Abstract
Ferrocene is perhaps the most popular and well-studiedorganometallicmolecule, but our understanding of its structure and electronic propertieshas not changed for more than 70 years. In particular, all previousattempts of chemically oxidizing pure ferrocene by binding directlyto the iron center have been unsuccessful, and no significant changein structure or magnetism has been reported.
Using a metal organicframework host material, we were able to fundamentally change theelectronic and magnetic structure of ferrocene to take on a never-beforeobserved physically stretched/bent high-spin Fe(II) state, which readilyaccepts O-2 from air, chemically oxidizing the iron fromFe(II) to Fe(III). We also show that the binding of oxygen is reversiblethrough temperature swing experiments.
Our analysis is based on combiningMo''ssbauer spectroscopy, extended X-ray absorption finestructure, in situ infrared, SQUID, thermal gravimetric analysis,and energy dispersive X-ray fluorescence spectroscopy measurementswith ab initio modeling.