In this study, we describe the crystallization of specific niobium oxide-fluoride anions (either [NbOF4]- or [NbOF 5]2-) by increasing the fluoride concentration with the appropriate use of organic bases with varied corresponding pKa values to create suitable equilibria for the formation of each anion. HpyNbOF 4 (I; py = pyridine) contains the [NbOF4]- anion, while [H2(4,4′-bpy)]NbOF5] (II; 4,4′-bpy = 4,4′-bipyridyl) contains the [NbOF5] 2- anion; their identity is correlated with reagent ratios. The increase of basic species (proton acceptors) results in an increase in the fluoride concentration and high fluoride-containing anions. The crystallization of [NbOF4]- in [NbO2/2F4] ∞ chains in I was controlled with the use of weak base pyridine (pKa = 5.23), while isolated [NbOF5]2- crystallized in II with strong base 4,4′-bipyridyl (pKa = 10.5). This approach can be broadly applied to target-specific basic building units for fundamentally new and potentially functional solid-state materials.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry