Synthesis and crystal structure analysis of KAg11(VO 4)4

Article abstract of DOI:10.1002/zaac.200500411

New potassium silver vanadate KAg₁₁(VO₄)₄ was obtained by reacting the stoichiometric mixture of Ag₂O and V₂O₅ at elevated oxygen pressure, adding a small portion of aqueous KOH. The synthesis was done at 573 K and 430 MPa of oxygen pressure. The crystal structure was solved by direct methods basing on single crystal diffraction data (Pbca, Z = 4, a = 16.533(1), b = 10.6286(7), c = 10.5452(7) A, 3983 independent reflections, R₁ = 5.4%). The optical band gap for KAg₁₁(VO₄)₄ was determined as 2.0 eV. According to magnetic measurements, KAg₁₁(VO₄)₄ is diamagnetic.

Full text of DOI:10.1002/zaac.200500411

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DOI: 10.1002/zaac.200500411
Synthesis and Crystal Structure Analysis of KAg11(VO4)4
Anton Kovalevskiy and Martin Jansen
Stuttgart, Max-Planck-Institut für Festkörperforschung
Received September 12th, 2005.
Abstract. New potassium silver vanadate KAg11(VO4)4 was ob-
tained by reacting the stoichiometric mixture of Ag2O and V2O5 at
elevated oxygen pressure, adding a small portion of aqueous KOH.
The synthesis was done at 573 K and 430 MPa of oxygen pressure.
The crystal structure was solved by direct methods basing on single
crystal diffraction data (Pbca, Z ϭ 4, a ϭ 16.533(1), b ϭ
5.4 %). The optical band gap for KAg11(VO4)4 was determined as
2.0 eV. According to magnetic measurements, KAg11(VO4)4 is dia-
magnetic.
Keywords: Potassium silver vanadate; Elevated oxygen pressure;
Crystal structure
˚
10.6286(7), c ϭ 10.5452(7) A, 3983 independent reflections, R1 ϭ
Introduction
Table
1
Most intensive observed powder reflections for
˚
KAg11(VO4)4 (d > 1.5 A, I > 1 %). Results of a profile fit using the
positional parameters from the single crystal investigation
(Tab. 2Ϫ4).
In a systematic approach we continue to explore ternary
silver oxide systems by reacting mixtures of the constituent
binary oxides, applying elevated oxygen pressures [1Ϫ11].
During these studies we have noticed that adding small por-
tions of aqueous KOH frequently enhances reactivity and
promotes crystal growth. Surprisingly, the more basic
KOH, as compared to Ag2O, was not included in the pro-
ducts, at least in not detectable amounts [5Ϫ8]. However,
applying this procedure at investigating the Ag2O/V2O5
system we obtained a potassium silver vanadate(V),
KAg11(VO4)4, containing stoichiometric amounts of potas-
sium. The synthesis and structural characterization of
KAg11(VO4)4 are discussed below.
˚
˚
Nr.
h
k
l
d / A
I / %
Nr.
h
k
l
d / A
I / %
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
2
1
2
4
0
3
3
4
5
0
0
3
0
1
6
2
3
2
7
6
0
1
0
1
2
0
2
3
1
2
1
4
0
3
4
3
0
4
3
2
1
2
4
3
0
1
0
0
2
1
3
2
2
0
4
2
1
3
2
2
3
4
1
2
3
4
8.2667
6.8197
4.4704
4.1334
3.7431
2.8679
2.8548
2.7745
2.7089
2.6572
2.6364
2.5945
2.5767
2.4674
2.4422
2.2808
2.2732
2.2709
2.2525
2.2191
2.1197
2.0980
1.8
13.9
1.7
2.7
2.0
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
1
8
1
5
3
3
3
4
0
8
1
6
5
3
8
8
4
7
7
4
4
5
0
1
3
3
5
1
4
4
2
3
4
1
1
4
0
6
5
1
6
2
1
0
5
3
4
1
5
3
4
2
5
2
5
6
0
4
1
1
5
2
6
2.0675
2.0667
2.0528
1.9919
1.9746
1.9492
1.9368
1.8862
1.8715
1.8092
1.8015
1.7981
1.7538
1.6541
1.6314
1.6265
1.6092
1.5626
1.5562
1.5558
1.5474
3.9
12.2
3.4
3.2
1.8
1.1
1.2
1.2
12.9
1.4
1.2
1.2
1.6
1.7
10.5
10.1
1.3
4.7
3.6
2.8
3.5
100.0
2.4
17.4
17.2
1.1
1.2
4.4
2.5
1.1
7.9
1.8
2.4
1.2
1.1
1.4
Experimental Part
Reacting a mixture of Ag2O and V2O5 (molar ratio 2.75:1),
to which a small portion of aqueous KOH was added, at
elevated oxygen pressure, has yielded KAg11(VO4)4 as a
coarse crystalline, brilliant red product.
