Facile formation of luminescent terbium(III) aryloxide complexes directly from terbium metal including the x-ray crystal structures Tb(OC6H3Me2-2,6)3 (THF)3 and Tb(OC6H3i</s

Article abstract of DOI:10.1016/S0277-5387(00)00629-X

Direct reaction of terbium metal in refluxing isopropanol and phenols provides the luminescent terbium aryloxide species Tb(OC₆H₃Me₂-2,6)₃ (THF)₃ (1) and Tb(OC₆H₃ⁱPr

Full text of DOI:10.1016/S0277-5387(00)00629-X

www.elsevier.nl/locate/poly
Polyhedron 20 (2001) 277–280
Facile formation of luminescent terbium(III) aryloxide complexes
directly from terbium metal including the X-ray crystal structures
ꢀ
of Tb(OC6H3Me2-2,6)3(THF)3 and Tb(OC6Hi3Pr2-2,6)3(THF)2
William J. Evans *, Matthew A. Johnston, Michael A. Greci, Joseph W. Ziller
Department of Chemistry, Uni6ersity of California, Ir6ine, CA 92697-2025, USA
Received 26 June 2000; accepted 25 October 2000
Abstract
Direct reaction of terbium metal in refluxing isopropanol and phenols provides the luminescent terbium aryloxide species
Tb(OC6H3Me2-2,6)3(THF)3 (1) and Tb(OC6Hi3Pr2-2,6)3(THF)2 (2) in good yield. Crystallographic studies showed 1 to be
fac-octahedral and 2 to be trigonal bipyramidal with the THF molecules in the axial positions. © 2001 Elsevier Science B.V. All
rights reserved.
Keywords: Luminescence; Terbium(III) aryloxide complexes; X-ray crystal structures; Aryloxide
directly with isopropanol and 2,6-dialkylphenols in the
presence of catalytic amounts of mercury salts to make
highly luminescent arene-soluble terbium aryloxide
complexes.
1. Introduction
The narrow line luminescence of europium and ter-
bium make them important components in energy-effi-
cient optical devices [1]. The continual demand for
systems utilizing these metals which have better optical
performance at lower cost requires increased efforts to
incorporate these elements into optically inert host
matrices by easier and more homogeneous methods.
Syntheses starting with the elemental metal are highly
desirable in this regard compared to ionic metathesis
reactions starting with metal salts since they avoid the
possibility of contamination with counteranions [2].
Recent studies have shown several ways to generate
potential europium precursors directly from the metal
[3,4], but little is known about convenient syntheses of
soluble terbium complexes directly from the metal.
Since terbium metal is less reactive than europium
metal, this is more challenging.
2. Experimental
All manipulations were performed under nitrogen
with rigorous exclusion of air and water by using
Schlenk, vacuum line, and glovebox techniques. Physi-
cal measurements were obtained and solvents were
purified as previously described [5]. Terbium metal was
purchased from Rhone–Poulenc and used as received.
Isopropanol was dried over sodium metal. 2,6-Diiso-
propylphenol was purchased from Aldrich and distilled
,
from 4 A molecular sieves. 2,6-Dimethylphenol was
purchased from Aldrich and sublimed before use. IR
spectra were obtained using a Perkin–Elmer series 1600
FTIR spectrophotometer and UV–Vis spectra were
obtained using a Shimadzu 160 spectrophotometer. Lu-
minescence measurements were performed on a Hitachi
F-4500 spectrometer. Magnetic susceptibility measure-
ments were made following the Evans method [6].
Elemental analyses were performed by Desert Analyt-
ics, Tuscon, AZ.
We report here that terbium metal can be reacted
ꢀ These results were communicated in part at the 217th National
Meeting of the American Chemical Society.
* Corresponding author. Tel.: +1-714-824-5174; fax: +1-714-824-
2210.
E-mail address: wevans@uci.edu (W.J. Evans).
0277-5387/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0277-5387(00)00629-X

