Density functional theory of the iron–nitrosyl (S = 3/2) complex

On the basis of density functional theory (DFT), the iron–nitrosyl complex Fe[Me 3 TACN](NO)(N 3 ) 2 (S = 3/2) is studied via the B3LYP hybrid method. Its Raman vibrational frequencies, atomic net charges, and spin densities are analyzed. The related complexes Fe(NH 3 )   n + 6( n = 1, 2, and 3) are employed as reference compounds to determine the characteristics of the central iron. Our results indicate that the S = 3/2 spin ground state of Fe[Me 3 TACN](NO)(N 3 ) 2 is best described by the presence of Fe II (S = 2) anti ‐ferromagnetically coupled to NO 0 (S = 1/2) yielding Fe II [Me 3 TACN](NO 0 )(N   − 3 ) 2 . This is clearly different from the previous Fe III ‐NO − theoretical assignment. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005