Synthesis and luminescent properties of Eu3+-complexes with 2-acyl-1,3-indandionates (ACIND) and TPPO ligands: The first X-ray structure of Eu-ACIND complex

Article abstract of DOI:10.1016/j.poly.2006.06.035

Europium complexes presenting general formulas [Eu(ACIND)₃(H₂O)₂] and [Eu(ACIND)₃(TPPO)₂] have been synthesized and characterized. In these formulas ACIND is stands for the ligands 2-acetyl-1,3-indandionate (AIND), 2-isovaleryl-1,3-indandionate (ISOVIND) or 2-benzyl-1,3-indandionate (BIND). The [Eu(ISOVIND)₃(H₂O)(EtOH)] complex was also prepared and its structure determined by single crystal X-ray analysis, showing that this complex crystallize in a monoclinic space group P2₁/n with the water molecules bridging through the hydrogen bond. The Eu(III) ion is eight-coordinate in a bicapped trigonal prismatic geometry defined by the oxygen donor atoms with a site of symmetry close to C_2ν. Isovaleryl groups in the ISOVIND molecules in the structure are disordered over two positions of the europium complex. Carbon atoms in ethanol molecule are disordered by the thermal vibration. Photoluminescence properties of these complexes in solid state were investigated both experimentally and theoretically, suggesting an efficient ligand-to-metal intramolecular energy transfer process.

Full text of DOI:10.1016/j.poly.2006.06.035

Polyhedron 25 (2006) 3488–3494
www.elsevier.com/locate/poly
Synthesis and luminescent properties of Eu3+-complexes with
2-acyl-1,3-indandionates (ACIND) and TPPO ligands:
The first X-ray structure of Eu–ACIND complex
a,
a
a
b
Ercules E.S. Teotonio *, Hermi F. Brito , Hans Viertler , Wagner M. Faustino ,
b
b
c
´
´
Oscar L. Malta , Gilberto F. de Sa , Maria Claudia F.C. Felinto ,
d
e
Regina H.A. Santos , Marco Cremona
a
Departamento de Quı´mica Fundamental, Instituto de Quı´mica da, Universidade de Sa˜o Paulo, 05508-900 Sa˜o Paulo, SP, Brazil
Departamento de Quı´mica Fundamental, Universidade Federal de Pernambuco, Cidade Universita´ria, CEP 50670-910, Recife, Brazil
b
c
Instituto de Pesquisas Energe´ticas e Nucleares, Travessa R 400, Cidade Universita´ria, Sa˜o Paulo-SP, CEP 05508-970, Brazil
d
Instituto de Quı´mica de Sa˜o Carlos, USP, C.P. 780, 13560-970 Sa˜o Carlos, SP, Brazil
Departamento de Fı´sica, Pontificia Universidade, Cato´lica do Rio de Janeiro, PUC-Rio, Brazil
e
Received 5 April 2006; accepted 28 June 2006
Available online 14 July 2006
Abstract
Europium complexes presenting general formulas [Eu(ACIND)3(H2O)2] and [Eu(ACIND)3(TPPO)2] have been synthesized and char-
acterized. In these formulas ACIND is stands for the ligands 2-acetyl-1,3-indandionate (AIND), 2-isovaleryl-1,3-indandionate (ISOV-
IND) or 2-benzyl-1,3-indandionate (BIND). The [Eu(ISOVIND)3(H2O)(EtOH)] complex was also prepared and its structure
determined by single crystal X-ray analysis, showing that this complex crystallize in a monoclinic space group P21/n with the water mol-
ecules bridging through the hydrogen bond. The Eu(III) ion is eight-coordinate in a bicapped trigonal prismatic geometry defined by the
oxygen donor atoms with a site of symmetry close to C2m. Isovaleryl groups in the ISOVIND molecules in the structure are disordered
over two positions of the europium complex. Carbon atoms in ethanol molecule are disordered by the thermal vibration. Photolumines-
cence properties of these complexes in solid state were investigated both experimentally and theoretically, suggesting an efficient ligand-
to-metal intramolecular energy transfer process.
ꢀ 2006 Elsevier Ltd. All rights reserved.
