NaV₁₋xP₂S₆ (x = 0.16): A New Compound with Infinite Straight (¹/∞)[V0.837P₂S₆]⁻ Chains that Exfoliate Forming Gels

The new 1D chalcogenophosphate material NaV 0.837(6) P 2 S 6 has been synthesized and its structure determined by X-ray powder diffraction analysis. This compound crystallizes in the monoclinic space group P 2 1 / n with a = 6.9677(3) Å, b = 5.9059(2) Å, c = 21.4537(8) Å, and β = 92.962(2)° [ Z = 4, V = 881.66(8) Å 3 ]. The Rietveld refinement led to R p / R wp = 0.0208/0.0271 (for 94 parameters refined). The material is isostructural with 1D-NaCrP 2 S 6 and contains infinite ( 1 / ∞ )[V 0.837(6) P 2 S 6 ] - chains consisting of randomly occupied edge-sharing [VS 6 ] octahedra defining zigzag ( 1 / ∞ )[VS 4 ] ribbons that are capped by tetradendate [P 2 S 6 ] ethane-like groups linked to three successive [VS 6 ] polyhedra. Because of the nonstoichiometry of the phase, the charge balance can be written as Na + (V 4+ ) 0.486 (V 3+ ) 0.351 (P 4+ ) 2 (S 2- ) 6 . NaV 0.837(6) P 2 S 6 is soluble in strongly polar organic solvents such as N -methylformamide (NMF). The exfoliation of NaV 0.837(6) P 2 S 6 in NMF leads to gels or to colored colloidal solutions with complex fluid behavior that depends strongly on concentration.