Successive protonation of Lindqvist hexaniobate, [Nb₆O₁₉]⁸⁻: electronic properties and structural distortions

Abstract

Lindqvist Hexaniobate, [Nb6O19]8-, is an intriguing type of polyoxoniobate presenting a significant negative charge, high symmetry, robust structure and applications in photocatalysis. In this work, the [Nb6O19]8- polyanion was submitted...

Water‐Tolerant Superbase Polyoxometalate [H2(Nb6O19)]6− for Homogeneous Catalysis

“…In theoretical studies, Steffler et al. reported triply protonated states similar to that in our [H 3 (Nb 6 O 19 )] 5− model [25] . Thus, for n =4–7, we referred to their reported models and optimized the structure with solvation; for quadruply protonated [H 4 (Nb 6 O 19 )] 6− , the protonation to O t was more favorable than that to O b , and further proton adsorption ( n =5–7) occurred at O b [25] .…”

Water‐Tolerant Superbase Polyoxometalate [H2(Nb6O19)]6− for Homogeneous Catalysis

“…[25] Thus, for n = 4-7, we referred to their reported models and optimized the structure with solvation; for quadruply protonated [H 4 (Nb 6 O 19 )] 6À , the protonation to O t was more favorable than that to O b , and further proton adsorption (n = 5-7) occurred at O b . [25] Based on the optimized structure, the O b sites of [H n (Nb 6 O 19 )] (8À n)À maintained relatively high NBO charges, while that of O t decreased with increasing protons. The NBO charges as a function of adsorbed proton numbers indicated that O b and O t of [H n (Nb 6 O 19 )] (8À n)À maintained its base property in the presence of additional protons.…”

“…UV/Vis spectrometric titration revealed the degree of protonation of [Nb 6 O 19 ] 8À as a function of consumed base ] À were assigned with reference to Steffler et al [25]…”

“…In theoretical studies, Steffler et al reported triply protonated states similar to that in our [H 3 (Nb 6 O 19 )] 5À model. [25] Thus, for n = 4-7, we referred to their reported models and optimized the structure with solvation; for quadruply protonated [H 4 (Nb 6 O 19 )] 6À , the protonation to O t was more favorable than that to O b , and further proton adsorption (n = 5-7) occurred at O b . [25] Based on the optimized structure, the O b sites of [H n (Nb 6 O 19 )] (8À n)À maintained relatively high NBO charges, while that of O t decreased with increasing protons.…”

“…Gray bars are the protonated sites. Color codes: red sphere, O; green sphere, Nb; gray sphere, C; light blue sphere, H. The proton adsorption sites of [H 4 (Nb 6 O 19)] 4À , [H 5 (Nb 6 O 19 )] 3À , [H 6 (Nb 6 O 19 )] 2À , and [H 7 (Nb 6 O 19)] À were assigned with reference to Steffler et al[25]…”