Keywords: Europium; Luminescence; 2-Acyl-1,3-indandionate; b-Diketonate; TPPO
1. Introduction
of ligand has been successfully employed as ‘‘antenna’’
[5]. In order to increase the europium luminescence inten-
sity in the diketonate complexes a second kind of uniden-
tate or bidentate ligands such as sulfoxide, heterocyclic,
or phosphine oxides are usually bonded to europium ion
[5]. These ligands coordinated to lanthanide ions, substitut-
ing organic solvent or water molecules that act as lumines-
cence quencher for this metal ion. Among these ligands
triphenylphosphine oxide (TPPO) has been the focus of
some studies in the literature [4]. When coordinated to
the metal ion substituting the water molecules TPPO may
improves the volatility, thermal stability, carrier-transport
to electroluminescence devices and also increases the
There is a great interest in the study and development of
new trivalent rare earth complexes (RE3+) that present
strong luminescence for application such as selective lumi-
nescent probes of biological structures [1], fluoroimmuno-
assay agents [2] and organic electroluminescent devices
(OLEDs) [3,4].
A particular attention has been given to the studies of
complexes containing b-diketonates as ligands. This kind
*
Corresponding author. Tel.: +55 11 3091 3708; fax: +55 11 3815 5579.
E-mail address: ercules@iq.usp.br (E.E.S. Teotonio).
0277-5387/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2006.06.035

E.E.S. Teotonio et al. / Polyhedron 25 (2006) 3488–3494
3489
emission quantum efficiency (g) by protecting the metal ion
from the luminescence quencher such as O–H and N–H
oscillators [5].
atmosphere (50 mL minꢀ1
)
and
a
heating rate of
10 ꢁC minꢀ1. Excitation and emission spectra at room
(ꢁ298 K) and liquid nitrogen temperatures were collected
at an angle of 22.5ꢁ (front face) in a spectrofluorimeter
(SPEX-Fluorolog 2) with double grating 0.22 m mono-
chromator (SPEX 1680), and a 450 W Xenon lamp as exci-
tation source. Luminescence decay curves were measured
using a phosphorimeter SPEX 1934D accessory coupled
to the spectrofluorimeter.
The spectroscopic properties of the 2-acyl-1,3-indandi-
one complexes have been only moderately studied. Up to
now, the main investigation about rare earth complexes
with 2-acyl-1,3-indandiones have been concerned with
complexation investigation and luminescence properties
of these systems in solution [6–9]. They made a correlation
between the intensity parameter g for the Eu3+-complexes,
which was defined as the ratio between the intensity of the
All reagents diethyl phthalate, acetone, methyl isobutyl
ketone, acetophenone and Eu2O3 were purchased from
Aldrich Chemical Co., EuCl3 Æ 6H2O were prepared
according to Ref. [10] by reaction between europium oxide
and hydrochloric acid.
7
5
7
5D0 ! F2 and D0 ! F1 transitions, and dielectric con-
stant of the solvents and the average polarizability of the
ligand molecules. However, to the best of our knowledge,
so far, no detailed studies of luminescence, including inten-
sity parameters and ligand-to-metal energy transfer pro-
cesses in solid state and X-rays structural information on
these kinds of complexes have been reported yet.
2.2. Synthesis of the ligands
2-Acetyl-1,3-indandione (AIND), 2-isovaleryl-1,3-indan-
dione (ISOVIND) and 2-benzoyl-1,3-indandione (BIND)
ligands were synthesized using a method reported by Kilg-
ore and co-workers [11]. Firstly, sodium ethoxide was
formed by reacting 5.7 g (0.25 mol) of sodium with 12 mL
(0.25 mol) of dried ethanol in benzene (200 mL), under stir-
ring. A mixture of 55.5 g (0.25 mmol) of diethyl phthalate
and the appropriate methyl ketone (acetone, isopropyl
methyl ketone or acetophenone) was added, and refluxed
at 80 ꢁC for 6 h. After that, the solvent was evaporated
under reduced pressure to give a yellow precipitate, which
was diluted in 1 L of water and it was allowed to stand over-
night. After acidifying with hydrochloric acid a yellow oil
was produced, which after 24 h yield a solid product. This
product was filtered, dried and recrystallized in methanol
to give compound in 40% yield.
