Structural and spectroscopic investigations of the EuIII-CDTA system

Article abstract of DOI:10.1016/j.poly.2006.09.031

Two crystal structures of Eu^III complexes with CDTA (trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetate), [C(NH₂)₃]₃[Eu₂(CDTA)₂(H₂O)₂]ClO₄ · 7H₂O (I) and [C(NH₂)₃][Eu(CDTA)(H₂O)] · 2.375H₂O (II), are presented. Both structures are polymeric and the central metal ions are eight-coordinate. The first coordination sphere of each Eu^III cation contains five carboxylate oxygen atoms, two nitrogen ones and a water molecule. For I, as well as for water solutions of the Eu^III-CDTA complex at various pH values, the spectroscopic (UV-Vis) properties were investigated.

Full text of DOI:10.1016/j.poly.2006.09.031

Polyhedron 26 (2007) 845–850
www.elsevier.com/locate/poly
III
Structural and spectroscopic investigations of the Eu –CDTA system
Rafał Janicki, Anna Mondry, Przemysław Starynowicz *
Wydział Chemii, Uniwersytet Wrocławski, ul. F. Joliot-Curie 14, 50-383 Wrocław, Poland
Received 20 July 2006; accepted 14 September 2006
Available online 27 September 2006
Abstract
III
Two crystal structures of Eu complexes with CDTA (trans-1,2-diaminocyclohexane-N,N,N ,N -tetraacetate), [C(NH
0
0
2 3 3 2
) ] [Eu -
(
CDTA) (H O) ]ClO Æ 7H O (I) and [C(NH ) ][Eu(CDTA)(H O)] Æ 2.375H O (II), are presented. Both structures are polymeric and
2
2
2
4
2
2 3
2
2
III
the central metal ions are eight-coordinate. The first coordination sphere of each Eu cation contains five carboxylate oxygen atoms,
two nitrogen ones and a water molecule. For I, as well as for water solutions of the Eu –CDTA complex at various pH values, the
III
spectroscopic (UV–Vis) properties were investigated.
ꢀ
2006 Elsevier Ltd. All rights reserved.
Keywords: Europium(III); CDTA; Structure; UV–Vis spectroscopy
1
. Introduction
aspects. Their stability constants are higher by an order or
two of magnitude, depending on the lanthanide, than those
of the EDTA complexes [7], and generally saying, they
are thermodynamically stable [8]. The spectroscopic stud-
Lanthanide polyaminopolycarboxylate chelates play an
important role both in fundamental investigations and in
several areas of practical applications. They are used,
among others, as shift reagents in NMR spectroscopy [1],
contrast agents in MRI imaging [2], structural probes [3]
and luminescent tags in immunoassays [4]. This family of
III
ies have revealed that in solutions of Eu –CDTA com-
plexes an equilibrium exists between two different species,
nine- and eight-coordinate, the dissimilarity between them
consisting of a different number of coordinated water mol-
ecules (three or two) [9]. The average number of these mol-
ecules has been found to be 2.3–2.6 and is a little lower
than that found in water solutions of the EDTA complexes
(2.6–2.8) [5f,5h].
