Two anhydrous salts of tetrafluoroterephthalic acid (H2tF-BDC): K2tF-BDC and Rb2tF-BDC

Article abstract of DOI:10.1002/zaac.201300480

Two new anhydrous salts of tetrafluoroterephthalic acid (H ₂tF-BDC), namely K₂tF-BDC (1) and Rb₂tF-BDC (2), were synthesized and structurally characterized. The crystal structure of 1 (I2/m, Z = 2) was solved and refined from X-ray single crystal data. K ⁺ (CN = 8) is coordinated by six oxygen atoms of five different tF-BDC^2- linkers and two fluorine atoms of two of these linkers, which connect the KO₆F₂ polyhedra to a 3D network. The crystal structure of 2 (P1, Z = 1) was refined from X-ray powder diffraction data. It crystallizes in a structure type already known from Tl ₂tF-BDC. Rb⁺ (CN = 8) is also coordinated by six oxygen and two fluorine atoms. But six tF-BDC^2- linkers are involved in the coordination. Again, a 3D network is formed. Both compounds can be obtained as single-phase samples. They are not porous and stable in air. The thermal stability was investigated by DTA/TG measurements. The decomposition starts at approx. 200°C (1) and 230°C (2). Their good solubility in water makes them interesting starting materials for the synthesis of new MOFs with the perfluorinated linker tF-BDC^2-. Copyright

Full text of DOI:10.1002/zaac.201300480

ARTICLE
DOI: 10.1002/zaac.201300480
Two Anhydrous Salts of Tetrafluoroterephthalic Acid (H2tF-BDC):
K2tF-BDC and Rb2tF-BDC
Melanie Werker,[a] Benedikt Dolfus,[a] and Uwe Ruschewitz*[a]
Dedicated to Professor Bernt Krebs on the Occasion of His 75th Birthday
Keywords: Coordination polymer; Crystal structure; Perfluorinated carboxylates; Potassium; Rubidium
Abstract. Two new anhydrous salts of tetrafluoroterephthalic acid (CN = 8) is also coordinated by six oxygen and two fluorine atoms.
(H2tF-BDC), namely K2tF-BDC (1) and Rb2tF-BDC (2), were synthe-
But six tF-BDC2– linkers are involved in the coordination. Again, a
sized and structurally characterized. The crystal structure of 1 (I2/m, 3D network is formed. Both compounds can be obtained as single-
Z = 2) was solved and refined from X-ray single crystal data. phase samples. They are not porous and stable in air. The thermal
K+ (CN = 8) is coordinated by six oxygen atoms of five different
stability was investigated by DTA/TG measurements. The decomposi-
tF-BDC2– linkers and two fluorine atoms of two of these linkers, which tion starts at approx. 200 °C (1) and 230 °C (2). Their good solubility
connect the KO6F2 polyhedra to a 3D network. The crystal structure in water makes them interesting starting materials for the synthesis of
new MOFs with the perfluorinated linker tF-BDC2–.
¯
of 2 (P1, Z = 1) was refined from X-ray powder diffraction data. It
crystallizes in a structure type already known from Tl2tF-BDC. Rb+
tem-specific”.[5] This finding is a little draw-back for the pro-
posed high adsorption capacities of F-MOFs.
Introduction
It is well-known that the replacement of C–H by C–F enti-
ties in organic compounds leads to dramatic changes of their
properties and reactivity. Consequently, also in the field of co-
ordination polymers (CPs) and metal-organic frameworks
(MOFs) it has been attempted to adopt this finding by using
fluorinated or perfluorinated bridging ligands for the synthesis
of these compounds, as new or at least improved materials
properties are expected. Indeed, it was found that FMOF-1
shows a high H2 adsorption capacity.[1] This result was corrob-
orated by a theoretical investigation.[2] But in another experi-
mental work only a slightly enhanced H2 adsorption capacity
was reported[3] and Klopper et al. calculated an even lower H2
adsorption enthalpy for fluorobenzene compared to unsubsti-
tuted benzene.[4] These discrepancies can simply be explained
by the fact that no isostructural fluorous and non-fluorous
compounds are compared and the influence of the specific
crystal structure on the adsorption properties cannot be ne-
glected. Accordingly, Banerjee et al. reported some iso-
structural porous coordination polymers with fluorinated and
non-fluorinated ligands and found that the H2 uptake is “sys-
In a different approach focusing on the optical properties
it was reported that CPs with perfluorinated ligands show a
significantly enhanced luminescence.[6] In this context, we
have started to investigate CPs with fluorinated and perfluori-
nated aromatic carboxylates as bridging ligands.[7–10] Indeed,
we observed a bright luminescence in CPs of 4f elements with
tetrafluoroterephthalate (tF-BDC2–) as bridging ligand.[9,10]
Obviously, the replacement of C–H by C–F entities reduces
the C–H quenching significantly yielding CPs with quantum
yields of up to 73% at room temperature.[10] Unfortunately,
for many systems the synthesis of CPs with tF-BDC2– as linker
is hampered by the fact that H2tF-BDC only shows a very low
solubility in water. This problem may be circumvented by
using simple salts of H2tF-BDC. But to the best of our knowl-
edge, only (NH4)2tF-BDC has been described in the literature
in more details.[7] In this contribution we report the synthesis
and crystal structure of two further simple salts of H2tF-BDC,
namely K2tF-BDC (1) and Rb2tF-BDC (2). Even more, 1 and
2 are two of the very few examples of solvent-free homoleptic
coordination polymers with tF-BDC2– as bridging ligand.
