|Name||Miss Jessica Lopez|
|Organization or Institution||Florida International University|
Synthesis and characterization of Pyrazolate-Supported Fe3(µ3-O) complexes and their redox properties
Jessica M. López Plá and Raphael G. Raptis
Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199
Trinuclear complexes with formula [Fe3(μ3-O)(μ-4-NO2-pz)6X3]n- (X = Cl, Br, NCS, CN, py and, 4-Me-py; n = 2 and 3) show one reversible redox process, where the potential is fully dependent on the electron donating and/or withdrawing properties of the terminal ligand. One-electron reduction of the H.S. all-ferric thiocyanate complex, [Fe3(μ3-O)(μ-4-NO2-pz)6(SCN)3]2-, to its mixed-valent [Fe3]3- trianionic analogue triggers a cascade of H.S. to L.S. electronic reorganization. It is expected that terminal ligands with similar electron donating capacity like SCN (NCO and N3) will exhibit similar behavior. The all-ferric complexes [Fe3(μ3-O)(μ-4-NO2-pz)6(NCO)3]2- (A) and [Fe3(μ3-O)(μ-4-NO2-pz)6(N3)3]2- (B) have been synthesized by substitution of terminal Cl ligands of the parent compound [Fe3(μ3-O)(μ-4-NO2-pz)6Cl3]2- using NaNCO and NaN3. Complexes A and B were characterized by single crystal X-ray diffraction, UV-Vis-NIR, 1H-NMR, 57Fe-Mössbauer and cyclic voltammetry. Expected reversible reduction processes were observed for both complexes at more cathodic potential, -0.70 V, than the thiocyanate complex (-0.36 V). Additionally, compound 2 shows a unique reversible oxidation process at 0.82 V (vs. Fc+/Fc) to [Fe3(μ3-O)(μ-4-NO2-pz)6(N3)3]-, a mixed-valent, formally Fe23+/ Fe4+ species.