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Ammonium gadolinium polyphosphate, NH4Gd(PO3)4, (I), and ammonium gadolinium cyclotetraphosphate, NH4GdP4O12, (II), were synthesized by flux growth with excess (NH4)2HPO4. In (I), the PO4 tetrahedra share vertices to produce corrugated ribbons along the c direction, while in (II) they form P4O12 rings arranged in layers perpendicular to the c axis. In both structures, isolated GdO8 polyhedra link the phosphate anions into a three-dimensional framework with channels containing the NH4+ cations. The Gd and N atoms are located in general positions in (I) and on twofold axes in (II).
Supporting information
Chacun des composés étudiés a été préparé par la méthode de flux à partir d'un mélange de (NH4)2HPO4 et Gd2O3, pris dans les rapports molaires 15:1 pour NH4Gd(PO3)4 et 13:1 pour NH4GdP4O12. Ces mélanges ont été finement broyés, placés dans des creusets en carbone vitreux et portés respectivement à 573 e t 553 K pendant 10 jours. Après refroidissement, les cristaux formés ont été extraits du mélange réactionnel par lavage avec de l'eau bouillante.
Pour les deux composés, les positions des atomes H ont été déterminées par séries de Fourier-différence. Les distances N—H1, N—H2, N—H3 et N—H4, dans NH4Gd(PO3)4, ont été fixées à 0.90 Å par l'option DFIX du programme SHELXL97 (Sheldrick, 1997). Les Uiso de ces atomes H ont été fixés à 0.08 Å2. Dans NH4GdP4O12, les positions des atomes H ainsi que leurs Uiso ont été affinés sans contrainte.
For both compounds, data collection: CAD-4 EXPRESS (Duisenberg, 1992; Macíček & Yordanov, 1992); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 1998); software used to prepare material for publication: SHELXL97.
(I) ammonium gadolinium tetrakis(phosphate)
top
Crystal data top
NH4Gd(PO3)4 | F(000) = 924 |
Mr = 491.17 | Dx = 3.325 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71069 Å |
Hall symbol: -P 2ybc | Cell parameters from 25 reflections |
a = 10.951 (3) Å | θ = 10.3–15.0° |
b = 8.998 (1) Å | µ = 7.48 mm−1 |
c = 12.803 (5) Å | T = 293 K |
β = 128.94 (2)° | Prism, colourless |
V = 981.2 (5) Å3 | 0.21 × 0.14 × 0.12 mm |
Z = 4 | |
Data collection top
Enraf-Nonius CAD-4 diffractometer | 1771 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.028 |
Graphite monochromator | θmax = 27.0°, θmin = 2.4° |
ω/2θ scans | h = −13→13 |
Absorption correction: ψ scan (North et al., 1968) | k = −1→11 |
Tmin = 0.373, Tmax = 0.473 | l = −13→16 |
2364 measured reflections | 2 standard reflections every 120 min |
2011 independent reflections | intensity decay: −2% |
Refinement top
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.024 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.056 | w = 1/[σ2(Fo2) + (0.019P)2 + 1.0728P] where P = (Fo2 + 2Fc2)/3 |
