Sodium Transition Metal Vanadates from Hydrothermal Brines: Synthesis and Characterization of NaMn<sub>4</sub>(VO<sub>4</sub>)<sub>3</sub>, Na<sub>2</sub>Mn<sub>3</sub>(VO<sub>4</sub>)<sub>3</sub>, and Na<sub>2</sub>Co<sub>3</sub>(VO<sub>4</sub>)<sub>2</sub>(OH)<sub>2</sub>
Tiffany M. Smith Pellizzeri, Gregory Morrison, Colin D. McMillen, Hans‐Conrad zur Loye, Joseph W. Kolis
Abstract
Three new examples of transition metal vanadates have all been synthesized by a related hydrothermal synthetic route using variations of sodium hydroxide/sodium chloride brines as mineralizers. Compound 1 , NaMn 4 (VO 4 ) 3 , is built from equivalent interlocking chains of Mn 2+ edge shared octahedra, further coordinated to one another by (VO 4 ) 3– vanadate groups to form a three‐dimensional structure. Compound 2 , Na 2 Mn 3 (VO 4 ) 3 , forms a complex three‐dimensional structure of mixed‐valence 2+/3+ manganese edge‐sharing octahedra forming chains, with (VO 4 ) 3– tetrahedra acting as space‐fillers in the structure. Structure 3 , Na 2 Co 3 (VO 4 ) 2 (OH) 2 , is built of a two‐dimensional distorted honeycomb of edge shared Co 2+ layers decorated by, but not connected by, vanadate groups. The layers bear a relationship to Kagome nets but the structure contains no ideal trigonal symmetry. All compounds were characterized by single‐crystal X‐ray diffraction. Compounds 1 and 3 were characterized by magnetic susceptibility. The magnetic susceptibility of 1 displays the moment characteristic of Mn 2+ and a transition at 46 K to a spin canted antiferromagnet. Compound 3 shows evidence of spin–orbit coupling in the Co 2+ ions with antiferromagnetic ordering at 4.4.K and highly anisotropic field‐dependent behavior with multiple metamagnetic transitions.