Theoretical Study of the Transition Energies of the Visible Absorption Spectra of [RhCl6]3− and [RhCl5(H2O)]2− Complexes in Aqueous Solution

Abstract

Abstract Electron absorption spectra of [RhCl6]3− and [RhCl5(H2O)]2− complexes are studied theoretically by the ab initio symmetry adapted cluster (SAC)/SAC-CI method. Two maximum peaks of the visible absorption spectra in the range of 300—600 nm observed in aqueous solution are assigned to (1T1g; 1T2g) and mixing-(1B1, 1A2, 1B2; 2B1, 2A2, 2B2) states for [RhCl6]3− and [RhCl5(H2O)]2− complexes, respectively, in good agreement. These states are due to the forbidden d–d transitions from the Rh(dπ) + Ligand(pπ) bonding MOs to the Rh(dσ)-Ligand(pσ) antibonding MOs, leading to an weakening of the metal–ligand bonds.