Two new tin(iv)-containing phosphate fluorides with two types of Sn(iv)–P–O–F frameworks and short cutoff edges

Abstract

Two new tin(IV)-containing phosphate fluorides, K₂SnPO₄F₃ and K₆Sn(P₂O₇)₂F₂, have been obtained in a sealed system. Interestingly, K₂SnPO₄F₃ and K₆Sn(P₂O₇)₂F₂ are the first tin(IV)-containing phosphate fluorides in the K–Sn(IV)–P–O–F system. Both of them crystallize in the monoclinic space group P2₁/c; however, the 2D [SnPO₄F₃]_∞ layer and isolated [Sn(P₂O₇)₂F₂] units can be found in K₂SnPO₄F₃ and K₆Sn(P₂O₇)₂F₂, respectively. A structural comparison indicates that K₆Sn(P₂O₇)₂F₂ is the first inorganic tin(IV)-containing phosphate with an isolated Sn(IV)–P–O framework. Meanwhile, the structural evolution from KSnOPO₄ to K₂SnPO₄F₃ is discussed in detail. And the optical properties, including UV-Vis-NIR diffuse reflectance spectra and infrared spectra, are also reported. In addition, first-principle theoretical studies help us understand the electron structures of the title compounds.