Synthesis, structure, and luminescence of rare earth cyanurates

Article abstract of DOI:10.1002/ejic.201402697

Rare earth cyanurates were prepared by exothermic solid-state metathesis reactions of appropriate proportions of A(OCN) (A = K, Rb, Cs) and RECl₃ (RE = La, Ce, Pr) at 500 °C. A DTA study of this mixture revealed the reaction to occur around 450 °C. The crystal structure of RbLa₂Cl(O₃C₃N₃)₂ was refined from a powder X-ray diffraction pattern. Homologous ARE₂Cl(O₃C₃N₃)₂ compounds with A = K, Rb, Cs and RE = La, Ce, Pr were indexed isotypically. Photoluminescence and reflection properties of doped samples and an infrared study are reported.

Full text of DOI:10.1002/ejic.201402697

FULL PAPER
DOI:10.1002/ejic.201402697
Synthesis, Structure, and Luminescence of Rare Earth
Cyanurates
[
a]
[a]
[b]
Markus Kalmutzki, Markus Ströbele, David Enseling,
[b]
[a]
Thomas Jüstel,* and H.-Jürgen Meyer*
Keywords: Luminescence / Solid-state structures / Solid-state reactions / Metathesis / Cyanurates
Rare earth cyanurates were prepared by exothermic solid-
state metathesis reactions of appropriate proportions of
Cl(O
3
C
3
N
3
)
2
was refined from a powder X-ray diffraction
Cl(O compounds with A =
pattern. Homologous ARE
2
3 3 3 2
C N )
A(OCN) (A = K, Rb, Cs) and RECl
A DTA study of this mixture revealed the reaction to occur
around 450 °C. The crystal structure of RbLa -
2
3
(RE = La, Ce, Pr) at 500 °C.
K, Rb, Cs and RE = La, Ce, Pr were indexed isotypically. Pho-
toluminescence and reflection properties of doped
samples and an infrared study are reported.
Introduction
Reactions between Li(OCN) and SrCl
O C N ), and reactions between Li(OCN) and SrF
2
2
yielded LiSr-
(
3
3
3
Isocyanates are well-known in organic chemistry and
of great importance in contemporary polymer chemistry
as they can undergo polymerization reactions including
di- and trimerization.[1,2] Cyclotrimerzation reactions of
isocyanates (R–N=C=O) can occur under various condi-
tions and are generally considered to be promoted by elec-
tron-withdrawing groups.
Preparations of inorganic cyanurate compounds have
been described by neutralization reactions of cyanuric acid
to yield mono-, di-, or tri-anions. However, the removal of
an increasing number of (1, 2, 3) hydrogen atoms from
cyanuric acid can be regarded to become increasingly diffi-
cult, and until now there is no proof that this way of synthe-
[4]
yielded Li Sr F(O C N ) . It turned out that the use of
3
2
3
3
3 2
Li(OCN) in these reactions is limited to its melting point
approximately 475 °C) because decomposition occurs right
(
[6]
above this temperature. Better performance was obtained
in reactions with K(OCN), which can be heated up to at
least 550 °C without decomposition. This temperature
[5]
seems to be sufficient because several reactions occur in the
temperature region around 500 °C. Another interesting
example is the binary cyanurate Ba (O C N ) , which was
3
3
3
3 2
[5]
recently prepared from a mixture of BaCl and K(OCN).
2
With this simple procedure we now approach the field of
rare earth cyanurates with a number of examples reported
herein.
3– [3]
sis has been accomplished for the trianion (O C N ) .
3
3
3
Hence, the chemistry of inorganic cyanurate is orphaned
[
1,3]
because no other way of synthesis has been available.
Results and Discussion
Recently we explored reactions of alkali cyanate com-
pounds with metal halides in solid-state metathesis (SSM)
reactions. All reactions we have performed under thermo-
analytically controlled conditions involve cyclotrimerization
reactions of cyanate into cyanurate.[4,5]
The field of inorganic cyanurates is represented by few
structurally defined compounds and is still at its beginning.
