Tetranuclear lanthanide-based silsesquioxanes: towards a combination of a slow relaxation of the magnetization and a luminescent thermometry

Lanthanide-based silsesquioxanes constitute an emerging family of cage-like metallasilsesquioxanes with exciting optical and magnetic properties. We report here the synthesis, structures and luminescence properties of a series of tetranuclear lanthanide-silsesquioxane compounds of general formula [NEt(4)](2)[(Ph(4)Si(4)O(8))(2)(Ln/Ln′)(4)(NO(3))(6)(EtOH)(2)(MeCN)(2)]·4(MeCN) with different lanthanide ions (where Ln/Ln′ = Dy(3+)/Eu(3+) (1), Dy(3+)/Tb(3+) (2) and Eu(3+)/Tb(3+)/Y(3+) (3)) and investigate the impact of the lanthanide ions combination on magnetic and photo-luminescent properties. Compound 1 behaves as a field-induced Single Molecule Magnet (SMM) and presents temperature-dependent luminescence characteristics of Eu(3+) making it an emissive thermometer working in the temperature range 293–373 K with the maximum relative sensitivity of 1.15% K(−1) achieved at 293 K. Compounds 2 and 3 are paramagnets, which demonstrate a characteristic photoluminescence with Dy(3+) to Tb(3+) and Tb(3+) to Eu(3+) energy transfers, respectively.