Synthesis of an Isostructural Series of 12-Coordinate Lanthanide Nitrate Hybrid Double Perovskites with Cubic Symmetry.

In efforts to study the periodic chemical properties of the rare earth elements and their structural chemistry, a hybrid double perovskite phase AB'BX with the formula ((CH)N)KLn(NO) (Ln = La-Lu, Y ex. Pm) was synthesized that crystallizes in the cubic space group, 3̅. This series was obtained via evaporative crystallization from a mixture of Ln(NO), KNO, and (CH)N·NO in a 1:1:2 ratio from either HO or 4.0 M HNO. 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 (CH)N 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.