After some alkali and alkali earth cyanurates were recently
reported, we attempted the preparation of a rare earth
cyanurate, considering the simple target compound
RE(O C N ) (RE = rare earth metal ion). Instead of this
[
a] Abteilung für Festkörperchemie und Theoretische
Anorganische Chemie, Institut für Anorganische Chemie,
Universität Tübingen,
3
3
3
composition, we obtained a compound that can be consid-
ered as a salt adduct of our target compound, namely
RE(O C N )·1/2RbCl. A similar, but slightly different re-
Auf der Morgenstelle 18, 72076 Tübingen, Germany
E-mail: markus.kalmutzki@student.uni-tuebingen.de;
Juergen.Meyer@uni-tuebingen.de
3
3
3
sult was previously found for the cyanurate LiSr(O C N )·
3
3
3
http://www.mnf.uni-tuebingen.de/fachbereiche/chemie/institute/
anorganische-chemie/institut/ag-meyer/startseite.html
b] Fachbereich Chemieingenieurwesen, Institut für Optische
Technologien, FH Münster,
[
4]
1/2LiCl.
[
Stegerwaldstr. 39, 48565 Steinfurt, Germany
E-mail: tj@fh-muenster.de
Synthesis and DTA
https://www.fh-muenster.de/fb1/personal/professoren/juestel/
index.php
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201402697.
New compounds with the general formula ARE Cl-
2
(O C N ) were synthesized by SSM reactions at 500 °C
3
3
3 2
Eur. J. Inorg. Chem. 2015, 134–140
134
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from RECl (RE = La, Ce, Pr) and A(OCN) (A = K, Rb, set at 450 °C. The exothermic formation of RbLa2-
3
Cs) according to Equation (1).
Cl(O C N ) can be assumed to be centered at 500 °C (2)
3 3 3 2
and is framed by the (endothermic) melting of starting ma-
terials (1) and the melting of the product mixture at 531 °C
2
RECl
3
+ 6 A(OCN)ǞARE
2
Cl(O
3
C
3
N
3
)
2
+ 5 ACl
(1)
(
3). The cooling curve (4) shows the crystallization of reac-
This reaction proceeded quantitatively and produced
tion products.
crystalline reaction products for several examples of A and
RE which are stable towards moisture and air, so that the
coproduced metathesis salt could be extracted simply with
water.
A pattern corresponding to the melting (3, 528 °C) and
crystallization (4, 460 °C) of the reaction products [RbLa2-
Cl(O C N ) and RbCl] can be obtained in the second
cycle, which was performed with the same sample,
immediately after the first cycle.
3
3
3 2
The reaction involves a cyclotrimerization reaction of
cyanate ions into cyanurate, as has been recently reported
for compounds LiSr(O C N ), Li Sr F(O C N ) , and
3
3
3
3
2
3
3
3 2
Ba (O C N ) . All these compounds were prepared by
3
3
3
3 2
SSM reactions, which seem to be a useful method for the Crystal Structure
development of cyanurates.
The formation of RbLa Cl(O C N ) was studied by
differential thermal analysis (DTA; Figure 1). A DTA curve
starting from a reaction mixture of LaCl and Rb(OCN)
according to Equation (1) was recorded between room tem-
perature and 550 °C (heating and cooling rate 2 K/min).
All compounds of the general chemical formula ARE2-
Cl(O C N ) with A = K, Rb and RE = La, Ce, Pr, Cs were
2
3
3
3 2
3
3
3 2
indexed isotypically to RbLa Cl(O C N ) in the hexagonal
2
3
3
3 2
[7]
3
space group P6 /m using WinXPOW. The crystal struc-
3
ture of RbLa Cl(O C N ) shows structural similarities to
2
3
3
3 2
that of Li Sr F(O C N ) , which also crystalizes in P6 /m.