S = 1.03 | (Δ/σ)max < 0.001 |
2011 reflections | Δρmax = 0.81 e Å−3 |
176 parameters | Δρmin = −0.65 e Å−3 |
4 restraints | Extinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: heavy method | Extinction coefficient: 0.0005 (1) |
Crystal data top
NH4Gd(PO3)4 | V = 981.2 (5) Å3 |
Mr = 491.17 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 10.951 (3) Å | µ = 7.48 mm−1 |
b = 8.998 (1) Å | T = 293 K |
c = 12.803 (5) Å | 0.21 × 0.14 × 0.12 mm |
β = 128.94 (2)° | |
Data collection top
Enraf-Nonius CAD-4 diffractometer | 1771 reflections with I > 2σ(I) |
Absorption correction: ψ scan (North et al., 1968) | Rint = 0.028 |
Tmin = 0.373, Tmax = 0.473 | 2 standard reflections every 120 min |
2364 measured reflections | intensity decay: −2% |
2011 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.024 | 4 restraints |
wR(F2) = 0.056 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.03 | Δρmax = 0.81 e Å−3 |
2011 reflections | Δρmin = −0.65 e Å−3 |
176 parameters | |
Special details top
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) top | x | y | z | Uiso*/Ueq | |
Gd | 0.18496 (3) | 0.22554 (3) | 0.49962 (2) | 0.00597 (9) | |
P1 | 0.1127 (1) | 0.5920 (1) | 0.3545 (1) | 0.0064 (2) | |
P2 | 0.1790 (1) | 0.8263 (1) | 0.5407 (1) | 0.0064 (2) | |
P3 | 0.3036 (1) | 0.3940 (1) | 0.3246 (1) | 0.0069 (2) | |
P4 | 0.4775 (1) | 0.5265 (1) | 0.2520 (1) | 0.0065 (2) | |
O1 | 0.2237 (4) | 0.7032 (4) | 0.4790 (3) | 0.0109 (7) | |
O2 | 0.0734 (4) | 0.7612 (4) | 0.5647 (4) | 0.0114 (7) | |
O3 | 0.3404 (4) | 0.2904 (4) | 0.4322 (3) | 0.0116 (7) | |
O4 | 0.2013 (4) | 0.3408 (4) | 0.1838 (3) | 0.0122 (7) | |
O5 | 0.3480 (4) | 0.8433 (4) | 0.6861 (3) | 0.0083 (7) | |
O6 | 0.4638 (4) | 0.4551 (4) | 0.3597 (3) | 0.0087 (7) | |
O7 | 0.6359 (4) | 0.5954 (4) | 0.3296 (3) | 0.0096 (7) | |
O8 | 0.2358 (4) | 0.5478 (4) | 0.3322 (3) | 0.0119 (7) | |
O9 | 0.1360 (4) | 0.9651 (4) | 0.4612 (3) | 0.0117 (7) | |
O10 | 0.0746 (4) | 0.4591 (4) | 0.3989 (3) | 0.0118 (7) | |
O11 | −0.0185 (4) | 0.6775 (4) | 0.2378 (3) | 0.0127 (8) | |
O12 | 0.4338 (4) | 0.4159 (4) | 0.1463 (3) | 0.0109 (7) | |
N | 0.2643 (6) | 0.9316 (7) | 0.3057 (5) | 0.025 (1) | |
H1 | 0.366 (4) | 0.90 (1) | 0.364 (7) | 0.080* | |
H2 | 0.190 (8) | 0.878 (9) | 0.233 (6) | 0.080* | |
H3 | 0.25 (1) | 1.022 (5) | 0.272 (9) | 0.080* | |
H4 | 0.24 (1) | 0.92 (1) | 0.364 (7) | 0.080* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Gd | 0.0057 (1) | 0.0054 (1) | 0.0059 (1) | −0.00010 (9) | 0.0032 (1) | 0.00062 (9) |
P1 | 0.0080 (5) | 0.0047 (6) | 0.0061 (6) | 0.0004 (5) | 0.0043 (5) | −0.0004 (5) |
P2 | 0.0061 (5) | 0.0055 (6) | 0.0071 (6) | −0.0004 (5) | 0.0039 (5) | −0.0004 (5) |
