Panchromatic Absorption and Oxidation of an Iron(II) Spin Crossover Complex

• Published in: Inorganic chemistry 2022-01, Vol.61 (3), p.1659-1671
• Main Authors: Moll, Johannes, Förster, Christoph, König, Alexandra, Carrella, Luca M, Wagner, Manfred, Panthöfer, Martin, Möller, Angela, Rentschler, Eva, Heinze, Katja
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.1c03511

In order to expand and exploit the useful properties of d6-iron­(II) and d5-iron­(III) complexes in potential magnetic, photophysical, or magnetooptical applications, crucial ligand-controlled parameters are the ligand field strength in a given coordination mode and the availability of suitable metal and ligand frontier orbitals for charge-transfer processes. The push–pull ligand 2,6-diguanidylpyridine (dgpy) features low-energy π* orbitals at the pyridine site and strongly electron-donating guanidinyl donors combined with the ability to form six-membered chelate rings for optimal metal–ligand orbital overlap. The electronic ground states of the pseudo-octahedral d6- and d5-complexes mer -[Fe­(dgpy) 2 ] 2+ , cis-fac -[Fe­(dgpy) 2 ] 2+ , and mer -[Fe­(dgpy) 2 ] 3+ as well as their charge-transfer (CT) and metal-centered (MC) excited states are probed by variable temperature UV/vis absorption, NMR, EPR, and Mössbauer spectroscopy, magnetic susceptibility measurements at variable temperature as well as quantum chemical calculations.