3
2
3
3
3 2
3
The crystal structure of ARE Cl(O C N ) contains one
2
3
3
3 2
crystallographic cyanurate ring in the structure which intro-
duces a layered appearance to the structure. The arrange-
ment of cyanurate units can be considered to follow the
motif of a closest packed layer within the in the ab plane
(Figure 2). The stacking of cyanurate ions with the se-
quence AABB along the c direction results in a hexagonal
close packing of sticks, following a 6 -screw axis. Lanth-
3
anum and rubidium ions as well as chloride ions are located
in between individual cyanurate layers (Figure 3).
Figure 1. DTA measurement starting from a mixture LaCl
3
and
Rb(OCN) according to Equation (1).
The reaction between LaCl and Rb(OCN) can be as-
3
signed to a relatively small temperature region and is related
to the thermal effects displayed in Figure 1. Cycle 1 shows
the formation reaction of RbLa Cl(O C N ) on heating
2
3
3
3 2
Figure 2. Arrangement of cyanurate ions within the ab plane of the
(
red curve), and the recrystallization of products up on
cooling (blue curve). The second heating and cooling cycle
cycle 2) was performed to verify the completeness of the away (large black spheres) from the layer formed by cyanurate
crystal structure of RbLa
2 3 3 3 2
Cl(O C N ) with lanthanum ions being
situated at different heights, closer (small black spheres) or further
(
reaction, and to assign the melting recrystallization of the rings.
product mixture.
Thermal effects occurring in the heating curve of the first
Interestingly, there seems to be a close relationship be-
cycle appear within a small temperature interval, and an tween the crystal structures of Li Sr F(O C N ) and
3
2
3
3
3 2
interpretation of these effects does not appear to be an easy RbLa Cl(O C N ) , both crystallizing in the space group
2
3
3
3 2
task. However, since we have already reported several DTA- P6 /m (Figure 4). The primary feature of both structures is
3
(
or DSC-)controlled SSM reactions that all follow the same due to the cyanurate ions introducing a layered structure.
sequence, we will consider an analogous sequence of effects In addition, the sequence of cyanurate layers follows one
for this reaction pattern: same AABB stacking sequence. Differences between the
The reaction is initiated by the melting of the starting two structures are the different types of ions, their numbers,
materials (1), marked by an endothermic effect with an on- and their interlayer positions in the two structures.
Eur. J. Inorg. Chem. 2015, 134–140
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Photoluminescence and Reflection Spectra
ALa Cl(O C N ) (with A = K, Rb) samples were doped
2
3
3
3 2
by 1 or 5% of the rare earth ions Eu3 or Tb . Figure 5
+
3+
shows the photoluminescence (left) and the reflection spec-
3+
tra (right) of KLa Cl(O C N ) :Eu . The reflection spec-
2
3
3
3 2
tra reveal that the host material has a strong absorption at
20 nm and below 250 nm, whereby the latter (250 nm) is
3
assigned to a valence band to conduction band absorption
process (Figure 5, right). The absorption band at lower en-
3–
3+
ergy (320 nm) is likely caused by a (O C N ) –Eu ligand
3
3
3
to metal charge-transfer (LMCT) process, which is located
at rather low energy due to the high alkalinity of the triple
negatively charged cyanurate ions. Excitation at 320 nm,
that is, into this LMCT band yields photoluminescence in
Figure 3. Comparison of the unit cells of Li
3 2 3 3 3 2
Sr F(O C N ) (left)
and RbLa Cl(O (right) viewed along the a axis.
2
3 3 3 2
C N )
5
7
the red spectral range due to the D Ǟ F transitions of
0
J
3+[8]
Eu
and two broad bands at 370 and 410 nm, whereby
3+
the former band is quenched by increasing the Eu con-
tent. Therefore, we assume that the optical transitions caus-
ing the UV to blue emission bands are quenched by Eu3
due to energy transfer. This interpretation is supported by
the decay curves upon excitation at 320 nm, which demon-
+
3+
strate that the Eu decay constant slightly increases by en-
hancing the Eu3 concentration (Table 1).
