The search for high-density information storage devices induces an increasing
interest in molecules exhibiting bi- or multistable behaviour. Bi- or
Multistability can be achieved by exploiting changes in intrinsic molecular
properties such as spin or redox states. Furthermore, it has been shown that
low-dimensional molecular systems of transition metals with exactly four metal
ions organized in a square-like fashion are accessible by spontaneous
self-assembly . In addition, such tetrameric complexes can be deposited
as monolayers on graphite and single molecules (2.5 nm x 2.5 nm) can be
manipulated by means of scanning tunneling microscopy (STM) . Series of
novel M4II complexes were synthesized and their magnetic
and electrochemical properties investigated. The magnetic moment of the
Fe4II can be switched over a range of different magnetic
levels using three external triggers (temperature, pressure, light).
The analogous Co4II complex has been found to undergo
eleven electron reduction in ten well-resolved reversible steps .
The reduced species exhibit a remarkable stability in solution.
 E. Breuning, M. Ruben, J.-M. Lehn, F.Renz, Y. Garcia, V. Ksenofontov, P. Gütlich, E. Wegelius, K. Rissanen; Angew.Chem.Int.Ed. Engl.39, 2000, 2504-2507
 A. Semenow, J.P. Spatz, M. Möller, J.-M. Lehn, B. Sell, D. Schubert, C. H. Weidl, U. S. Schubert; Angew.Chem.Int.Ed. Engl.38, 1999, 2547-2550
Research Centre Karlsruhe, Institute for Nanotechnology
P.O. BOX 3640, Karlsruhe, Baden-Wuertemberg D-76021 GERMANY
email: firstname.lastname@example.org http://www.fzk.de/int/