On the EPR spectra of iron(III) spin-equilibrium compounds

Coordination and Organometallic Chemistry of Metal−NO Complexes

“…Magnetic susceptibility and Mössbauer measurements on [Fe(NO)(salen)] 2+ have detected transitions between the S = 3/2 and S = 1/2 spin states . In contrast to this behavior, the isoelectronic five-coordinate iron(I) complexes Fe(NO)(E 2 CNR 2 ) 2 (E = S, Se) and [Fe(NO)(S 2 CC(CN) 2 ) 2 ] 2- have been found to be pure low-spin species by ESR spectroscopic and magnetic susceptibility methods. − Kirmse and co-workers have utilized isotopic labeling techniques to prove that trace amounts of Fe(NO)(S 2 CNEt 2 ) 2 are responsible for a previously ill-explained triplet at g = 2.0 in the ESR spectrum of Fe(S 2 CNEt 2 ) 3 . The nitrosyl-containing impurity is present as a result of traces of nitrate ions in the FeCl 3 starting materials .…”

Iron(III) Spin Crossover Compounds

“…The EPR spectra demonstrate two kinds of signals associated with the 6 A 1 and 2 T 2 states [51][52][53][54][55][56], albeit some controversy still exists concerning the reliability of some of these data. This is motivated by the difficulties encountered in, for instance, the preparation of a pure sample, the possibility of sample decomposition and in the definitive assignment of the EPR signals [51,55]. Hall and Hendrickson reported that it was only possible to observe EPR signals for the magnetically concentrated solids at temperatures approaching 4.2 K. However, the spin crossover could be followed for the complex in a CH 3 Cl glass [51].…”