Structural and spectroscopic studies of neodymium complexes with S(+)-mandelic acid

Article abstract of DOI:10.1016/j.molstruc.2011.10.031

The crystal structure of tetraaquahexakis-S(+)-mandelatodineodymium trishydrate was determined by the X-ray diffraction method. The compound crystallizes in the monoclinic space group P2₁ with the following unit cell parameters: a = 10.536(2),

Full text of DOI:10.1016/j.molstruc.2011.10.031

Journal of Molecular Structure 1006 (2011) 672–677
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Structural and spectroscopic studies of neodymium complexes
with S(+)-mandelic acid
⇑
Michał Babij, Przemysław Starynowicz, Anna Mondry
Faculty of Chemistry, University of Wrocław, F. Joliot-Curie 14, 50-383 Wrocław, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 15 June 2011
Received in revised form 17 October 2011
Accepted 17 October 2011
Available online 26 October 2011
The crystal structure of tetraaquahexakis-S(+)-mandelatodineodymium trishydrate was determined by
the X-ray diffraction method. The compound crystallizes in the monoclinic space group P2
following unit cell parameters: a = 10.536(2), b = 16.089(3), c = 15.316(3) Å, b = 97.96(2)°. The structure
consists of polymeric [Nd (Man) (H O) O] chains (where ManH = S(+)-2-hydroxy-2-phenylacetic
1
with the
2
6
2
4
ꢀ3H
2
1
+
3
acid or S(+)-mandelic acid), with two symmetry independent Nd ions. Both neodymium ions are
nine-coordinate but differ in their environments. Nd(1) is surrounded by two water molecules, five car-
boxylate and two hydroxyl oxygen atoms, Nd(2) is coordinated by two water molecules, four carboxylate
and three hydroxyl oxygen atoms. Crystals of neodymium mandelate complex were characterized by
thermal analysis as well as by IR and UV–vis–NIR absorption spectroscopy.
Keywords:
Neodymium
Mandelic acid
X-ray structure
UV–vis–NIR–IR spectroscopy
Rare earths
Ó 2011 Elsevier B.V. All rights reserved.
1
. Introduction
Lanthanide complexes with aromatic carboxylic acids have
5 and higher). The obtained Nd3+ crystals have been also character-
ized by thermogravimetric and spectroscopic methods.
been of increasing interest in chemical research due to their poten-
tial applications as optical materials and biological sensors [1]. One
of such ligands containing carboxyl and hydroxyl groups, namely
mandelic acid (Scheme 1) due to its two functional groups is a good
candidate to construct various coordination motifs with lanthanide
ions. There have been reports associated with stability of lantha-
nide mandelates [2] and with stoichiometry of these complexes
in the form of powders [3]. It was found that light lanthanide ions
2
. Experimental section
2.1. Materials
3 2 3
A solution of NdCl was prepared by dissolving Nd O (99.9%
Merck) in 2 M hydrochloric acid. The solution was standardized
with EDTA using xylenol orange as an indicator. A stock solution
of S(+)-mandelic acid (>98% Fluka AG) was also prepared.
The solution of Nd complex with S(+)-mandelic acid used for
spectroscopic measurements (marked as Nd-Man = 1:3) was pre-
pared by mixing NdCl
1
lue to 3. The Nd concentration in the aqua ion solution (assigned
as aqua ion) was 0.02 M and pH of this solution was 1.7.
3
+
form complexes of the formula Ln(Man)
ones form Ln(Man) O compounds [3].
ꢀ2H
Up to date two crystal structures of lanthanide mandelates are
known [4]. The structures were determined for the Pr(R,S-Man)
ManH) complex and for the Er(R-Man) (H O) compound [4]. Both
3
2
ꢀ3H O, while the heavy
3
2
3
and ligand solution in the molar ratio of
3
:3 and of cNd = 0.02 M. NaOH solution was added to adjust pH va-
3
+
(
3
2
2
lanthanide ions are eight-coordinate and are chelated by three
mandelate anions, each of the chelate rings being formed by a car-
boxylate oxygen atom and the oxygen atom from the hydroxyl
group. The inner sphere of the Pr3 ion is completed by the oxygen
atoms from the two functional groups of the mandelic acid mole-
cule (ManH), whereas in the case of erbium by two water
molecules.
