Variable temperature inelastic neutron scattering study of chromium(II) Tutton salt: manifestation of the 5E⊗e Jahn–Teller effect

Inelastic neutron scattering (INS) data are presented for the salt (ND4)2Cr(OD2)6(SO4)2, which enable the zero-field-splitting of the 5Ag(Ci) ground term of the [Cr(OD2)6]2+ cation to be defined in the temperature range 1.5–297 K. Above ∼100 K, the energies of the INS transitions are strongly temperature-dependent, as are the documented Cr–O bond lengths. The experimental data are interpreted using a 5E⊗e Jahn–Teller Hamiltonian perturbed by low symmetry strain. Good agreement is obtained using a parameter set analogous to that employed to describe the electronic and molecular structure of the [Cu(OD2)6]2+ cation in the isostructural copper(II) salt.