Synthesis and characterization of trigonal bipyramidal FeIII complexes and their solution behavior

• DOI: 10.1016/j.poly.2021.115384
• Publication Date: 2021-07-30T17:16:39Z
• Authors: Adriana Lugosan; Sophi R. Todtz; Andrew Alcázar; Matthias Zeller; James J. Devery III; Wei-Tsung Lee
• Keywords: 01 natural sciences; 0104 chemical sciences

A series of air-stable trigonal bipyramidal FeIII complexes supported by a redox non-innocent NNN pincer ligand, Cz tBu(PyrR)2 - (R = iPr, Me, or H), were synthesized, fully characterized, and utilized for the investigation of the interaction between acetone and the FeIII center. The magnetic moments determined from the paramagnetic 1H NMR spectra in conjunction with EPR and Mössbauer spectroscopy indicate the presence of a high-spin ferric center. Cyclic voltammetry studies feature two quasi-reversible events corresponding to a metal-centered FeIII/II reduction around -0.40 V (vs. Fc) and a ligand-centered Cz tBu(PyrR)2/Cz tBu(PyrR)2 •+ oxidation at potentials near +0.70 V (vs. Fc). UV-Visible spectroscopy in CH2Cl2 showcases ligand-metal charge transfer (LMCT) bands, as well as coordination of acetone to Cz tBu(PyrH)2FeCl2. In situ IR spectroscopy and solution conductivity (κ) measurements of Cz tBu(PyrR)2FeCl2 with varied equivalents of acetone reveal that acetone is weakly associated with the iron center.