Exposing the inadequacy of redox formalisms by resolving redox inequivalence within isovalent clusters

• DOI: 10.1073/pnas.1907699116
• Publication Date: 2019-07-20T00:15:37Z
• Authors: Amymarie K. Barth...; Justin J. Teesdale; Raúl Hernández Sá...; Brian J. Malbrecht; Cristin E. Juda; Gabriel Ménard; Wei Bu; Diana A. Iovan; Alexandre A. Mikh...; Shao-Liang Zheng; Ritimukta Sarangi; SuYin Grass Wang; Yu-Sheng Chen; Theodore A. Betley
• Keywords: Anomalous scattering; Coordination sphere; Oxidation state

In this report we examine a family of trinuclear iron complexes by multiple-wavelength, anomalous diffraction (MAD) to explore the redox load distribution within cluster materials free refinement atomic scattering factors. Several effects were explored that can impact factors clusters, including 1) metal atom primary coordination sphere, 2) M−M bonding, and 3) delocalization in formally mixed-valent species. Complexes investigated which vary from highly symmetric fully asymmetric 57 Fe Mössbauer X-ray relationship between MAD-derived data available these widely used characterization techniques. The compounds examined include all-ferrous clusters [ n Bu 4 N][( tbs L)Fe 3 (μ –Cl)] (1) ([ L] 6– = [1,3,5-C 6 H 9 (NC - o -NSi t BuMe 2 ) ] ]), ( (py) (2), [K(C 222 )] [( –NPh)] (4) (C 2,2,2-cryptand), –NPh) (3). Redox was with cyclic voltammetry (CV), zero-field Mössbauer, near-infrared (NIR) spectroscopy, crystallography We find MAD results show an excellent correspondence data; yet also distinguish subtle changes local geometries where cannot. Differences aggregate oxidation levels are evident systematic shifts factor envelopes increasingly higher energies. However, distinguishing iso- or be dramatically obscured degree covalent intracore bonding. emphasize in-edge features often difficult analyze absorption near edge spectroscopy (XANES). Thus, relative most reliably ascertained comparing entire envelope data.