SUBSITE-SPECIFIC REACTIONS OF A CYCLOTRIVERATRYLENE [4FE-4S] CLUSTER COMPLEX

Ligand exchange reactions are carried out exclusively at the unique ir on site of a subsite-differentiated cyclotriveratrylene [4Fe-4S] clust er complex. The effect of a variety of thiolate, phenolate, bidentate, and bridging ligands on the redox potential of the subsite-differenti ated [4Fe-4S] cluster complex is studied and compared with the effects of such ligands on an [Fe4S4Cl4](2-) cluster. The redox potential can be modulated within the range of -1.60 to -1.80 V (vs. Fc(0/+)) by va rying the ligand. The introduction of an electron releasing substituen t shifts the redox potential to more negative values, whereas an elect ron withdrawing substituent has the opposite effect. A linear relation ship exists between the number of substituted sites and the reduction potential of the cluster.