+
Figure 4. Distorted octahedral coordination environment of the
lanthanum ion (left) and trigonal-prismatic coordination of the
rubidium ion (right) with oxygen atoms of cyanurate in RbLa Cl-
2
2 3 3 3 2
Table 1. Decay times of ARE Cl(O C N ) compounds doped with
3
+
3+
Eu or Tb
.
(
O
3
C
3
N
3
)
2
.
χ2
τ
1
[μs], fraction [%]
73 (Ϯ16), 11
86 (Ϯ6), 17
17 (Ϯ3), 42
297 (Ϯ3), 39
51 (Ϯ11), 10
30 (Ϯ2), 28
2
τ [μs], fraction [%]
2 2
Cl(CY)
:Eu3+
KLa
1 mol-%)
KLa Cl(CY)
2
928 (Ϯ8), 89%
900 (Ϯ5), 83%
876 (Ϯ6), 58%
814 (Ϯ5), 61%
1182 (Ϯ10), 90%
877 (Ϯ6), 72%
1.138
1.149
1.147
1.151
1.119
1.184
(
:Eu3+
:Eu3+
:Eu3+
2
2
2
Lanthanum ions in RbLa Cl(O C N ) are surrounded (5 mol-%)
2
3
3
3 2
RbLa
1 mol-%)
RbLa Cl(CY)
5 mol-%)
RbLa Cl(CY)
2 2
Cl(CY)
by six oxygen atoms of six neighboring cyanurate rings in a
distorted octahedral manner (Figure 4, left). Moreover
three La–N contacts are found at dLa–N = 274.2 pm, which
can be explained by the rigid nature of the cyanurate ion.
The rubidium ion exhibits a trigonal prismatic coordination (1 mol-%)
by six exocyclic oxygen atoms belonging to six adjacent
cyanurate rings (Figure 4, right).
3
(
2
2
(
:Tb3+
2
2
2
2 2
Cl(CY)
:Tb3+
RbLa
5 mol-%)
1
(
2 3 3 3 2
Cl(O C N )
:Eu3+ for two different concentrations
Figure 5. Excitation and emission spectra (left) and reflection spectra (right) of KLa
of Eu3+ (λexc = 320 nm, λem = 615 nm, reflection spectrum vs. BaSO
as a white standard).
4
Eur. J. Inorg. Chem. 2015, 134–140
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Figure 6. Excitation and emission spectra (left) and reflection spectra (right) of RbLa
2
Cl(O
3
C
3
N
3
)
2
:Eu3+ for two different concentrations
of Eu3+ (λexc = 320 nm, λem = 615 nm, reflection spectrum vs. BaSO
as a white standard).
4
Figure 7. Excitation and emission spectra (left) and reflection spectra (right) of RbLa
2
Cl(O
3
C
3
N
3
)
2
:Tb3+ for two different concentrations
of Tb3+ (λexc = 355 nm, λem = 542 nm, reflection spectrum vs. BaSO
as a white standard).
4
Figure 6 shows the photoluminescence and reflection sorption edge is according to our expectations at the same
3
+
spectra of RbLa Cl(O C N ) :Eu . The absorption edge is position, namely, at around 380 nm as observed for RbLa -
2
3
3
3 2
2
3+
red-shifted by 50 nm in comparison to KLa Cl- Cl(O C N ) :Eu . This result shows that the absorption
O C N ) :Eu . This finding can be interpreted by as- edge is indeed related to the host matrix and not governed
suming that the (O C N ) -La LMCT band is shifted to by the luminescent dopant. Upon excitation at 355 nm we
2
3
3
3 2
3
+
(
3 3 3 2
3
–
3+
3
3
3
lower energy, which is in line with the assumption that the obtained an emission spectrum showing the typical
5
7
3+
rubidium compound has a higher alkalinity. The emission
D Ǟ F emission line multiplet of Tb and an emission
4 J
spectrum upon 320 nm excitation exhibits mainly red emis- band at 430 nm, which is caused by the host material as
5
7
3+
sion lines due to the D Ǟ F transitions of Eu , while the observed for the formerly discussed materials. We observe
0
J
5
7
most intense lines are due to the hypersensitive D Ǟ F
again that the relative intensity of the host matrix related
0
2
transition, which is an indicator for a site deviating from emission to the rare earth ion line emission is weaker at a
inversion symmetry.[ The broad-band emission in the blue higher Tb concentration. The decay curves of Tb upon
8]
3+
3+
range is much weaker as observed for the potassium com- 355 nm excitation indicate concentration quenching of the
3+
pound and indicates a higher crystallinity, that is, less de- Tb luminescence due the strong decrease of the decay
3+
fect-related luminescence. This result is also in line with the constant upon enhancement of the Tb concentration (see
3
+
longer decay time of the Eu luminescence upon 365 nm Table 1).
