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Acta Crystallogr Sect E Struct Rep Online. 2010 November 1; 66(Pt 11): i74.
Published online 2010 October 2. doi:  10.1107/S1600536810038717
PMCID: PMC3009017

The γ-polymorph of AgZnPO4 with an ABW zeolite-type framework topology

Abstract

The γ-polymorph of the title compound, silver zinc orthophos­phate, was synthesized under hydro­thermal conditions. The structure consists of ZnO4, PO4 and AgO4 units. The coord­ination spheres of ZnII and PV are tetra­hedral, whereas the AgI atom is considerably distorted from a tetra­hedral coordination. Each O atom is linked to each of the three cations. An elliptic eight-membered ring system is formed by corner-sharing of alternating PO4 and ZnO4 tetra­hedra, leading to a framework with an ABW-type zeolite structure. The framework encloses channels running parallel to [100] in which the Ag cations are located, with Ag(...)Ag contacts of 3.099 (3) Å. This short distance results from d 10(...)d 10 inter­actions, which play a substantial role in the crystal packing. The structure of γ-AgZnPO4 is distinct from the two other polymorphs α-AgZnPO4 and β-AgZnPO4, but is isotypic with NaZnPO4-ABW, NaCoPO4-ABW and NH4CoPO4-ABW.

Related literature

For general background to A I B IIPO4 phosphates, see: Elouadi & Elammari (1990 [triangle]); Bu et al. (1996 [triangle]); Moring & Kostiner (1986 [triangle]). For the α- and β- polymorphs of AgZnPO4, see: Hammond et al. (1998 [triangle]); Elammari et al. (1987 [triangle], 1988 [triangle]). For bond-valence analysis, see: Brown & Altermatt (1985 [triangle]). For d 10(...)d 10 inter­actions, see: Jansen (1987 [triangle]). For compounds with isotypic structures, see: Chippindale et al. (1999 [triangle]); Feng et al. (1997 [triangle]); Ng & Harrison (1998 [triangle]). For nomenclature of zeolites, see: Baerlocher et al. (2007 [triangle]).

Experimental

Crystal data

  • AgZn(PO4)
  • M r = 268.21
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is e-66-00i74-efi7.jpg
  • a = 5.1664 (2) Å
  • b = 10.4183 (3) Å
  • c = 7.3263 (2) Å
  • β = 90.304 (2)°
  • V = 394.33 (2) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 11.32 mm−1
  • T = 296 K
  • 0.25 × 0.08 × 0.05 mm

Data collection

  • Bruker X8 APEXII diffractometer
  • Absorption correction: multi-scan (SADABS; Bruker, 2005 [triangle]) T min = 0.351, T max = 0.568
  • 9307 measured reflections
  • 1745 independent reflections
  • 1621 reflections with I > 2σ(I)
  • R int = 0.033

Refinement

  • R[F 2 > 2σ(F 2)] = 0.019
  • wR(F 2) = 0.044
  • S = 1.08
  • 1745 reflections
  • 65 parameters
  • Δρmax = 1.18 e Å−3
  • Δρmin = −1.30 e Å−3

Data collection: APEX2 (Bruker, 2005 [triangle]); cell refinement: SAINT (Bruker, 2005 [triangle]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 [triangle]) and DIAMOND (Brandenburg, 2006 [triangle]); software used to prepare material for publication: WinGX (Farrugia, 1999 [triangle]).

Table 1
Selected bond lengths (Å)

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810038717/wm2407sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810038717/wm2407Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Acknowledgments

The authors thank the Unit of Support for Technical and Scientific Research (UATRS, CNRST) for the X-ray measurements.

supplementary crystallographic information

Comment

A crystal-chemical classification of AIBIIPO4 compounds was carried out by Elouadi and Elammari (1990) who used the combination of the coordination number and the correlative cationic radii r(A) and r(B) as basic parameters to predict the structural evolution versus the nature of both A and B elements. In fact, the appearance of a structural variety does not depend only on the size and the nature of both cations A and B, but could also be favored by specific parameters such as the Jahn-Teller effect, which mainly characterizes compounds containing Cu(II). In addition, the structural stability is also expected to be both temperature- and pressure-dependent. Therefore, the thermodynamic conditions for the preparation of all phases considered are of prime importance. This is also corroborated by the fact that most of the compounds AIBIIPO4 undergo at least one phase transition (Elammari et al., 1988). For instance, it has been found that the thermal treatment (quenching, sintering, etc.) is a key parameter to foresee the structural variety to be stabilized at room temperature (Moring & Kostiner 1986; Bu et al., 1996). In addition to α-AgZnPO4 and β-AgZnPO4 characterized by Hammond et al.(1998), we report here on the crystal structure of a new form of silver zinc phosphate (γ-AgZnPO4) that was hydrothermally synthesized.

