Theoretical study of the electronic structure of a tetragonal chromium(III) complex

► The electronic structure of [CrCl2(H2O)4]+ complex was performed. ► The theoretical study permits us to deduce the energy levels, which are not observed experimentally. ► The vibronic structure observed in the luminescence spectra reveals a manifestation of a Jahn-Teller effect. ► Both Jahn-Teller and spin-orbit coupling are necessary to account for the spectroscopic observation. ► The Jahn-Teller stabilization energy was deduced.