13.7
11.1
potassium vanadates formed simultaneously as a by-product, thus
fixing a part of the vanadium oxide. Therefore, in order to obtain
single phase KAg11(VO4)4 an excess of vanadium oxide was used
at the same temperature and oxygen pressure conditions (the 2:1
Ag:V molar ratio was used instead of 2.75:1, corresponding to the
empirical formula) to compensate for the formation of soluble
potassium vanadates which stay dissolved in the aqueous solution.
If despite of this procedure, the row product contained the silver
oxide admixture, it was removed by post washing with dilute
aqueous acetic acid. The as obtained final product consists of
coarse red KAg11(VO4)4 crystals, which are insensitive to air and
light.
The starting silver and vanadium oxides were obtained by adding
aqueous KOH to a AgNO3 (Sigma-Aldrich 99ϩ %) aqueous solu-
tion, and decomposition of solid NH4VO3 (Sigma-Aldrich 99ϩ %)
under oxygen flow at 300 °C, respectively. The mixture was anne-
aled for 10 hours in gold crucibles, placed in a stainless-steel auto-
clave [12], at 573 K and 430 MPa of oxygen pressure and post
washed with distilled water. Following this experimental procedure
a mixture of KAg11(VO4)4 and Ag2O was obtained because soluble
* Prof. Dr. Martin Jansen
Max-Planck-Institut für Festkörperforschung
Heisenbergstraße 1
D-70569 Stuttgart
Fax: ϩ49-711-6891502
X-ray investigations on powder samples were performed using the
Stoe StadiP diffractometer supplied with a position sensitive detec-
tor and a curved germanium monochromator with Cu-Kα1 radia-
˚
E-mail: M.Jansen@fkf.mpg.de
tion (λ ϭ 1.54056 A), at room temperature. The powder diffraction
Z. Anorg. Allg. Chem. 2006, 632, 413Ϫ416
 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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A. Kovalevskiy, M. Jansen
2
Table 2 X-ray and crystallographic dataa) for KAg11(VO4)4.
Table 4 Anisotropic thermal displacement parametersa) (in A )
˚
for KAg11(VO4)4.
Crystal data
Empirical formula
KAg11V4O16
1685.4
orthorhombic
Pbca (No. 61), 4
Atom U11
U22
U33
U12
U13
U23
Formula weight / g molϪ1
Crystal system
Ag1 0.0277(2) 0.02152(18) 0.0269(2)
Ag2 0.0282(2) 0.02288(19) 0.0261(2)
Ag3 0.0283(2) 0.02193(18) 0.0252(2) Ϫ0.00160(14) Ϫ0.00517(15) Ϫ0.00045(14)
Ag4 0.0300(2) 0.0255(2)
Ag5 0.0441(3) 0.0301(2)
Ag6 0.0252(3) 0.0293(3)
0.00190(14) 0.00638(15) Ϫ0.00069(14)
0.00027(15) Ϫ0.00575(15) Ϫ0.00137(15)
Space group, Z
Lattice constants (from powder)
˚
0.0244(2)
0.0261(2)
0.0233(3)
0.0180(3) Ϫ0.0002(3)
0.0150(3) Ϫ0.0010(3)
0.00353(15) 0.00696(16)
0.0033(2)
0.0007(2)
0.00143(15)
a / A
16.533(1)
10.6286(7)
10.5452(7)
1853.0(2)
0.00256(19) Ϫ0.00477(16)
˚
b / A
0.0003(2)
0.0008(3)
0.0000(3)
0.0024(7)
0.0065(2)
0.0005(3)
Ϫ0.0011(3)
Ϫ0.0002(7)
˚
c / A
V1
V2
K1
O1
O2
O3
O4
O5
O6
O7
O8
0.0153(3) 0.0153(3)
