Bimetallic Trifluoroacetates as Single-Source Precursors for Alkali-Manganese Fluoroperovskites.

Alkali-manganese(II) trifluoroacetates were synthesized, and their potential as single-source precursors for the solid-state and solution-phase synthesis of AMnF3 fluoroperovskites (A = Na, K, Rb, Cs) was demonstrated. Crystals of Na2Mn2(tfa)6(tfaH), K2Mn2(tfa)6(tfaH)2·H2O, Rb2Mn2(tfa)6·H2O, and CsMn(tfa)3 (tfa = trifluoroacetato) were grown via solvent evaporation and their crystal structures solved using single-crystal X-ray diffraction (XRD). Chemical purity was confirmed using thermal analyses (TGA/DTA) and Rietveld analysis of powder XRD patterns. Thermal decomposition of Na2Mn2(tfa)6(tfaH), K2Mn2(tfa)6(tfaH)2·H2O, Rb2Mn2(tfa)6·H2O, and CsMn(tfa)3 in both the solid state and solution phase yielded crystalline, single-phase NaMnF3, KMnF3, RbMnF3, and CsMnF3 fluoroperovskites, respectively. Nanocrystals (<100 nm) and submicrocrystals (<500 nm) were obtained in a mixture of high-boiling-point organic solvents. Crystal structures of bimetallic trifluoroacetates displayed a variety of building blocks, coordination environments of the alkali atoms, and coordination modes of the trifluoroacetato ligand. Alkali-fluorine interactions ranging from chemical bonds to short contacts were observed throughout the series. The coordination flexibility of the trifluoroacetato ligand was attributed to the ability of the -CF3 groups to interact with alkali atoms over a broad range of distances. The synthetic approach described in this investigation provides a starting point to expand the library of fluorinated single-source precursors suitable for solution-phase routes to mixed-metal fluorides.