278
W.J. E6ans et al. / Polyhedron 20 (2001) 277–280
10−5. v
: 9.6. IR (KBr): 3307 m, 3025 w, 2825 s,
298 K
eff
2.1. Tb(OC6H3Me2-2,6)3(THF)3 (1)
2496 w, 1860 m, 1795 m, 1607 s, 1472 m, 1161 s, 1020
Isopropanol was vacuum transferred into a 100 ml
Schlenk flask containing terbium metal (0.347 g, 2.3
mmol), 2,6-dimethylphenol (0.791 g, 6.8 mmol), HgCl2
(0.005 g, 0.01 mmol) and Hg(OAc)2 (0.005 g, 0.02
mmol). The reaction was attached to a Schlenk line and
heated at reflux for 48 h. The solvent was removed
under vacuum to yield dark green solids. Extraction of
the solids with THF and removal of solvent yielded
Tb(OC6H3Me2-2,6)3(THF)3 (1) as a white microcrys-
talline powder (1.13 g, 66%). Recrystallization of 1
from a toluene–THF mixture at −35°C yielded color-
less crystals suitable for X-ray analysis. Anal. Calc. for
m, 890 m, 826 w cm−1
.
2.4. Structure and refinement data for 2
X-ray diffraction data on 2 were collected and refined
as described above for 1. A colorless crystal of the
approximate dimensions 0.50×0.45×0.17 mm3 was
found to have diffraction symmetry of 2/m and the
systematic absences were consistent with the centrosym-
metric monoclinic space group P21which was later de-
termined to be correct. At convergence, wR2=0.0927
and GOF=1.047 for 448 variables refined against 3107
unique data (as a comparison for refinement on F,
R1=0.0353 for those 2910 data with with [I\2|(I)]).
TbO6C36H51: Tb, 21.5. Found: Tb, 22.0. 298 K: 5.35×
g
10−5. v
: 9.7. IR (KBr): 3001 m, 2982 m, 2907 s,
298 K
eff
2848 w, 1589 m, 1455 s, 1415 m, 1272 m, 1231 s, 1196
m, 1090 s, 1025 w, 861 m, 761 s cm−1
.
2.5. Luminescence studies
For both 1 and 2, approximately 0.01 mM solutions
were prepared in either THF or toluene and transferred
to a quartz cell equipped with a 14/20 vacuum adapter.
The vessel was removed from the glovebox and trans-
ferred to the sample chamber of the spectrometer.
Emission data were collected between 250 and 690 nm
with excitation between 200 and 680 nm. For 1 in THF,
excitation at 285 nm produced emission at 490 and 550
nm. For 1 in toluene, excitation at 295 nm produced
emission at 490 and 545 nm. For 2 in THF, excitation
at 280 nm produced emission at 485 and 540 nm. For 2
in toluene, excitation at 295 nm produced emission at
490 and 545 nm.
2.2. Structure and refinement data for 1
A colorless crystal of approximate dimensions 0.48×
0.23×0.20 mm3 was mounted on a glass fiber and
transferred to a Bruker CCD platform diffractometer.
The SMART [7] program package was used to determine
the unit-cell parameters and for data collection (20
s/frame scan time for a hemisphere of diffraction data).
The raw frame data was processed using SAINT [8] and
SADABS [9] to yield the reflection data file. Subsequent
calculations were carried out using the SHELXTL [10]
program. The diffraction symmetry was 2/m and the
systematic absences were consistent with the centrosym-
metric monoclinic space group P21/n which was later
determined to be correct.
The structure was solved by direct methods and
refined on F2 by full-matrix least-squares techniques.
The analytical scattering factors [11] for neutral atoms
were used throughout the analysis. Hydrogen atoms
were included using a riding model. At convergence,
wR2=0.0937 and GOF=1.211 for 388 variables
refined against 8284 unique data (as a comparison for
refinement on F, R1=0.0439 for those 7267 data with
[I\2|(I)]).
3. Results and discussion
3.1. Synthesis
Terbium metal reacts with 2,6-disubstituted phenols
in isopropanol at reflux in the presence of mercury salts
to produce solvated tris-aryloxide species in good yield
as shown in Eq. (1). The complexes were characterized
by IR spectroscopy,
2.3. Tb(OC6Hi3Pr2-2,6)3(THF)2 (2)
Terbium metal (0.7206 g, 4.4 mmol), 2,6-diisopropy-
lphenol (2.37 g, 13.3 mmol), HgCl2 (0.005 g, 0.01
mmol) and Hg(OAc)2 (0.005 g, 0.02 mmol) were reacted
in isopropanol as described above for 1. The dark green
solution was worked up by a procedure identical to that
of 1 and produced, Tb(OC6Hi3Pr2-2,6)3(THF)2 (2) as a
microcrystalline white powder (2.66 g, 73%). Recrystal-
lization from toluene at −35°C provided crystals suit-
able for X-ray analysis. Anal. Calc. for TbO5C44H67: C,
(1)
magnetic moment measurement, and elemental analy-
sis. Due to the highly paramagnetic nature of Tb(III)
compounds (veff=9.4–9.7vB) [12], X-ray diffraction
studies were performed to unambiguously characterize
the reaction products. The structures are shown in Figs.
1 and 2.
Reactions in the absence of the mercury salts failed
to produce isolable terbium complexes. Attempts to
63.30; H, 8.09. Found: C, 63.40; H, 8.07. 298 K: 4.57×
g