* Prof. Dr. U. Ruschewitz
Fax: +49-221-470-3933
Results and Discussion
E-Mail: Uwe.Ruschewitz@uni-koeln.de
[a] Department für Chemie
K2tF-BDC (tF-BDC2– = [p-(OOC)C6F4(COO)]2–) (1)
Universität zu Köln
Institut für Anorganische Chemie
Greinstraße 6
Single crystals of K2tF-BDC (1) were synthesized by an
evaporation method using a volatile base (see Experimental
Section) starting from H2tF-BDC and KCl. The sample is sin-
gle-phase, as revealed by elemental analysis and X-ray powder
50939 Köln, Germany
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.201300480 or from the au-
thor.
Z. Anorg. Allg. Chem. 2013, 639, (14), 2487–2492
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M. Werker, B. Dolfus, U. Ruschewitz
ARTICLE
diffraction. 1 can also be obtained by a mechanochemical ap-
proach starting from H2tF-BDC and K(CH3COO) (Experimen-
tal Section). But the powder diffractogram of the latter sample
shows some weak impurity reflections, although the elemental
analysis also points to a sample of high purity.
The crystal structure of 1 was solved and refined from
X-ray single crystal data. 1 crystallizes in the monoclinic space
group I2/m with Z = 2. The non-standard setting was chosen,
as for the standard setting C2/m β was larger than 120°. Se-
lected crystallographic and refinement data are given in
Table 1, some interatomic distances and angles are listed in
Table 3. In Figure 1 the ORTEP plot of 1 is shown, where the
numbering of the atoms of the asymmetric unit is given. K+
occupies the special position 4g, whereas the tF-BDC2– anion
is placed on the twofold axis (along C1–C2) with the mirror
plane perpendicular to it. So the whole anion is generated from
only five crystallographically distinct atoms (C1, C2, C3, F1,
O1).
Figure 1. ORTEP plot of K2tF-BDC (1) with labelling of the atoms of
the asymmetric unit. Thermal ellipsoids are drawn at the 50% prob-
ability level.
Table 1. Selected crystal and structure refinement data for K2tF-BDC
(1), X-ray single crystal data (STOE IPDS I, Mo-Kα radiation).
Molecular formula
C8F4K2O4
Mr /g·mol–1
Crystal system
Space group, Z
T /K
314.283
monoclinic
I2/m, 2
295
a /Å
b /Å
c /Å
4.0394(9)
19.953(3)
6.0480(13)
91.25(3)
487.3(2)
2.142
β /°
V /Å3
D /g·cm–3
Crystal size /mm3
μ /mm–1
0.7ϫ0.4ϫ0.2
1.04
Θmax /°
28.2
Number of reflections
measured
2937
independent
Number of parameters
R-factors
570 [464 with I Ͼ 2σ(I)]
44
Io Ͼ 2σ(Io)
R1 = 0.054
wR2 = 0.143
R1 = 0.061
wR2 = 0.147
0.077
All data
Figure 2. Projection of the crystal structure of K2tF-BDC (1) along
[100]. KO6 trigonal prisms as well as the unit cell are emphasized.
K···F contacts are shown as dotted lines.
