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.

[1]  B. Bent,et al.  Iodobenzene on Cu(111): formation and coupling of adsorbed phenyl groups , 1992 .

[2]  P. Hohenberg,et al.  Inhomogeneous Electron Gas , 1964 .

[3]  Paul S. Weiss,et al.  Imaging Benzene Molecules and Phenyl Radicals on Cu{111} , 1998 .

[4]  G. Henkelman,et al.  A climbing image nudged elastic band method for finding saddle points and minimum energy paths , 2000 .

[5]  Michele Parrinello,et al.  Quickstep: Fast and accurate density functional calculations using a mixed Gaussian and plane waves approach , 2005, Comput. Phys. Commun..

[6]  Roald Hoffmann,et al.  A Chemical and Theoretical Way to Look at Bonding on Surfaces. , 1987 .

[7]  B. Sumpter,et al.  Structure and bonding between an aryl group and metal surfaces. , 2006, Journal of the American Chemical Society.

[8]  R. Bader.  Atoms in molecules : a quantum theory , 1990 .

[9]  B. Koel,et al.  Adsorption of iodobenzene (C6H5I) on Au(1 1 1) surfaces and production of biphenyl (C6H5-C6H5) , 2001 .

[10]  W. Kohn,et al.  Self-Consistent Equations Including Exchange and Correlation Effects , 1965 .

[11]  Bruce E. Koel,et al.  Identification of adsorbed phenyl (C6H5) groups on metal surfaces: Electron-induced dissociation of benzene on Au(111) , 2001 .

[12]  X. Zhou,et al.  INTERACTIONS OF UV PHOTONS AND LOW ENERGY ELECTRONS WITH CHEMISORBED BENZENE ON AG(111) , 1990 .

[13]  Jinming Cai,et al.  Porous graphenes: two-dimensional polymer synthesis with atomic precision. , 2009, Chemical communications.

[14]  B. Bent,et al.  Mechanisms of the Ullmann coupling reaction in adsorbed monolayers , 1993 .

[15]  K. Rieder,et al.  Selective bond breaking of single iodobenzene molecules with a scanning tunneling microscope tip , 2003 .

[16]  Roald Hoffmann,et al.  Bonding and coupling of C1 fragments on metal surfaces , 1988 .

[17]  Michele Parrinello,et al.  A hybrid Gaussian and plane wave density functional scheme , 1997 .

[18]  X. Zhou,et al.  Photon‐ and electron‐induced chemistry of chlorobenzene on Ag(111) , 1990 .

[19]  Burke,et al.  Generalized Gradient Approximation Made Simple. , 1996, Physical review letters.

[20]  Paul S Weiss,et al.  Identifying reactive intermediates in the Ullmann coupling reaction by scanning tunneling microscopy and spectroscopy. , 2009, The journal of physical chemistry. A.

[21]  J. White,et al.  Thermal and photon-stimulated reactions of iodobenzene on Ag(111) , 1998 .

[22]  Feibelman.  Interaction between adsorbed chalcogen and Al atoms on Al(001). , 1988, Physical review. B, Condensed matter.

[23]  F. Rosei,et al.  Synthesis of polyphenylene molecular wires by surface-confined polymerization. , 2009, Small.

[24]  B. Bent,et al.  Adsorbed phenyl groups as traps for radical intermediates in reactions on copper surfaces , 1994 .

[25]  Stefan Grimme,et al.  Semiempirical GGA‐type density functional constructed with a long‐range dispersion correction , 2006, J. Comput. Chem..

[26]  Teter,et al.  Separable dual-space Gaussian pseudopotentials. , 1996, Physical review. B, Condensed matter.