Muon Implantation of Metallocenes: Ferrocene

Abstract

Muon Spin Relaxation and Avoided Level Crossing (ALC) measurements of ferrocene are reported. The main features observed are five high field resonances in the ALC spectrum at about 3.26, 2.44, 2.04, 1.19 and 1.17 T, for the low-temperature phase at 18 K. The high-temperature phase at 295 K shows that only the last feature shifted down to about 0.49 T and a muon spin relaxation peak at about 0.106 T which approaches zero field when reaching the phase transition temperature of 164 K. A model involving three muoniated radicals, two with muonium addition to the cyclopentadienyl ring and the other to the metal atom, is postulated to rationalise these observations. A theoretical treatment involving spin-orbit coupling is found to be required to understand the Fe-Mu adduct, where an interesting interplay between the ferrocene ring dynamics and the spin-orbit coupling of the unpaired electron is shown to be important. The limiting temperature above which the full effect of spin-orbit interaction is observable in the muSR spectra of ferrocene was estimated to be 584 K. Correlation time for the ring rotation dynamics of the Fe-Mu radical at this temperature is 3.2 ps. Estimated electron g values and the changes in zero-field splittings for this temperature range are also reported.

Muon‐Substituted Malonaldehyde: Transforming a Transition State into a Stable Structure by Isotope Substitution

“…Muons, μ − s, (negatively charged) and anti‐muons, μ + s, (positively charged) are exact duplications of electrons and positrons, respectively, except from the facts that they are approximately 206.8 heavier than the electrons and intrinsically unstable . The half‐life of μ − and μ + are around micro‐seconds, approximately 2.2×10 −6 s, and this is long enough to make them accessible, as “radio‐isotopes”, for various physical and chemical studies; they are usually produced in particle accelerators and used directly in coupled chemical reactors and detected by various muon spin related spectroscopic techniques . Particularly, both fields of radical chemistry and the kinetics of radical‐mediated reactions have been benefited enormously from the muon spin related spectroscopic techniques .…”

Muonium Chemistry at Diiron Subsite Analogues of [FeFe]‐Hydrogenase

“…To date, there have been only a very small number of studies on application of μSR to organometallic systems . These have been focused on silylenes, or cyclopentadienyl or arene (half)sandwich systems; in these compounds protonation and proton‐coupled electron transfer are of limited relevance to the key chemical reactions of the metal complexes. In contrast, the spectroscopic data we have so obtained can be modelled by ab initio DFT calculations and we show that this provides compelling evidence for the muono‐formyl Fe‐C(Mu)=O and bridging Fe‐Mu‐Fe or terminal Fe‐Mu muonide transients, light isotopes of paramagnetic species that are implicit in hydrogen evolution and uptake …”

Developing effective electronic-only coupled-cluster and Møller–Plesset perturbation theories for the muonic molecules

“…16,17 In most cases there are various atoms or bonds in a molecule that may act as potential binding sites making the interpretation of the spectrum nontrivial. [18][19][20][21][22][23] Thus, it is vital to have a clear picture of the conceivable attachment sites in order to deduce the local electronic information by the spectrum analysis. Without having any other complementary experimental sources on the molecular structure of the muonic species, the only available means to discern the addition sites is theoretical and computational modeling.…”