Determining the Effects of Zero-Field Splitting and Magnetic Exchange in Dimeric Europium(II) Complexes

Abstract

Related BAP [BAP = bis(acyl)phosphide] and Acac (Acac = β-diketonate) molecules perform as robust supports for both lanthanide and actinide metals. Here, a molecular bimetallic Eu2+ complex was successfully targeted and isolated by employing sodium bis(mesitoyl)phosphide [Na(mesBAP)] in a salt metathesis with EuI2, producing [Eu(mesBAP)2(et2o)]2 (et2o = metal-coordinated diethyl ether). The corresponding Acac-Eu2+ complex was targeted using mesAcac- (1,3-dimesityl-1,3-propanedione), generating [Eu(mesAcac)2(et2o)]2. Both complexes were characterized by single-crystal X-ray diffraction, UV-vis, IR, and NMR spectroscopies, and variable-temperature magnetic susceptibility. [Eu(mesBAP)2(et2o)]2 was persistent under anaerobic, anhydrous conditions, whereas the analogous [Eu(mesAcac)2(et2o)]2 showed evidence of decomposition under identical conditions. Variable-temperature magnetic susceptibility and magnetization studies of [Eu(mesBAP)2(et2o)]2 and [Eu(mesAcac)2(et2o)]2 were performed, resulting in similar magnetic exchange coupling values of Jex = −0.018 and −0.023 cm-1 and axial zero-field-splitting D values of −0.38 and −0.51 cm-1, respectively.