An ab initio insight into the Cu(111)-mediated Ullmann reaction.
The coupling process of phenyl radicals-the important intermediates in the prototypal Ullmann reaction-on Cu(111) is addressed using density functional theory. Consistent with experiments, we prove that the fragments interact attractively already at relatively large distances. An intermediate state involving a "popping-out" surface atom is reached through a non-trivial surface diffusion path. The overall process of coupling to the final biphenyl state (with a barrier of 0.38 eV) is governed by a subtle electronic mechanism that reminds the concepts postulated by Hoffmann about the alignment of molecular frontier orbitals with the metallic Fermi level. Our results can be applied to more complex surface processes in the field of molecular self-assembly.
EMPA - Swiss Federal Laboratories for Materials Science and Technology, nanotech@surfaces Laboratory, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland. manh-thuong.nguyen@empa.ch
Manh-Thuong
MT
Nguyen
Carlo A
CA
Pignedoli
Daniele
D
Passerone
D000327:Adsorption; D001713:Biphenyl Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D011789:Quantum Theory; D013499:Surface Properties
D001713:Biphenyl Compounds; D003300:Copper; C010574:biphenyl