Redox-Active 1D Coordination Polymers of Iron–Sulfur Clusters

Here we describe the combination
of an archetypal redox-active
metal sulfide cluster, Fe4S4, with an organic
linker, 1,4-benzenedithiolate, to prepare coordination polymers containing
infinite chains of Fe4S4 clusters. The crystal
structures of two solid materials have been solved from synchrotron
X-ray powder diffraction data using simulated annealing and refined
by a least-squares Rietveld refinement procedure. The electronic properties
of these chains have also been characterized by UV–visible
and Mössbauer spectroscopies. Additional experiments demonstrated
that these chains can be solubilized by variation of the countercation
and that the chain structure is maintained in solution. The redox-activity
of the Fe4S4 clusters can be accessed with chemical
reagents. Introduction of charge carriers by reduction of the Fe4S4 clusters is found to increase the electrical
conductivity of the materials by up to 4 orders of magnitude. These
results highlight the utility of Fe4S4 clusters
as redox-active building blocks in preparing new classes of coordination
polymers.