Dresden 2011 – scientific programme
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DS: Fachverband Dünne Schichten
DS 66: Organic Electronics and Photovoltaics O-I (jointly with CPP, HL, and O)
DS 66.3: Talk
Friday, March 18, 2011, 11:45–12:00, WIL B122
Elucidation of Partial Charge Transfer from the Methoxy Groups of Substituted Pyrene as Donor in Complexes with Tetracyanoquinodimethane — •Katerina Medjanik1, Sergej Nepijko1, Hans-Joachim Elmers1, Gerd Schönhense1, Peter Nagel2, Stefan Schuppler2, Dennis Chercka3, Martin Baumgarten3, and Klaus Müllen3 — 1Ins. für Physik, Johannes Gutenberg-Universität,Mainz — 2Karlsruhe Institute of Technology, ANKA — 3Max-Planck Ins. for Polymer Research, Mainz
Novel charge transfer (CT) compounds can be synthesized on the basis of large polycyclic aromatic hydrocarbons [1]. Microcrystals of the CT-compounds tetra- and hexamethoxypyrene/tetracyanoquinodimethane (TMPx/HMPx-TCNQy) in different stoichiometries x:y=1:1, 1:2 and 2:1 were grown from solution via vapour diffusion. These crystallite fractions were studied by NEXAFS with particular emphasis on direct fingerprints of a charge transfer. Oxygen and nitrogen K-edge NEXAFS gives direct access to the unoccupied orbitals in the donor and acceptor, respectively. With increasing HMP content, a strongly rising O 1s pre-edge signal comes along with a substantial drop of N 1s resonance intensity. Charge is transferred from the π*-orbital of the methoxy-group to the σ*-orbitals b1g and b2u and - to a weaker extent - to the π*-orbitals b3g and au of the cyano-group of TCNQ, particularly strong for the 2:1 compound. Funded by DFG/TR49, Graduate School of Excellence MAINZ, Centre of Complex Materials COMATT.
[1] K. Medjanik et al., Phys. Chem. Chem. Phys. 12, 7184 (2010)