W.J. E6ans et al. / Polyhedron 20 (2001) 277–280
279
isolate 1 or 2 from the direct reaction of terbium metal,
the 2,6-dialkylphenol, and mercuric salts in refluxing
THF or toluene were also unsuccessful. This suggests
the intermediacy of terbium–isopropoxide species dur-
ing the course of the reaction. Previous studies of
reactions with yttrium and the lanthanide metals with
isopropanol at reflux have formed complex structures
such as Y5O(OiPr)13 [13], Yb5O(OiPr)13 [14], and
Nd6Cl(OiPr)17 [15]. Y5O(OiPr)13 has subsequently found
to react with Ph3SiOH to form [Y(OSiPh3)3(THF)3]-
(THF) [16]. Step-wise reaction of Tb metal with iso-
propanol followed by reaction with 2,6-dimethylphenol
produced luminescent terbium products, but definitive
structural information was not obtained.
This geometry has been observed for the yttrium com-
pound, Y(OC6H3Me2-2,6)3(THF)3, which crystallized in
another space group [17]. Since the yttrium crystals
were of poor quality, a detailed description of bond
lengths and angles was not available, but high quality
metrical data were obtained on 1. In 1, the average
,
Tb–O(OAr) distance is 2.132(3) A, while the average
,
Tb–O(THF) distance is 2.452(3) A.
The product of the 2,6-diisopropylphenol reaction,
Tb(OC6Hi3Pr2-2,6)3(THF)2 (2) is isostructural with the
Ln(OC6Hi3Pr2-2,6)3(THF)2 (Ln=Er, Lu, Pr, Gd) com-
,
plexes reported previously [18]. The 2.110(7) A average
Tb–O(OAr) distance in 2 is slightly shorter than the
,
2.130 A Gd–O(OAr) average distance as expected
based on the difference in ionic radii. The Tb–O(THF)
,
average distance of 2.382(6) A is equal within error
limits to the Gd–O(THF) distance of 2.394(15).
3.2. Structural features
The product of the 2,6-dimethylphenol reaction,
Tb(OC6H3Me2-2,6)3(THF)3 (1) crystallizes with a dis-
torted octahedral environment around the terbium and
a fac-arrangement of the aryloxide and THF ligands.
4. Conclusions
These reactions clearly show that luminescent ter-
bium aryloxide products are obtainable directly from
the elemental metal and the appropriate phenols. These
syntheses avoid the need to dry lanthanide precursors
and preclude the possibility of alkali metal or chloride
incorporation during preparation.
Acknowledgements
For support of this research, we thank the Division
of Chemical Sciences of the Office of Basic Energy
Sciences of the Department of Energy. We would like
to thank Dr Wytze Van der Veer for his help with the
luminescence studies.
Fig. 1. Thermal ellipsoid plot of Tb(OC6H3Me2-2,6)3(THF)3 (1) with
ellipsoids drawn at the 50% probability level.
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