2.2. Crystal syntheses
+
Neodymium mandelate crystals (Nd-Man) were synthesized by
two methods.
In the present work the solutions applied to grow crystals had
lower pH (between 2 and 3) than those used previously (around
I. Aqueous solutions of NdCl
mixed in the molar ratio of 1:3 (0.2 mmol of NdCl
.6 mmol ManH). The pH of the resulting solution (10 ml)
3
and S(+)-mandelic acid were
3
and
0
was adjusted to around 3 with the NaOH solution. After
few days of evaporation needle shaped, violet crystals were
obtained.
⇑
Corresponding author. Tel./fax: +48 71 3282348.
E-mail address: anna.mondry@chem.uni.wroc.pl (A. Mondry).
0
022-2860/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2011.10.031

M. Babij et al. / Journal of Molecular Structure 1006 (2011) 672–677
673
UV–vis–NIR absorption spectroscopy: The UV–vis–NIR spectra of
neodymium complexes in aqueous solution and in the form of sin-
gle crystal were recorded on a Cary 500 UV/VIS/NIR spectropho-
tometer. The spectra of the crystal were measured at room and
4
.2 K temperatures in a continuous flow helium cryostat (Optistat,
Oxford).
Scheme 1. S(+)-mandelic acid (ManH).
2.4. Calculations
The experimental oscillator strength (P) values of f–f transitions
were determined using the equation:
Table 1
Crystal data and structure refinement for the neodymium mandelate complex.
Z
r
n
1
c ꢀ d
P ¼ 4:33 ꢁ 10ꢂ9
ꢀ
ꢀ
Að
rÞdr
ð1Þ
Parameter
Value
r
1
Chemical formula
24
C H28NdO12.5
where c is the concentration of the Nd3+ ion in M, d is the length of
M
r
660.70
the optical path in cm and A(
r) is the absorbance as the function of
Crystal system, space group
Temperature (K)
a, b, c (Å)
Monoclinic, P2
100
1
ꢂ1
the wavenumber in cm
.
10.536(2), 16.089(3),
5.316(3)
According to the Judd–Ofelt theory [8,9], the oscillator strengths
of f–f transitions can be expressed as:
1
b (°)
V (Å )
Z
97.96(2)
2571.3(8)
4
3
p2mc
r
hð2J þ 1Þ
X
8
3
n
ðkÞ
n
0
0
2
P ¼
v
X
k
ðf wJkU kf w J Þ
ð2Þ
Radiation type
Mo K
2.09
a
k¼2;4;6
ꢂ1
l
(mm
)
2
2
Crystal size (mm)
Absorption correction (analytical), Tmin, Tmax
No. of measured, independent and observed
0.35 ꢁ 0.20 ꢁ 0.04
0.633, 0.931
35,089, 18,615, 12,832
where
v
¼ ðn þ 2Þ =9n and n is the refractive index (1.33 for solu-
tions and 1.50 for the crystal), m is the electron mass, c is the veloc-
ity of light, is the wavenumber of band maximum, h is the
Planck’s constant, J is the total quantum number of the ground
r
[I > 2r(I)] reflections
R
int
0.043
0.047, 0.096, 0.92
18,615
676
1
ðkÞ
n
0
0
2
2
2
n
R[F > 2
r
(F )], wR(F ), S
state, ðf wJkU kf w J Þ is the reduced matrix element of the unit
ðkÞ
No. of reflections
No. of parameters
No. of restraints
tensor operator U tabulated by Carnall et al. [10] and
X
k
are the
phenomenological intensity parameters determined by a least-
squares fit. The root-mean-square error was estimated from the
equation:
ꢂ3
D
q
max
,
D
q
min (e Å
)
3.71, ꢂ1.02
Flack parameter
ꢂ0.032 (11)
vffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
u
n
uP
2
u
t
ðPexp ꢂ PcalcÞ
i¼n
rms ¼
ð3Þ
n ꢂ 3
II. A suspension of Nd
2
O
3
(0.1682 g, 0.5 mmol) in an aqueous
solution of S(+)-mandelic acid (1 mmol) in 50 ml water
was prepared. After 4 months of a slow evaporation of the
mixture the crystals were formed. The crystals were of bet-
ter quality than those obtained by the former method.