Rint
GooF
1.06
–1.07 / 0.49
Δρmin/max /e·Å–3
K+ is coordinated by six oxygen atoms of five different 3.077(4) Å to 3.174(3) Å and only slightly larger Cs–F dis-
tF-BDC2– ligands forming a distorted trigonal prism (Figure 4, tances starting at 3.329(4) Å. The KO6 trigonal prisms are con-
left). K+ is located in the basal plane of the trigonal prism and nected by common edges with other KO6 units thus forming
its coordination is completed by two K···F contacts layers perpendicular to the [010] direction. This is shown in
[2.840(2) Å] to two of the five coordinating ligands. The trigo- Figure 2. Within these layers each K+ is surrounded by six K+
nal prism is formed by one chelating carboxylate group cations with distances ranging from 4.039 Å to 4.355 Å. This
[K1–O1 = 2.852(3) Å, 2ϫ] and four monodentately coordinat- arrangement is not planar like in a hexagonal close packing,
ing carboxylate groups [K1–O1 = 2.723(2) Å, 2ϫ and but strongly corrugated (see Figure 2). These layers of compo-
2.864(2) Å, 2ϫ]. These distances are in reasonable agreement sition (KO2)ϱ are connected by the tF-BDC2– ligands to form
with the K–O distances found in ionic K2O (K–O = 2.787 Å) a non-porous 3D network (Figure 2). Thereby, each K+ cation
[11] and somewhat longer than the K–F distances found in ionic and each carboxylate group act as a 5-connector. The distances
KF (K–F = 2.672 Å)[12]. In Cs(C6F3H2COO)(C6F3H2COOH)[15] and angles within the tF-BDC2– ligand are in the expected ran-
a similar trend was observed, i.e. Cs–O distances in the range ges. Only the torsion angle O1–C1–C2–C3 = 33.2(2)° is re-
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Anhydrous Salts of Tetrafluoroterephthalic Acid (H2tF-BDC)
markable, as it indicates that the carboxylate groups and the Table 2. Selected crystal and structure refinement data for Rb2tF-BDC
(2), X-ray powder diffraction data (STOE Stadi P, Cu-Kα1 radiation).
aromatic ring are not coplanar. But this has already been ob-
served earlier[7–10] and was attributed to the repulsion between
Molecular formula
C8F4O4Rb2
the fluorine atoms of the ring and the oxygen atoms of the
carboxylate groups.[13,14] Calculations on 2,4,6-trifluoroben-
zoates confirmed these large torsion angles.[15]
Mr /g·mol–1
Crystal system
Space group, Z
T /K
407.02
triclinic
¯
P1, 1
293
a /Å
b /Å
c /Å
3.7562(1)
6.6247(2)
10.2326(4)
Rb2tF-BDC (tF-BDC2– = [p-(OOC)C6F4(COO)]2–) (2)
α /°
β /°
106.792(3)
92.148(2)
92.897(2)
243.09(2)
2.780
0.028
0.037
0.043
8251
49
16
396
Attempts to synthesize single crystals of 2 suitable for a
structural analysis failed. But a crystalline powder of reason-
able quality was obtained by an evaporation method using a
volatile base (see Experimental Section) starting from
H2tF-BDC and RbNO3.
γ /°
V /Å3
D /g·cm–3
Rp
wRp
RBragg
The crystal structure of 2 was refined from X-ray powder
diffraction data (Figure 3), which also confirms that the sample
is single-phase. Details are given in the Experimental Section.
2 crystallizes in a structure type that was found earlier for
Data points
No. of refined parameters
No. of restraints
No. of reflections
Background
Profile function
Data range
Tl2tF-BDC (P1, Z = 1).[8] Selected crystallographic and refine-
¯
a)
9
ment data are given in Table 2, some interatomic distances and
angles are listed in Table 3. In Figure 4 (right) the coordination
of the Rb+ cation is shown with the numbering of the atoms
of the asymmetric unit. Rb+ as well as all atoms of the
tF-BDC2– ligand occupy the general position 2i. The center of
the anion is located on a center of symmetry so that the whole
anion is generated from eight crystallographically distinct
atoms (C1, C2, C3, C4, F1, F2, O1, O2).
Pseudovoigt,[25] 2 coefficients
7.5° Յ 2θ Յ 90°
a) No. of terms (linear interpolation function).
Table 3. Selected interatomic distances /Å and angles /° in K2tF-BDC
(1) and Rb2tF-BDC (2).