The present work is devoted to the synthesis, character-
ization and study of the photoluminescence behavior of
seven trivalent Eu3+-complexes [Eu(ACIND)3(H2O)2] and
[Eu(ACIND)3(TPPO)2] (where ACIND is stands for the
ligands 2-acetyl-1,3-indandionate (AIND), 2-isovaleryl-
1,3-indandionate (ISOVIND) or 2-benzyl-1,3-indandionate
(BIND) in solid state with 2-acyl-1,3-indandionates (Fig. 1).
X-ray crystal structure of the [Eu(ISOVIND)3 Æ (H2O)-
(EtOH)] complex is also presented, which, to our knowl-
edge, it is the first report on structural analysis of a complex
with the 2-acyl-1,3-indandione ligand. An analysis of the
intramolecular energy transfer processes for these com-
pounds was also performed by theoretical methods.
2. Experimental
Anal. Calc. for AIND, C11H8O3: C, 70.20; H, 4.30.
Found: C, 69.48; H, 4,35%. IR (KBr, cmꢀ1): 3416br,
1762w, 1712s, 1660s, 1627s, 1593s, 1424s, 1390s, 1367s,
1209s, 1147m, 876s, 740s, 695m, 543m. For ISOVIND,
C14H14O3: C, 73.02; H, 6.13. Found: C, 72.48; H, 5.67%.
IR (KBr, cmꢀ1): 3440br, 2962m, 1713s, 1651s, 1584s,
1465w, 1398w, 1330m, 1286w, 1218m, 1139m, 886s, 745s,
650w. For BIND, C16H10O3: C, 76.80; H, 4.03. Found:
C, 77.04; H, 4.16%. IR (KBr, cmꢀ1): 3439br, 3055w,
1711s, 1649s, 1599s, 1559s, 1497m, 1441m, 1401m, 1333s,
1293m, 1169m, 927m, 740s, 684m, 622m, 531w.
2.1. Materials and methods
Carbon and hydrogen contents were determined by
usual microanalytical procedures using an elemental ana-
lyzer model CHN 2400 (Perkin–Elmer). Infrared spectra
were recorded in the range from 4000 to 400 cmꢀ1 in
KBr pellets by using a Bomem model MB102 FTIR
spectrophotometer. TG analysis were performed with a
TG-50 thermobalance (Shimadzu) by using platinum
crucibles with 2 mg of sample, under a dynamic nitrogen
2.3. Synthesis of the hydrated Eu3+-complexes
O
H
The preparation method of europium indandionate
complexes were similar to those used in Ref. [12]. Sodium
2-acetyl-1,3-indandionate was prepared by neutralizing
1.0 g (5.3 mmol) of the ligand 2-acetyl-1,3-indandione with
NaOH (1 mol Lꢀ1) using deionized water and pH adjusted
to 7. To the resulting solution was added dropwise an
aqueous solution of EuCl3 Æ 6H2O (0.5 g, 1.4 mmol), form-
ing immediately a yellow precipitated that was filtered,
washed with water and dried under vacuum to give the
desired product (yields ꢁ90%). The same procedure, was
O
R
O
R= CH3, CH2CH(CH3)2, C6H5
Fig. 1. Structural formula of the 2-acyl-1,3-indandione ligands.

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E.E.S. Teotonio et al. / Polyhedron 25 (2006) 3488–3494
used to synthesize hydrated Eu3+-complex with 2-iso-
valeril-1,3-indandionate and 2-benzoyl-1,3-indandionate
ligands. In the case of the hydrated Eu3+-complex with
ISOVIND, a single crystal suitable for X-ray structure
analysis was obtained by slow evaporation from an ethanol
solution. The compositions of the complexes were con-
firmed by elemental analysis:
Anal. Calc. for [Eu(AIND)3(H2O)2], C33H25EuO11: C,
52.88; H, 3.36. Found: C, 52.58; H, 3.83%. IR (KBr,
cmꢀ1): 3452m, 1676s, 1624s, 1582s, 1510s, 1565s, 1357s,
1211m, 1155m, 1082w, 987m, 885m, 736s, 662m, 534s.