3
. Results and discussion
.1. Crystal structure
It was found that crystals obtained by both methods of synthe-
3
2.3. Methods
sis are isomorphic. The crystal structure of the neodymium man-
delate complex determined by the X-ray diffraction method
differs from those previously presented [4]. The structure contains
X-ray crystal analysis: An appropriate crystal was cut from a lar-
ger one, mounted on a Kuma KM4 diffractometer equipped with a
CCD counter and measured at 100 K. The structure was solved and
refined routinely. The C-bonded hydrogen atoms were placed in
positions calculated from the geometry, the O-bonded ones were
not found. The final refinement was anisotropic for all non-H
atoms. The positions of hydrogen atoms were geometrically con-
strained and the isotropic temperature factors of these atoms were
set as 1.2 of the trace of the anisotropic factors of the respective C
atoms. Thermal vibration components perpendicular to the phenyl
ring planes of some ring carbon atoms (C27, C28, C44 through C48,
+
3
two symmetry independent Nd ions (Fig. 1) connected through
mandelate bridges into [Nd (Man) (H O) O] chains running
2
6
2
4
ꢀ3H
2
1
along the [100] direction (Fig. 2). Both neodymium ions are
nine-coordinate but differ in their environments. The Nd-ligand
distances are presented in Table 2. Each of the metal ion is bonded
to four mandelate anions and two water molecules. All carboxylic
groups of mandelic acid are deprotonated and display three types
3
+
of coordination modes with Nd ions (monodentate, bridging-
0
2
0
bidentate (1jO,2jO ) and bridging-tridentate(1jO;1:2j O ))
2
C54 through C58) were very large (up to 0.527 Å ), what may indi-
which may be inspected in Fig. 3. Two pairs of mandelate anions
(O13, O23, O43 and O53; the mandelate anions are labeled here
after their hydroxyl oxygen atoms) chelate each Nd3+ ion in the
same fashion, namely through one oxygen atom from the carboxyl
group (O21, O41; O11, O51) and the oxygen atom from the hydro-
xyl group (O23, O43; O13, O53). The carboxyl groups from the
remaining two mandelate anions are connected with Nd3+ ions in
bi- (the O33 anion) or tridentate (the O3 anion) modes. Such a
coordination gives rise to formation of polymeric chains running
cate an unaccounted mild disorder of the relevant phenyl groups.
The computations were performed with SHELXS-97 [5] and SHEL-
XL-97 [6] programs and the molecular graphic was prepared with
DIAMOND [7]. The crystal data and structure refinement are given
in Table 1.
TG/DTA: Thermogravimetric (TG) and differential thermal (DTA)
analyses were carried out from 30 to 1000 °C under nitrogen atmo-
sphere on a SETSYS 16/18 Setaram thermogravimetric analyzer.
IR spectroscopy: The IR spectra of the ligand and neodymium
crystals were measured on a IFS 113 V Bruker, using KBr pellets.
2
along the [100] direction. The NdAO(H O) bond lengths are in
the range from 2.483(4) Å to 2.547(4) Å, whereas those of hydroxyl

6
74
M. Babij et al. / Journal of Molecular Structure 1006 (2011) 672–677
Table 2
NdAO bond distances (Å) determined for neodymium mandelate crystal
Nd (Man) (H O) O]
ꢀ3H
[
2
6
2
4
2
1
.