0.0220(4) 0.0146(3)
0.0339(9) 0.0381(10) 0.0202(7) Ϫ0.0040(7)
0.0227(17) 0.033(2)
0.0221(17) 0.0234(17) 0.0215(17) 0.0040(14) Ϫ0.0035(14) Ϫ0.0017(14)
0.0206(16) 0.0177(15) 0.032(2) 0.0011(13) Ϫ0.0010(15) Ϫ0.0001(15)
3
˚
V / A
Calculated density / g cmϪ3
Crystal shape, color
Crystal size / mm
6.041
compact, red transparent
0.1 x 0.1 x 0.1
0.0179(17) 0.0005(15) Ϫ0.0011(14) Ϫ0.0061(15)
Data collection
Diffractometer
Monochromator
0.051(3)
0.031(2)
0.025(2)
0.029(2)
0.0129(19) Ϫ0.021(2)
Ϫ0.0083(17)
0.0058(16)
Bruker AXS Smart-CCD
Graphite
0.71073
293
0.0283(19) 0.0254(19) Ϫ0.0077(16) Ϫ0.0121(16)
0.0241(18) 0.0250(18) 0.0242(18) Ϫ0.0055(14)
0.049(3)
0.032(2)
0.0052(15) Ϫ0.0034(15)
0.022(2)
0.0154(18)
˚
0.030(2)
0.032(2)
0.033(2) Ϫ0.017(2)
0.031(2) 0.0129(18)
Ϫ0.0135(18)
0.0110(18)
Wavelength / A
Temperature / K
2Θ range for data collection
hkl-range
Total no. reflection
Unique reflections
2Θ < 70.1
a) The anisotropic displacement factors exponent takes the form:
Ϫ2π2(a*2h2U11 ϩ b*2k2U22 ϩ c*2l2U33ϩ 2b*c*klU23 ϩ 2a*c*hlU13 ϩ 2a*b*hkU12
Ϫ26 Յ h Յ 25, Ϫ16 Յ k Յ 16, Ϫ16 Յ l Յ 16
36995
3983
)
Magnetic measurements were performed on a SQUID-Magneto-
meter (MPMS 5.5, Quantum Design) between 5 and 300 K in ma-
gnetic fields 0.1 and 1 T. A diffuse reflectance spectrum was re-
corded on a Perkin Elmer Lambda 9 UV/VIS/NIR Spectrophoto-
meter.
Unique reflections with I > 2σ(I) 3685
Absorption coefficient / mmϪ1
F(000)
13.54
3024
Structure refinement
Structure solution, refinement
Parameters refined
ShelXL’97
149
R1 I > 2σ(I), all data
wR2 I > 2σ(I), all data
∆Fmax, ∆Fmin / e A
0.0500, 0.0540
0.1033, 0.1052
1.25, Ϫ1.75
0.00070(4)
Results and Discussion
Ϫ3
˚
Extinction coefficient
KAg11(VO4)4 has been obtained by the solid state reaction
at elevated oxygen pressure [12] as a coarse crystalline red
product. Experimental X-ray powder diffraction patterns
(Tab. 1), which could be indexed orthorhombic with the
a) Further details of the crystal structure investigation are available from the
Fachinformationszentrum Karlsruhe, D-76344 Eggenstein-Leopoldshafen
(Germany), on quoting the depository number CSD-391344, the name of
authors, and citation of the paper.
˚
˚
refined lattice constants a ϭ 16.533(1) A, b ϭ 10.6286(7) A,
˚
c ϭ 10.5452(7) A, have shown, that the sample was single
Table 3 Atomic coordinates and isotropic thermal displacement
phase; also, the measured pattern agrees perfectly with the
calculated one.
parameters (Ueq)a) for KAg11(VO4)4.
The crystal structure of the new potassium silver vana-
date was determined from single crystal data collected at
293 K. For details of the structure refinement and crystallo-
graphic data see Tab. 2-4. For interatomic distances, coordi-
nation numbers (CN), effective coordination numbers
(ECoN) and mean fictive ionic radii (MEFIR) [15] see
Tab. 5.
