Discrete polynuclear manganese(ii) complexes with thiacalixarene ligands: synthesis, structures and photophysical properties†
The synthesis, crystal structure and photophysical properties of the new compound [Mn4(ThiaSO2)2F][K(18-crown-6)], ThiaSO2 = p-tert-butylsulphonylcalixarene, are presented and compared to the ones of [Mn4(ThiaSO2)2F]K. The strong orange luminescence is attributed to the Mn2+ centred 4T1→6A1 transition. Its temperature and pressure dependence and quenching by molecular dioxygen are reported. The latter is attributed to energy transfer from the 4T1 state exciting dioxygen to its 1∑+g state. In the solid state, the quenching is much more efficient in [Mn4(ThiaSO2)2F][K(18-crown-6)] than in [Mn4(ThiaSO2)2F]K. This is attributed to the open pore structure of the former allowing fast diffusion of dioxygen into the crystal lattice.