For [Eu(ISOVIND)3(H2O)2], C42H43EuO11: C, 57.60; H,
4.95. Found: C, 58.30; H, 4.69%. IR (KBr, cmꢀ1): 3415m,
3068m, 2956m, 2870m, 1680s, 1620s, 1579s, 1465s, 1355s,
1284m, 1207m, 1155m, 1072m, 894m, 734s, 667m, 670w,
530m. For [Eu(ISOVIND)3 (H2O)(EtOH)]. C44H47EuO11:
C, 58.47; H, 5.24. Found: C, 58.33; H, 5.20%. IR (KBr,
cmꢀ1): 3367m, 3078m, 2952m, 2867m, 1677s, 1629s,
1585s, 1510s, 1470s, 1650s, 1282m, 1205m, 1153m, 1072m,
896m, 733m, 654m, 532m. For [Eu(BIND)3(H2O)2]. Calc.
for C48H31EuO11: C, 61.61; H, 3.34. Found: C, 61.68; H,
3.27%. IR (KBr, cmꢀ1): 3427m, 3062m, 1620s, 1585s,
1490s, 1454s, 1425s, 1363m, 1153w, 885m, 800w, 742m,
702m, 640m, 534m.
3/1 (v/v). The resulting solution was kept in stand by
for a week, resulting in yellow hexagonal crystals. A crys-
tal of this compound was mounted in a Enraf-Nonius
CAD4 diffractometer with graphite-monochromated Mo
˚
Ka (k = 0.71073 A), at 293 K. The structure was solved
by direct methods using the SIR92 program [13] and
refined by full-matrix least-squares methods on F2 by
the SHELX97 program package [14]. The hydrogen atoms
for the water molecule was found in the Fourier difference
map, and refined with U equal to 1.3 times the Ueq of the
Ow. All others non-hydrogen atoms were refined aniso-
tropically and the hydrogen atoms position were calcu-
lated in ideal geometry with thermal parameters equal to
1.5 times the Ueq of the attached C atom for the methyl
groups and 1.2 for the others. Crystallographic data for
the Eu(ISOVIND)3(H2O)(EtOH) complex are shown in
Table 1.
3. Results and discussion
IR spectra of the complexes as compared to the free
indandione ligands show a displacement of the C@O
stretching to lower frequencies (about 70 cmꢀ1), suggesting
that the indandionate ligands are coordinated through
oxygen atoms. In the case of the complexes Eu(ACIND)3-
(TPPO)2, the displacement of the P@O stretching from
1190 cmꢀ1 in the free TPPO ligand to 1170 cmꢀ1 in the
compounds provides good evidence that the coordination
of the TPPO to europium ion is also occurring through
oxygen atom.
2.4. Synthesis of the Eu3+-complexes with TPPO
Europium complexes with TPPO as a second kind of
ligand were synthesized using the correspondent hydrated
[Eu(ACIND)3(H2O)2] complexes as precursors. A solution
of TPPO (0.37 g, 1.3 mmol) in acetone (10 mL) was added
to a solution of [Eu(ACIND)3(H2O)2] (0.5 g, ꢁ0.6 mmol)
in acetone (20 mL), and the mixture was stirred for 2 h at
room temperature. After solvent evaporation, a precipi-
tated was produced, which was filtered, washed with etha-
nol and dried in vacumm. Yield: ꢁ80%. The compositions
of the complex systems were confirmed by elemental anal-
ysis and IR data: Anal. Calc. for [Eu(AIND)3(TPPO)2],
C69H51EuO11P2: C, 65.25; H, 4.05. Found: C, 64.93; H,
4.11%.IR (KBr, cmꢀ1): 3107m, 1558s, 1531s, 14317s,
1396s, 1342m, 1227m, 1120m, 1080w, 1037m, 862m, 820s,
777s, 725s, 659m, 430m. For [Eu(ISOVIND)3(TPPO)2],
C78H69EuO11P2: C, 67.09; H, 4.98. Found: C, 67.04; H,
5.27%. IR (KBr, cmꢀ1): 3056m, 1689m, 1589s, 1491m,
1452s, 1425s, 1362m, 1340m, 1340m, 1167m, 1118m,
1018w, 881m, 798w, 742m, 694m, 636m, 540s. For
[Eu(BIND)3(TPPO)2], C84H57EuO11P2: C, 69.28; H, 3.95.
