In another example Rieder’s group induced all the elementary steps of the Ullmann synthesis [94], the formation of biphenyl from iodobenzene on copper, on
individual molecules with an STM in a controlled step-by-step manner utilizing
a variety of manipulation techniques [80]. Two reactant molecules are shown in
Figure 17.13a. The first reaction step is the separation of iodine from iodobenzene by using tunneling electrons (Figure 17.13b,c). After dissociation, iodine
was moved to terrace sites of the copper surface by lateral manipulation (Figure
17.13d). One chemisorbed phenyl reactant was then moved close to another phenyl
by soft lateral manipulation [95] (Figure 17.13e). Finally the two phenyls were
brought together by molecular excitation by inelastic tunneling (Figure 17.13f ).
Successful chemical association was then verified by pulling the synthesized molecule by its front end with the STM tip.
Fig. 17.13. Schematic illustration and STM
images of the STM tip-induced synthesis steps
of biphenyl molecule from iodobenzene. (a)
Two iodobenzene molecules adsorbed at a
Cu(111) step edge. (b), (c) Iodine is abstracted
from both molecules by applying a voltage
pulse. (d) Iodine atoms and phenyl molecules
are separated by lateral manipulation. (e) An
iodine atom is removed onto the lower terrace.
(f ) The two phenyl molecules are moved
together.
17.4 Chemical Reactions Induced by Confined Electrons 585
individual molecules with an STM in a controlled step-by-step manner utilizing
a variety of manipulation techniques [80]. Two reactant molecules are shown in
Figure 17.13a. The first reaction step is the separation of iodine from iodobenzene by using tunneling electrons (Figure 17.13b,c). After dissociation, iodine
was moved to terrace sites of the copper surface by lateral manipulation (Figure
17.13d). One chemisorbed phenyl reactant was then moved close to another phenyl
by soft lateral manipulation [95] (Figure 17.13e). Finally the two phenyls were
brought together by molecular excitation by inelastic tunneling (Figure 17.13f ).
Successful chemical association was then verified by pulling the synthesized molecule by its front end with the STM tip.
Fig. 17.13. Schematic illustration and STM
images of the STM tip-induced synthesis steps
of biphenyl molecule from iodobenzene. (a)
Two iodobenzene molecules adsorbed at a
Cu(111) step edge. (b), (c) Iodine is abstracted
from both molecules by applying a voltage
pulse. (d) Iodine atoms and phenyl molecules
are separated by lateral manipulation. (e) An
iodine atom is removed onto the lower terrace.
(f ) The two phenyl molecules are moved
together.
17.4 Chemical Reactions Induced by Confined Electrons 585