Synthesis and electronic structure of a two dimensional pi-conjugated polythiophene

Luis Cardenas (1, 2) , Rico Gutzler (1, 2) , Josh Lipton-Duffin (1) , Chaoying Fu (2) , Jaclyn L. Brusso (2) , Laurentiu E. Dinca (1) , Martin Vondracak (3, 4) , Yannick Fagot-Révurat (5) , Daniel Malterre (5) , Federico Rosei (1, 2) , Dmitrii F. Perepichka (2)

1 EMT-INRS - Énergie Matériaux Télécommunications - INRS
2 CSACS - Center for Self-Assembled Chemical Structures
3 FZU / CAS - Institute of Physics of the Czech Academy of Sciences
4 Elettra Sincrotrone Trieste
5 IJL - Institut Jean Lamour

We report the synthesis and first electronic characterization of an atomically thin two dimensional pi-conjugated polymer. Polymerization via Ullmann coupling of a tetrabrominated tetrathienoanthracene on Ag(111) in ultra-high vacuum (UHV) produces a porous 2D polymer network that has been characterized by scanning tunnelling microscopy (STM). High-resolution X-ray photoelectron spectroscopy (HRXPS) shows that the reaction proceeds via two distinct steps: dehalogenation of the brominated precursor, which begins at room temperature (RT), and C-C coupling of the resulting Ag-bound intermediates, which requires annealing at 300 degrees C. The formation of the 2D conjugated network is accompanied by a shift of the occupied molecular states by 0.6 eV towards the Fermi level, as observed by UV photoelectron spectroscopy (UPS). A theoretical analysis of the electronic gap reduction in the transition from monomeric building blocks to various 1D and 2D oligomers and polymers yields important insight into the effect of topology on the electronic structure of 2D conjugated polymers.

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Luis Cardenas, Rico Gutzler, Josh Lipton-Duffin, Chaoying Fu, Jaclyn L. Brusso, et al.. Synthesis and electronic structure of a two dimensional pi-conjugated polythiophene. Chemical Science, 2013, 4 (8), pp.3263-3268. ⟨10.1039/c3sc50800e⟩. ⟨hal-01273655⟩