III
compounds has been epitomized by complexes of Ln
with the ethylenediaminetetraacetate (EDTA) anion, which
have been extensively studied both in solution e.g. [5] and
in the solid state e.g. [6] and now may serve as a kind of
standard when the structure, spectroscopic and/or thermo-
dynamic properties of lanthanide polyaminopolycarboxy-
lates are discussed. It is therefore of interest to find how
the properties are altered when the EDTA skeleton is
modified. In this work we present a study of two Eu com-
plexes with such a ligand, i.e. trans-1,2-diaminocyclohex-
ane-N,N,N ,N -tetraacetate (CDTA). The investigations
Because of difficulties connected with growing of mono-
III
crystals of adequate quality, structural data for Ln –
CDTA complexes are scarce. To the best of the authors’
knowledge only three crystal structures of these complexes
4
ꢀ
III
have been published. Two of them, NH [Ln(CDTA)-
4
III
III
(H O) ] Æ 4.5H O (Ln = Gd , Ho ), are monomeric and
2 2 2
0
0
isostructural [10,11] whereas in the third one, Na[Eu-
III
of Ln –CDTA complexes carried out so far have been
focused to a great part on their properties in aqueous solu-
tions and included thermodynamic as well as spectroscopic
(CDTA)(H O)] Æ 4H O [12], dimeric anions of [Eu(CDTA)–
2
2
2
ꢀ
l-(H O) –Eu(CDTA)] are formed. For the last system
2 2
luminescence properties were also reported. In all these
III
complexes the Ln ions are eight-coordinate.
III
*
In the crystal, the coordination surrounding of Ln ion
Corresponding author.
E-mail address: psta@wchuwr.chem.uni.wroc.pl (P. Starynowicz).
is unambiguously defined, therefore the spectra of the
0
277-5387/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2006.09.031

846
R. Janicki et al. / Polyhedron 26 (2007) 845–850
crystals may be a good starting point for interpretation of
spectral data of solution systems. The paucity of such data
has motivated us to attempt the preparation of Eu –
formed during slow evaporation. The other crystals,
[C(NH ) ][Eu(CDTA)(H O)] Æ 2.375H O (II), were ob-
2
3
2
2
III
tained as follows: a suspension of Eu O and H CDTA
2 3 4
CDTA complexes in the crystalline state, to study their
crystal structures and spectroscopic properties and to com-
pare the latter with the analogous properties of Eu –
was heated at ca. 80 ꢁC. After dissolution of the substrates,
the solution was alkalized with [C(NH ) ] CO to a final
2
3 2
3
III
pH value of 3, and left for crystallization.
.2. X-ray study
Appropriate crystals were cut from larger ones and
CDTA complexes in solution.
2
2
. Experimental
2
.1. Materials
mounted on a Kuma KM4 diffractometer equipped with
a CCD counter. The collected data were corrected for
polarization, Lorentz and absorption, the last calculated
from the crystal habit captured from photo scans. Both
crystals turned out to be twinned. The twinning of crystal
I was pseudo-merohedral; this was brought about by the
fact that the unit cells spanned by vectors a, b, c, and a,
a–b, a–c have very similar lattice constants. The fraction
of the first twin component found from the refinement
was 0.676(1). The twinning matrix in II was (ꢀ1/2 ꢀ1/2 0/
ꢀ3/2 1/2 0/ ꢀ1/2 1/2 ꢀ1) with the result that only reflec-
tions with h + k even overlapped. The structure of I was
solved and refined against all reflections, while that of II
was solved using one twin component and refined against
both. The positions of Eu were found from Patterson
maps, the rest of the non-H atoms from difference Fourier
Solutions for spectroscopic measurements: A stock solu-
tion of europium chloride was prepared by dissolving
Eu O (99.99%; Standford materials) in 2 mol dm hydro-
chloric acid. The Eu ion concentration was determined
complexometrically using xylenol orange as an indicator.
The stock solution of H CDTA (98%; Lancaster) was pre-
ꢀ3
2
3
III
4
pared by half-neutralization with NaOH. The pH of the
III
1
:1.1 Eu –CDTA solutions was adjusted by a carbonate-
free NaOH water solution.
