Synthesis of an Isostructural Series of 12-Coordinate Lanthanide Nitrate Hybrid Double Perovskites with Cubic Symmetry
Michael L. Tarlton, S. Skanthakumar, Danielle C. Hutchison, Alexander J. Gremillion, Allen G. Oliver, Richard E. Wilson
Abstract
In efforts to study the periodic chemical properties of the rare earth elements and their structural chemistry, a hybrid double perovskite phase A2B′BX6 with the formula ((CH3)4N)2KLn(NO3)6 (Ln = La–Lu, Y ex. Pm) was synthesized that crystallizes in the cubic space group, Fm3̅m. This series was obtained via evaporative crystallization from a mixture of Ln(NO3)3, KNO3, and (CH3)4N·NO3 in a 1:1:2 ratio from either H2O or 4.0 M HNO3. In this double perovskite structure, the B site containing the lanthanide ion is coordinated by six bidentate nitrate ligands, with the distal N═O oxygen atoms coordinating the potassium on the B′ site in an octahedral six-coordinate environment. The two remaining charge-compensating (CH3)4N+ cations occupy the interstitial voids in the lattice on the A site. This periodic series was characterized via single-crystal X-ray diffraction, powder X-ray diffraction, IR, and Raman spectroscopy. Emission spectra of the Eu complex indicate a phase transition to trigonal symmetry upon cooling. This series is unique as it represents a rare isostructural series spanning the entirety of the rare earth elements excluding promethium with homoleptic 12-coordinate rare earth metal ions.