EXAFS Study on the Coordination Chemistry of the Solvated Copper(II) Ion in a Series of Oxygen Donor Solvents

Abstract

The structures of the solvated copper(II) ion in water and nine organic oxygen donor solvents with similar electron-pair donor ability, but with different space-demanding properties at coordination, have been studied by EXAFS. N,N′ -Dimethylpropyleneurea and N,N,N′,N′ -tetramethylurea are sufficiently space demanding at coordination to make the axial positions not accessible, resulting in square-planar copper(II) solvate complexes with an intense green color. The mean Cu–O bond distances in these two solvate complexes are 1.939(3) and 1.935(3) Å, respectively. The best fits of the remaining solvates, which are light blue in different hues, are obtained with a Jahn–Teller distorted-octahedral model consisting of four strongly bound solvent molecules in the equatorial positions at 1.96(2) Å and two in the axial positions but with different Cu–O ax bond distances: ca. 2.15 and 2.32 Å. This is in agreement with observations in solid-state structures of compounds containing hexaaquacopper(II) complexes crystallizing in noncentrosymmetric space groups and all reported crystal structures containing a [Cu(H 2 O) 5 (O-ligand)] complex with Jahn–Teller distortion. Such a structure is in agreement with previous EPR and EXAFS studies proving the hydrated copper(II) ion to be a noncentrosymmetric complex in aqueous solution. The refinements of the EXAFS data of the solids [Cu(H 2 O) 6 ](ClO 4 ) 2 , [Cu(H 2 O) 6 ](BrO 3 ) 2 , [Cu(H 2 O) 6 ]SiF 6 , Cu(NO 3 ) 2 ·2.5H 2 O, and CuSO 4 ·5H 2 O gave Cu–O bond distances significantly different from those reported in the crystallographic studies but similar to the configuration and bond distances in the hydrated copper(II) ion in aqueous solution. This may depend on whether the orientation of the axial positions is random in one or three dimensions, giving a mean structure of the solid with symmetry higher than that of the individual complexes. This study presents the very first experimental data from the new X-ray absorption spectroscopy beamline Balder at the MAX IV synchrotron radiation facility in Lund, Sweden, as well as the utilized properties of the beamline.

Nitrosonium and Nitronium Salts of New Mixed‐Cation Hexafluoridoantimonates(V)

“…In the case of three isotypic hexaaqua metal(II) bromates the ⟨▵d 2 ⟩ values (in 10 −4 Å 2 ) for the complexes of Co, Ni and Cu, are equal to 48, 38 and 216 respectively, [40] This was interpreted as signifying the presence of a dynamic Jahn‐Teller effect in crystals of the copper salt, with the tacit conclusion that the augmented ligand displacements were caused principally by motion and not by static disorder [49] . Dynamic Jahn‐Teller effect was later confirmed by EXAFS spectroscopy [44,46] . All these suggest that no significant dynamic Jahn‐Teller disorder is taking place in the Cu−F2 polyhedron of cubic (NO) 0.25 (NO 2 ) 0.75 Cu(SbF 6 ) 3 and (H 3 O) 0.25 (NO 2 ) 0.75 Cu(SbF 6 ) 3 , salts (Figure 4 and Figure S9).…”

“…In all cases the Cu atoms are located at the special positions in higher‐symmetry space groups: Na 4 CuU 6 F 30 ( P c1 ; 100 and 298 K), [30] [Cu( en ) 3 ][MO 4 ] ( en =ethylenediamine; P 1c at 300 K for M=Cr and at 390 K for M=Mo, W), [31,32,33] [Cu( en ) 3 ][SO 4 ] ( P 1c at RT), [34] [Cu(tris(2‐pyridyl)methane) 2 ][NO 2 ] 2 ( R , 173 and 295 K), [35] Cu(XeF 6 ) 6 (SbF 6 ) 2 ( R , 200 K),[36 ] [Cu(ONC 5 H 5 ) 6 ][ClO 4 ] ( R , 292 K), [37] Cu(ONC 5 H 5 ) 6 ][BF 4 ] ( R , 292 K), [37] [Cu(H 2 O) 6 ][SiF 6 ] ( R at 213 K and RT), [38,39] [Cu(H 2 O) 6 ][BrO 3 ] 2 ( Pa , 296 K), [40] α‐M 2 Pb[Cu(NO 2 ) 6 ] (M=K, Cs, Tl; Fm3 at RT for M=K, at 420 K for M=Cs and at 295 K for M=Tl) [41,42,43] . Many of these crystal structures do not show obviously enlarged temperature factors for the coordinated ligand atoms [35,44] . However, for [Cu( en ) 3 ][SO 4 ], [45] [Cu(tris(2‐pyridyl)methane) 2 ][NO 2 ] 2 , [35] [Cu(H 2 O) 6 ][BrO 3 ] 2 , [44,46] [Cu(H 2 O) 6 ][SiF 6 ], [44,46] [Cu(ONC 5 H 5 ) 6 ][ClO 4 ] 2 , [46] and α‐K 2 Pb[Cu(NO 2 ) 6 ] [45] the EXAFS spectroscopy revealed the presence of the existence of the dynamic Jahn‐Teller distortions of Cu(II).…”

“…[49] Dynamic Jahn-Teller effect was later confirmed by EXAFS spectroscopy. [44,46] All these suggest that no significant dynamic Jahn-Teller disorder is taking place in the CuÀ F2 polyhedron of cubic (NO) 0.25 (NO 2 ) 0.75 Cu(SbF 6 ) 3 and (H 3 O) 0.25 (NO 2 ) 0.75 Cu(SbF 6 ) 3 , salts (Figure 4 and Figure S9). In order [51,52] It consists of infinite zig-zag [À CuÀ FÀ CuÀ FÀ ] chains.…”

“…[41,42,43] Many of these crystal structures do not show obviously enlarged temperature factors for the coordinated ligand atoms. [35,44] However, for [Cu(en) 3 ][SO 4 ], [45] [Cu(tris(2pyridyl)methane) 2 ][NO 2 ] 2 , [35] [Cu(H 2 O) 6 ][BrO 3 ] 2 , [44,46] [Cu-(H 2 O) 6 ][SiF 6 ], [44,46] [Cu(ONC 5 H 5 ) 6 ][ClO 4 ] 2 , [46] and α-K 2 Pb[Cu(NO 2 ) 6 ] [45] the EXAFS spectroscopy revealed the presence of the existence of the dynamic Jahn-Teller distortions of Cu(II). In the case of the IF 6 Ag(SbF 6 ) 3 (P31c, 200 K) the single crystal X-ray structure determination also showed the apparently regular octahedral coordination of Ag(II) (d 9 electron configuration as in Cu 2 + ).…”

Fabrication and characterisation of a silicon-borosilicate glass microfluidic device for synchrotron-based hard X-ray spectroscopy studies

“…First, the top Al lm with resist was etched (RF power 800 W, using 26 sccm Cl 2 and 50 sccm BCl 3 ). The Al thin lm acted both as hard mask (front side layer) and etch stop (back side layer) for the subsequent throughwafer dry etching of the Si wafer, which was done using the DRIE Bosch process (RF power 900 W, deposition using 30 plasma (Tepla 300, Tepla) followed by 70 C concentrated HNO 3 for 10 min. All wafers were extensively rinsed in DI water and dried by N 2 .…”