P3 | 0.0073 (5) | 0.0071 (6) | 0.0069 (6) | −0.0007 (5) | 0.0048 (5) | 0.0002 (5) |
P4 | 0.0064 (5) | 0.0062 (6) | 0.0070 (6) | 0.0001 (5) | 0.0042 (5) | 0.0004 (5) |
O1 | 0.010 (2) | 0.010 (2) | 0.010 (2) | −0.001 (1) | 0.006 (1) | −0.005 (1) |
O2 | 0.010 (2) | 0.015 (2) | 0.012 (2) | −0.001 (1) | 0.008 (1) | 0.002 (1) |
O3 | 0.010 (2) | 0.014 (2) | 0.011 (2) | 0.002 (1) | 0.006 (1) | 0.005 (1) |
O4 | 0.009 (2) | 0.019 (2) | 0.009 (2) | −0.003 (1) | 0.006 (1) | −0.005 (1) |
O5 | 0.006 (1) | 0.007 (2) | 0.005 (2) | −0.003 (1) | 0.000 (1) | −0.001 (1) |
O6 | 0.004 (1) | 0.014 (2) | 0.008 (2) | −0.001 (1) | 0.003 (1) | −0.001 (1) |
O7 | 0.006 (1) | 0.010 (2) | 0.012 (2) | −0.002 (1) | 0.005 (1) | −0.002 (1) |
O8 | 0.017 (2) | 0.009 (2) | 0.018 (2) | 0.003 (1) | 0.016 (2) | 0.002 (1) |
O9 | 0.010 (2) | 0.006 (2) | 0.008 (2) | −0.000 (1) | 0.001 (1) | 0.001 (1) |
O10 | 0.011 (2) | 0.009 (2) | 0.014 (2) | −0.000 (1) | 0.007 (1) | 0.003 (1) |
O11 | 0.015 (2) | 0.013 (2) | 0.007 (2) | 0.007 (1) | 0.005 (1) | 0.003 (1) |
O12 | 0.011 (2) | 0.010 (2) | 0.013 (2) | 0.001 (1) | 0.008 (1) | −0.001 (1) |
N | 0.020 (2) | 0.034 (3) | 0.026 (3) | −0.001 (2) | 0.016 (2) | −0.001 (2) |
Geometric parameters (Å, º) top
Gd—O4i | 2.328 (3) | P2—O9 | 1.488 (4) |
Gd—O10 | 2.363 (3) | P2—O2 | 1.491 (4) |
Gd—O9ii | 2.386 (4) | P2—O1 | 1.605 (4) |
Gd—O2iii | 2.402 (4) | P2—O5 | 1.606 (3) |
Gd—O11iv | 2.405 (3) | P3—O4 | 1.481 (4) |
Gd—O3 | 2.415 (3) | P3—O3 | 1.494 (4) |
Gd—O7v | 2.416 (3) | P3—O8 | 1.602 (4) |
Gd—O12i | 2.477 (3) | P3—O6 | 1.610 (3) |
P1—O11 | 1.480 (4) | P4—O7 | 1.487 (3) |
P1—O10 | 1.492 (4) | P4—O12 | 1.496 (4) |
P1—O8 | 1.594 (3) | P4—O5vi | 1.610 (3) |
P1—O1 | 1.607 (4) | P4—O6 | 1.612 (3) |
| | | |
O11—P1—O10 | 118.3 (2) | O3—P3—O8 | 110.4 (2) |
O11—P1—O8 | 110.1 (2) | O4—P3—O6 | 107.9 (2) |
O10—P1—O8 | 109.8 (2) | O3—P3—O6 | 109.9 (2) |
O11—P1—O1 | 109.1 (2) | O8—P3—O6 | 98.8 (2) |
O10—P1—O1 | 109.8 (2) | O7—P4—O12 | 117.2 (2) |
O8—P1—O1 | 97.8 (2) | O7—P4—O5vi | 108.7 (2) |
O9—P2—O2 | 121.1 (2) | O12—P4—O5vi | 109.5 (2) |
O9—P2—O1 | 107.8 (2) | O7—P4—O6 | 106.9 (2) |
O2—P2—O1 | 110.3 (2) | O12—P4—O6 | 111.1 (2) |
O9—P2—O5 | 110.6 (2) | O5vi—P4—O6 | 102.3 (2) |
O2—P2—O5 | 106.1 (2) | P2—O1—P1 | 130.0 (2) |
O1—P2—O5 | 98.7 (2) | P2—O5—P4vii | 132.1 (2) |
O4—P3—O3 | 118.7 (2) | P3—O6—P4 | 124.6 (2) |
O4—P3—O8 | 109.2 (2) | P1—O8—P3 | 134.6 (2) |
Symmetry codes: (i) x, −y+1/2, z+1/2; (ii) x, y−1, z; (iii) −x, −y+1, −z+1; (iv) −x, y−1/2, −z+1/2; (v) −x+1, −y+1, −z+1; (vi) x, −y+3/2, z−1/2; (vii) x, −y+3/2, z+1/2. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N—H2···O2vi | 0.90 (2) | 2.10 (3) | 2.965 (7) | 163 (8) |
N—H4···O9 | 0.90 (2) | 2.23 (4) | 3.091 (6) | 160 (8) |
Symmetry code: (vi) x, −y+3/2, z−1/2. |
