Selective bond breaking of single iodobenzene molecules with a scanning tunneling microscope tip

Controlled step-by-step dissociation of single iodobenzene molecules has been performed at Cu(111) step-edges using tunneling electrons from a scanning tunneling microscope (STM) tip at 12 K. We show that the threshold tunneling electron energies to break a single bond inside a polyatomic molecule can be determined by using I-V spectroscopy of single molecules. Electron energies of 1.5 +/- 0.1 eV are necessary to break the sigma(C-I) bond. This selective bond breaking procedure is possible due to the inherent bond energy differences inside the molecule. It requires electron energies of 3.1 +/- 0.1 eV or higher to further disrupt the pi ring. (C) 2003 Elsevier Science B.V. All rights reserved.