excitation (see Table 1), since the decay time is correlated to
the quantum efficiency. In other words, the higher crystal-
linity and thus reduced defect luminescence results in higher
Infrared Spectroscopy
5
7
3+ [9]
quantum efficiency of the D Ǟ F luminescence of Eu .
0
J
Figure 7 shows the photoluminescence (left) and reflec-
An infrared spectrum of a washed sample of RbLa -
2
–1
3
+
tion spectra (right) of RbLa Cl(O C N ) :Tb . The ab- Cl(O C N ) was measured in the range 2000–400 cm .
2
3
3
3 2
3
3
3 2
Eur. J. Inorg. Chem. 2015, 134–140
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Absorption bands in the region 1500–1300 cm–1 can be as- ampoules were opened in air, and products were rinsed several
times with water and finally with ethanol. White to greyish crystal-
signed to stretching vibrations ν(C N ). Out of plain bend-
3
3
–1
line powders were obtained after this procedure, with hardly any
side-phase being detectable in the X-ray powder diffraction pat-
terns.
ing vibrations δ (C N ) can be found between 830 cm
oop
3
3
–
1
and 800 cm , and in plain bending vibrations δ (C N ) are
ip
3
3
–
1
located at 610 cm . The fingerprint region of the IR spec-
[
5,10]
trum of RbLa Cl(O C N ) is depicted in Figure 8.
Thermal Analysis: Differential thermal analysis (DTA) studies were
performed under a flow of argon in a Netzsch Jupiter, STA 449 F3
apparatus, with about 100 mg of the reaction mixture being filled
into a corundum sample holder, in a temperature regime from
room temperature to 550 °C in a cyclic procedure.
2
3
3
3 2
X-ray Diffraction
Products of reactions were inspected by powder X-ray diffraction
(
XRD) patterns, recorded with a Stadi-P (STOE, Darmstadt, Ger-
many) powder diffractometer, using germanium monochromated
Cu-Kα1 radiation. It has been shown that the products of our prep-
arations were ARE Cl(O C N ) (A = K, Rb, Cs; RE = La, Ce,
2 3 3 3 2
Pr, Nd) and the co-produced metathesis salt (ACl) without any
other phase being detectable in the diffraction patterns. The crystal
2 3 3 3 2
structure of RbLa Cl(O C N ) was solved from XRD data by
using the Rietveld method (Figure 9). Due to a strong size/strain
2
effect of crystallites resulting in high RBragg and χ values it was
necessary to refine the profile parameters beforehand with the Le-
Bail Method using the spherical harmonics size model 19 of the
FullProf Program[ with the additional relaxation of some reflec-
tions. Owing to the low scattering values of carbon, nitrogen, and
oxygen in comparison to those of lanthanum and rubidium, the
concluding refinement of C–N distances was restrained to 135(1)
pm, the N–C–N angle to 125(1)°, and the temperature factors of
these three elements to be equivalent.
12]
Figure 8. Fingerprint region of the IR absorption spectrum of
RbLa Cl(O
2
3 3 3 2
C N ) .
Conclusion
Solid-state metathesis reactions have been shown once
more to be a reliable tool for the development of cyanurates.
