We report lanthanide-based MOFs with interesting magnetic behaviours. To the best of our knowledge, Nd³⁺ and Yb³⁺ materials are the first examples of 3D- and 2D-MOFs, respectively, that show slow relaxation of magnetization.

The compound [La(pmtz)(TzC)(H₂O)₃](H₂O) (pmtz = 5-(pyrimidyl)-tetrazolato, TzC = 5-carboxylato-tetrazolato) has been prepared under hydrothermal conditions and exhibits a 3D diamondoid network. This three-dimensional metal–organic framework has channels with hosted water molecules inside and shows an intense blue-greenish long lifetime photoluminescence emission at room temperature in the solid state with two lifetime decay values of 0.26 and 27 ms.

Slow magnetization relaxation via the second excited state with a U_eff = 186 cm⁻¹ has been observed in a Zn–Dy–Zn complex.

Eleven dimetallic Zn^II–Ln^III complexes of the general formula [Zn(µ-L)(µ-OAc)Ln(NO₃)₂]·CH₃CN (Ln^III = Pr (1), Nd (2), Sm (3), Eu (4), Gd (5), Tb (6), Dy (7), Ho (8), Er (9), Tm (10), Yb (11)) have been prepared in a one-pot reaction from the compartmental ligand N,N′-dimethyl-N,N′-bis(2-hydroxy-3-formyl-5-bromo-benzyl)ethylenediamine (H₂L). In all these complexes, the Zn^II ions occupy the internal N₂O₂ site whereas the Ln^III ions show preference for the O₄ external site. Both metallic ions are bridged by an acetate bridge, giving rise to triple mixed diphenoxido/acetate bridged Zn^IILn^III compounds. The Nd, Dy, Er and Yb complexes exhibit field induced single-ion magnet (SIM) behaviour, with U_eff values ranging from 14.12 to 41.55 K. The Er complex shows two relaxation processes, but only the second relaxation process with an energy barrier of 21.0 K has been characterized. The chromophoric L²⁻ ligand is able to act as an “antenna” group, sensitizing the near-infrared (NIR) Nd^III and Yb^III-based luminescence in complexes 2 and 11 and therefore, both compounds can be considered as magneto-luminescent materials. In addition, the Sm^III, Eu^III and Tb^III derivatives exhibit characteristic emissions in the visible region.