Thermal evolution and crystal structures of the 3,5-pyrazole dicarboxylic acid (hydrated form and anhydrous): Ligations with nickel II and barium II

Article abstract of DOI:10.1016/j.molstruc.2006.03.074

A crystalline form of anhydrous 3,5-pyrazole dicarboxylic acid (H₃pdc), H₃pdc-α, which is the most stable form at room temperature, has been identified by a variable temperature diffraction study of the commercial form, H₃pdc,H₂O. Single crystals of H₃pdc,H₂O, anhydrous H₃pdc-β, the high temperature form, as well as Ni(Hpdc),4H₂O and Ba(H₂pdc)₂(H₃pdc)₂ have been prepared, and their crystal structures determined. The structures of H₃pdc,H₂O, and H₃pdc-β consist of a planar central pyrazole ring, with two carboxylic groups slightly twisted from coplanarity, due to a complex hydrogen bonding scheme. The α form transforms into the β variety upon heating (>240 °C). The mononuclear complex, Ni(Hpdc),4H₂O, in which deprotonated H₃pdc serves as a bidentate ligand, has been characterized. The crystal structure of Ba(H₂pdc)₂(H₃pdc)₂ displays a 50% cationic partial occupancy, with double layers of [Ba_0.5(H₂pdc)(H₃pdc)]_∞ planar, polymeric type ribbons along the [010] direction, linked to each other via the Ba coordination scheme along the a axis of the unit cell, with a stacking of Ba(H₂pdc)₂(H₃pdc)₂ layers parallel to (001).

Full text of DOI:10.1016/j.molstruc.2006.03.074

Journal of Molecular Structure 798 (2006) 134–140
www.elsevier.com/locate/molstruc
Thermal evolution and crystal structures of the 3,5-pyrazole
dicarboxylic acid (hydrated form and anhydrous):
Ligations with nickel II and barium II
Pascal Roussel , Fouad Bentiss , Michel Drache , Pierre Conflant , Michel Lagrenee a,*,
a
b
a
a
a
Jean-Pierre Wignacourt
a
Unit e´ de Catalyse et de Chimie, CNRS UMR 8181, ENSCL, B.P. 90108, F-59652 Villeneuve d’Ascq Cedex, France
Laboratoire de Chimie de Coordination et d’Analytique, Universit e´ Chouaib Doukkali, Facult e´ des Sciences, B.P. 20, El Jadida, Morocco
b
Received 30 January 2006; accepted 20 March 2006
Available online 11 May 2006
Abstract
A crystalline form of anhydrous 3,5-pyrazole dicarboxylic acid (H
has been identified by a variable temperature diffraction study of the commercial form, H
3
pdc), H
3
pdc-a, which is the most stable form at room temperature,
pdc,H O. Single crystals of H pdc,H O, anhy-
3
2
3
2
drous H pdc-b, the high temperature form, as well as Ni(Hpdc),4H O and Ba(H pdc) (H pdc) have been prepared, and their crystal
3
2
2
2
3
2
3 2 3
structures determined. The structures of H pdc,H O, and H pdc-b consist of a planar central pyrazole ring, with two carboxylic groups
slightly twisted from coplanarity, due to a complex hydrogen bonding scheme. The a form transforms into the b variety upon heating
(
>240 ꢀC). The mononuclear complex, Ni(Hpdc),4H O, in which deprotonated H pdc serves as a bidentate ligand, has been character-
2
3
ized. The crystal structure of Ba(H pdc) (H pdc) displays
a
50% cationic partial occupancy, with double layers of
2
2
3
2
[
Ba0.5(H
along the a axis of the unit cell, with a stacking of Ba(H
2006 Elsevier B.V. All rights reserved.
2
pdc)(H
3
pdc)]
1
planar, polymeric type ribbons along the [010] direction, linked to each other via the Ba coordination scheme
2
pdc) (H pdc) layers parallel to (001).