Crystal preparations: An aqueous solution of equimolar
quantities of europium perchlorate and H CDTA was
heated at ca. 80 ꢁC. Next, solid [C(NH ) ] CO was added
until the pH value was 5. Large colourless crystals of
4
2
3 2
3
[
C(NH ) ] [Eu (CDTA) (H O) ]ClO Æ 7H O (I) were
2 3 3 2 2 2 2 4 2
Table 1
Crystal data and structure refinement for both crystals
Crystal
I
II
Empirical formula
Formula weight
Temperature (K)
C
31
H
72ClEu
2
N
O
13 29
15 5 11.38
C H30.25EuN O
1430.39
100(2)
0.71073
614.65
100(2)
0.71073
˚
Wavelength (A)
ꢀ
ꢀ
Crystal system, space group
triclinic, P1
triclinic, P1
Unit cell dimensions
˚
a (A)
10.652(8)
16.075(13)
17.943(14)
69.31(7)
73.24(7)
70.86(7)
12.09(9)
18.83(2)
23.328(15)
66.82(14)
77.15(12)
77.47(12)
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
˚
3
Volume (A )
Z, Calculated density (Mg/m )
2663(4)
2, 1.784
2.484
4712(36)
8, 1.733
2.727
3
ꢀ
1
Absorption coefficient (mm
F(000)
)
1448
2474
Crystal size (mm)
0.27 · 0.20 · 0.15
0.27 · 0.18 · 0.11
Theta range for data collection (ꢁ)
3.03–28.43
2.25–29.07
Index ranges
ꢀ9 6 h 6 14, ꢀ21 6 k 6 21, ꢀ23 6 l 6 23
18077/11545 (0.0341)
86.0%
ꢀ15 6 h 6 16, ꢀ25 6 k 6 23, ꢀ31 6 l 6 31
Reflections collected/unique (Rint
)
25498/25498
Completeness to 2h
69.1%
Absorption correction
Maximum and minimum transmission
Refinement method
analytical, from the shape
0.710 and 0.520
full-matrix least-squares on F
analytical, from the crystal shape
0.768 and 0.529
full-matrix least-squares on F
2
2
Data/restraints/parameters
Goodness-of-fit on F
Final R indices [I > 2r(I)]
R indices (all data)
Largest differences in peak and hole (e A
11545/0/686
1.063
R(F) = 0.0434, Rw(F ) = 0.1031
R(F) = 0.0484, Rw(F ) = 0.1059
2.654 and ꢀ2.604
25498/0/1176
0.998
R(F) = 0.0790, Rw(F ) = 0.1403
R(F) = 0.1388, Rw(F ) = 0.1620
1.800 and ꢀ1.616
2
2
2
2
2
˚
ꢀ3
)

R. Janicki et al. / Polyhedron 26 (2007) 845–850
847
maps. The positions of the C- and N-bonded hydrogen
atoms were calculated geometrically. The refinement was
full-matrix with all ordered non-H atoms anisotropic.
The oxygen atoms from disordered water molecules (in
II) were refined isotropically and C- and N-bonded H
atoms were constrained to 1.2 times the factors of the rel-
evant C atoms. Because of twinning and partial overlap-
ping of some reflections the precision of the structure
determination of II unfortunately deteriorated. Our several
attempts to find an untwinned sample failed and therefore
we decided to solve and refine the structure against the twin
data. The large volume of the asymmetric part seems upset-
ting. However we could not find a cell with smaller volume
and herein we present the best model of twinning and the
crystal structure which we have been able to find. Both
structures were solved and refined by SHELXS97 [13] and
SHELXL97 [14], respectively, and the program DIAMOND
through its four carboxylate oxygen atoms and two nitro-
gen atoms, filling thus six coordinate sites. The seventh site
is occupied by a water molecule. Apart from that each mer
donates one of its carboxylate oxygen atoms to the first
III
coordination sphere of an Eu ion in a neighbouring mer
(accepting at the same time an analogous O atom from
the other neighbour). In this way infinite polymeric chains
are formed and the europium cations are eight-coordinate.