Found: C, 69.06; H, 3.83%. IR (KBr, cmꢀ1): 3055w,
1687m, 1620s, 1589s, 1490m, 1452s, 1425s, 1340m,
1164m, 1121m, 1020w, 743m, 696m, 636m, 540s.
Table 1
Crystal data and structure refinement for the [Eu(ISOVIND)3(H2O)-
(EtOH)] complex
Formula
C44H47Eu1O11
Formula weight
Crystal system
Space group
903.78
monoclinic
P21=n (no. 14)
15.361(1)
18.364(2)
15.705(2)
106.373(8)
4250.6(8)
4
˚
a (A)
˚
b (A)
˚
c (A)
b (ꢁ)
3
˚
V (A )
Z
Dcalc (g/cm3)
l(Mo Ka) (/mm)
F(000)
1.412
1.533
1848
Crystal size (mm)
Temperature (K)
Radiation (A) Mo Ka
0.08 · 0.10 · 0.15
293
0.71069
˚
h(Min.–Max.) (ꢁ)
2.6, 28.5
Data set hkl, min:max
Total, unique data, Rint
Observed data [I > 2r(I)]
Nref, Npar
R, wR2, S
Maximum and average shift/error
ꢀ19:20; 0:24; ꢀ21:0
11178, 10809, 0.054
4859
10809, 518
0.0516, 0.1360, 0.94
0.22, 0.01
ꢀ0.89, 0.78
2.5. X-ray structure determination of
Eu(ISOVIND)3(H2O)(EtOH)
A suitable crystal of the Eu(ISOVIND)3(H2O)(EtOH)
complex for X-ray diffraction was obtained dissolving
the complex in a mixture of ethanol and water in a ratio
3
˚
Minimum and maximum residual density [e/A ]
2
w ¼ 1=r2ðF 2oÞ þ 0:0517PÞ where P ¼ ðF o2 þ 2F 2c Þ=3.

E.E.S. Teotonio et al. / Polyhedron 25 (2006) 3488–3494
3491
Thermogravimetric curves for the [Eu(ACIND)3(H2O)2]
3.1. Structure of [Eu(ISOVIND)3(H2O)(EtOH)]
complexes exhibited similar profiles (figure not shown).
The curves show a first weight loss in the range from 120
to 190 ꢁC, which is assigned to the release of two water
molecules coordinated to the Eu(III) ion. For [Eu(ISOV-
IND)3(H2O)(EtOH)] complex the first weight loss corre-
sponds to 6.8%, which agrees to the release of one water
and one ethanol molecule. The complexes with the TPPO
ligand present no weight loss until 230 ꢁC, confirming the
anhydrous character of these complexes.
X-ray analysis reveals that eight oxygen atoms are coor-
dinated to the central europium ion (six from the bidentate
ISOVIND ligand, one from the water molecule and
another from the ethanol). A key feature of the structure
described herein is that, to the best of our knowledge, it
is the first example of a rare earth coordination compound
with a 2-acyl-1,3-indandionate ligand to be reported. The
carbon atoms –CH2 and –CH3 from the ligands (2-acyl-1,
C5A
C14B
C6A
a
C4A
b
C7A
C12B
C11B
C13B
C8A
C3A
O3A
C2A
C1A
C10B
C9A
O3B
O1A
C10A
C2
C8B
C11A
C9B
C1
O2B
O5
C12A
C14A
C7B
O2A
Eu
C6B
C1B
C2B
O2C
O1C
O1B
C13A
O1W
C14C
C10C
C1C
C3C
C3B
C5B
C2C
C4B
C4C
C12C
C9C
C5C
C11C
C8C
C13C
C7C
C6C
O3C
c
O3C*
O3B*
O1W
O3A***
O5
O1W**
O3B
* 1-x,-y,2-z
**-x,-y,2-z
***-x,-y,1-z
Fig. 2. (a) ORTEP drawing (50% of probability) displaying the X-ray structure of [Eu(ISOVIND)3(H2O)(EtOH)] complex; the thermal disordered methyl
carbon atoms are arbitrary taken with Ueq equal to 0.05. (b) Coordination polyhedron of Eu3+ ion and (c) Molecules of [Eu(ISOVIND)3(H2O)(EtOH)]
complex showing intermolecular H-bonding connections as dashed lines.

