DFT calculations for model diimine-iron complexes with nitric oxide and water ligands

DFT, TDDFT and ZINDO/S calculations were carried out for the nitrosyl-aqua (I) and di-aqua (II) iron complexes with diimines as equatorial ligands. The electronic structure of the nitric oxide complex can be characterized as a low spin d6 iron cation bonded to the NOradical dot moiety. On the basis of TDDFT and ZINDO/S calculations, the two bands of divalent iron with nitric oxide, water and Me4[14]tetraeneN4 ligand (1) at about 600 and 400 nm are found to consist of d → d, image, image and image transitions. In the case of di-aqua complex, the band at 575 nm is assigned as a image transition.