In I there are two symmetry independent Eu sites, and
accordingly two different mers. In II the number of symme-
try independent Eu sites is 4. Nevertheless, superimposition
of all six mers (Fig. 1) shows that their conformations are
very similar, the difference being only in small variations
of bond lengths and angles. The Eu–O and Eu–N distances
(see Table 2) are similar to those found in the europium
dimeric complex with CDTA, Na[Eu(CDTA)H O] Æ 4H O
2
2
[12], however the Eu–OH bond distances are significantly
2
[
15] was used for the molecular graphics. The data concern-
longer in the present structures. The Eu–OH average dis-
2
˚
˚
ing the crystal parameters, data collection and refinement
details are presented in Table 1.
tances are 0.125 A (compound I) and 0.103 A (compound
II) longer than in the quoted dimer. These variations may
be caused by different modes of interaction of guanidinium
and sodium cations with the CDTA moiety, because these
cations induce different hydrogen bond networks. In both
presented structures the shortest bonds are those involving
3
. Spectroscopy
3
.1. UV–Vis measurements
carboxylate O atoms, the Eu–OH ones are longer, and the
2
Electronic absorption spectra were recorded on a Cary
00 UV–VIS–near-IR spectrophotometer. The solutions
5
were measured at room temperature. Only spectra of I were
recorded because we could not obtain a good sample of II.
The absorption spectra of I were measured at 293 and 30 K
(
in an Oxford CF 1204 continuous flow helium cryostat).
The oscillator strengths (P) were determined using the
equation:
Z
ꢀ
9
ꢀ1
P ¼ 4:32 ꢁ 10 ðcdÞ
AðrÞdr
III
where c is the concentration of the Eu ion in M, d is the
length of the optical way in cm and A(r) is the absorbance
ꢀ1
as the function of the wavenumber in cm . The P values
7
were not corrected for the population of the F state at
1
room temperature. Corrected emission spectra were mea-
sured on a SLM Aminco 500 spectrofluorometer at 293
III
and 77 K. For luminescence, the Eu ion was excited with
a wavelength of 394 nm.
Fig. 1. Superimposed Eu coordination environments in I and II. The
shortened atomic labels stand: OA for O1 and O11 in I, O13, O23, O31,
O41 in II; OB–O2, O12 (I), O14, O24, O32, O42 (II); OC–O4, O14 (I),
O11, O21, O33, O43 (II); OD–O3, O13 (I), O12, O22, O34, O44 (II); OE–
O7, O16 (I), O17, O27, O37, O47 (II); OF–O8, O15 (I), O18, O28, O38,
O48 (II); OG–O5, O17 (I), O15, O25, O35, O45 (II); OH–O6, O18 (I),
4
. Results and discussion
4
.1. Structure
i
j
O16, O26, O36, O46 (II); OI–O8, O15 (I), O48 , O18, O28, O38 (II); OW–
OW1, OW2 (I), OW1, OW2, OW3, OW4 (II); NA–N12, N21 (I), N11,
N21, N31, N41 (II); NB–N11, N22 (I), N12, N22, N32, N42 (II); CA–C1,
C21 (I), C13, C33, C51, C71 (II); CB–C2, C22 (I), C14, C34, C52, C72 (II);
CC–C4, C24 (I), C11, C31, C53, C73 (II); CD–C3, C23 (I), C12, C32, C54,
C74 (II); CE–C5, C25 (I), C15, C35, C55, C75 (II); CF–C10, C30 (I), C16,
C36, C56, C76 (II); CG–C9, C29 (I), C17, C37, C57, C77 (II); CH–C8,
C28 (I), C18, C38, C58, C78 (II); CI–C7, C27 (I), C19, C39, C59, C79 (II);
CJ–C6, C26 (I), C20, c40, C60, C80 (II); CK–C11, C33 (I), C24, C44, C64,
C84 (II); CL–C12, C34 (I), C23, C43, C63, C83 (II); CM–C13, C31 (I),
C22, C42, C62, C82 (II); CN–C14, C32 (I), C21, C41, C61, C81 (II).