K2tF-BDC (1)
Rb2tF-BDC (2)
K1–O1 (2ϫ)
K1–F1 (2ϫ)
K1–O1 (2ϫ)
K1–O1 (2ϫ)
2.723(2)
2.840(2)
2.852(3)
2.864(2)
Rb1–O1
Rb1–O2
Rb1–F1
Rb1–O1
Rb1–F2
Rb1–O1
Rb1–O2
Rb1–O2
2.847(5)
2.868(7)
2.910(3)
2.954(7)
3.007(4)
3.019(7)
3.020(7)
3.052(7)
K1–K1 (2ϫ)
K1–K1 (2ϫ)
K1–K1 (2ϫ)
C1–O1 (2ϫ)
C1–C2
C2–C3 (2ϫ)
C3–C3
C3–F1
4.0394(9)
4.293(1)
4.355(1)
1.252(3)
1.522(6)
1.393(4)
1.379(6)
1.343(3)
126.2(4)
Rb1–Rb1 (2ϫ) 3.7562(1)
Rb1–Rb1
Rb1–Rb1
C1–O (2ϫ)
C1–C2
3.794(3)
4.040(3)
a)
1.25
1.52
a)
a)
Carom–Carom
1.38
a)
Carom–F
1.34
O1–C1–O1
O1–C1–C2 (2ϫ) 116.9(2)
O1–C1–O2
O1–C1–C2
O2–C1–C2
122.5(6)
120.0(6)
117.4(6)
Figure 3. Rietveld refinement of X-ray powder diffraction data O1–C1–C2–C3
(293 K, STOE Stadi P, Cu-Kα1 radiation) of Rb2tF-BDC (2). Experi-
mental data points (+), calculated profile (solid line), and difference
curve (below) are shown. Vertical bars mark the positions of Bragg
33.2(2)
O1–C1–C2–C3 –40.2(2)
O1–C1–C2–C3 139.1(2)
O2–C1–C2–C3 –45.7(2)
O2–C1–C2–C3 135.0(2)
reflections.
a) Soft constraints.
Rb+ is coordinated by six oxygen atoms of five different tF-
BDC2– ligands forming a polyhedron that might be described Rb1–O2 = 3.052(7) Å] and four monodentately coordinating
as a very distorted octahedron (Figure 4, right). Rb+ is located carboxylate groups [Rb1–O1 = 2.847(5) Å and 2.954(7) Å,
in one of the trigonal faces of this octahedron and its coordina- Rb1–O2 = 2.868(7) Å and 3.020(7) Å]. These distances are in
tion is completed by two Rb···F contacts [2.910(3) Å and reasonable agreement with the Rb–O distances found in ionic
3.007(4) Å] to two tF-BDC2– ligands. In contrast to 1 by these Rb2O (Rb–O = 2.925 Å)[16] and somewhat longer than the Rb–
Rb···F contacts a sixth ligand is included in the coordination F distances found in ionic RbF (Rb–F = 2.820 Å)[17]. The
sphere of 2 (cp. Figure 4). The distorted octahedron is formed RbO6 polyhedra are connected by common edges with other
by one chelating carboxylate group [Rb1–O1 = 3.019(7) Å, RbO6 units thus forming layers of composition (RbO2)ϱ, which
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M. Werker, B. Dolfus, U. Ruschewitz
ARTICLE
and the aromatic ring were refined freely. Like in 1 torsion
angles between 40.2° and 45.7° (Table 3) indicate that the
carboxylate groups and the aromatic ring are not coplanar due
to the repulsion between the fluorine atoms of the ring and the
oxygen atoms of the carboxylate groups.[13,14]
Thermal Properties
Compounds 1 and 2 show good solubility in water. Both are
stable in air, an uptake of water was not observed. The thermal
behavior of 1 (Figure S4, Supporting Information) and 2 (Fig-
ure S5, Supporting Information) was investigated by DTA/TG
measurements. In an inert atmosphere a slow decomposition
starts at approx. 200 °C (1) and 230 °C (2), respectively. The
exothermic maximum is reached at 350 °C (1) and 370 °C (2).
The decomposition seems to occur in at least two steps. For
the release of two CO2 molecules a mass loss of 28% (1) and
21.6% (2) is calculated. Thus, a more complex decomposition
than a simple decarboxylation must occur. The remaining
masses at 600 °C are 35% (1) and 41% (2) being in the range
Figure 4. Coordination spheres around K+ in 1 (left) and around Rb+
in 2 (right). K···F / Rb···F contacts are shown as dotted lines. For 2
the labelling of the atoms of the asymmetric unit is given.
of the possible residues K2O (mcalc = 30%), 2ϫKF (mcalc
37%), Rb2O (mcalc = 46%) and 2ϫRbF (mcalc = 51%).