3492
E.E.S. Teotonio et al. / Polyhedron 25 (2006) 3488–3494
Table 2
3-indandionate and ethanol) presents disorder by the ther-
mal vibration. An ORTEP drawing displaying the molecu-
lar structure, with the methyl carbon atoms assuming an
isotropical displacement supposition, the coordination
polyhedron of the Eu(III) ion, and representation of the
intermolecular hydrogen bonds in [Eu(ISOVIND)3(H2O)-
(EtOH)], are presented in Fig. 2.
˚
Selected bond distances (A), angles (ꢁ) and hydrogen bonds in the
[Eu(ISOVIND)3(H2O)(EtOH)] complex
˚
Distance (A)
Eu–O1a
Eu–O1b
Eu–O1c
Eu–O1w
2.400(4)
2.403(4)
2.410(5)
2.420(5)
Eu–O2a
Eu–O2b
Eu–O2c
Eu–O5
2.401(5)
2.382(3)
2.348(4)
2.448(4)
The geometrical arrangement of the oxygen atoms in the
first coordination sphere can be described as a bicapped tri-
gonal prism presenting a site symmetry close to C2m
(Fig. 2b). The Eu–O distances fall into two distinct ranges
where those including O atoms from ISOVIND are shorter
Angles (ꢁ)
O1a–Eu–O1b
O1a–Eu–O1c
O1a–Eu–O1w
O1a–Eu–O2a
O1a–Eu–O2b
O1a–Eu–O2c
O1a–Eu–O5
O1b–Eu–O1c
O1b–Eu–O1w
O1b–Eu–O2a
O1b–Eu–O2b
O1b–Eu–O2c
O1b–Eu–O5
O1c–Eu–O1w
78.5(2)
140.9(2)
149.5(2)
71.2(2)
76.2(2)
98.2(1)
97.2(1)
129.9(2)
76.3(2)
134.0(1)
72.5(2)
71.17(2)
145.0(2)
69.6(2)
O1c–Eu–O2a
O1c–Eu–O2b
O1c–Eu–O2c
O1c–Eu–O5
O1w–Eu–O2a
O1w–Eu–O2b
O1w–Eu–O2c
O1w–Eu–O5
O2a–Eu–O2b
O2a–Eu–O2c
O2a–Eu–O5
O2b–Eu–O2c
O2b–Eu–O5
O2c–Eu–O5
69.8(2)
132.7 (1)
73.0(1)
74.0(2)
139.3(2)
80.1(2)
89.6(2)
93.8(2)
129.2(2)
79.8(2)
74.0(1)
143.6(2)
72.7(2)
143.3(2)
˚
(Eu–O ꢁ 2.40 A) than those from neutral aqua and ethanol
ligands, which present Eu–O distances of 2.422(5) and
˚
2.447(4) A, respectively (Table 2). It is also important to
observe in the crystal structure of Eu(ISOVIND)3(H2O)-
(EtOH) that the hydrogen bond scheme (Table 2) gives rise
to a supermolecular polymer (Fig. 2c). The water molecule
coordinated to the Eu3+ ion is simultaneously hydrogen-
bonded to two uncoordinated carbonyl oxygen atom of
ISOVIND of two adjacent molecules (symmetry operation
A
H
B
d
d
d
Angle Symmetry
ꢀ
1), and the OH from ethanol is connected to the third CO
(A–H) (H. . .B) (A. . .B) (ꢁ)
operation
˚
˚
˚
(A)
(A)
(A)
group of ISOVIND through O–Hꢂ ꢂ ꢂO hydrogen bonds.