2
3
2
ꢁ
Keywords: Pyrazole; Crystal structures; Thermolysis; Barium complex; Nickel complex
1
. Introduction
multidentate structure often favours the formation of poly-
meric patterns which can help to control the distribution of
the active metals on the surface; the thermal decomposition
of these ligands into well-defined and finely dispersed pow-
dered samples occurs at moderate temperatures that allow
limiting sintering effects. This approach has been previous-
ly used for the preparation of ionic conductors [10,11].
They may also be useful in extraction of harmful metals
from the environment [12]. 3,5-Pyrazole dicarboxylic acid
(H pdc),H O is a commercial product, which has been used
for the preparation of coordination complexes with transi-
tion metals such as copper(II), in order to investigate their
magnetic properties. Oxovanadium(IV), rare earth, cadmi-
um and bismuth complexes were also prepared and their
physicochemical properties were characterized [13,14].
Thermal evolution and crystal structure of a polymeric
complex of lead have also been reported [15]. In order to
Metal ions complexed by low molecular weight ligands
including oxalic acid, citric acid and ethylene-diamine-tet-
raacetic acid, are often used as starting materials for prep-
aration of metal oxides by low temperature degradation of
the complexes [1–8]. Heterocyclic acids or diacids such as
picolinic acid, 2,3-pyrazine dicarboxylic acid and 3,6-pyrid-
azine dicarboxylic acid have been used for preparation of
various metallic complexes [9–11]. These compounds
exhibit usually well-defined structures and stoichiometries
depending on the nature of carboxylate chain; they
can be designed in order to contain no other heteroelement
than carbon, nitrogen, oxygen and hydrogen. Their
3
2
*
Corresponding author. Tel.: +33 320 337746; fax: +33 320 436814.
E-mail address: michel.lagrenee@ensc-lille.fr (M. Lagrenee).
0
022-2860/$ - see front matter ꢁ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2006.03.074

P. Roussel et al. / Journal of Molecular Structure 798 (2006) 134–140
135
understand the correlation of physical and structural prop-
erties of H pdc and H pdc derivatives with the aim of
at ambient temperature. After 12 h, the colorless com-
pound crystallized. Crystals were washed with water and
dried under vacuum (yield: 0.2 g; 73% based on pdc). These
crystals were used as isolated from the batch for single crys-
tal X-ray analysis.
3
3
developing depolution or corrosion inhibition agents
16,17], we have undertaken a study of compounds of this
family. We report here the thermal behavior of H pdc,H O
[
3
2
as elucidated by thermodiffractometry (HTXRD), the
Densities were measured by the floatation method.
The TGA of a sampling of these crystals shows a two steps
ligand decomposition first occurring abruptly between 250
and 300 ꢀC, of about 37% in weight, and a second identical
mass loss occurring smoothly between 300 and 450 ꢀC,
which leave a solid residue identified by XRD as BaCO3.
Lattice constants were refined from the angular posi-
tions of 25 independent reflections randomly. Crystal data
of H pdc,H O, H pdc-b and Ni(Hpdc),4H O were mea-
crystal structures of H pdc,H O and H pdc-b, and those
3
2
3
of complexes of H pdc first with a hazardous metal:
3
Ni(Hpdc),4H O, and secondly with a big size cation:
2
Ba(H pdc) (H pdc) .
2
2
3
2
2
. Experimental
The commercial product, H pdc,H O, was used as a
3
2
3
2
3
2
starting material for the preparation of samples for this
investigation.
sured on a Philips PW1100 automated diffractometer,
using MoKa radiation, and a graphite monochromator,
while data of Ba(H pdc) were recorded on a Bruker Smart
Characterization of the structural and chemical changes
occurring on heating of commercial H pdc,H O up to the
3
4
CCD 1K with the same radiation.
3
2
point of decomposition of the organic framework was car-
ried out with the aid of X-ray thermodiffractometry using a
Guinier Lenne camera (heating rate 20 ꢀC h , k CuKa,
gold sample holder). Thermal analysis [1] had already iden-
tified the temperatures at which dehydration and phase
change occurred.
