On the Photochemistry of the Low-Lying Excited State of Fe2(CO)6S2. A DFT and QTAIM Investigation

Abstract

The photochemistry originated by the Fe2(CO)6S2 low-lying excited states is investigated using density functional theory (DFT), time-dependent density functional theory (TDDFT), and the quantum theory of atoms in molecules (QTAIM) methods.The 11A1 excitation is the most intense among the low-lying excited states computed at the TDDFT level, which is assigned to the 449 nm metal-to-ligand charge transfer (MLCT) band observed experimentally. We then investigated the nine excited states in a range of ±35 nm centered on the 11A1 excitation energy, which reproduces the range of wavelengths covered by a recent 450 ± 35 nm low-energy laser photolysis experiment. The results presented in this paper suggest that the 450 nm photochemistry recently investigated proceeds mainly through the 11B2 lowest energy singlet excited state. The comparison between tetrahedrane ground state and 11B2 vertical excited state QTAIM atomic net charges evidenced the Fe→S MLCT character but also a significant CO→S ligand-to-ligand char...