Both structures are built up from polymeric complex
chains, guanidinium cations, water of crystallization (par-
tially disordered in II), and, in the case of I, also perchlorate
anions. The polymeric chains are composed of europium
0
0
cations, trans-1,2-diaminocyclohexane-N,N,N ,N -tetraace-
tate (CDTA) anions and water molecules coordinated to
III
europium. Each polymer unit (mer) contains a Eu cation
and a CDTA anion which is coordinated to the metal

848
R. Janicki et al. / Polyhedron 26 (2007) 845–850
Table 2
˚
The Eu–O,N distances in I and II (A)
I
II
j
Eu(1)–O(1)
2.314(6)
2.339(5)
2.343(6)
2.362(6)
2.364(5)
2.469(6)
2.615(6)
2.626(6)
2.311(6)
2.364(5)
2.363(5)
2.369(5)
2.407(5)
2.458(6)
2.597(6)
2.604(6)
Eu(1)–O(48 )
Eu(1)–O(17)
Eu(1)–O(13)
Eu(1)–O(15)
Eu(1)–O(11)
Eu(1)–OW1
Eu(1)–N(12)
Eu(1)–N(11)
Eu(2)–O(18)
Eu(2)–O(23)
Eu(2)–O(27)
Eu(2)–O(25)
Eu(2)–O(21)
Eu(2)–OW2
Eu(2)–N(21)
Eu(2)–N(22)
Eu(3)–O(28)
Eu(3)–O(31)
Eu(3)–O(37)
Eu(3)–O(35)
Eu(3)–O(33)
Eu(3)–OW3
Eu(3)–N(31)
Eu(3)–N(32)
Eu(4)–O(38)
Eu(4)–O(45)
Eu(4)–O(43)
Eu(4)–O(41)
Eu(4)–O(47)
Eu(4)–OW4
Eu(4)–N(42)
Eu(4)–N(41)
2.327(8)
2.353(9)
2.374(7)
2.387(8)
2.398(11)
2.464(16)
2.602(8)
2.613(19)
2.317(13)
2.354(8)
2.356(7)
2.378(8)
2.387(8)
2.429(12)
2.607(11)
2.608(19)
2.301(9)
2.341(10)
2.350(11)
2.395(7)
2.415(10)
2.429(15)
2.596(19)
2.667(9)
2.297(12)
2.370(8)
2.374(10)
2.375(9)
2.388(7)
2.444(12)
2.595(17)
2.642(14)
i
Eu(1)–O(15 )
Eu(1)–O(7)
Eu(1)–O(4)
Eu(1)–O(5)
Eu(1)–OW1
Eu(1)–N(11)
Eu(1)–N(12)
Eu(2)–O(8)
Eu(2)–O(11)
Eu(2)–O(14)
Eu(2)–O(17)
Eu(2)–O(16)
Eu(2)–OW2
Eu(2)–N(21)
Eu(2)–N(22)
Fig. 2. A fragment of the polymeric chain in I.
Fig. 3. A fragment of the polymeric chain in II.
different to that of its analogue, i.e. ethylenediaminetetrac-
etate (EDTA). The Eu –EDTA complexes are monomeric,
and the europium cation is nine-coordinate [6d,6e,6f], con-
trary to the polymeric structures with eight-coordinate Eu
ions in the present structures. Fragments of the polymeric
complex chains are presented in Figs. 2 and 3.
III
i
Symmetry transformations used to generate equivalent atoms: ꢀx ꢀ 1, y,
j
z; ꢀx + 1, y ꢀ 1, z.