=
Conclusions
We have synthesized and structurally characterized two new
anhydrous salts of tetrafluoroterephthalic acid (H2tF-BDC),
namely K2tF-BDC (1) and Rb2tF-BDC (2). Both can be classi-
fied as coordination polymers, as (K/RbO2)ϱ layers are con-
nected by the tF-BDC2– ligand to form a non-porous 3D net-
work. 1 and 2 are two of the very few examples of a homolep-
tic solvent-free coordination polymer of H2tF-BDC. To the
best of our knowledge only Tl2tF-BDC, which was also syn-
thesized and characterized in our group,[8] has been reported
up to now. Compound 2 crystallizes in the same structure type
¯
as Tl2tF-BDC (P1, Z = 1). The crystal structure of 1 (I2/m,
Z = 2) is similar to that of 2, but shows some significant differ-
ences. In 1 a slightly distorted KO6 trigonal prism is found
with K+ located in one of the rectangular faces of this polyhe-
dron. In 2, however a heavily distorted RbO6 octahedron is
formed with Rb+ located in one of the trigonal faces. In both
crystal structures the coordination spheres are completed by
two K···F and Rb···F contacts, respectively. In 1, however K+
acts as a 5-connector, whereas Rb+ in 2 acts as a 6-connector.
Both compounds 1 and 2 show a good solubility in water,
which makes them interesting starting materials for the synthe-
sis of new MOFs with the perfluorinated linker tF-BDC2–. At
the moment we are exploring the field of solvent-free homo-
leptic tetrafluoroterephthalates in more detail with respect to
their luminescent properties[6,9,10] as well as possible porous
representatives.
Figure 5. Projection of the crystal structure of Rb2tF-BDC (2) along
[010]. RbO6 polyhedra as well as the unit cell are emphasized. Rb···F
contacts are shown as dotted lines.
are shown in Figure 5. In contrast to 1 within these layers each
Rb+ is surrounded by four Rb+ cations – instead of six neigh-
boring K+ ions in 1 – with distances ranging from 3.7562 Å to
4.040 Å. Like in 1 this arrangement is not planar, but strongly
corrugated (Figure 5). These (RbO2)ϱ layers are connected by
the tF-BDC2– ligands to form a non-porous 3D network (Fig-
ure 5). Including all Rb···O and Rb···F contacts each Rb+ cation
and each side of the linker – including the carboxylate and
C–F groups – act as a 6-connector. The distances and angles
within the tF-BDC2– ligand were constrained in the refinement
of the XRPD data using values obtained from the single crystal
structure analysis of 1 (for details see Experimental Section).
Experimental Section
H2tF-BDC was synthesized according to the procedure described in
However, the torsion angles between the carboxylate groups the literature.[7]
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Anhydrous Salts of Tetrafluoroterephthalic Acid (H2tF-BDC)
K2[p-(OOC)C6F4(COO)] (1): (a) KCl (16.4 mg, 0.2 mmol) and
H2tf-BDC (23.8 mg, 0.1 mmol) were dissolved in EtOH/H2O (1 mL,
of neighboring atoms were set to 120(1)°. The atoms O1, O2, C1, C2
as well as the atoms C1, C2, C3, C4, F1, F2 were defined as planar
1:1, v:v). In an open vial this solution was placed in a desiccator, units. Finally, the Uisos of O1 and O2 as well as those of C1, C2, C3,
whose bottom was filled with EtOH/DMF (100 mL, 3:1, v:v). A beaker
with EtOH/DMF (40 mL, 3:1, v:v) and triethylamine (40 mL) was also
placed in the desiccator, which was closed afterwards. After four
weeks colorless single crystalline blocks of 1 were obtained, from
which a single crystal suitable for a single crystal structure analysis
was isolated. The resulting XRPD pattern and IR spectrum are given
in the Supporting Information (Figures S1 and S3). Both as well as
the elemental analysis indicate a single-phase sample. Elemental analy-
sis for K2(C8F4O4) (314.28 g·mol–1): calcd. C 30.57, H 0%; found C
30.50, H 0%.
C4, F1, F2 were constrained. The quality of the data and the refinement
can be estimated from Figure 3. Some crystallographic and refinement
data are summarized in Table 2.
Elemental Analysis: Elemental analyses were carried out with a
CHNS Euro EA 3000 Analyzer (HEKAtech GmbH).
IR Spectroscopy: FT-IR measurements were carried out on solid KBr
pellets with a Bruker ALPHA-T spectrometer.
