Sulfonamido tripods: tuning redox potentials via ligand modifications.

A series of Fe-OH complexes were synthesized with ligands based on the tetradentate sulfonamido tripod ,',"-[2,2',2"-nitrilotris(ethane-2,1-diyl)]-tris-({R-Ph}-sulfonamido). These complexes differ by the substituent on the aryl rings and were fully characterized, including their molecular structures via X-ray diffraction methods. All the complexes were five-coordinate with trigonal bipyramidal geometry. A linear correlation was observed between the electronic effects of each ligand, given by the Hammett constants of the -substituents, and the potential of the Fe/Fe redox couple, which were determined using cyclic voltammetry. It was found that the range of redox potentials for the complexes spanned approximately 160 mV.