2
˚
Atom
Site
x
y
z
Ueq (in A )
Ag1
Ag2
Ag3
Ag4
Ag5
Ag6
V1
V2
K1
O1
O2
O3
O4
O5
O6
O7
O8
8c
8c
8c
8c
8c
4b
8c
8c
4a
8c
8c
8c
8c
8c
8c
8c
8c
0.13298(3)
0.13204(3)
0.12597(3)
0.12335(3)
0.25382(3)
0
0.26841(5)
0.99897(5)
0
0.9998(2)
0.2136(2)
0.9971(2)
0.9154(3)
0.3196(3)
0.2055(2)
0.0844(3)
0.3326(3)
0.22291(4)
0.78619(4)
0.99027(4)
0.02192(4)
0.24531(5)
0
0.01345(8)
0.26367(8)
0
0.3164(4)
0.1089(4)
0.1023(4)
0.3221(4)
0.1091(4)
0.9156(4)
0.3164(4)
0.9210(4)
0.51847(4)
0.47373(4)
0.28506(4)
0.71563(4)
0.74492(4)
1/2
0.50124(8)
0.75947(8)
0
0.9164(4)
0.3960(4)
0.7564(5)
0.6846(4)
0.6040(4)
0.5892(4)
0.6850(5)
0.4187(4)
0.0254(1)
0.0257(1)
0.0252(1)
0.0266(1)
0.0334(1)
0.0259(1)
0.0162(2)
0.0172(2)
0.0307(4)
0.0245(8)
0.0223(7)
0.0233(7)
0.0351(11)
0.0281(9)
0.0244(8)
0.0371(12)
0.0316(10)
˚
Table 5 Interatomic distances (in A), coordination numbers (CN),
effective coordination numbers (ECoN) and mean fictive ionic radii
˚
(MEFIR, in A) [15] for KAg11(VO4)4.
Atom O1 O2 O3 O4 O5 O6 O7 O8 CN ECoN MEFIR
Ag1
Ag2
Ag3
Ag4
Ag5
Ag6
2.486 2.216
2.489
2.172 2.421 4 3.4
0.80
0.80
0.88
0.84
0.95
0.74
a)
U
ϭ 1/3(U11ϩU22ϩU33)
eq
2.174 2.464 2.202
2.361
4
4
3.3
3.9
2.249 2.301
2.410
2.299 2.456
2.890 2.342 2.535 2.969 2.920 6 3.4
2.0
2.211
2.341 4 3.8
data were collected in the range of 5 to 80 degrees in 2Θ. Experi-
mental d values and relative intensities are given in Table 1. The
profile refinement was performed using the JANA2000 program
package [13]. The single crystal diffraction data were collected on
a Bruker AXS Smart-CCD diffractometer (Mo-Kα radiation, gra-
phite monochromator). The structure was solved by direct methods
and refined using full-matrix least-squares techniques [14]. The
final refinement included anisotropic displacement parameters for
all atoms. See Table 2 for crystallographic data.
2.320
1.756
2.141
2.141
2
V1
V2
K1
1.710 1.739
1.688 4 4.0
4.0
0.29
0.31
1.48
1.747
3.477
3.477
5
1.716 1.708
1.710
4
2.790 3.053 3.383
2.790 3.053 3.383
3.092 3.017 12 8.9
3.092 3.017
CN
4
4
5
5
4
5
5
ECoN 3.6 4.0 4.0 3.8 4.1 3.8 3.8 3.9
MEFIR 1.46 1.42 1.42 1.45 1.46 1.44 1.45 1.47
414
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Z. Anorg. Allg. Chem. 2006, 413Ϫ416

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Synthesis and Crystal Structure Analysis of KAg11(VO4)4
Fig. 2 Coordination environments of silver and potassium atoms
in KAg11(VO4)4. (a)Ϫ(d) Irregular sawing horse, Ag1ϪAg4. (e)
Three-fold planar, Ag5. (f) Two-fold coordinated, Ag6. (g) Distor-
ted bi-capped trigonal antiprism, K1. Light gray spheres represent
silver atoms, white sphere represents potassium atom, dark gray
spheres represent oxygen atoms.
Fig 1 Crystal structure of KAg11(VO4)4. Dark gray spheres repre-
sent silver atoms, white spheres represent potassium, vanadium
oxide tetrahedra are gray.
The crystal structure of KAg11(VO4)4 is made up of isola-
ted, fairly regular VO43Ϫ tetrahedra based on two crystallo-
˚
graphically unique vanadium atoms with 1.69 Ϫ 1.76 A
VϪO bond lengths (Tab. 5) and OϪVϪO angels varying
from 107° to 111°. The metallic ions sit in the pockets bet-
ween the negatively charged vanadium oxide tetrahedra,
which leads to irregular coordination environments. The
different coordination environment around the cations
creates six crystallographically independent silver sites and
one potassium site (Fig. 1).