Eu–N ones are the longest. As far as the conformation of
the ligand is concerned, two subsets of methylenecarboxy-
late groups may be discerned. In each CDTA ligand two
such groups are almost parallel. In II the angles between
the least-squares fitted planes of such planes (namely C13
and C23, C33 and C43, C51 and C63, C71 and C83; the
methylenecarboxylate groups are labelled after their central
C atoms) are in the range 0.6–10.0ꢁ. In I the relevant angles
differ more: the planes of the groups C1 and C12 are mutu-
ally twisted by 21.0ꢁ, whereas the groups C21 and C34 are
twisted by only 4.5ꢁ. The other pairs are twisted by 54.9ꢁ
and 59.7ꢁ in I, and 60.1–70.5ꢁ in II. Apart from that it
may be noticed that the C–O bonds are generally longer
when the O atom is coordinated to Eu, although the differ-
ence between the C–O lengths with O atoms coordinated
and uncoordinated falls often within the range of experi-
mental error. The approximate symmetry of all Eu first
5. Spectroscopic results
7
5
For the F ! D transition in I we were able to
0
0
ꢀ
1
observe one peak at 17245 cm
while at 30 K two components at 17241 and 17234 cm
appeared. The ground ( F ) and emitting ( D ) states of
at room temperature
ꢀ
1
7
5
0
0
the europium ion are non-degenerate, therefore the number
of peaks observed in the range 578–582 nm indicates the
III
number of various chemical surroundings of the Eu
ion. Accordingly we may assume existence of two different
europium sites at 30 K and of one site at room tempera-
ture. In the absorption spectrum of a related compound,
7
5
[
C(NH ) ][Eu(EDTA)(H O) ], only one F ! D peak
2
3
2
3
0
0
ꢀ1
was observed at a very similar energy, 17252 cm at room
ꢀ1
temperature [16] and 17243 cm
at 77 K. Also in the
7
5
7
5
coordination spheres in both structures is C (after neglect-
2
F ! D and F ! D transitions the number of com-
0
1
0
2
ing the difference between the water and the bridging car-
boxylate O atoms); the axis passes through the center of
the cyclohexyl ring, Eu and the bisector of the relevant
water–Eu–bridging O atom angle. It is noteworthy that in
the presented crystals the CDTA ligand behaves in a way
ponents in the spectrum recorded at 77 K is greater than
that found in the spectrum taken at 293 K. For the low
III
local symmetry of the Eu ion in each symmetry indepen-
dent site the number of the components should be 3 and 5,
respectively. At room temperature the number of crystal

R. Janicki et al. / Polyhedron 26 (2007) 845–850
849
7
5
field levels in the absorption spectrum for F ! D and
Table 3
Oscillator strength values (P) of the Eu complexes with CDTA
0
1
III
7
5
F ! D are actually 3 and 5, whereas in the low temper-
0
2
7
5
7
5
7
5
ature (30 K) transitions 5 and 7 crystal field components in
Complex
F
0
! D
0
F
0
! D
1
F
0
! D
2
8
8
8
ꢀ
1
P · 10
P · 10
P · 10
the range 19050–19120 and 21390–21550 cm , respec-
tively, may be seen (Fig. 4). This may suggest that between
93 and 100 K (taking into account the structural data
reported above) a phase transition occurs. The oscillator
strengths found in I at 293 and 30 K are presented in Table
Eu–CDTA pH 5.26
Eu–CDTA pH 7.40
Eu–CDTA pH 9.16
Eu–CDTA pH 11.0
Crystal T = 293 K
Crystal T = 30 K
1.20
1.25
1.18
0.59
0.50
1.38
1.61
1.62
1.52
1.50
1.44
3.20
5.90
5.34
6.20
11.4
3.35
11.0
2
3
. Inspection of these data reveals somewhat anomalous
behaviour of these quantities. Namely, the intensities of
all the presented transitions increase on lowering the tem-
perature. Such a change might be attributed to a phase
3.5 and 9. The most significant changes in the absorption
spectra are observed above pH 10. In Fig. 4 the absorption
spectra of Eu –CDTA solutions at pH 7.40 and 11.0 have
7
5
7
5
transition in the case of F ! D and F ! D . The
0
0
0
2
III
most surprising thing is, however, the anomalous growth
7
5
of the intensity of the F ! D transition, which is more
been juxtaposed. For both solutions two maxima at 17250
0
1
ꢀ
1
7
5
than twice as intense as theoretically predicted [17]. Such
and 17239 cm may be observed for the F
0
! D
tran-
0
an increase cannot be explained by thermal population of
sition, which confirms the equilibrium of nine- and eight-
coordinate isomers, as was previously reported at
pH = 6.0 [9]. These values are similar both to the maxi-
mum found in the crystal at room temperature and to
7
the F state, which would account only for the loss of
1
approximately 20 % of the intensity at room temperature.