(II) ammonium gadolinium cyclotetraphosphate
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Crystal data top
NH4GdP4O12 | F(000) = 924 |
Mr = 491.17 | Dx = 3.344 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71069 Å |
Hall symbol: -C 2yc | Cell parameters from 25 reflections |
a = 7.865 (1) Å | θ = 10.4–15.0° |
b = 12.599 (2) Å | µ = 7.52 mm−1 |
c = 10.535 (1) Å | T = 293 K |
β = 110.83 (1)° | Prism, colourless |
V = 975.7 (2) Å3 | 0.27 × 0.16 × 0.13 mm |
Z = 4 | |
Data collection top
Enraf-Nonius CAD-4 diffractometer | 1021 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.013 |
Graphite monochromator | θmax = 27.0°, θmin = 3.2° |
ω/2θ scans | h = 0→10 |
Absorption correction: ψ scan (North et al., 1968) | k = −1→16 |
Tmin = 0.332, Tmax = 0.469 | l = −13→12 |
1211 measured reflections | 2 standard reflections every 120 min |
1040 independent reflections | intensity decay: 2% |
Refinement top
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: without restraint |
R[F2 > 2σ(F2)] = 0.017 | All H-atom parameters refined |
wR(F2) = 0.044 | w = 1/[σ2(Fo2) + (0.0275P)2 + 1.3792P] where P = (Fo2 + 2Fc2)/3 |
S = 1.08 | (Δ/σ)max < 0.001 |
1040 reflections | Δρmax = 1.62 e Å−3 |
92 parameters | Δρmin = −0.79 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: heavy method | Extinction coefficient: 0.0039 (2) |
Crystal data top
NH4GdP4O12 | V = 975.7 (2) Å3 |
Mr = 491.17 | Z = 4 |
Monoclinic, C2/c | Mo Kα radiation |
a = 7.865 (1) Å | µ = 7.52 mm−1 |
b = 12.599 (2) Å | T = 293 K |
c = 10.535 (1) Å | 0.27 × 0.16 × 0.13 mm |
β = 110.83 (1)° | |
Data collection top
Enraf-Nonius CAD-4 diffractometer | 1021 reflections with I > 2σ(I) |
Absorption correction: ψ scan (North et al., 1968) | Rint = 0.013 |
Tmin = 0.332, Tmax = 0.469 | 2 standard reflections every 120 min |
1211 measured reflections | intensity decay: 2% |
1040 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.017 | 0 restraints |
wR(F2) = 0.044 | All H-atom parameters refined |
S = 1.08 | Δρmax = 1.62 e Å−3 |
1040 reflections | Δρmin = −0.79 e Å−3 |
92 parameters | |
Special details top
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) top | x | y | z | Uiso*/Ueq | |
Gd | 0.5000 | 0.37958 (1) | 0.2500 | 0.0059 (1) | |
P1 | 0.2166 (1) | 0.52166 (6) | −0.06264 (8) | 0.0064 (2) | |
P2 | 0.0390 (1) | 0.33092 (6) | −0.00470 (8) | 0.0067 (2) | |
O1 | 0.1001 (3) | 0.6257 (2) | −0.0634 (3) | 0.0126 (5) | |
O2 | 0.0678 (3) | 0.4289 (2) | −0.0912 (2) | 0.0100 (4) | |
O3 | −0.0590 (3) | 0.2463 (2) | −0.1028 (2) | 0.0124 (5) | |
O4 | 0.3552 (3) | 0.5070 (2) | 0.0767 (2) | 0.0115 (5) | |
O5 | 0.2749 (3) | 0.5295 (2) | −0.1813 (2) | 0.0114 (5) | |
O6 | 0.2084 (3) | 0.3027 (2) | 0.1105 (2) | 0.0108 (4) | |