DTA/TG Measurements: DTA/TG measurements were performed
with a Perkin-Elmer STA 6000 using alumina crucibles in a constant
argon stream (20 mL·min–1). The heating rate was 10 K·min–1. Sample
masses were 7.2 mg (1) and 2.5 mg (2).
(b) K(CH3COO) (196.3 mg, 2 mmol) and H2tf-BDC (238.3 mg,
1 mmol) were ground in an agate mortar by adding distilled water
(50 μL). After the smell of acetic acid was no longer noticed, the re-
sulting product was dried in vacuo. The resulting XRPD pattern is
given in the Supporting Information (Figure S2). Some weak extra
reflections indicate a small amount of an unknown impurity. The ele-
mental analysis however does not indicate any impurities. Elemental
analysis for K2(C8F4O4) (314.28 g·mol–1): calcd. C 30.57, H 0%;
found C 30.68, H 0%.
Supporting Information (see footnote on the first page of this article):
Experimental and simulated X-ray powder diffraction patterns, IR
spectrum, and DTA/TG diagram of compounds 1 and 2.
Crystallographic data (excluding structure factors) for the structure in
this paper have been deposited with the Cambridge Crystallographic
Data Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK. Copies
Rb2[p-(OOC)C6F4(COO)] (2): RbNO3 (29.5 mg, 0.02 mmol) and of the data can be obtained free of charge on quoting the depository
H2tf-BDC (24 mg, 0.01 mmol) were dissolved in EtOH/DMF (1.5 mL, number CCDC-959837 (1) (Fax: +44-1223-336-033; E-Mail:
3:1, v:v) and filled into a small vial, which was closed with a perfora- deposit@ccdc.cam.ac.uk, http://www.ccdc.cam.ac.uk).
ted foil. The vial was placed in a snap cap tube, which had been filled
with EtOH/DMF (4 mL, 3:1, v:v) and triethylamine (3:1, v:v) before.
After two weeks colorless single crystals of 2 were obtained, which
Acknowledgements
were used to determine the unit cell of 2, but the quality did not allow
a complete single crystal structure analysis. These crystals were ground
to a fine powder, which was used for the final structure analysis and
refinement (Figure 3).
We thank Dr. Ingo Pantenburg for X-ray single crystal data collection,
Marc Effertz for the DTA/TG measurements, and Silke Kremer for
elemental analyses. The help of Dr. Rainer Lamann, Miriam Sobieray,
Stefanie Busch, and Ireneus Grzesiak with structural analysis and re-
finement is greatly acknowledged.
Single Crystal Diffraction: A single crystal of 1 was isolated from
the precipitate described above and measured with a Stoe IPDS I single
crystal diffractometer (T ≈ 295 K). Data collection and reduction was
performed with the Stoe program package.[18] The crystal structure
was solved by direct methods using SIR-92.[19] The structural models
were completed using difference Fourier maps calculated with
SHELXL-97,[20] which was also used for the refinements. All pro-
grams are part of the WINGX program suite.[21] A numerical absorp-
tion correction was applied using X-Red[22] and X-Shape.[23] All atoms
were refined anisotropically. More details of the crystal structure solu-
tion and refinement are given in Table 1.
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in a capillary (Ø = 0.3 mm). Samples are typically measured for 90 min
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As the unit cell of 2 could be determined from a single crystal (see
above), it was already concluded from this unit cell that 2 crystallizes
in the Tl2tF-BDC type structure.[8] The final refinement of the crystal
structure of 2 was performed on the X-ray powder diffraction data
(Figure 3) using the Rietveld method.[24] The atomic coordinates of
Tl2tF-BDC were used as starting parameters. The following soft con-
straints for the tF-BDC2– linker were used to obtain a stable and con-
verging refinement: C–F = 1.34(1) Å, C–O = 1.25(1) Å, Carom–Carom
= 1.38(1) Å, and C1–C2 = 1.52(1) Å. All C–C–C and F–C–C angles
Z. Anorg. Allg. Chem. 2013, 2487–2492
© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
2491

M. Werker, B. Dolfus, U. Ruschewitz
[22] X-Red, Stoe & Cie GmbH: Darmstadt, 2001.
[23] X-Shape, 1.06; Stoe & Cie GmbH: Darmstadt, 1999.
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ARTICLE
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Received: September 20, 2013
Published Online: October 25, 2013
2492
www.zaac.wiley-vch.de
© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2013, 2487–2492