At a maximum coordination distance for silver atoms of
˚
2.7 A, Ag1, Ag2, Ag3 and Ag4 are four-coordinate, Ag5 is
three-coordinate and Ag6 is two-coordinate. Both Ag1 and
Ag2 are prevailingly two-fold linearly coordinated (by O2,
O7, and O4, O6, respectively) with AgϪO distances varying
from 2.174 A to 2.216 A, with two oxygen atoms (O1, O8,
and O5, O1, respectively) in the second coordination sphere
forming a sawing horse geometry. The other four-coordina-
ted silver atoms, Ag3 and Ag4, are coordinated in irregular
sawing horse geometry as well, but without a distinguished
two-fold coordination. The AgϪO distances vary from
Fig. 3 Three-dimensional cation packing of KAg11(VO4)4 (a, view
along [0 1 1]) and of Ag6(SO4)(SiO4) [16] (b, view along [0 1 0]).
Black spheres represent the tetrahedron-forming atoms (vanadium
in case of KAg11(VO4)4 and sulfur and silicon in case of Ag6(SO4)-
(SiO4)). Silver atoms are gray, and potassium atoms are white. The
oxygen atoms are not shown.
˚
˚
faces of the antiprism capped by O7. See Figure 2 and
Table 5 for interatomic distances.
˚
˚
˚
˚
2.249 A to 2.410 A for Ag3, and from 2.211 A to 2.456 A
for Ag4. The triangular planar coordination geometry of
Ag5 is made up of O2, O5 and O6. It can be described as
a two-fold linear coordination by O2 and O5, with O6 in
the second coordination sphere. Ag6 is two-fold linearly
coordinated by O1 ϫ 2. The K1 coordination forms a di-
storted bi-capped trigonal antiprism geometry. The anti-
prism is made up of O3 ϫ 2, O4 ϫ 2 and O8 ϫ 2 with two
The cation partial structure of KAg11(VO4)4 can be rela-
ted to one in Ag6(SiO4)(SO4) [16, 17]. Following this ana-
logy, the structure (see Fig. 3) may be described as alternate
[Ag4]4ϩ and [Ag2(VO4)2]4Ϫ layers, where in every second of
the latter one half of silver atoms is substituted by potas-
sium. The resulting stacking sequence is:
{Ϫ[Ag4]4ϩϪ[Ag2(VO4)2]4ϪϪ[Ag4]4ϩϪ[KAg(VO4)2]4ϪϪ}
Z. Anorg. Allg. Chem. 2006, 413Ϫ416
 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
zaac.wiley-vch.de
415

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A. Kovalevskiy, M. Jansen
Acknowledgements. We thank J. Nuss for collecting X-ray single
crystal data, E. Brücher for carrying out the magnetic measure-
ments and W. König for the diffuse reflectance spectrum recording.
References
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186, 147.
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Chem. Int. Ed. Engl. 1992, 31, 653.
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[6] S. Deibele, J. Curda, E.-M. Peters, M. Jansen, Chem. Commun.
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Fig. 4 Diffuse reflectance spectrum of KAg11(VO4)4 (R-reflec-
tance).
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Chem. 2005, 631, 723.
[12] C. Linke, M. Jansen, Z. Anorg. Allg. Chem. 1997, 623, 1441.
[13] V. Petricek, M. Dusek, L. Palatinus, JANA2000, Institute of
Physics, Praha, Czech Republic, 2000.
[14] SHELXTL version 6.14, Brucker AXS Inc., Madison, Wis-
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[15] R. Hoppe, Z. Kristallogr. 1979, 150, 23.
[16] H.-L. Keller, Hk. Müller-Buschbaum, Z. Anorg. Allg. Chem.
1974, 408, 205.
The accommodation of large potassium cations in the
structure of KAg11(VO4)4 causes a significant distortion of
the cation partial structure, in comparison with the one
found in Ag6(SiO4)(SO4).
Using the diffuse reflectance spectrum data (Fig. 4) the
optical band gap for KAg11(VO4)4 was determined as
2.0 eV, which is in good agreement with the red color of the
crystals and the absorption data for other red ternary silver
3Ϫ
oxides [18]. Since VO4 anions are colorless, the absorp-
[17] M. Jansen, K. Heidebrecht, Z. Kristallogr. 1991, 196, 95.
[18] C. Friebel, M. Jansen, Z. Naturforsch. 1984, 39b, 739.
[19] M. Jansen, Angew. Chem. 1987, 99, 1136, Angew. Chem. Int.
Ed. Engl. 1987, 26, 1098.
tion band was attributed to Ag-Ag interactions [19]. Accor-
ding to the magnetic measurements, KAg11(VO4)4 is dia-
magnetic.
416
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 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2006, 413Ϫ416