Rare earth cyanurates attempted as RE(O C N ) from a
3
3
3
SSM reaction of rare earth chloride (RECl ) and alkali
3
cyanate [A(OCN)] turned out to exist as ARE Cl-
2
(
O C N ) with A = K, Rb, Cs and RE = La, Ce, Pr. Reac-
3 3 3 2
tions occur in a melt of the employed cyanate with typical
ignition temperatures around 450 °C. Cyanurate rings tend
to introduce layered structures to cyanurate compounds.
ARE Cl(O C N ) compounds substituted on the rare
2
3
3
3 2
3
+
3+
earth site with a few mol.-% of Tb or Eu ions show
intense photoluminescence properties.
Experimental Section
Preparation: A(OCN) compounds with A = K, Rb, and Cs were
prepared by heating a mixture of urea with A (CO ) in a 4:1 molar
2 3
ratio in a corundum vessel (in air) to the melting point of the mix-
ture. This heating stage was retained for about 1 h before the tem-
perature was raised to 275 °C for 30 min, and then lowered to
2 3 3 3 2
Figure 9. Structure refinement of RbLa Cl(O C N ) based on
powder XRD data. Circles represent measured data; the calculated
pattern is superimposed with the observed pattern (red). Ticks
mark the Bragg reflections (green) of RbLa Cl(O C N ) . The dif-
2 3 3 3 2
ference curve between the observed and calculated pattern is shown
in the lower part of the graph (blue).
1
00 °C for 12 h. Rare earth chlorides were synthesized as described
[
11]
in the literature.
Handling of all starting materials was per-
formed in a glove box under dry argon atmosphere. Samples of
RECl and A(OCN) were mixed in 2:3 molar ratios (total mass
50 mg), carefully ground in a agate mortar, and then transferred
into fused silica tubes. Doped samples were prepared by substitut-
3
2
ing RE = La with (about 5 mol.-%) Eu3 or Tb , introduced into
+
3+
Some results of the structure refinement for RbLa
and final R values are given in Table 2. The atomic positions of
RbLa Cl(O are provided in Table 3. Selected distances and
angles of RbLa Cl(O are collected in Table 4.
2
3 3 3 2
Cl(O C N )
the reaction as RECl . Reaction mixtures were heated to 500 °C
3
within 4 h and remained at this temperature for 15 h before they
were cooled down with the natural cooling rate of the furnace. The
2
3 3 3 2
C N )
2
3 3 3 2
C N )
Eur. J. Inorg. Chem. 2015, 134–140
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Table 2. Selected crystal data and refinement conditions for the
2 3 3 3 2
Table 5. Lattice parameters of ARE Cl(O C N ) compounds for
different combinations of A and RE, as refined from XRD patterns
with the 2θ window and the figure of merit (FOM) of refinements.
crystal structure of RbLa
2
Cl(O
3
C
3
N
3
)
2
.
Chemical formula
2 3 3 3 2
RbLa Cl(O C N )
A; RE
K; La
Rb; La Cs; La
K; Ce
K; Pr
–
1
Formula weight [gmol ]
T [K]
567.04
298(2)
1.54060
a [Å]
c [Å]
6.779(1)
6.782(1) 6.787(3) 6.746(4) 6.772(4)
Wavelength (Cu-K
Crystal system
Space group
a [pm]
α
) [Å]
14.263(3) 14.637(2) 15.150(7) 14.211(8) 14.178(7)
3
hexagonal
V [Å ]
567.7(2)
0.0300
118
583.0(2) 604.4(4) 560.1(7) 554.7(6)
P6
3
/m (Nr. 176)
2θ window
FOM
0.0200
78
0.0300
27
0.0300
57
0.0300
45
678.4(1)
1463.27(3)
2
0.58320(2)
63.46
3.706
2.5–50.0
245
c [pm]
Z
3
Volume [nm ]
Luminescence and Reflection Spectroscopy
–1
α
Absorption coefficient μ(Cu-K ) [mm ]
–
3
D
c
[gcm ]
Luminescence spectra were collected with a fluorescence spectrom-
eter FLS920 (Edinburgh Instruments) equipped with a 450 W
ozone-free xenon arc lamp (OSRAM) and a sample chamber in-
stalled with a mirror optic for powder samples. For detection, a
R2658P single-photon counting photomultiplier tube (Hamam-
atsu) was used. All luminescence spectra were recorded in triplicate
with a spectral resolution of 1 nm, a dwell time of 0.4 s in 1 nm
steps. Reflection spectra were monitored by placing the sample into
an integrating sphere coated with barium sulfate and using a syn-
chronic scan, that is, the excitation and emission monochromators
were adjusted to the same wavelength and tuned synchronously.
