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Acta Crystallographica Section E: Crystallographic Communications logoLink to Acta Crystallographica Section E: Crystallographic Communications
. 2020 Apr 3;76(Pt 5):621–624. doi: 10.1107/S2056989020004387

Dehydration synthesis and crystal structure of terbium oxychloride, TbOCl

Saehwa Chong a,*, Brian J Riley a, Zayne J Nelson a
PMCID: PMC7199267  PMID: 32431920

Terbium oxychloride, TbOCl, was synthesized via the simple heat-treatment of TbCl3·6H2O and its structure was determined by refinement against X-ray powder diffraction data. TbOCl crystallizes with the matlockite (PbFCl) structure in the tetra­gonal space group P4/nmm and is composed of alternating (001) layers of (TbO)n and n Cl−.

Keywords: oxychloride, rare-earth oxyhalide, powder diffraction

Abstract

Terbium oxychloride, TbOCl, was synthesized via the simple heat-treatment of TbCl3·6H2O and its structure was determined by refinement against X-ray powder diffraction data. TbOCl crystallizes with the matlockite (PbFCl) structure in the tetra­gonal space group P4/nmm and is composed of alternating (001) layers of (TbO)n and n Cl−. The unit-cell parameters, unit-cell volume, and density were compared to the literature data of other isostructural rare-earth oxychlorides in the same space group and showed good agreement when compared to the calculated trendlines.

Chemical context  

Rare-earth oxychlorides, REOCl, are promising materials for various applications including use as catalysts, sensors, and phosphors (Podkolzin et al., 2007 ▸; Au et al., 1997 ▸; Peringer et al., 2009 ▸; Marsal et al., 2005 ▸,; Kim et al., 2019 ▸; Berdowski et al., 1984 ▸; Imanaka et al., 2001a ▸,b ▸; Okamoto et al., 2002 ▸; Kim et al., 2014 ▸). LaOCl is a stable catalyst for converting methane to methyl chloride (Podkolzin et al., 2007 ▸) and can be used as a sensor material to detect CO2 and Cl2 gases (Marsal et al., 2005 ▸; Imanaka et al., 2001b ▸). The EuOCl catalyst showed high efficiency in converting ethyl­ene to vinyl chloride (Scharfe et al., 2016 ▸). The luminescent properties of REOX (RE = La, Eu; X = F, Cl, Br, I) can be controlled to emit a wide range of visible light from blue to red by changing the crystal symmetries and compositions (Kim et al., 2014 ▸, 2019 ▸). As part of our studies in this area, we now describe the dehydration synthesis and structure of the title compound.

Structural commentary  

The structural parameters of REOCl (RE = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho) in the literature and current study are summarized in Table 1 ▸. All these REOCl compounds crystallize in the matlockite (PbFCl; Bannister, 1934 ▸) structure within the tetra­gonal P4/nmm space group. The crystal structure of TbOCl contains alternating (001) layers of (TbO)n and n Cl− (Fig. 1 ▸ a). The Tb cation is coordinated by five chloride ions and four oxygen atoms, forming a mono-capped TbO4Cl5 square anti­prism (Fig. 1 ▸ b and 1c). The RE—Cl and RE—O bond lengths in the REOCl compounds are provided in Table 1 ▸. With larger RE cations in the structures, the RE—Cl and RE—O bond lengths increase (Fig. 2 ▸).

Table 1. Structural parameters of REOCl compounds.

All compounds crystallize in the P4/nmm space group. For the RE—Cl bond lengths, the first value refers to one neighboring Cl atom, and the second number refers to four neighboring Cl atoms. Densities are calculated from crystallographic data.

