AVS 46th International Symposium
    Nanometer-scale Science and Technology Division Tuesday Sessions
       Session NS2-TuM

Paper NS2-TuM1
Single Molecule Engineering: Synthesis of Individual Biphenyl Molecules on Cu (111) with STM Tip

Tuesday, October 26, 1999, 8:20 am, Room 6C

Session: Molecular Electronics
Presenter: S.W. Hla, Freie Universitat Berlin, Germany
Authors: S.W. Hla, Freie Universitat Berlin, Germany
L. Bartels, Columbia University
G. Meyer, Freie Universitat Berlin, Germany
K.-H. Rieder, Freie Universitat Berlin, Germany
Correspondent: Click to Email
In 1904, Fritz Ullmann et al. discovered the way to produce biphenyl from iodobenzene by using Cu as a catalyst. Ever since this process is known as Ullmann reaction and becomes a basic Chemistry textbook case. Due to its varsatility to use different substituted benzenes allowing large number of products and high purity results, it is widely used in lab-style synthetic chemistry. Altogether three elementary steps involve in this reaction process; iodine dissociation from iodobenzene, migration to meet two phenyl radicals and their association to form biphenyl. Here we show that we can perform all elementary steps of Ullmann reaction over single molecules in controlled manner and can synthesize individual biphenyl molecules on the Cu(111) surface for the first time by utilising various single atom and molecule manipulation techniques with a low temperature scanning tunneling microscope (STM) at 20 K. The synthesis steps involve iodine dissociation from single iodobenzene molecules with tunneling electrons and the resulting phenyl radicals were put together by laterally moving them with STM tip. The association of two phenyl radicals to form a bi-phenyl molecule was realised by simultanuously exciting them with tunneling electrons. The threshold tunneling voltage to dissociate the iodobenzene and the energy range of phenyl oscillation on Cu(111) were determined by using I-V single molecule tunneling spectroscopy.