the OPV molecule is plastic crystalline at room temperature with an ordered columnar superstructure. In apolar solvents, the molecules self-assemble via a highly cooperative fashion into right-handed chiral superstructures, which are stable even at high temperatures and low concentration. Atomic force microscopy revealed right-handed fibers with a diameter of 6 nm, indicating π-stacked aggregates; on a silicon oxide substrate, supercoiled chiral structures were observed. STM studies on a liquid−solid interface showed that the star-shaped OPV molecule forms an organized monolayer having a chiral hexagonal lattice.
  11/2007;
• Article: Helical Packing of Discotic Hexaphenyl Hexa-peri-hexabenzocoronenes:  Theory and Experiment

  Wojciech Pisula, Željko Tomović, Mark D. Watson, Klaus Müllen
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  ABSTRACT: The arrangement of discotic hexa-peri-hexabenzocoronenes (HBCs) into columnar helical superstructures has been investigated in relation to their molecular architecture. The supramolecular structure of two hexaphenyl-substituted HBC derivatives, differing only in the chiral/achiral nature of the attached alkyl side chains, was studied by circular dichroism and temperature-dependent wide-angle X-ray diffraction on oriented filaments. A structural model in agreement with the experimental observations was developed on the basis of accompanying quantum-chemical calculations. The helical organization along the self-assembled columnar structures was induced by the steric requirements of the bulky phenyl rings near the aromatic core, i.e., by their rotation out-of-plane with respect to the aromatic core. On the other hand, a uniform handedness of the twist was generated by chiral alkyl substituents. At higher temperatures the degree of helical organization decreases due to lateral and longitudinal dynamics of the discotic molecules. Annealing at ambient conditions improved the long-range arrangement of the discs along the columnar structures. This reorganization indicated a self-healing of the plastic material which is desirable for application of discotics as active layers in electronic devices. The helical packing resulted in a considerable stability of the mesophase up to 500 °C, which has not been reported for a discotic so far.
  06/2007;
• Article: Columnare Flüssigkristalle auf Superphenalen‐Basis

  Željko Tomović, Mark D. Watson, Klaus Müllen
  Angewandte Chemie 01/2004; 116(6):773 - 777.
• Article: High Anisotropy of the Field-Effect Transistor Mobility in Magnetically Aligned Discotic Liquid-Crystalline Semiconductors

  Igor O Shklyarevskiy, Pascal Jonkheijm, Natalie Stutzmann, Dorothee Wasserberg, Harry J Wondergem, Peter C M Christianen, Albertus P H J Schenning, Dago M. de Leeuw, Željko Tomović, Jishan Wu, Klaus Müllen, Jan C Maan
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  ABSTRACT: A magnetic field has been utilized for producing highly oriented films of a substituted hexabenzocoronene (HBC). Optical microscopy studies revealed large area HBC monodomains that covered the entire film, while wide-angle X-ray measurements showed that the HBC molecules are aligned with their planes along the applied field. On the basis of this method, solution-processed field-effect transistors (FET) have been constructed with charge carrier mobilities of up to 10-3 cm2/V·s, which are significantly enhanced with respect to the unaligned material. Exceptionally high mobility anisotropies of 25-75 for current flow parallel and perpendicular to the alignment direction have been measured as a function of the channel length. Atomic force microscopy performed on the FET structures reveals fibril superstructures that are oriented perpendicularly to the magnetic field direction, consisting of molecular columns with a slippage angle of 40° between the molecules. For channel lengths larger than 2.5 μm, the fibrils are smaller than the electrode spacing, which adversely affects the device performance.