Hetero-hexalanthanide Complexes: A New Synthetic Strategy for Molecular Thermometric Probes.

Reactions in solvothermal or microwave-assisted conditions between a hexanuclear rare-earth entity ([Ln6] with Ln = Eu-Dy) and m-halogeno-benzoic acids lead to three series of isostructural complexes with respective chemical formulas [Ln6(μ3-OH)2(H2O)2(NO3)2(3-cb)14]·4CH3CN, [Ln6(μ3-OH)2(H2O)2(NO3)2(3-bb)14]·6CH3CN, and [Ln6(μ3-OH)2(H2O)2(NO3)2(3-ib)14]·6CH3CN, where 3-cb-, 3-bb-, and 3-ib- represent 3-chloro-, 3-bromo-, and 3-iodo-benzoate, respectively. These three series of compounds are almost isostructural. Their luminescent properties, in the solid and solution states, have been studied in detail and compared. This study shows that hexanuclear complexes own strong intermetallic energy transfers. This makes these complexes good candidates for thermometric probes in solid state or in solution state.