Nd(1)
Nd(2)
Nd1AO31
Nd1AO41
Nd1AO21
Nd1AO2
Nd1AOW2
Nd1AO23
Nd1AOW1
Nd1AO43
Nd1AO1
2.357(4)
Nd2AO32i
Nd2AO11
Nd2AO51
Nd2AO1
Nd2AOW3
Nd2AO53
Nd2AOW4
Nd2AO13
Nd2AO3
2.362(3)
2.426(4)
2.439(6)
2.497(3)
2.500(4)
2.522(4)
2.547(4)
2.550(5)
2.561(3)
2.415(6)
2.433 (4)
2.476 (3)
2.483 (4)
2.491 (5)
2.539 (4)
2.541 (4)
2.718 (3)
Fig. 1. Molecular structure of [Nd
2
6
(Man) (H
2
O)
4
ꢀ3H
2 1
O] together with atom labels.
Fig. 3. Coordination modes of S(+)-mandelate anions in [Nd
2
(Man)
6
(H
2
O)
4
ꢀ3H
2 1
O] .
The distance between the Nd cations linked with bridging tri-
dentate O3 mandelate anion is 5.025(1) Å, whereas the metal cat-
ions connected by the bridging bidentate O33 anion, Nd1 and Nd2
(
ꢂ1 + x,y,z), are 5.515(1) Å away.
The hydroxyl oxygen atoms are involved in some hydrogen
bonds as donors; these hydrogen bonds run within the polymeric
neodymium–mandelate chains. The latter are connected through
the H-bonds formed by the water molecules, both coordinated
and uncoordinated.
3.2. Thermal analyses
The results obtained with the use of thermogravimetric analysis
of neodymium mandelate crystals are presented in Fig. 4. The stud-
ies indicate two stages of dehydration. The first weight loss of
3
.48% (calc. 4.10%) in the range 30–120 °C corresponds to the loss
of three uncoordinated water molecules, what is consistent with
the single crystal X-ray analysis. This endothermic process is
confirmed by the DTA curve. Heating of the sample in the range
1
20–300 °C brings about the mass loss of 16.77%. The calculated
value for the release of four coordinated water molecules is
.54% indicating that in this stage the decomposition of the organic
9
ligand, as it is observed in the DTA curve, also takes place. Upon
further heating a continuous, very complex weight loss with an
intense exothermic peak at 580 °C is observed. At 970 °C the com-
pound starts to convert into neodymium oxide.
Fig. 2. Crystal packing diagram for [Nd
have been omitted for the sake of clarity.
2
6
(Man) (H
2
O)
4
ꢀ3H
2 1
O] . The hydrogen bonds
3.3. IR and NIR spectroscopy
groups are generally slightly longer and range from 2.491(5) to
.561(3) Å. The NdAO(monodentate carboxyl groups) bond dis-
2
The IR spectra were measured for the neodymium mandelate
tances (2.415(6)–2.439(6) Å) are longer than NdAO(bridging
bidentate) lengths (2.357(4) and 2.362(3) Å). The NdAO bonds
with a bridging tridentate group are the most differentiated. They
are equal to 2.433(4), 2.497(3) and 2.718(3) Å. It should be noticed
that with the exception of the longest Nd1AO1 distance all the
remaining Nd1AO bond lengths are shorter than those of Nd2AO
bond distances.
complex ([Nd
2
(Man)
6
(H
2
O)
4
ꢀ3H
2 1
O] ) and the S(+)-mandelic acid
(ManH). The spectra of both compounds are shown in Fig. 5 and
differ significantly from each other in the region of the character-
istic vibrations of carboxylic group as well as OH oscillations. The
spectrum of ManH shows an intense band at 1724 cm , corre-
sponding to the
ꢂ1
mC@O (COOH) vibration of the protonated carbox-
ꢂ1
ylic group [11–13], the peak at 862 cm related to the wagging

M. Babij et al. / Journal of Molecular Structure 1006 (2011) 672–677
675
Fig. 4. TG and DTA curves of [Nd
2
(Man)
6
(H
2
O)
4
ꢀ3H
2 1
O] crystal.