RE a(Å) c(Å) V (Å3) Density(g cm−3) RE—O(Å) RE—Cl(Å) Cl⋯Cl(Å) Cl⋯O(Å) O⋯O (Å) ICSD/PDF
Ho 3.893 6.602 100.1 7.182 2.247 3.04, 3.05 3.24 3.12 2.753 76171 (Templeton & Dauben, 1953 ▸)
Dy 3.91 6.62 101.2 7.023           00–047-1725 (Kirik et al., 1996 ▸)
Tb 3.9269 6.648 102.5 6.815           00–048-1648 (Kirik et al., 1996 ▸)
Tb 3.9279 6.6556 102.7 6.804 2.2649 3.064, 3.082 3.271 3.151 2.7774 Current study
Gd 3.9495 6.6708 104.1 6.661 2.2839 3.036, 3.098 3.267 3.176 2.7927 59232 (Meyer & Schleid, 1986 ▸)
Gd 3.9698 6.7008 105.6 6.564 2.28 3.212, 3.071 3.428 3.089 2.8071 77820 (Hölsä et al., 1996 ▸)
Eu 3.9646 6.695 105.2 6.42 2.286 3.08, 3.11 3.3 3.17 2.8034 28529 (Bärnighausen et al., 1965 ▸)
Eu 3.9668 6.6955 105.4 6.412 2.2901 3.062, 3.1103 3.289 3.183 2.80492 54682 (Schnick, 2004 ▸)
Sm 3.982 6.721 106.6 6.289 2.296 3.09, 3.12 3.31 3.19 2.8157 26581 (Templeton & Dauben, 1953 ▸)
Nd 4.04 6.77 110.5 5.882 2.359 3.114, 3.11 3.428 3.165 2.86 31665 (Zachariasen, 1949 ▸)
Nd 4.0249 6.7837 109.9 5.914 2.3362 3.082, 3.141 3.343 3.221 2.84603 59231 (Meyer & Schleid, 1986 ▸)
Pr 4.053 6.799 111.7 5.723 2.3674 3.128, 3.116 3.441 3.178 2.866 31664 (Zachariasen, 1949 ▸)
Ce 4.0866 6.8538 114.5 5.558 2.3687 3.1190, 3.1846 3.3942 3.2572 2.8897 412069 (Schnick, 2004 ▸)
Ce 4.0785 6.8346 113.7 5.596 2.36413 3.103, 3.180 3.38 3.254 2.88393 72154 (Wołcyrz & Kepinski, 1992 ▸)
La 4.109 6.865 115.9 5.454 2.39 3.14, 3.18 3.45 3.24 2.9055 24611 (Sillen & Nylander, 1941 ▸)
La 4.117 6.881 116.6 5.42 2.3866 3.126, 3.2046 3.416 3.2751 2.9112 40297 (Brixner & Moore, 1983 ▸)
La 4.1351 6.904 118.1 5.355 2.395 3.165, 3.209 3.457 3.268 2.92397 77815 (Hölsä et al., 1996 ▸)
La 4.1162 6.8746 116.5 5.428 2.3832 3.138, 3.201 3.425 3.265 2.9106 84330 (Hölsä et al., 1997 ▸)
La 4.12 6.882 116.8 5.412           00–008-0477 (Swanson et al., 1957 ▸)
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Figure 1.

Figure 1

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(a) Crystal structure of TbOCl, (b) the coordination environment of Tb, and (c) polyhedron representation of the Tb environment.

Figure 2.

Figure 2

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The RE—Cl and RE—O bond lengths in the REOCl compounds listed in Table 1 ▸ as a function of RE crystal radius (coordination = 9) according to Shannon (1976 ▸). Where multiple values were available, averages and standard deviations are included for the datapoints. For (a), 1-nd and 4-nd denote 1 and 4 neighbor distances, respectively

The shortest Cl⋯Cl separation in TbOCl is 3.271 (4) Å, which compares with the van der Waals diameter of a Cl− ion of about 3.62 Å. The Cl⋯Cl distances of other REOCl compounds are also short, ranging from 3.24 to 3.46 Å on going from Ho3+ to La3+. With non-bonded vectors shorter than the van der Waals separation, strong inter­actions between atoms are expected in the structure (Maslen et al., 1996 ▸). Templeton & Dauben (1953 ▸) mention the presence of weaker anion–anion repulsion between Cl atoms in REOCl structures. The structural parameters of TbOCl were compared with the trendlines calculated using the values from Table 1 ▸ (Fig. 3 ▸). The unit-cell parameters and volumes increase linearly with the larger RE cations (Shannon, 1976 ▸) whereas the densities decrease non-linearly, fitting well to a 2nd order polynomial trend.