The reasons for this phenomenon are unclear, and perhaps
need more detailed investigations, which however lie out-
side the scope of the present paper.
The splitting of the bands may also be observed in emis-
sion spectra at 77 K. At room temperature the transition
III
the analogous maxima found in solutions of the Eu –
ꢀ
1
EDTA complex (17254 and 17240 cm ) [16]. There is
another similarity that perhaps should be mentioned.
Namely, the most intense crystal field components in the
transition in both solutions very closely match
2
the analogous components in the spectrum of I at room
temperature.
5
7
5
7
7
5
D ! F was unsplit, whereas the D ! F and
F
0
! D
0
0
0
1
5
7
D ! F transitions had 3 and 4 discernible components.
0
2
At 77 K the number of observed components was 2 for
5
7
5
7
5
7
D ! F , 6 for D ! F and 7 for D ! F .
The most remarkable changes may be observed in the
values of the oscillator strengths (Table 3). The P value
0
0
0
1
0
2
The results presented above may serve as a background
7
5
for the interpretation of the spectroscopic properties of
of the transition F
0
! D
remains practically constant
0
III
water solutions of the Eu –CDTA system. These proper-
up to approximately pH = 9 and then decreases by about
ties remain essentially the same in the pH range between
half, reaching a value very similar to that calculated for I
7
F0
5
D0
7
F0
5
D1
7
F0
5
D2
0,02
0,02
0,12
Eu:CDTA
:1.1
pH = 11.0
Eu:CDTA
1:1.1
pH = 11.0
Eu:CDTA
:1.1
pH = 11.0
1
1
0
,00
,04
0,00
0,02
0,00
0,1
0
Eu:CDTA
Eu:CDTA
1:1.1
pH= 7.40
Eu:CDTA
1:1.1
1:1.1
pH= 7.40
pH= 7.40
0
,00
0,00
0,03
0,0
0
,024
0,044
crystal
T = 293 K
crystal
T = 293 K
crystal
T = 293 K
0
,000
0,00
0,000
0,2
0
,1
0
,1
,0
crystal
T = 30 K
crystal
T = 30 K
crystal
T = 30 K
0
,0
0
,0
462
0
5
24
526
528
464
466
468
5
78
579
580
581
λ / nm
λ / nm
λ / nm
7
5
III
Fig. 4. Absorption spectra of the F
Eu = 2.49 M, d = 0.102 cm.
0
! D0,1,2 transitions of Eu complexes with CDTA in solution: cEu = 44.1 mM, d = 5 cm and in the monocrystal
c

850
R. Janicki et al. / Polyhedron 26 (2007) 845–850
at room temperature. The magnetic-dipole allowed transi-
References
7
5
tion F ! D in the solutions and in I at 293 K is con-
0
1
[
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stant with the P value close to the theoretical value [17].
7
5
The intensity of the hypersensitive F ! D transition is,
0
2
out of the three presented ones, the most affected by
changes in the europium ion first coordination sphere.
The oscillator strength of this band, like that of
1
24;
(
b) J.A. Peters, J. Huskens, D.J. Raber, Prog. Nucl. Magn. Reson.
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(
(
1998) 19;
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9
9 (1999) 2293.
III
the first coordination sphere of the Eu ion, consisting
[
[
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of partial substitution of coordinated water molecules by
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(
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(
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. Conclusions
(
(
(
(
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The presented results suggest that the CDTA anion
behaves in a somewhat different way in comparison to
EDTA as far as the structural aspects are concerned.
