Dinitrosyl Iron Complexes (DNICs)—DFT Calculations of the Structure and Reactions With Thiol Ligands and Water Molecules

ABSTRACT Despite decades of research, dinitrosyl iron complexes (DNICs) remain insufficiently understood among NO‐metabolites. To elucidate their structural and reactivity features, we conducted quantum chemical calculations on [Fe(SR) 2 (NO) 2 ] (R = CH 3 ) using the BP86‐D3/6‐311++G(d,p)//CPCM(water) method. Both anionic {Fe(NO) 2 }⁹ and cationic {Fe(NO) 2 }⁷ DNICs have tetrahedral geometries. Protonation facilitates interconversion between anionic, neutral, and cationic forms. While anionic and neutral complexes are coordination‐saturated, the cationic species readily bind a water molecule, promoting thiolate‐to‐disulfide conversion followed by ligand elimination. The hypothesized square–planar geometry for the cationic complex is unstable unless stabilized by two water molecules. This hydrated adduct can release NO fragment, the latter may be scavenged by a thiolate anion.