Figure 3.

Figure 3

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(a, b) Unit-cell parameters (a and c, respectively), (c) unit-cell volumes, and calculated unit-cell densities as a function of the crystal radius of the RE (coordination = 9) according to Shannon (1976 ▸) compared to literature values provided in Table 1 ▸.

Synthesis and crystallization  

The title compound was synthesized by a simple heat treatment of TbCl3·6H2O (Alfa Aesar, 99.99%). About 0.5 g of TbCl3·6H2O was placed in an alumina crucible, heated to 400°C at 5°C min−1, held for 8 h, and then cooled to room temperature at 5°C min−1. This synthesis method was used in our previous study (Riley et al., 2018 ▸). The resulting product was a light-brown powder, which was ground in a mortar and pestle for X-ray powder diffraction analysis.

Refinement  

Crystal data, data collection and structure refinement details are summarized in Table 2 ▸. The unit-cell parameters were obtained using TOPAS (version 4.2; Bruker, 2009 ▸) by refining the GdOCl pattern (ICSD 77820) with geometrical and chemical resemblance as a starting model. The Rietveld refinement was performed using JANA2006 (Petříček et al., 2014 ▸) with the obtained unit-cell parameters as initial values. A pseudo-Voigt function with other peak-shape parameters were used to fit peaks, and the background was modeled with a Chebychev polynomial. The plot of the Rietveld refinement result is shown in Fig. 4 ▸. The final refinement converged at R wp = 3.22%.

Table 2. Experimental details.

Crystal data
Chemical formula TbOCl
M r 210.4
Crystal system, space group Tetragonal, P4/n m m
Temperature (K) 293
a, c (Å) 3.9279 (2), 6.6556 (5)
V (Å3) 102.68 (1)
Z 2
Radiation type Cu Kα, λ = 1.54188 Å
Specimen shape, size (mm) Cylinder, 25 × 25
 
Data collection
Diffractometer Bruker D8 Advance
Specimen mounting Packed powder pellet
Data collection mode Reflection
Scan method Step
2θ values (°) 2θmin = 5, 2θmax = 68.977, 2θstep = 0.019
 
Refinement
R factors and goodness of fit R p = 0.020, R wp = 0.032, R exp = 0.009, R(F) = 0.033, χ2 = 13.690
No. of parameters 17
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Computer programs: XRD Commander (Kienle & Jacob, 2003 ▸), TOPAS (Bruker, 2009 ▸), SUPERFLIP (Palatinus & Chapuis, 2007 ▸), JANA2006 (Petříček et al., 2014 ▸), VESTA (Momma & Izumi, 2011 ▸) and publCIF (Westrip, 2010 ▸).

Figure 4.

Figure 4

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Measured, calculated, and difference XRD patterns of TbOCl.

Supplementary Material

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S2056989020004387/hb7896sup1.cif

e-76-00621-sup1.cif (14KB, cif)

Rietveld powder data: contains datablock(s) I. DOI: 10.1107/S2056989020004387/hb7896Isup2.rtv

e-76-00621-Isup2.rtv (88.4KB, rtv)

Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989020004387/hb7896Isup3.hkl

CCDC reference: 1993793

Additional supporting information: crystallographic information; 3D view; checkCIF report

Acknowledgments

The Pacific Northwest National Laboratory is operated by Battelle under Contract Number DE-AC05–76RL01830.

supplementary crystallographic information

Crystal data

TbOCl Z = 2
Mr = 210.4 Dx = 6.804 Mg m−3
Tetragonal, P4/nmm Cu Kα radiation, λ = 1.54188 Å
a = 3.9279 (2) Å T = 293 K
c = 6.6556 (5) Å light brown
V = 102.68 (1) Å3 cylinder, 25 × 25 mm
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Data collection

Bruker D8 Advance diffractometer Data collection mode: reflection
Radiation source: sealed X-ray tube Scan method: step
Specimen mounting: packed powder pellet 2θmin = 5°, 2θmax = 68.977°, 2θstep = 0.019°
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Refinement

