Neutral water-soluble μ-S nitrosyl iron complex with acetylcysteine non-silent in EPR spectra

The water-soluble neutral binuclear nitrosyl iron complex with N-acetyl-L-cysteine was synthesized. As follows from X-ray analysis, the complex crystallizes in the monoclinic crystal system, space group P2(1). The distance between iron atoms is 2.7 & Aring; The complex belongs to Roussin's red salt esters (RRE) and is expected to be diamagnetic. However, in the EPR-spectrum there is a broad line with a g-factor of 2.010, which disappears upon the dissolution of the complex in water or alcohol. However, dissolution of the complex in DMSO leads to an increase in the classical signal for mononuclear nitrosyl iron complex with a g-factor of 2.03. The IR-spectrum of the crystalline sample of the complex shows an atypical pattern among RREs. This behaviour was studied with quantum-chemical calculations. The magnetic properties of the complex are also unusual for a complex of this structural type. The complex was also studied by Mo<spacing diaeresis>ssbauer and UV-spectroscopy.