Low-temperature phase transition in crystals of an optically active lanthanide complex

Abstract

A second-order crystalline phase transition occurs between 120 and 5 K in trisodium lanthanide tris(oxydiacetate) di(sodium perchlorate) hexahydrate single crystals, Na₃Ln(C₄H₄O₅)₃·2NaClO₄·6H₂O. Results from optical, circular dichroism and electron paramagnetic resonance spectroscopy are used to define the low-temperature space group. The transition is from the room-temperature space group R32 to P3₁21 or its mirror image P3₂21. It lowers the site symmetry of the lanthanide from D₃ to C₂ and results in movement of a sodium ion off a three-fold axis.