Raman spectroscopic study of the uranyl mineral pseudojohannite Cu_6.5[(UO₂)₄O₄(SO₄)₂]₂(OH)₅·25H₂O

Abstract

Raman spectra of pseudojohannite were studied and related to the structure of the mineral. Observed bands were assigned to the stretching and bending vibrations of (UO 2 ) 2+ and (SO 4 ) 2− units and of water molecules. The published formula of pseudojohannite is Cu 6.5 (UO 2 ) 8 [O 8 ](OH) 5 [(SO 4 ) 4 ]·25H 2 O. Raman bands at 805 and 810 cm −1 are assigned to (UO 2 ) 2+ stretching modes. The Raman bands at 1017 and 1100 cm −1 are assigned to the (SO 4 ) 2− symmetric and antisymmetric stretching vibrations. The three Raman bands at 423, 465 and 496 cm −1 are assigned to the (SO 4 ) 2− ν 2 bending modes. The bands at 210 and 279 cm −1 are assigned to the doubly degenerate ν 2 bending vibration of the (UO 2 ) 2+ units. U-O bond lengths in uranyl and O-H· · ·O hydrogen bond lengths were calculated from the Raman and infrared spectra.

From Two-Dimensional Layers to Three-Dimensional Frameworks: Expanding the Structural Diversity of Uranyl Compounds by Cation–Cation Interactions

“…The antisymmetrical stretching mode of (UO 2 ) 2+ shows a shift to lower frequencies from CsUW-1 to CsUW-2 in the region 930–960 cm –1 . This deviation might be explained as a consequence of the different U–O terminal bond distances. , Owing to CCIs, the U–O bond distances are more abnormal in CsUW-2 (U–O terminal ranging from 1.80(1) Å to 1.82(1) Å for CsUW-1 whereas, from 1.76(2) Å to 1.99(2) Å for CsUW-2 ). The peaks between 750 and 800 cm –1 for both compounds could be assigned to the symmetric stretching ( v 1 ) of UO 2 2+ .…”

Recent advances in linear and nonlinear Raman spectroscopy. Part IV

“…This paper was followed by another by Frost and Keeffe182 that describes a Raman spectroscopic study of the metatellurate mineral xocomecatlite Cu 3 TeO 4 (OH) 4 . Frost et al 183 published a Raman spectroscopic study of the uranyl mineral pseudojohannite Cu 6.5 [(UO 2 ) 4 O 4 (SO 4 ) 2 ] 2 (OH) 5 ·25H 2 O, and another Raman spectroscopic study of the antimonate mineral brandholzite Mg[Sb 2 (OH) 12 ]·6H 2 O in the same issue184. A spectroscopic study of the uranyl mineral metauranospinite Ca[(UO 2 )(AsO 4 )] 2 ·8H 2 O by Cejka et al 185 described the IR and Raman vibrational spectra of this mineral along with its structural implications.…”