Fig. 6. NIR spectra of S(+)-mandelic acid (ManH) and neodymium mandelate
2 2 c
crystal (Nd-Man). H Ounc and H O stand for uncoordinated and coordinated water
molecules.
the alcoholic groups. Such assignments of dOH(H
and OH(COH) oscillations are consistent with the positions of
overtone bands appearing in the NIR spectra of both compounds
Fig. 6). Though in the NIR region the f–f bands also appear, they
2 2
O), mOH(H O)
m
(
are very often weaker than the bands of overtones of higher molec-
ular vibrations and/or their combinations [14–16]. Two bands with
the peak maxima at 1671 nm and at 2472 nm shown in Fig. 6 con-
4
4
tain besides the overtone bands also the
I
I
9/2 ? I15/2 and
4
4
3+
9/2 ? I13/2 transitions of the Nd ion. Therefore, the band ob-
served between 1900 and 2000 nm (5000–5260 cm ), may be
classified as the combination band of the second overtones of the
ꢂ1
2
mas(COO) and dOH(H O) vibrations [14].
3.4. UV–vis spectroscopy
Absorption spectra of f–f transitions of the neodymium mandel-
Fig. 5. IR spectra of S(+)-mandelic acid (ManH) and neodymium mandelate crystal
Nd-Man).
ate crystal were recorded in two different positions with respect to
the partially polarized incident light beam. One of the crystal posi-
tion, named vertical was perpendicular to the second one (horizon-
tal). In order to compare the spectral properties of the single crystal
with those of the neodymium complex in solution, the spectra of
the solution which was prepared in the same experimental condi-
tions as the solution for the method I of crystal synthesis (Experi-
mental section), were also measured. In addition, for comparison
purposes, the f–f spectra of the neodymium aqua ion have been
also recorded.
(
mode of the carboxyl OH vibration [12,13] and a wide absorption
ꢂ1
band in the range 2250–3250 cm attributed to the
mOH oscilla-
tion of the ACOOH group. In this region one can also find some
peaks of the methylenic and aromatic ACH stretches. As it was
ꢂ1
revealed previously [11–13], the sharp peak at 3447 cm belongs
to the alcoholic group mOH vibration indicating the absence of inter-
molecular dimerization in the acid. The remaining absorption
bands in the spectrum of ManH are composed from many complex
oscillation modes of an aromatic ring and alcoholic as well as car-
boxylic groups, as it results from normal-coordinate analysis [13].
The intense and well separated peak at 1586 cm attributed to
the mas COO in the spectrum of the neodymium complex points out
Since from all f–f transitions, the hypersensitive transition
4I9/2 ? G5/2, G7/2 is the most strongly affected by changes of the
4
2
3
+
nearest surrounding of the Nd ion, the spectra of this transition
were compared for the studied complexes and are presented in
Fig. 7. As it can be seen from the figure, the neodymium mandelate
solution spectrum does not differ very much in comparison with
the spectrum of the aqua ion but is significantly different from
those of the single crystal. The measurements of the crystal in dif-
ferent directions do not reveal differences in the positions of the
crystal field components but in their intensities, indicating a high
sensitivity of the crystal on the light polarization. The low temper-
ature spectrum of the hypersensitive transition shows a very com-
plex structure.
ꢂ1
that carboxylic groups are deprotonated and coordinated to the
ꢂ1
metal ion. This band, however has a weak shoulder at 1721 cm
what, in the absence of protonated carboxylic groups in the crystal
is probably responsible for dOH(H O) vibration of inner sphere
2
water molecules found in the neodymium complex. It may also
belong to one of three coordination modes of the carboxyl group.
