We are quite fond of [3Fe-4S] clusters.
We discovered this cluster form (Emptage et al. 1980) and
reported the first [3Fe-4S] ↔ [4Fe-4S] cluster interconversion (Kent et al. 1982 ).
The Mössbauer spectrum of the reduced [3Fe-4S] cluster from D.
gigas FdII, attached to the logo cluster, required a
novel Hamiltonian for exchange coupling in clusters (double
exchange, Papaefthymiou et al. 1987). The same cluster, in
the oxidized state, has an unusual EPR signal which we were
able to explain by considering the rarely observed antisymmetric
exchange (Sanakis et al. 2000).
Double exchange was introduced in the fifties into solid state physics by
C. Zener and P.W. Anderson (and then nearly forgotten). Double
exchange is also referred to as “spin-dependent