Namely CDTA shows a more pronounced tendency to
form polymeric structures with lanthanides. Apart from
(f) H.G. Brittain, G.R. Choppin, P.P. Barthelemy, J. Coord. Chem.
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2
(
8
(
III
that the coordination numbers of all Eu –CDTA com-
plexes are eight while in all known crystal structures of
[
6] (a) J.L. Hoard, B. Lee, M.D. Lind, J. Am. Chem. Soc. 87 (1965) 1612;
(b) J.L. Hoard, E. Willstadter, J. Silverton, J. Am. Chem. Soc. 87
III
III
Eu –EDTA systems the Eu
ion is nine-coordinate.
III
(
(
(
1965) 1611;
The spectroscopic properties of the presented Eu –
CDTA systems in water solutions rather closely resemble
c) H.Y.D. Ke, E.R. Birnbaum, J. Luminen. 63 (1995) 9;
d) K. Nakamura, T. Kurisaki, H. Wakita, T. Yamaguchi, Acta
III
III
those of related Eu –EDTA ones. For instance for Eu
Crystallogr. C51 (1995) 1559;
(e) J. Wang, X.D. Zhang, W.G. Jia, Y. Zhang, Z.R. Liu, Koord.
Khim. 30 (2004) 141;
7
5
complexes with both ligands the F ! D
transitions
0
0,1,2
ꢀ
lie at very similar energies. The [Eu(CDTA)(H O)3 or 2]
2
(
f) J. Wang, X.D. Zhang, Y. Zhang, Y. Wang, X.Y. Liu, Z.R. Liu,
species remain stable up to pH ꢂ 9, then partial
hydrolysis and/or polymerization take place. The spec-
tra of [C(NH ) ] [Eu (CDTA) (H O) ]ClO Æ 7H O at
Koord. Khim. 30 (2004) 901.
7] (a) T.F. Gritmon, M.P. Goedken, G.R. Choppin, J. Inorg. Nucl.
Chem. 39 (1977) 2021;
[
2
3 3
2
2
2
2
4
2
various temperatures reveal a phase transition in the
crystal.
(
b) S.L. Wu, W.DeW. Horrocks Jr., J. Chem. Soc., Dalton Trans.
(1997) 1497.
[
[
8] T.F. Gritmon, M.P. Goedken, G.R. Choppin, J. Inorg. Nucl. Chem.
3
9] N. Graeppi, D.H. Powell, G. Laurenczy, L. Z e´ k a´ ny, A.E. Merbach,
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9 (1977) 2025.
Acknowledgements
The authors would like to thank Ing. Halina Treli n´ ska-
Nowak for the spectroscopic measurements and Dr.
Andrzej Kochel for help in the X-ray data collection.
[
[
[
[
[
[
[
10] J. Wang, X.D. Zhang, W.G. Jia, H.F. Li, X. Ling, Huaxue Xuebao
(Chin.) (Acta Chim. Sinica) 60 (2002) 1452.
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14] G.M. Sheldrick, SHELXL-97. Program for structure refinement, Uni-
versity of G o¨ ttingen, 1997.
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16] A. Mondry, R. Janicki, Dalton Trans. (2006) 4702.
Appendix A. Supplementary material
CCDC 615028 and 615027 contain the supplementary
crystallographic data for I and II. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/
conts/retrieving.html, or from the Cambridge Crystallo-
graphic Data Centre, 12 Union Road, Cambridge CB2
1
EZ, UK; fax: (+44) 1223-336-033; or e-mail:
[17] W.T. Carnall, T.R. Fields, K. Rajnak, J. Chem. Phys. 49 (1968) 4412.
18] L. Spaulding, H.G. Brittain, Inorg. Chem. 22 (1983) 3486.
[
deposit@ccdc.cam.ac.uk.