Electron Transfer: Classical Approaches and New Frontiers
Helmut Tributsch,
*
Ludwig Pohlmann
Electron transfer, under conditions of weak interaction and a
medium acting as a passive thermal bath, is very well understood. When
electron transfer is accompanied by transient chemical bonding, such as
in interfacial coordination electrochemical mechanisms, strong
interaction and molecular selectivity are involved. These mechanisms,
which take advantage of "passive self-organization," cannot yet be
properly described theoretically, but they show substantial
experimental promise for energy conversion and catalysis. The biggest
challenge for the future, however, may be dynamic, self-organized
electron transfer. As with other energy fluxes, a suitable positive
feedback mechanism, through an active molecular environment, can lead
to a (transient) decrease of entropy equivalent to an increase of
molecular electronic order for the activated complex. A resulting
substantial increase in the rate of electron transfer and the
possibility of cooperative transfer of several electrons (without
intermediates) can be deduced from phenomenological theory. The need to
extend our present knowledge may be derived from the observation that
chemical syntheses and fuel utilization in industry typically require
high temperatures (where catalysis is less relevant), whereas
corresponding processes in biological systems are catalyzed at
environmental conditions. This article therefore focuses on interfacial
or membrane-bound electron transfer and investigates an aspect that
nature has developed to a high degree of perfection: self-organization.
The authors are at the Hahn-Meitner-Institut, Department Solare
Energetik, Glienecker Strasse 100, D-14109 Berlin, Germany.
*
To whom correspondence should be addressed. E-mail:
Tributsch{at}hmi.de
