Mono-, Di-, and Tetranuclear Manganese(II) Complexes with p-Phenylsulfonylcalix[4]arene Macrocycles as Ligand Antennas: Synthesis, Structures, and Emission Properties

Three manganese(II) coordination compounds with a p-phenylsulfonylcalix[4]arene (ppThiaSO(2)) ligand were synthetized and are denoted as follows: [Mn-II(ppThiaSO(2))(DMF)(4)] (1) (DMF = N,N-dimethylformamide), [Mn2II(ppThiaSO(2))(DMF)(6)] (2), and K-[Mn-4(II)(ppThiaSO(2))(2)F] in the form of two pseudo-polymorphs (3a and 3b). Their electronic emission spectra were studied in the solid state at different temperatures and at various excitation wavelengths. All compounds (2, 3a, and 3b) except 1 present luminescent properties at UV excitation wavelength, with emission maxima centered at 695, 602, and 675 nm, respectively. Their structural and optical properties were compared to those of previously reported analogous compounds bearing the p-tert-butylsulfonylcalix[4]arene (ThiaSO(2)) ligand. The luminescence of these complexes was attributed to the spin-forbidden T-4(1) -> (6)A(1) d-d transition of manganese(II). The emission depends on the coordination of the metal center, the conformation of the macrocycle, and the structural packing. Hereafter, we present the synthesis, structure, and excitation and emission spectra of each compound, together with the dependence of the emission quenching on molecular dioxygen.