The crystal structures of H pdc,H O, H pdc-b and
3
2
3
Ni(Hpdc),4H O were solved and refined using JANA2000
2
ꢀ
1
[20]. In the nickel complex, the nickel atomic position
was determined from a Patterson synthesis. Non-hydrogen
atoms were located from a difference Fourier synthesis and
refined with anisotropic thermal parameters. Hydrogen
atoms were located from a final Fourier difference synthe-
sis. Structures drawings were prepared with the Diamond
package [21].
2
.1. H pdc,H O
3 2
Single crystal samples were obtained from solutions of the
commercial material, H pdc,H O, in a slightly acidic medi-
The structure of the Ba complex was solved from direct
methods; one barium location was identified in a general 2i
crystallographic site, thus generating a too short Ba–Ba
distance: the subsequent refinement of the occupancy fac-
tor converged to 0.5. The other non-hydrogen atoms were
identified and refined with anisotropic thermal parameters.
Two hydrogen atoms related to the central carbon atom of
the pyrazole ring were located from Fourier difference syn-
theses and refined isotropically. The remaining H atoms
were not found, probably in relation with the statistic dis-
order on the Ba cation, which bears residual electronic den-
sity in its surroundings; their theoretical positions were
calculated and included in the drawings for clarity, but
were not included in the last refinement cycles since they
were not significant.
3
2
um. Depending on crystallization conditions, two different
single crystal types could be prepared: crystals of parallelepi-
ped form, shown to be H pdc,H O and anhydrous H pdc
3
2
3
(
b form), were obtained by slow evaporation, respectively,
at room temperature and at 100 ꢀC in a drying oven.
2
.2. Ni(Hpdc),4H O
2
Solutions of the commercial material, H pdc,H O, react-
3
2
ed with nickel chloride solution yielding systematically a blue
precipitate which was identified as Ni(H pdc) ,4H O [18].
2
2
2
Aiming at preparing heteropolynuclear complexes the addi-
tion of NiCl , 6 H O (1.4 g, 6 mmol) to a solution of
2
2
Cu(H pdc) ,4H O (1.34 g, 3 mmol) [19] in 100 ml of 1 M
2
2
2
nitric acid led to deep blue needle-shaped crystals which
revealed to be Ni(Hpdc),4H O (0.5 g, 1.75 mmol; yield:
2
2
9% based on pdc): a TG analysis displayed a two steps evo-
lution, with dehydration occurring first between 120 and
1
4
70 ꢀC, followed by ligand decomposition between 240 and
00 ꢀC, and leaving a solid residue identified by X-ray dif-
fraction as NiO, thus corroborating the complex formula.
2
.3. Ba(H pdc) (H pdc)
2
2
3
2
Barium perchlorate (1 g, 3 mmol) dissolved in 20 ml of
hot water was added to 3,5-pyrazole dicarboxylic acid
monohydrate (0.26 g, 1.5 mmol) dissolved in 10 ml of hot
ethanol. The solution was filtered, and allowed to stand
3 2
Fig. 1. High temperature X-ray diffraction of H pdc,H O.

136
P. Roussel et al. / Journal of Molecular Structure 798 (2006) 134–140
˚
b = 9.351(5), c = 3.630(2) A; M11 = 24, F11 = 25
3
. Results and discussion
ꢀ3
(0.0133;34)). The measured density, Dobs = 1.707(1) g cm ,
3
.1. Thermal behaviour
is in good agreement with the calculated one D
= 1.71(5)
calc.
ꢀ
3
g cm , Z = 4, for anhydrous H pdc, thus labelled a. The X-
3
The X-ray diffraction pattern of H pdc,H O (Fig. 1) evi-
ray pattern of H pdc-a is shown in Table 1.
3
2
3
dences the stability of this compound between room temper-
ature and 150 ꢀC, where a structural modification occurs.
