Structural and spectroscopic study of Mg_13.4(OH)₆(HVO₄)₂(H_0.2VO₄)₆

Abstract

Key words magnesium hydrogen vanadate(V), hydrothermal synthesis, crystal structure, infrared spectra, hydrogen vanadate(V). PACS 61.66. Fn, 81.05.Rm, 61.05.cp, 78.30.Hv Single-crystals of the polar compound magnesium hydrogen vanadate(V), Mg 13.4 (OH) 6 (HVO 4 ) 2 (H 0.2 VO 4 ) 6 , were synthesized hydrothermally. It represents the first hydrogen vanadate(V) among inorganic compounds. Its structure was determined by single-crystal X-ray diffraction [space group P6 3 mc, a = 12.9096(2), c = 5.0755(1) Å, V = 732.55(2) ų, Z = 1]. The crystal structure of Mg 13.4 (OH) 6 (HVO 4 ) 2 (H 0.2 VO 4 ) 6 consists of well separated, vacancy-interrupted chains of face sharing Mg2O 6 octahedra, with short Mg2-Mg2 distances of 2.537(1) Å, embedded in a porous magnesium vanadate 3D framework having the topology of the zeolite cancrinite. All three hydrogen positions in the structure were confirmed by FTIR spectroscopy. Dedicated to Prof. Ladislav Bohatý on the occasion of his 60th birthday

Crystal structure, infrared spectroscopy and thermodynamic properties of a manganese member of the ellenbergerite family

“…The first 3550–3400 cm −1 region contains three weak bands corresponding to the stretching vibrations of O–H bonds. Similar wave numbers observed for structurally related magnesium hydrogen vanadate Mg 13.4 (OH) 6 (HVO 4 ) 2 (H 0.2 VO 4 ) 6 20 and phosphorus-rich ellenbergerite 21 are characteristic of weak hydrogen bonds. 22…”

“…These bands are typical for stretching vibrations of OH groups with a low degree of O–H bond covalence as in the case of acid salts, including inorganic compounds containing [HVO 4 ] 2− groups. 20,23,24 Also, the bands at 1557 and 1418 cm −1 can be attributed to O–H bending vibrations combined with Mn atoms. 25,26…”

“…Summarizing, the essential feature of Mn 6.75 (OH) 3 H 1.20 (VO 4 ) 4-2z -(V 2 O 7 ) z (z = 0.15) is the coexistence of disordered V 2 O 7 , HVO 4 and H 2 VO 4 groups localized in the triangular channels. 20 and phosphorus-rich ellenbergerite 21 are characteristic of weak hydrogen bonds. 22 The second wide region of weak absorption bands can be traced in the range of 1750-1100 cm À1 with a maximum of B1418 cm À1 .…”