The Owater–Hꢂ ꢂ ꢂOcarbonyl hydrogen bonds are similar to those
found for rare earth complexes with aliphatic b-diketonate
ligands reported in the literature [15].
Hydrogen bonds for the [Eu(ISOVIND)3(H2O)(EtOH)] complex
2.717(7) 166(8) 1 ꢀ x,
O1w H1Ow O3b 0.76(8) 1.98(8)
O1w H2Ow O3c 0.87(8) 1.93(8)
ꢀy, 2 ꢀ z
2.793(7) 168(5) ꢀx, ꢀy,
2 ꢀ z
Excitation spectra of the europium complexes with
2-acyl-1,3-indandione ligands, recorded at 77 K in the spec-
tral range 250–590 nm (Fig. 3) were obtained with emission
O5
H1O5 O3a 0.93
2.12
2.770(7)
125 ꢀx, ꢀy,
1 ꢀ z
5
7
monitored at D0 ! F2 hypersensitive transition around
[Eu(AIND)3(H2O)2]
a
b
[Eu(AIND)3(TPPO)2]
[Eu(ISOVIND)3(TPPO)2]
[Eu(BIND)3(TPPO)2]
[Eu(ISOVIND)3(EtOH)(H2O)]
[Eu(BIND)3(H2O)2]
350
250
450
λ / nm
550
250
350
450
λ/ nm
550
Fig. 3. Excitation spectra of (a) [Eu(ACIND)3 Æ (H2O)2] and (b) [Eu(ACIND)3 Æ (TPPO)2] complexes in solid state, at 77 K. The spectra were recorded
with emission monitored at 612 nm.

E.E.S. Teotonio et al. / Polyhedron 25 (2006) 3488–3494
3493
612 nm. These spectra present a strong broad band
between 270 and 470 nm assigned to the photoexcitation
process of the Eu(III) ion via the S0 ! S1 transition. The
excitation spectra also exhibit narrow bands assigned to
the 4f–4f transitions from the 7F0 ground level to the
excited states. However, these bands are less intense than
those bands corresponding to the S0 ! S1 transition. This
result gives evidence of europium luminescence sensitiza-
tion through intramolecular energy transfer from the
2-acyl-1,3-indandione ligands.
sion spectra of all europium complexes do not exhibit
ligand centered transitions, indicating that there is an effi-
cient intramolecular energy transfer from the indandionate
ligands to the Eu3+ ion.
In order to get further information on the chemical envi-
ronment of the Eu3+ ions in these complexes, experimental
intensity parameters Xk (k = 2 and 4), radiative rates (A0J)
5
7
5
7
for the D0 ! F2 and D0 ! F4 transitions and emission
quantum efficiency (g) were determined (Table 3) according
to Refs. [16,18].
Photoluminescence spectra of the hydrated complexes
and those with the TPPO ligand, at 77 K, are displayed
in Fig. 4. The emission spectra show characteristic
Experimental intensity parameter X2 exhibits values
around 40 · 10ꢀ20 cm2 for the hydrated complexes, sug-
gesting the presence of a highly polarizable chemical envi-
ronment around the Eu3+ ion [5]. These values are as high
as those presented for europium complexes containing ali-
phatic b-diketonate, such as TTA and DBM-europium
complexes [3]. It is also observed a decrease in X2 for
complexes with TPPO as compared to the hydrated ones.
This result may be a consequence of steric hindrance due
to phenyl groups that belong to the TPPO ligand.
