Syntheses of Two Vanadium Oxide–Fluoride Materials That Differ in Phase Matchability

The
syntheses of two noncentrosymmetric (NCS) vanadium oxide–fluoride
compounds that originate from the same synthetic reagent concentrations
are presented. Hydrothermal and low-temperature syntheses allow the
isolation of metastable products that may form new phases (or decompose)
upon heating and allow creation of chemically similar but structurally
different materials. NCS materials synthesis has been a long-standing
goal in inorganic chemistry: in this article, we compare two chemically
similar NCS inorganic materials, NaVOF4(H2O)
(I) and NaVO2–xF2+x (II; x = 1/3). These materials originate from the same, identical
reagent mixtures but are synthesized at different temperatures: 100
°C and 150 °C, respectively. Compound I crystallizes
in Pna21: a = 9.9595(4)
Å, b = 9.4423(3) Å, and c = 4.8186(2) Å. Compound II crystallizes in P21: a = 6.3742(3) Å, b = 3.5963(2) Å, c = 14.3641(7) Å,
and β = 110.787(3)°. Both materials display second-harmonic-generation
activity; however, compound I is type 1 non-phase-matchable,
whereas compound II is type 1 phase-matchable.