Origin and consequences of aromatic back-bonding at a transition metal surface: Benzyne on Ir{100}

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Abstract
Recent low energy electron diffraction experiments have shown that partial dissociation of benzene at the Ir{100} surface yields an ordered overlayer of ortho-benzyne radicals ( C 6 H 4 ) with ring-planes inclined at 47.2° to the normal. The primary molecule-surface interaction may be attributed to σ bonds between radical C and surface Ir atoms, but this characteristic alone does not uniquely constrain the adsorbate to the observed orientation. Through first-principles density functional theory which gives good agreement with the experimental structure, we now demonstrate that the molecular tilt arises due to interaction of the aromatic π orbitals with the surfaced orbitals, and not because of any dispersive intermolecular forces.