Comparing the values of g for the complexes containing
the TPPO ligand with their respective hydrated com-
pounds, it is concluded that indeed a substitution of water
7
5D0 ! FJ (J = 0–4) transitions of Eu(III), with the hyper-
7
sensitive 5D0 ! F2 transition (at 612 nm) as the most
prominent one. The local-ligand field splitting is particu-
5
7
larly evident for D0 ! F1–4 transitions, presenting Stark
(2J + 1)-components, indicating that the Eu3+ ion occupies
a site with low symmetry [16,17]. It is observed that, in gen-
eral, emission spectra of complexes with TPPO present dif-
ferent profiles from the respective hydrated compounds,
reflecting changes in the chemical environment around
the Eu3+ ion. It is also important to mention that the emis-
[Eu(ISOVIND)3(TPPO)2]
b
a
[Eu(BIND)3(TPPO)2]
[Eu(BIND)3(H2O)2]
[Eu(ISOVIND)3(H2O)(EtOH)]
[Eu(ISOVIND)3(H2O)2]
[Eu(AIND)3(H2O)2]
[Eu(AIND)3(TPPO)2]
500
550
600
λ / nm
650
700
450
500
550
600
λ / nm
650
700
Fig. 4. Emission spectra of (a) [Eu(ACIND)3 Æ (H2O)2] and (b) [Eu(ACIND)3 Æ (TPPO)2] complexes in solid state, at 77 K, recorded under excitation at
350 nm.
Table 3
Intensity parameters (Xk), radiative (Arad), non-radiative (Anrad) rates and emission quantum efficiency of the 5D0 emitting level determined for the 2-acyl-
1,3-indandionate complexes
Compound
X2 (10ꢀ20 cm2)
X4 (10ꢀ20 cm2)
s (ms)
Arad (sꢀ1
)
Anrad (sꢀ1
)
Atot (sꢀ1
)
g (%)
[Eu(AIND)3 Æ (H2O)2]
42.1
35.5
40.4
40.9
35.3
40.5
29.4
14.8
8.9
0.1079
0.5309
0.0387
0.056
0.5071
0.0539
0.3181
1532
1255
1499
1537
1283
1482
1165
7739
628
24330
16320
688
9261
1883
25830
17860
1972
16.5
66.7
5.8
8.6
65.1
8.0
[Eu(AIND)3 Æ (TPPO)2]
[Eu(ISOVIND)3 Æ (H2O)2]
[Eu(ISOVIND)3 Æ (H2O)(EtOH)]
[Eu(ISOVIND)3 Æ (TPPO)2]
[Eu(BIND)3 Æ (H2O)2]
15.8
17.5
11.4
14.2
15.9
17080
1978
18560
3143
[Eu(BIND)3 Æ (TPPO)2]
37.1

3494
E.E.S. Teotonio et al. / Polyhedron 25 (2006) 3488–3494
molecules in the first coordination sphere of the Eu3+ ion
by the TPPO ligand occurs. This result reflects a decrease
in the non-radiative rates (Anrad) that is a consequence of
the absence of O–H oscillators present in coordinated
water molecules, which causes multiphonon deactivation
process in the Eu3+ ion [5].
Theoretical structure for the [Eu(ISOVIND)3(H2O)-
(EtOH)] complex was calculated using the Sparkle/AM1
model [16]. The result obtained agrees with those deter-
mined by X-rays diffraction (Fig. 2), indicating that the
Sparkle/AM1 model has also proved to be very useful in
predicting coordination geometries of the Eu-indandionate
complexes.
Appendix A. Supplementary data
Crystallographic data (excluding structure factors) for
the structure have been with the Cambridge Crystallo-
graphic Data Centre as supplementary publication no.
CCDC 296851. Copies of the data can be obtained free
of charge on application to CCDC, 12 Union Road, Cam-
bridge CB2 1EZ, UK [fax: int. code + 44 1223 336 033; e-
mail:deposit@ccdc.cam.ac.uk]. Supplementary data associ-
ated with this article can be found, in the online version, at
doi:10.1016/j.poly.2006.06.035.
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7
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It has been demonstrated that the first structurally char-
acterized Eu3+–(2-acyl-1,3-indandione) complex indicated
that their coordination to the metal ion occurs in similar
form as for aliphatic b-diketonates. Our results indicate that
an efficient ligand-metal ion energy transfer process occurs
for the Eu–(2-acyl-1,3-indandione) complexes, and that the
channels (1) and (2) are the most probable ones involved
in photoluminescent mechanism for [Eu(ISOVIND)3(H2O)-
(EtOH)] complex.
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Acknowledgments
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1837.
The authors acknowledge FAPESP, CNPq, RENAMI
and IMMC for financial support.
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