The structure of this monophosphate consists of zinc and phosphorus atoms tetrahedrally coordinated to oxygen atoms, whereas the silver atom is surrounded by four O atoms in a considerably distorted coordination, with Ag–O bond lengths between 2.2992 (13) and 2.4975 (14) Å. As shown in Fig. 1, the PO4 and ZnO4 tetrahedra share a vertex and are almost regular with P–O and Zn–O distances in the range 1.5283 (14)–1.5415 (13) Å and 1.9372 (13)–1.9516 (13) Å, respectively (Table 1). The expected +I, +II and +V oxidation states of the Ag, Zn and P atoms were confirmed by bond valence sum calculations (Brown & Altermatt, 1985) with 0.94, 2.09 and 4.93 valence units, respectively.

A three-dimensional polyhedral view of the crystal structure is represented in Fig. 2. It shows PO4 tetrahedra linked to ZnO4 tetrahedra by sharing corners in the way to build an eight-membered ring system surrounding the silver atoms. This arrangements give rise to eight-membered elliptical channels running parallel to [100] where the AgI atoms are located with short Ag···Ag contacts of 3.099 (3) Å. This short distance is due to d10···d10 interactions (Jansen, 1987) that play an important role in the crystal structure.

It is particularly interesting to compare the crystal structures of the three different polymorphs of AgZnPO4: The high-temperature β-AgZnPO4 polymorph adopts a monoclinic beryllonite-type structure similar to that of NaZnPO4 (Elammari et al., 1987) whereas the low-temperature α-AgZnPO4 polymorph crystallizes with a hexagonal structure like that of high-p/low-T KZnPO4. In both α- and β- polymorphs, corner-sharing PO4 and ZnO4 tetrahedra form a fully ordered framework containing six-membered rings with distinct topologies around the AgI atoms (Hammond et al., 1998). As noted above, in the case of γ-AgZnPO4 they build up an elliptical eight-membered ring system of alternating PO4 and ZnO4 tetrahedra around the AgI atoms with an ABW zeolite topology UUUUDDDD, where U and D represent tetrahedra pointing up and down, respectively (Baerlocher et al., 2007).

Compounds isotypic with γ-AgZnPO4 are relatively rare, however, there are three phases which adopt the same stucture, viz. NaZnPO4-ABW (Ng & Harrison, 1998), NaCoPO4-ABW (Chippindale et al., 1999) and NH4CoPO4-ABW (Feng et al., 1997).

Experimental

The hydrothermal exploration of the Ag2O–ZnO–P2O5 system, in order to search for new phases, in particular with alluaudite-like structure, has allowed to isolate a new form of silver zinc orthophosphate. The reaction mixture contained silver nitrate (AgNO3; 0.1699 g), zinc oxide (ZnO; 0.1221 g), 85 %wt phosphoric acid (H3PO4; 0,10 ml) and water (12 ml) and was hydrothermally treated in a 23 ml Teflon-lined autoclave under autogeneous pressure at 468 K for two days. After being filtered off, washed with deionized water and air dried, the reaction product consists of a white powder and some colorless parallelepipedic crystals corresponding to the title compound.

Refinement

The highest peak and the deepest hole in the final Fourier map are 0.53 Å and 0.52 Å, respectively, from Ag1.

Figures

Fig. 1.
Plot of parts of the crystal structure of the title compound showing the most important interatomic bonds. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry codes: (i) -x + 1, -y + 2, -z; (ii) x - 1, y, z; (iii) x - 1/2, -y + 3/2, ...
Fig. 2.
A three-dimensional polyhedral view of the crystal structure of the monophosphate γ-AgZnPO4. PO4 tetrahedra are pink, ZnO4 tetrahedra are light-blue and silver atoms are grey.

Crystal data

AgZn(PO4)F(000) = 496
Mr = 268.21Dx = 4.518 Mg m3
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ynCell parameters from 1745 reflections
a = 5.1664 (2) Åθ = 3.4–35.0°
b = 10.4183 (3) ŵ = 11.32 mm1
c = 7.3263 (2) ÅT = 296 K
β = 90.304 (2)°Plate, colourless
V = 394.33 (2) Å30.25 × 0.08 × 0.05 mm
Z = 4

Data collection

Bruker X8 APEXII diffractometer1745 independent reflections
Radiation source: fine-focus sealed tube1621 reflections with I > 2σ(I)
graphiteRint = 0.033
[var phi] and ω scansθmax = 35.0°, θmin = 3.4°
Absorption correction: multi-scan (SADABS; Bruker, 2005)h = −7→8
Tmin = 0.351, Tmax = 0.568k = −16→16
9307 measured reflectionsl = −11→11

