A Homochiral Hexagadolinium Phosphonate Cluster: Structure, Chiral Electrochemical Recognition and a Large Magnetocaloric Effect

Abstract

Chiral lanthanide clusters have promising applications in chiral recognition, magneto‐optical memories, and spintronic devices. Nonetheless, the precise prediction and controlled development of homochiral polynuclear Ln‐complexes is still a challenge. Herein, through multidentate chelate synthetic strategy, a new homochiral hexagadolinium phosphonate cluster designated as R/S‐[Gd6(pmhpH)8(NO3)2(H2O)8]·19H2O (R/S‐1) was successfully obtained by reacting chiral phosphonomethylhomoproline(pmhpH3) with Gd(III) salt. The cluster, shaped like a lantern, is constructed from {GdO8} polyhedra and {PO3C} tetrahedra surrounded by eight pmhpH2‐ ligands. Within the structure, two types of gadolinium ions with different coordination modes are observed. Each Gd(III) ion is bound to two carboxylate oxygens and six phosphonate oxygens from the coordinated pmhpH2‐ ligands. Circular dichroism spectra comfirmed that R/S‐1 exists as a pair of enantiomers. Moreover, the cluster exhibits high thermal stability, decomposing at temperatures exceeding 335 °C. Notably, the chiral cluster materials can be used for enantiomeric recognition for tryptophan (Trp) with the differential pulse voltammetry (DPV) peak current ratio (ID/IL) 2.74. Besides, the magnetic measurements revealed that compound R‐1 exhibits a good magnetocaloric effect (MCE) with a maximum entropy change of −ΔSmmax =36.84 Jkg−1 K−1 at T = 2K and ΔH = 7 T.