Rp = 0.020 17 parameters
Rwp = 0.032 Weighting scheme based on measured s.u.'s
Rexp = 0.009 (Δ/σ)max = 0.030
R(F) = 0.033 Background function: 8 Chebyshev polynoms
3292 data points Preferred orientation correction: March & Dollase
Profile function: Pseudo-Voigt
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Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2)

x y z Uiso*/Ueq
Tb1 0.5 0 0.3305 (2) 0.002
Cl1 0 0.5 0.1298 (9) 0.002
O1 1 0 0.5 0.002
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Atomic displacement parameters (Å2)

U11 U22 U33 U12 U13 U23
Tb1 0.002 0.002 0.002 0 0 0
Cl1 0.002 0.002 0.002 0 0 0
O1 0.002 0.002 0.002 0 0 0
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Geometric parameters (Å, º)

Tb1—Tb1i 3.5784 (13) Tb1—O1v 2.2649 (7)
Tb1—Tb1ii 3.5784 (13) Tb1—O1 2.2649 (7)
Tb1—Tb1iii 3.5784 (13) Tb1—O1vi 2.2649 (7)
Tb1—Tb1iv 3.5784 (13) Tb1—O1vii 2.2649 (7)
Tb1i—Tb1—Tb1ii 66.57 (2) Tb1iii—Tb1—O1vii 99.31 (4)
Tb1i—Tb1—Tb1iii 66.57 (2) Tb1iv—Tb1—O1v 99.31 (4)
Tb1i—Tb1—Tb1iv 101.82 (4) Tb1iv—Tb1—O1 37.817 (14)
Tb1i—Tb1—O1v 37.817 (14) Tb1iv—Tb1—O1vi 99.31 (4)
Tb1i—Tb1—O1 99.31 (4) Tb1iv—Tb1—O1vii 37.817 (14)
Tb1i—Tb1—O1vi 37.817 (14) O1v—Tb1—O1 120.25 (6)
Tb1i—Tb1—O1vii 99.31 (4) O1v—Tb1—O1vi 75.63 (3)
Tb1ii—Tb1—Tb1iii 101.82 (4) O1v—Tb1—O1vii 75.63 (3)
Tb1ii—Tb1—Tb1iv 66.57 (2) O1—Tb1—O1vi 75.63 (3)
Tb1ii—Tb1—O1v 37.817 (14) O1—Tb1—O1vii 75.63 (3)
Tb1ii—Tb1—O1 99.31 (4) O1vi—Tb1—O1vii 120.25 (6)
Tb1ii—Tb1—O1vi 99.31 (4) Tb1—O1—Tb1viii 120.25 (4)
Tb1ii—Tb1—O1vii 37.817 (14) Tb1—O1—Tb1iii 104.37 (2)
Tb1iii—Tb1—Tb1iv 66.57 (2) Tb1—O1—Tb1iv 104.37 (2)
Tb1iii—Tb1—O1v 99.31 (4) Tb1viii—O1—Tb1iii 104.37 (2)
Tb1iii—Tb1—O1 37.817 (14) Tb1viii—O1—Tb1iv 104.37 (2)
Tb1iii—Tb1—O1vi 37.817 (14) Tb1iii—O1—Tb1iv 120.25 (4)
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Symmetry codes: (i) −x+1/2, y−1/2, −z+1; (ii) −x+1/2, y+1/2, −z+1; (iii) −x+3/2, y−1/2, −z+1; (iv) −x+3/2, y+1/2, −z+1; (v) x−1, y, z; (vi) −y+1/2, x−3/2, z; (vii) −y+1/2, x−1/2, z; (viii) x+1, y, z.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S2056989020004387/hb7896sup1.cif

e-76-00621-sup1.cif (14KB, cif)

Rietveld powder data: contains datablock(s) I. DOI: 10.1107/S2056989020004387/hb7896Isup2.rtv

e-76-00621-Isup2.rtv (88.4KB, rtv)

Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989020004387/hb7896Isup3.hkl

e-76-00621-Isup3.hkl (2KB, hkl)

CCDC reference: 1993793

Additional supporting information: crystallographic information; 3D view; checkCIF report

Articles from Acta Crystallographica Section E: Crystallographic Communications are provided here courtesy of International Union of Crystallography

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