Theta ranges for data collection [°]
Reflections collected
Refined parameters
26
15
4
Refined structure parameters
Restraints
R
R
χ
p
, Rwp
Bragg
4.670, 5.946
6.523
2.390
2
Reflection spectra were recorded on an Edinburgh Instruments
FS900 spectrometer equipped with a 450 W Xe arc lamp and
cooled single-photon counting photomultiplier (Hamamatsu
R928). BaSO4 (99%, Sigma–Aldrich) was used as a reflectance
standard.
Table 3. Atomic positions and isotropic displacement parameters
2
–1
(pm ϫ10 ) of RbLa
2 3 3 3 2
Cl(O C N ) .
[a]
Atom Wyckoff position
x
y
z
U
eq
La
Rb
Cl
C
N
O
4f
2d
2c
12i
12i
12i
2/3
1/3
2/3
1/3
2/3
1/3
0.55135(9) 0.0080(3)
3/4
3/4
0.043(1)
0.047(3)
Decay curves were measured with a fluorescence spectrometer
FLS920 (Edinburgh Instruments) with a Xe-μs-flash lamp also
with the R2658P single-photon counting photomultiplier tube
0.790(1) 0.831(1) 0.594(1) 0.018(2)
0.957(1) 0.776(1) 0.6019(8) 0.018(2)
0.5884(9) 0.667(1) 0.5812(5) 0.018(2)
(
Hamamatsu) in the mirror optic.
Infrared Spectra: Vibrational spectra were recorded with a Bruker
[
U
a] Ueq is defined as one third of the trace of the orthogonalized
ij tensor.
Tensor 27 and a Vertex 70-FTIR spectrometer within the range of
–
1
5
00–4000 cm by using KBr pellets.
Acknowledgments
Table 4. Selected interatomic distances [pm] and angles in the crys-
tal structure of RbLa Cl(O
Support of this research by the Deutsche Forschungsgemeinschaft
2
3 3 3 2
C N ) .
(
(
DFG) through the project Solid State Metathesis Reactions
ME914/25-1) is gratefully acknowledged from scientists of the
Atoms
La–O
Interatomic distances [pm]
260.8(8), 260.8(5), 260.8(6), 259.8(7) (2ϫ ),
Eberhard-Karls-University Tübingen. M. K. is indebted to the
Landesgraduiertenförderung of the Science Ministry of Baden-
Württemberg and the Institutional Strategy of the University of
Tübingen (DFG, ZUK 63) for supporting his work with a fellow-
ship. The authors would like to thank Dr. J. Glaser for helpful
discussions.
259.8(6)
La–N
La–Cl
Rb–O
Rb–Cl
C(1)–N(1)
C(1)–O(1)
274.2(6), 274.2(7), 274.2(9)
290.7(1)
301.5(7) (6ϫ )
391.68(4)
137(1), 136(1)
127.2(8)
[
[
[
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Powder patterns of ARE Cl(O C N ) compounds with A = K, Cs
and RE
WinXPOW,
=
La, Ce, Pr were indexed with the program
and the lattice parameters refined there from are
[
13,7]
collected in Table 5. The powder patterns of all ARE
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the desired cyanurate compounds, as displayed for RbLa Cl-
in Figure 9.
2
Cl-
3 3 3 2
(O C N )
2
3 3 3 2
C N )
3
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3 3 3 2
(O C N )
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139
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Received: July 24, 2014
Published Online: December 10, 2014
Eur. J. Inorg. Chem. 2015, 134–140
140
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim