Regensburg 2010 – wissenschaftliches Programm
O 6.3: Vortrag
Montag, 22. März 2010, 11:45–12:00, H36
Alkali-Crown Ether Complexes at Metal Surfaces — •Nicha Thontasen1, Giacomo Levita2, Zhitao Deng1, Nikola Malinowski1, 3, Stephan Rauschenbach1, and Klaus Kern1, 4 — 1Max Planck Institute for Solid State Research, Stuttgart, Germany — 2University of Trieste, Trieste, Italy — 3Bulgarian Academy of Sciences, Sofia, Bulgaria — 4EPFL, Lausanne, Switzerland
Crown ethers are polycyclic ethers which, in solution, selectively bind cations depending on the size of the ring cavity. The study of a single host-guest complex is highly desirable in order to reveal the characteristics of these specific interactions at the atomic scale. Such detailed investigation is possible at the surface where high resolution imaging tools like scanning tunneling microscopy (STM) can be applied.
Here, electrospray ion beam deposition (ES-IBD) is employed for the deposition of Dibenzo-24-crown-8 (DB24C8)-H+, -Na+ and -Cs+ complexes on a solid surface in ultrahigh vacuum (UHV). Where other deposition techniques have not been successful, this deposition technique combines the advantages of solution based preparation of the complex ions with a highly clean and controlled deposition in UHV.
Single molecular structures and the cation-binding of DB24C8 at the surface are studied in situ by STM and MALDI-MS (matrix assisted laser desorption ionization mass spectrometry). The internal structure of the complex, i.e. ring and cavity, is observable only when alkali cations are incorporated. The BD24C8-H+ complex in contrast appears as a compact feature. This result is in good agreement with theoretical models based on density functional theory calculations