N | 0.0000 | 0.1829 (4) | 0.2500 | 0.0206 (9) | |
H1 | 0.092 (8) | 0.235 (5) | 0.240 (6) | 0.05 (2)* | |
H2 | 0.025 (9) | 0.140 (4) | 0.316 (6) | 0.05 (2)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Gd | 0.0047 (1) | 0.0078 (1) | 0.0057 (1) | 0.000 | 0.00228 (9) | 0.000 |
P1 | 0.0043 (4) | 0.0092 (4) | 0.0069 (4) | 0.0004 (3) | 0.0032 (3) | 0.0007 (3) |
P2 | 0.0049 (4) | 0.0080 (4) | 0.0079 (4) | −0.0002 (3) | 0.0031 (3) | −0.0008 (3) |
O1 | 0.013 (1) | 0.011 (1) | 0.018 (1) | 0.0031 (8) | 0.011 (1) | 0.0016 (8) |
O2 | 0.007 (1) | 0.013 (1) | 0.009 (1) | −0.0034 (8) | 0.0018 (8) | 0.0016 (9) |
O3 | 0.009 (1) | 0.013 (1) | 0.014 (1) | −0.0034 (9) | 0.0033 (9) | −0.0054 (9) |
O4 | 0.011 (1) | 0.014 (1) | 0.008 (1) | −0.0023 (9) | 0.0015 (9) | 0.0014 (9) |
O5 | 0.009 (1) | 0.016 (1) | 0.012 (1) | −0.0014 (9) | 0.0071 (9) | 0.0006 (9) |
O6 | 0.008 (1) | 0.013 (1) | 0.011 (1) | 0.0001 (9) | 0.0025 (9) | −0.0003 (9) |
N | 0.032 (3) | 0.015 (2) | 0.015 (2) | 0.000 | 0.009 (2) | 0.000 |
Geometric parameters (Å, º) top
Gd—O3i | 2.376 (2) | P1—O4 | 1.496 (2) |
Gd—O3ii | 2.376 (2) | P1—O1 | 1.597 (2) |
Gd—O4iii | 2.394 (2) | P1—O2 | 1.605 (2) |
Gd—O4 | 2.394 (2) | P2—O6 | 1.491 (2) |
Gd—O5iv | 2.425 (2) | P2—O3 | 1.494 (2) |
Gd—O5v | 2.425 (2) | P2—O2 | 1.598 (2) |
Gd—O6 | 2.442 (2) | P2—O1vi | 1.603 (3) |
Gd—O6iii | 2.442 (2) | N—H1 | 1.01 (6) |
P1—O5 | 1.480 (2) | N—H2 | 0.84 (6) |
| | | |
O5—P1—O4 | 120.0 (1) | O6—P2—O2 | 112.5 (1) |
O5—P1—O1 | 106.9 (1) | O3—P2—O2 | 107.4 (1) |
O4—P1—O1 | 108.8 (1) | O6—P2—O1vi | 105.8 (1) |
O5—P1—O2 | 108.3 (1) | O3—P2—O1vi | 106.6 (1) |
O4—P1—O2 | 108.8 (1) | O2—P2—O1vi | 104.4 (1) |
O1—P1—O2 | 102.6 (1) | P1—O1—P2vi | 139.4 (2) |
O6—P2—O3 | 119.0 (1) | P2—O2—P1 | 134.2 (1) |
Symmetry codes: (i) −x+1/2, −y+1/2, −z; (ii) x+1/2, −y+1/2, z+1/2; (iii) −x+1, y, −z+1/2; (iv) −x+1, −y+1, −z; (v) x, −y+1, z+1/2; (vi) −x, −y+1, −z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N—H1···O6 | 1.01 (6) | 2.07 (7) | 2.973 (3) | 147 (5) |
N—H2···O4vii | 0.84 (6) | 2.06 (6) | 2.840 (4) | 154 (6) |
Symmetry code: (vii) −x+1/2, y−1/2, −z+1/2. |
Experimental details
| (I) | (II) |
Crystal data |
Chemical formula | NH4Gd(PO3)4 | NH4GdP4O12 |
Mr | 491.17 | 491.17 |
Crystal system, space group | Monoclinic, P21/c | Monoclinic, C2/c |
Temperature (K) | 293 | 293 |
a, b, c (Å) | 10.951 (3), 8.998 (1), 12.803 (5) | 7.865 (1), 12.599 (2), 10.535 (1) |
β (°) | 128.94 (2) | 110.83 (1) |
V (Å3) | 981.2 (5) | 975.7 (2) |
Z | 4 | 4 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 7.48 | 7.52 |
Crystal size (mm) | 0.21 × 0.14 × 0.12 | 0.27 × 0.16 × 0.13 |
|
Data collection |
Diffractometer | Enraf-Nonius CAD-4 diffractometer | Enraf-Nonius CAD-4 diffractometer |