The new pattern is observed through the temperature range
A careful examination of the powder diffraction pattern
shows that the modification occurring at 240 ꢀC corre-
sponds to the disappearance of a number of the diffraction
peaks. The transformation, which occurs without weight
loss, can be considered as a polymorphic transition
a fi b. The set of diffraction lines observed at temperatures
above 240 ꢀC can be indexed completely according to the
cell dimensions obtained from the single crystals prepared
at 100 ꢀC. The structure of these crystals was solved and
1
50–240 ꢀC. The reflections of the powder pattern observed
between 150 and 240 ꢀC were indexed (diffraction data
recorded with a Siemens D5000 diffractometer) in the ortho-
rhombic system using TREOR [22,23] (a = 17.877(8),
Table 1
X-ray pattern of anhydrous H
3
pdc-a
that compound clearly identified as H pdc-b, the anhy-
3
hkl I/I
d
obs.
d
calc.
o
hkl
d
obs.
d
calc.
I/I
o
drous high temperature variety.
1
2
3
0
1
2
4
1
0
1
4
6
3
10
10
10
20
20
20
10
01
11
11
20
00
11
8.2926
6.4643
5.0322
4.6744
4.5220
4.1407
4.0332
3.5508
3.3848
3.3265
3.2297
2.9791
2.9421
8.2861
6.4615
5.0254
4.6756
4.5235
4.1430
4.0324
3.5578
3.3843
3.3258
3.2307
2.9795
2.9428
6.93
29.75
19.54
25.18
12.91
29.05
9.55
610
221
321
700
511
131
231
521
810
630
621
341
2.8362
2.7297
2.5858
2.5548
2.4596
2.3468
2.2867
2.2364
2.1742
2.1529
2.0655
1.8662
2.8389
2.7304
2.5839
2.5539
2.4578
2.3445
2.2863
2.2370
2.1734
2.1534
2.0661
1.8666
31.52
9.95
4.52
5.49
3.44
7.59
5.04
16.56
5.44
5.48
4.09
3.63
3
.2. Crystal structures
Crystallographic data and final refinement results for
H pdc,H O, H pdc-b, Ni(Hpdc),4H O and [Ba(H pdc)
2
3
2
3
2
2
(H pdc) ] are summarized in Table 2.
3 2
6.58
100.0
41.44
11.85
34.31
12.59
3.2.1. H pdc,H O and the anhydrous high temperature form,
3 2
H pdc-b of 3,5-pyrazole dicarboxylic acid
3
Projection views of H pdc,H O and the anhydrous high
3
2
temperature form, H pdc-b, based on the final atomic
3
Table 2
Crystallographic data for H
3
pdc,H
2
O, anhydrous H
3
pdc-b, Ni(Hpdc),4H
2
O and Ba(H
2
pdc)
2
(H
Ni(Hpdc),4H
10Ni
3 2
pdc)
Compound
Formula
H
3 2
pdc,H O
H
3
pdc-b
2
O
Ba(H
(C
761.78
2
pdc)
2
(H
3
pdc)
N O H ) Ba
5 2 4 4 2
2
C
5
N
2
O
5
H
6
C
5
N
2
O
4
H
4
C
5
2
N O
8
H
5
N
2
O
4
H
3
)
2
(C
Mol. wt
174.11
Monoclinic
P2 /n
14.369(3)
3.750(1)
13.415(3)
90
101.75(3)
90
707.70(3)
4
156.11
Monoclinic
P2 /n
6.06(2)
28.26(9)
3.66(1)
90
91.78(3)
90
627.07(3)
4
284.80
Triclinic
Crystal system