The
m
OH(H
2
O) vibrations of coordinated and uncoordinated water
ꢂ1
molecules are in the range between 3000 and 3750 cm , while
the peak at 3487 cm corresponds to the
The most useful absorption bands from which the number of
different neodymium surroundings can be predicted are low
ꢂ1
mOH(COH) vibrations of

6
76
M. Babij et al. / Journal of Molecular Structure 1006 (2011) 672–677
Fig. 9. Absorption spectra of the 4
in solution (aqua ion, Nd:Man = 1:3;
I
9/2 ? 4
F
3/2 transition for neodymium complexes
Nd = 0.02 M, d = 5 cm) and in the
[Nd (Man) (H O) ꢀ3H O] crystal (Nd-Man; horizontal orientation, cNd = 1.56 M,
c
Fig. 7. Absorption spectra of the hypersensitive 4
I
9/2 ? 4
G
1/2, 2
G7/2 transition for
2
6
2
4
2
1
neodymium complexes in solution (aqua ion, Nd:Man = 1:3; cNd = 0.02 M, d = 5 cm)
and in the [Nd (Man) (H O) O] crystal (Nd-Man; Nd = 1.56 M,
ꢀ3H
d = 0.0185 cm). The spectra of crystal were recorded for two orientations (vertical
Ver, horizontal – Hor) with respect to the incident light beam.
d = 0.0185 cm).
2
6
2
4
2
1
c
temperature spectra (at 4.2 K) of the 4 9/2 ? 2P1/2 and 4 9/2 ? 4F3/2
I I
–
transitions. The excited state of the first transition is a Kramer’s
doublet and does not split in the ligand field of any symmetry,
4
whereas the splitting of the F3/2 manifold into two lines is indica-
3
+
tive of a single Nd site of a low symmetry. The spectra of both
transitions are presented in Figs. 8 and 9, respectively. One may
notice that, similarly like for the spectra of the hypersensitive tran-
sition, the surroundings of the neodymium mandelate species in
solution are considerably different from those which were found
for the single crystal. The energy of the first peak of the
4
2
I
9/2 ? P1/2 transition, which is generally used as an indicator of
the nephelauxetic effect [17], reveals that in the neodymium com-
plex in solution exists an equilibrium between the aqua ion and hy-
drated species of the complex. Thus the red shift of this peak for
ꢂ1
1
04 cm in the spectrum of the crystal in comparison with that of
the neodymium complex in solution confirms that the species
formed in the solution have different constitution and structure.
From the crystal spectra at room temperature it was possible to
4
determine the first crystal field component of the I9/2 state, only. It
ꢂ1
lies 60 cm above the ground level.
Though in the low temperature spectrum of the 4I9/2 ? 2P1/2
ꢂ1
transition one peak is observed only, its halfwidth of 16 cm indi-
cates that the band is composed of two or three lines which cannot
be resolved. Usually, in the low temperature spectrum, the half-
ꢂ1
width of this band for a single neodymium site is 5–8 cm
[
15,18]. The splitting is more manifest in the spectrum of the
4
4
I
9/2 ? F3/2 transition at 4.2 K (Fig. 9), where two doublets may
be observed, what is consistent with the X-ray analysis.
The oscillator strength values (Pexp) of f–f transitions from the
spectral range of 300–950 nm for the studied complexes were also
determined and the intensity
k
X parameters were calculated. The
Fig. 8. Absorption spectra of the 4
in solution (aqua ion, Nd:Man = 1:3;
Nd (Man) (H O) O] crystal (Nd-Man; horizontal orientation, cNd = 1.56 M,
ꢀ3H
d = 0.0185 cm).