Absorption correction | ψ scan (North et al., 1968) | ψ scan (North et al., 1968) |
Tmin, Tmax | 0.373, 0.473 | 0.332, 0.469 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2364, 2011, 1771 | 1211, 1040, 1021 |
Rint | 0.028 | 0.013 |
(sin θ/λ)max (Å−1) | 0.638 | 0.638 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.024, 0.056, 1.03 | 0.017, 0.044, 1.08 |
No. of reflections | 2011 | 1040 |
No. of parameters | 176 | 92 |
No. of restraints | 4 | 0 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement | All H-atom parameters refined |
Δρmax, Δρmin (e Å−3) | 0.81, −0.65 | 1.62, −0.79 |
Selected bond lengths (Å) for (I) topGd—O4i | 2.328 (3) | P2—O9 | 1.488 (4) |
Gd—O10 | 2.363 (3) | P2—O2 | 1.491 (4) |
Gd—O9ii | 2.386 (4) | P2—O1 | 1.605 (4) |
Gd—O2iii | 2.402 (4) | P2—O5 | 1.606 (3) |
Gd—O11iv | 2.405 (3) | P3—O4 | 1.481 (4) |
Gd—O3 | 2.415 (3) | P3—O3 | 1.494 (4) |
Gd—O7v | 2.416 (3) | P3—O8 | 1.602 (4) |
Gd—O12i | 2.477 (3) | P3—O6 | 1.610 (3) |
P1—O11 | 1.480 (4) | P4—O7 | 1.487 (3) |
P1—O10 | 1.492 (4) | P4—O12 | 1.496 (4) |
P1—O8 | 1.594 (3) | P4—O5vi | 1.610 (3) |
P1—O1 | 1.607 (4) | P4—O6 | 1.612 (3) |
Symmetry codes: (i) x, −y+1/2, z+1/2; (ii) x, y−1, z; (iii) −x, −y+1, −z+1; (iv) −x, y−1/2, −z+1/2; (v) −x+1, −y+1, −z+1; (vi) x, −y+3/2, z−1/2. |
Hydrogen-bond geometry (Å, º) for (I) top
D—H···A | D—H | H···A | D···A | D—H···A |
N—H2···O2vi | 0.90 (2) | 2.10 (3) | 2.965 (7) | 163 (8) |
N—H4···O9 | 0.90 (2) | 2.23 (4) | 3.091 (6) | 160 (8) |
Symmetry code: (vi) x, −y+3/2, z−1/2. |
Selected bond lengths (Å) for (II) topGd—O3i | 2.376 (2) | P1—O2 | 1.605 (2) |
Gd—O4 | 2.394 (2) | P2—O6 | 1.491 (2) |
Gd—O5ii | 2.425 (2) | P2—O3 | 1.494 (2) |
Gd—O6 | 2.442 (2) | P2—O2 | 1.598 (2) |
P1—O5 | 1.480 (2) | P2—O1iii | 1.603 (3) |
P1—O4 | 1.496 (2) | N—H1 | 1.01 (6) |
P1—O1 | 1.597 (2) | N—H2 | 0.84 (6) |
Symmetry codes: (i) −x+1/2, −y+1/2, −z; (ii) −x+1, −y+1, −z; (iii) −x, −y+1, −z. |
Hydrogen-bond geometry (Å, º) for (II) top
D—H···A | D—H | H···A | D···A | D—H···A |
N—H1···O6 | 1.01 (6) | 2.07 (7) | 2.973 (3) | 147 (5) |
N—H2···O4iv | 0.84 (6) | 2.06 (6) | 2.840 (4) | 154 (6) |
Symmetry code: (iv) −x+1/2, y−1/2, −z+1/2. |
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Ce travail s'inscrit dans un programme plus général de synthèse et de caractérization de phosphates de terres rares en vue d'examiner leurs propriétés spectroscopiques. L'intérêt porté à ces composés est dû principalement à leurs performances dans le domaine de la luminescence (Otsuka et al., 1975; Hashimoto et al., 1991; Jouini et al., 2003; Horchani-Naifer et al., 2006). Dans la présente étude, nous décrivons les modes de préparation et les structures cristallines de deux phosphates doubles d'ammonium et gadolinium, NH4Gd(PO3)4 et NH4GdP4O12.
