Discrete polynuclear manganese(ii) complexes with thiacalixarene ligands: synthesis, structures and photophysical properties

Abstract

The synthesis, crystal structure and photophysical properties of the new compound [Mn₄(ThiaSO₂)₂F][K(18-crown-6)], ThiaSO₂ = p-tert-butylsulphonylcalix[4]arene, 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.