Space group
Triclinic
ꢀ
ꢀ
1
1
P1
P1
˚
a (A)
10.683(3)
7.663(5)
6.075(5)
78.02(2)
80.54(3)
87.18(3)
479.88(4)
2
7.614(3)
9.106(2)
9.696(2)
80.44(1)
77.24(1)
75.48(1)
630.31(3)
2
˚
b (A)
˚
c (A)
a (ꢀ)
b (ꢀ)
c (ꢀ)
˚
3
V (A )
Z
ꢀ
ꢀ
3
Dobs (g cm
)
)
1.72(5)
1.63(3)
364
1.67(4)
1.65(2)
320
2.02(4)
1.97(1)
292
1.99(2)
2.00(2)
364
3
Dcalc (g cm
F(000)
Temperature (K)
Diffractomer
h range (ꢀ)
298
298
298
298
Philips PW1100
2.33–29.47
x/2h
Philips PW1100
2.88–30.97
x/2h
Philips PW1100
2.72–29.98
x/2h
Bruker Smart CCD 1K
2.17–31.02
x
Scan type
No. of data collected
No. of unique data
hkl range
2301
1437
2332
1296
3030
2276
6502
3438
ꢀ18:18; ꢀ5:5; 0:18
0:8; ꢀ39:39; ꢀ5:5
ꢀ15:15; ꢀ10:10; 0:8
ꢀ10:10; ꢀ13:12; ꢀ13:13
R
merge
0.020
0.038
0.023
0.031
ꢀ
ꢀ
ꢀ
ꢀ
ꢀꢀ
ꢀ
ꢀ
ꢀ
Standard reflections
No. of data used (I > 3r(I))
No. of parameters
(211); (111); (102)
(031); (021); (110)
(011); (400); (112)
1798
145
NA
2773
216
852
128
813
112
Final R (obs., all)
Weighting scheme
0.0510, 0.1213
w = 1/(r (F))
0.0488, 0.0699
0.0504, 0.1007
w = 1/(r (F) + 0.00001F )
0.0445, 0.0560
0.0421, 0.0597
w = 1/(r (F))
0.0439, 0.0507
0.0485, 0.0596
w = 1/(r (F) + 0.0009F )
0.0666, 0.0701
2
2
2
2
2
2
Final R
w
(obs., all)
Residual densities
0.44, ꢀ0.45
0.41, ꢀ0.38
0.48, ꢀ0.60
1.56, ꢀ0.37

P. Roussel et al. / Journal of Molecular Structure 798 (2006) 134–140
137
coordinates and equivalent isotropic thermal parameters of
a
b
Tables 3 and 4 are presented in Figs. 2 and 3, respectively.
In H pdc,H O, the two carboxylic functions are distort-
3
2
ed from coplanarity with the aromatic ring. The plane of
C(2), O(1) and O(3) subtends an angle of 1.87ꢀ with the
aromatic ring. The plane of C(5), O(2) and O(4) subtends
c
an angle of 3.44ꢀ. H pdc molecules are hydrogen bonded
3
in pairs to their centrosymmetric equivalents. These dimers
further hydrogen bond together, head to tail, forming a
chain-like polymer parallel to the a axis (Fig. 2). Hydrogen
bonding to water molecules located between the polymeric
chains further stabilizes the solid.
O
H
N
C
In the anhydrous and high temperature form, H pdc-b,
3
the H pdc molecule displays no internal symmetry element.
3
The aromatic pyrazole central ring is planar. The C(1),
C(2), O(1) and O(2) atoms are coplanar, as are C(4),
C(5), O(3) and O(4). Both planes are twisted from coplan-
arity with the plane of the pyrazole ring (1.84ꢀ and 1.56ꢀ,
respectively). The stability of the crystal structure results
Fig. 2. Hydrogen bonds in H
3 2
pdc,H O.
