Moessbauer effect and magnetic investigation of the S = 3/2 .tautm. S = 1/2 spin crossover in [Fe(salen)NO] and the S = 3/2 state in [Fe(5-salen)NO]

Electronic Structure Modulation in an Exceptionally Stable Non‐Heme Nitrosyl Iron(II) Spin‐Crossover Complex

“…At 4 K the spectrum is characterized by a sharp signal centered at g =2.02, which becomes wider without moving significantly ( g =2.05) at 300 K where, according to the magnetic properties, approximately 30 % of the molecules are in the S =3/2 state. This EPR spectrum is reminiscent of that reported for the classical SCO nitrosyl compound [Fe(salen)(NO)], for which no signal at g ≈4, which is characteristic of the S =3/2 state, is observed, which was considered consistent with an electron essentially residing in the NO molecule . Similarly, no observation of the S =3/2 signal was reported for the SCO complex [FeL pr (NO)] .…”

Spin crossover iron(III) complexes

“…H 2 salen and H 2 salphen are the most commonly used quadridentate ligands with an N 2 O 2 -donor set. Reactions of ligands with iron(III) and NO − ions yield five coordinated iron(III) complexes with FeN 3 O 2 core [28]. This class of complexes exhibits characteristic SCO between LS (S = 1/2) and intermediate spin ( [32].…”

Iron(III) Spin Crossover Compounds

“…The first and most extensively studied compound of this class is [Fe (salen)(NO)], which exhibits an abrupt S=1/2$S=3/2 spin transition with associated hysteresis centred at T=175 K and virtually complete over a temperature interval of a few degrees [169][170][171]. Such features are relatively uncommon for iron(III).…”

“…Such features are relatively uncommon for iron(III). In contrast, [Fe(5-Cl-salen)(NO)] is in the S=3/2 state [169].…”