Refinement

Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.019w = 1/[σ2(Fo2) + (0.0138P)2 + 0.5475P] where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.044(Δ/σ)max = 0.001
S = 1.08Δρmax = 1.18 e Å3
1745 reflectionsΔρmin = −1.30 e Å3
65 parametersExtinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraintsExtinction coefficient: 0.0685 (12)

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2)

xyzUiso*/Ueq
Ag10.20254 (3)0.891281 (15)0.021499 (19)0.01931 (6)
Zn10.19054 (4)0.840764 (19)0.52546 (3)0.01037 (6)
P10.69041 (8)0.89550 (4)0.29147 (6)0.00877 (8)
O10.3966 (2)0.87815 (14)0.31182 (18)0.0159 (2)
O20.7616 (3)1.03856 (12)0.27484 (18)0.0161 (2)
O30.8268 (3)0.83575 (14)0.45641 (19)0.0166 (2)
O40.7730 (3)0.83197 (12)0.11089 (18)0.0155 (2)

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
Ag10.02148 (8)0.02283 (8)0.01363 (8)0.00195 (5)0.00071 (5)0.00377 (5)
Zn10.01202 (9)0.00970 (9)0.00939 (9)−0.00034 (6)−0.00004 (6)0.00058 (6)
P10.00988 (16)0.00839 (16)0.00805 (16)−0.00085 (12)0.00051 (12)0.00001 (12)
O10.0099 (5)0.0272 (7)0.0107 (5)−0.0013 (5)0.0007 (4)0.0032 (5)
O20.0289 (7)0.0083 (5)0.0110 (5)−0.0043 (5)0.0007 (5)−0.0006 (4)
O30.0139 (5)0.0184 (6)0.0176 (6)−0.0014 (4)−0.0044 (4)0.0069 (5)
O40.0189 (6)0.0130 (5)0.0147 (6)−0.0045 (4)0.0059 (5)−0.0055 (4)

Geometric parameters (Å, °)

Ag1—O2i2.2992 (13)P1—O11.5366 (13)
Ag1—O12.3506 (13)P1—O21.5401 (13)
Ag1—O4ii2.3982 (13)P1—O41.5415 (13)
Ag1—O3iii2.4975 (14)O2—Zn1v1.9438 (13)
Ag1—Ag1iv3.0990 (3)O2—Ag1i2.2992 (13)
Zn1—O11.9372 (13)O3—Zn1vii1.9440 (13)
Zn1—O2v1.9439 (13)O3—Ag1viii2.4975 (14)
Zn1—O3ii1.9440 (13)O4—Zn1ix1.9516 (13)
Zn1—O4vi1.9516 (13)O4—Ag1vii2.3982 (13)
P1—O31.5283 (14)
O2i—Ag1—O1146.80 (5)O3—P1—O2110.33 (8)
O2i—Ag1—O4ii114.78 (5)O1—P1—O2110.97 (8)
O1—Ag1—O4ii97.40 (5)O3—P1—O4112.03 (8)
O2i—Ag1—O3iii95.66 (5)O1—P1—O4108.10 (8)
O1—Ag1—O3iii90.50 (5)O2—P1—O4106.28 (7)
O4ii—Ag1—O3iii92.72 (5)P1—O1—Zn1130.50 (8)
O2i—Ag1—Ag1iv74.30 (4)P1—O1—Ag1108.80 (7)
O1—Ag1—Ag1iv114.78 (4)Zn1—O1—Ag1120.61 (6)
O4ii—Ag1—Ag1iv65.84 (3)P1—O2—Zn1v126.57 (8)
O3iii—Ag1—Ag1iv147.90 (3)P1—O2—Ag1i113.75 (7)
O1—Zn1—O2v114.19 (6)Zn1v—O2—Ag1i119.64 (6)
O1—Zn1—O3ii109.25 (6)P1—O3—Zn1vii129.49 (8)
O2v—Zn1—O3ii109.40 (7)P1—O3—Ag1viii114.76 (7)
O1—Zn1—O4vi108.94 (6)Zn1vii—O3—Ag1viii103.00 (6)
O2v—Zn1—O4vi109.17 (6)P1—O4—Zn1ix127.61 (8)
O3ii—Zn1—O4vi105.52 (6)P1—O4—Ag1vii112.61 (7)
O3—P1—O1109.09 (8)Zn1ix—O4—Ag1vii110.53 (6)

Symmetry codes: (i) −x+1, −y+2, −z; (ii) x−1, y, z; (iii) x−1/2, −y+3/2, z−1/2; (iv) −x, −y+2, −z; (v) −x+1, −y+2, −z+1; (vi) x−1/2, −y+3/2, z+1/2; (vii) x+1, y, z; (viii) x+1/2, −y+3/2, z+1/2; (ix) x+1/2, −y+3/2, z−1/2.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: WM2407).

References

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