Improving the SMM and luminescence properties of lanthanide complexes with LnO9 cores in the presence of ZnII: an emissive Zn2Dy single ion magnet

Abstract

Mononuclear complexes of stoichiometry [Ln(H₃L)(H₂O)(NO₃)](NO₃)₂ (Ln = Tb, 1; Dy, 2, Er, 3), which crystallise with different solvates, and the heterotrinuclear compound [Zn₂Dy(L)(NO₃)₃(OH)] (4) can be obtained with the same H₃L compartmental ligand. The single X-ray crystal structure of the mononuclear complexes shows a LnO₉ core with a muffin-like disposition while the geometry of the DyO₉ core in 4 seems to be closer to spherical capped square antiprism. The analysis of the magnetic properties of all the complexes demonstrates that the mononuclear lanthanide compounds do not show slow relaxation of the magnetization, even when the samples are diluted with a diamagnetic matrix and subjected to a dc applied field of 1000 Oe. Nevertheless, the heterotrinuclear dysprosium complex 4·3H₂O is a field-induced single ion magnet, with an estimated U_eff barrier of 59 K. The luminescence characterisation of all the metal complexes in methanol solution at 298 K also shows a notable increase in the fluorescence emission of the heterotrinuclear complex with respect to the mononuclear ones, in such a way that 4 can be defined as a fluorescent single ion magnet.