I
9/2 ? 2
P
1/2 transition for neodymium complexes
Nd = 0.02 M, d = 5 cm) and in the
results are given in Table 3. From the data presented in this table,
one may notice that the oscillator strengths of f–f transitions for
the neodymium complex in solution resemble much more those
c
[
2
6
2
4
2
1

M. Babij et al. / Journal of Molecular Structure 1006 (2011) 672–677
677
Table 3
Oscillator strength values (Pexp) and
X
k
parameters for the neodymium complexes in solution and in the form of single crystal.
Solution
Aqua ion
Crystal
Nd:Man = 1:3
Vertical
Horizontal
98 K
108
2
4 K
108
Transition(s) 4
I
108
P
108
P
108
P
P
P
exp
9/2
?
exp
exp
exp
exp
4
F
F
F
F
3/2
242.14
850.97
849.32
53.77
246.91
907.07
916.54
58.76
197.06
710.69
741.35
40.78
185.57
971.75
807.51
51.21
463.68
4
4
4
2
4
2
2
2
4
5/2, 2
H
9/2
1178.12
816.20
87.64
4
7/2
, S
3/2
9/2
H
G
K
K
P
11/2
5/2, 2
12.62
15.36
7.00
10.07
50.00
G
7/2
932.32
662.51
179.97
31.36
944.44
1.27 ± 0.44
4.16 ± 0.40
7.74 ± 0.57
7.99
1306.13
734.02
189.81
33.59
983.01
2.88 ± 0.48
4.29 ± 0.43
8.34 ± 0.62
8.66
2272.77
700.63
152.32
31.27
1017.98
6.82 ± 0.30
3.64 ± 0.26
5.79 ± 0.39
6.15
3040.60
881.47
186.65
62.05
1843.07
7.72 ± 0.36
7.31 ± 0.32
6.18 ± 0.47
7.38
2407.37
1210.45
575.62
64.19
4
2
7/2, 4
13/2
15/2
1/2
3/2, 4
,
,
G
G
G
9/2
9/2, ( D, 2F)3/2, 4
2
G
11/2
D
D
5/2, 2
I
11/2, 4
2
D
1/2, 2
L
15/2
2597.32
2
0
X
X
X
2
4
6
ꢁ 10 (cm )
20 2
ꢁ 10 (cm )
2
0
2
ꢁ 10 (cm )
7
rms ꢁ 10
In solutions: cNd = 0.02 M, d = 5 cm; in the crystal: cNd = 1.56 M, d = 0.0185 cm.
of the aqua ion than those of the neodymium complex in the crys-
tal. This is especially well seen for the most intense transitions of
mandelate complex in solution is completely different from those
in the crystal.
3
+
4
4
2
4
4
4
the Nd ion like the
I
9/2 ? G5/2
,
G
7/2
,
I
9/2 ? F7/2
,
S
3/2 and
4
4
2
I
9/2 ? F5/2
,
H9/2, which play a significant role in the Judd–Ofelt
Supplementary material
intensity analysis [8,9]. While the hypersensitive transition is char-
(2)
acterized by the high value of the squared matrix element U , the
CCDC No. 829935 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge from
The Cambridge Crystallographic Data Centre via http://
www.ccdc.cam.ac.uk/data_request/cif.
(
6)
latter two transitions have high values of U [10]. According to
Mason [19], the ligand polarization mechanism is important
mainly for the hypersensitive transition and influences the
parameter value, while the crystal field mechanism contributes
mostly to the values.
X
2
X
6
References
It should be noted that oscillator strengths of majority of the f–f
transitions in the spectra of crystals are decreasing on going down
to 4.2 K [15,18]. This decrease is brought about the disappearance
of hot transitions from the crystal field components of the ground
state and/or by the vibronic mechanism. For the neodymium man-
delate crystal the direction of these changes is opposite. The
observed increase of Pexp may be tentatively attributed to shorten-
ing of the NdAO bond lengths at lower temperature.
