Chemistry Reference
In-Depth Information
Chapter 10
One-Dimensional Water-Hydroxyl Chain
Complexes: Hydrogen-Atom Relay
Reactions in Real Space
Abstract In this chapter I describe the real-space observation of H-atom relay
reactions in one-dimensional (1-D) water-hydroxyl complexes where a water and
hydroxyl molecules interact via H bond and are aligned along the [001] direction
on a Cu(110) surface. The 1-D chain-like complexes, represented by H
2
O-(OH)
n
(n = 2-4) are assembled in a fully controlled fashion using a combination of the
dissociation and manipulation of individual water molecules. H-atom relay reac-
tions are induced by an injection of energetic electrons from the STM tip. In the
relay a water molecule that is initially located at the end of the chain is structurally
transferred to the other end through the sequential H- and covalent bond exchange.
The relay rate is investigated using the time-resolved measurement of STM. The
voltage and current dependences of the rate clearly indicate that the vibrational
excitations trigger the relay. The experimental findings are rationalized by ab initio
calculations for the adsorption geometry, active vibration modes, and reaction
pathway of the H-atom relay, which provide a microscopic insight of the ele-
mentary processes.
Keywords Hydrogen transfer reactions
One-dimensionally hydrogen-bonding
system
Single molecule reactions through inelastic electron tunneling
10.1 Introduction
Assembling desirable nanoscale structures with the atomic-scale precision and
controlling their functions are not only a dream for chemist but also key challenges
towards developing molecule-based devices. As seen in the previous chapters,
STM enables us to image, manipulate and characterize single atoms and molecules
on conductive surfaces. Furthermore tunneling electrons from an STM tip can be
used as the energy source to control adsorbate motions such as hopping, rotation,
