The ferric chloride α-DI-imine systemVI: Electronic structure of the dimethyl formamide addcut of mono-1,10-phenanthroline ferric chloride and the by-product,tris-1,10-phenanthroline ferrous μ-oxo-bis[trichloro ferrate(III)]; field induced slow paramagnetic relaxation in monomeric ferric complexes

Magnetic susceptibility (1.45–300 K), zero and high field Mössbauer spectroscopy, IR and solution conductivity measurements were used to characterize the title DMR adduct, Fe(phen)Cl₃·DMF. The absence of magnetic hyperfine splitting in zero external field is correlated with D positive corresponding to an isolated, rapidly relaxing ground (M_s = ± $\text{1}\text{2}$ Kramers doublet. X-ray data show that the ferric ion centres are apparently sufficiently close (～ 7 Å) to allow for rapid spin-spin relaxation via dipolar interactions. The application of longitudinal magnetic fields (0–5 Tesla for 1.7–4.2 K) slows relaxation and results in fully resolved Zeeman split Mössbauer spectra for which the effective internal field, H_n = 354 kG at 1.7 K for H₀ = 5T. The complex [Fe(phen)₃] [O(FeCl₃)₂] contains an unusual binuclear anion based on tetrahedral FeOCl₃ units as recently found in [pyridinium]₂[O(FeCl₃)₂] and is obtained as a trace by-product in our preparation of Fe(phen)Cl₃·DMF. Further magnetic characterization of the latter pyridinium compound is presented.