Dans le polyphosphate d'ammonium gadolinium, NH4Gd(PO3)4, les anions phosphates sont formés de rubans ondulés (PO3)n, se développant le long de la direction c avec une période de huit tétraèdres, alors que dans le cyclotétraphosphate d'ammonium gadolinium, NH4GdP4O12, ils sont constitués de cycles centrosymétriques P4O12, disposés en couches perpendiculaires à l'axe c à z = 0 e t 1/2. Les cations Gd3+ sont coordinés à huit atomes d'oxygène externes aussi bien dans NH4Gd(PO3)4 que dans NH4GdP4O12. Chaque polyèdre GdO8 partage ses huit sommets avec quatre chaînes (PO3)n dans le polyphosphate et six cycles P4O12 dans le cyclotétraphosphate. Il en résulte pour chacun de ces composés une charpente tridimensionnelle délimitant des tunnels au sein desquels logent les groupements NH4+. Ces tunnels sont parallèles à la direction [101] dans NH4Gd(PO3)4 (Fig. 1) e t aux directions [100] e t [101] dans NH4GdP4O12 (Fig. 2). Notons que dans les deux structures, les polyèdres GdO8 sont isolés les uns des autres et ne partagent par conséquent aucun atome d'oxygène.
La distance minimale Gd···Gd dans le polyphosphate mesure 5,739 (1) Å, alors que celle observée dans le cyclotétraphosphate est plus longue et vaut 6,079 (1) Å. En outre, l'examen des distances P—O dans les tétraèdres PO4 révèle que les liaisons P—O correspondant aux atomes d'oxygène externes (Oe) sont plus courtes que celles mettant en jeu des atomes d'oxygène internes (Oi). Les moyennes des distances P—Oe et P—Oi sont respectivement de 1,489 (4) e t 1,606 (3) Å dans NH4Gd(PO3)4, et 1.490 (2) e t 1.601 (2) Å dans NH4GdP4O12.
Quant aux groupements NH4+, ils sont environnés d'atomes d'oxygène du type interne et externe avec une coordinence 8 e t de s distances N—O comprises entre 2.911 (6) e t 3.326 (7) Å dans le polyphosphate, et une coordinence 6 e t de s distances N—O variant entre 2.840 (4) e t 3.033 (4) Å dans le cyclotétraphosphate.
Les distances et angles interatomiques observés dans ces deux structures sont conformes à ceux rencontrés dans la littérature (Palkina et al., 1977; Masse et al., 1977; International Tables for X-ray Crystallography, 1968). La comparaison de la structure de NH4Gd(PO3)4 avec celle de la variété orthorhombique NH4Y(PO3)4 (Bagieu-Beucher & Guitel, 1988) montre que les chaînes (PO3)n deviennent plus complexes dans cette dernière du fait de l'augmentation de la période de la chaîne qui passe de huit tétraèdres dans NH4Gd(PO3)4 à seize tétraèdres dans la variété orthorhombique. Ceci affecte surtout l'environnement des cations NH4+ qui deviennent heptacoordinés. Par ailleurs, la comparaison de la structure de NH4GdP4O12 avec celle de la variété cubique NH4CeP4O12 (Rzaigui, 1983), montre que les cycles P4O12 présentent la symétrie interne −1 dans le premier composé et −4 dans le second. Contrairement aux atomes Gd et N qui occupent le site (4 e) dans NH4GdP4O12, les atomes Ce et N occupent respectivement les sites (12b) et (16c) dans la forme cubique NH4CeP4O12.