[1] (a) K. Binnemans, Chem. Rev. 109 (2009) 4283;
(
(
(
b) J.-C.G. Bünzli, Chem Rev. 110 (2010) 2729;
c) J.-C.G. Bünzli, C. Piguet, Chem. Soc. Rev. 34 (2005) 1048;
d) M.D. Allendorf, C.A. Bauer, R.K. Bhakta, R.J.T. Houk, Chem. Soc. Rev. 38
(2009) 1330.
[
[
[
2] A. Dadgar, G.R. Choppin, J. Inorg. Nucl. Chem. 34 (1972) 1297.
3] D.K. Koppikar, S. Soundararajan, Bull. Soc. Chim. Belg. 90 (1981) 1109.
4] C. Bromant, W. Nika, I. Pantenburg, G. Meyer, Z. Naturforsch. B 60 (2005) 753.
[5] G.M. Sheldrick, SHELXS-97. Program for Structure Solution, University of
Göttingen, 1997.
[
6] G.M. Sheldrick, SHELXL-97. Program for Structure Refinement, University of
Göttingen, 1997.
4
. Conclusions
[
7] DIAMOND Visual Crystal Structure Information System, CRYSTAL IMPACT,
Postfach 1251, D-53002 Bonn, Germany.
8] B.R. Judd, Phys. Rev. 127 (1962) 750.
The crystal structure of the Nd3+ complex with S(+)-mandelic
[
[
9] G.S. Ofelt, J. Chem. Phys. 37 (1962) 511.
acid was determined. The structure is different from those previ-
ously reported for eight-coordinate lanthanides with mandelic
acid. In the present crystal, two nine-coordinate neodymium ions
differ in coordination surroundings formed by variously bounded
carboxyl group. They are connected with neodymium ions in
mono-, bi- and tridentate modes what is a reason that the structure
consists of polymeric chains. The TGA-DTA analysis allows to pre-
dict the presence of three uncoordinated water molecules. The IR
and NIR data have permitted to point out the positions of OH vibra-
tions from coordinated and uncoordinated water molecules and of
hydroxyl groups. The results from optical spectroscopic studies
have confirmed that two different environments of the neodym-
ium ion are present in the mandelate crystal. It has also been
established that the inner sphere of the neodymium ion in the
[
10] W.T. Carnall, P.R. Fields, K. Rajnak, J. Phys. Chem. 49 (1968) 4424.
[11] N. Mori, Y. Asano, T. Irie, Y. Tsuzuki, Bull. Chem. Soc. Jpn. 42 (1969) 482.
[12] R.J. Davey, G. Dent, R.K. Mughal, S. Parveen, Cryst. Growth Des. 6 (2006)
1788.
[
[
13] H.M. Badawi, W. Förner, Spectrochim. Acta A 78 (2011) 1162.
14] A. Mondry, K. Bukiety n´ ska, J. Alloys Compd. 374 (2004) 27.
[15] A. Mondry, P. Starynowicz, Eur. J. Inorg. Chem. (2006) 1859.
[
[
[
16] R. Janicki, P. Starynowicz, A. Mondry, Eur. J. Inorg. Chem. (2011) 3601.
17] R.D. Peacock, Struct. Bond. 22 (1975) 83.
18] (a) A. Mondry, P. Starynowicz, J. Alloys Compd. 225 (1995) 367;
(b) A. Mondry, K. Bukiety n´ ska, J. Alloys Compd. 275-277 (1998) 818;
(
(
(
c) A. Mondry, P. Starynowicz, Inorg. Chem. 36 (1997) 1176;
d) A. Mondry, P. Starynowicz, J. Chem. Soc. Dalton Trans. (1998) 859;
e) A. Mondry, P. Starynowicz, Polyhedron (2000) 771.
[19] (a) S.F. Mason, Struct. Bond. 39 (1980) 43;
(
(
b) S.F. Mason, G.E. Taranter, Chem. Phys. Lett. 94 (1983) 29;
c) S.F. Mason, Inorg. Chim. Acta 94 (1984) 313.