Magnetically Induced Binary Ferrocene with Oxidized Iron

Ferrocene is perhaps the most popular and well-studied
organometallic
molecule, but our understanding of its structure and electronic properties
has not changed for more than 70 years. In particular, all previous
attempts of chemically oxidizing pure ferrocene by binding directly
to the iron center have been unsuccessful, and no significant change
in structure or magnetism has been reported. Using a metal organic
framework host material, we were able to fundamentally change the
electronic and magnetic structure of ferrocene to take on a never-before
observed physically stretched/bent high-spin Fe(II) state, which readily
accepts O2 from air, chemically oxidizing the iron from
Fe(II) to Fe(III). We also show that the binding of oxygen is reversible
through temperature swing experiments. Our analysis is based on combining
Mößbauer spectroscopy, extended X-ray absorption fine
structure, in situ infrared, SQUID, thermal gravimetric analysis,
and energy dispersive X-ray fluorescence spectroscopy measurements
with ab initio modeling.