Table 3
3 2
Atomic coordinates and isotropic thermal parameters for H pdc,H O
˚
2
Atom
x
y
z
U(eq)[A ]
O1
O2
O3
O4
N1
N2
C1
C2
C3
C4
C5
O5
HO3
HO4
HN2
HC4
HO51
HO52
0.55290(16)
0.08200(17)
0.50888(17)
0.10374(17)
0.27196(18)
0.36531(18)
0.3903(2)
0.4924(2)
0.2364(2)
0.3081(2)
0.1325(2)
0.6916(2)
0.571(3)
0.2673(7)
0.2047(8)
ꢀ0.0409(7)
ꢀ0.0708(8)
0.3332(8)
0.3350(8)
0.1767(9)
0.1406(10)
0.1634(9)
0.0603(10)
0.1012(10)
ꢀ0.1327(10)
ꢀ0.085(11)
ꢀ0.109(11)
0.438(9)
ꢀ0.063(9)
ꢀ0.058(12)
ꢀ0.280(14)
0.11522(19)
0.9556(2)
0.2403(2)
0.1065(2)
0.9832(2)
0.0185(2)
0.1101(3)
0.1560(3)
0.0552(3)
0.1366(3)
0.0349(3)
0.2951(2)
0.256(3)
0.0511(10)
0.0585(10)
0.0505(10)
0.0567(10)
0.0398(10)
0.0378(10)
0.0336(11)
0.0374(11)
0.0349(11)
0.0365(11)
0.0406(11)
0.0704(13)
0.0608
O
H
N
C
a
c
0.043(3)
0.401(2)
0.301(2)
0.713(3)
0.088(3)
0.983(3)
0.193(3)
0.361(4)
0.0682
0.0453
0.0440
0.0846
b
0.724(4)
0.278(4)
0.0846
Table 4
3
Atomic coordinates and isotropic thermal parameters for H pdc-b
˚
2
Atom
x
y
z
U(eq)[A ]
O1
O2
O3
O4
N1
N2
C1
C2
C3
C4
C5
HO2
HO4
HN2
HC3
0.5374(4)
0.2508(4)
0.05758(7)
0.01999(7)
0.17643(7)
0.23662(7)
0.18019(7)
0.14366(8)
0.05754(10)
0.10195(8)
0.11169(9)
0.16105(9)
0.19182(10)
0.4705(6)
0.7402(7)
1.2326(6)
1.0337(6)
0.7558(6)
0.6499(6)
0.6372(8)
0.7376(8)
0.9095(8)
0.9167(7)
1.0791(8)
0.666(9)
0.0483(8)
0.0546(9)
0.0453(8)
0.0486(9)
0.0294(7)
0.0294(8)
0.0364(10)
0.0290(8)
0.0300(9)
0.0263(9)
0.0301(9)
0.0655
ꢀ0.2971(3)
ꢀ0.0869(4)
0.2194(4)
0.3436(4)
0.3588(5)
0.2471(5)
0.0490(5)
0.0397(5)
ꢀ0.1345(5)
0.312(6)
Fig. 3. Hydrogen bonds in H
3
pdc-b.
from the three-dimensional hydrogen bonding scheme
(Fig. 3), which includes dimers of carboxylic functional
groups, (linked via COAHO), and organized in herring-
bone head to tail fashion, in a 12-membered ring utilizing
NAH donor and N acceptor moieties.
ꢀ0.0043(11)
0.2543(11)
0.1487(10)
0.0901(10)
ꢀ0.190(6)
1.125(9)
0.533(8)
1.002(7)
0.0583
0.0353
0.0359
3.2.2. Nickel complex
Good quality single crystals of Ni(Hpdc),4H O allowed
0.475(5)
2
ꢀ0.061(5)
complete structural characterization. Atomic positions of

138
P. Roussel et al. / Journal of Molecular Structure 798 (2006) 134–140
Ni(Hpdc),4H O are presented in Table 5. The structure
2
exists as a mononuclear complex in which Hpdc serves as
a bidentate ligand, contributing one nitrogen atom from
the pyrazole ring and one oxygen atom from a deprotonat-
ed carboxylic acid functional group to nickel.
a
b
The octahedral coordination sphere of Ni is completed
by four oxygen atoms, from four independent water mole-
cules. Thermal gravimetric analysis of a sample made of
crushed crystals shows that dehydration occurs in a single
step.
The Ni atom is involved in a five-membered ring with
four atoms from Hpdc: N(1) and O(1), plus C(4) and
C(2). There is no significant difference in ligand geometry
c
O
H
N
C
Ni
(
bond distances and angles) as seen in the Ni complex, in
H pdc,H O and in anhydrous H pdc-b; nevertheless,
3
2
3
deprotonation results in modification of the hydrogen
bonding pattern, making the ligand Hpdc more planar.
The crystal structure of Ni(Hpdc),4H O shows a hydro-
2
gen bonding network as seen in Fig. 4. Four water mole-
cules are involved in hydrogen bonds with the
nonchelated oxygen atoms of carboxylato groups of three
neighbouring ligands and with the pyrazole ring proton.
Bond lengths and angles, specific details of hydrogen bond-
ing and structure data for all four structures are available
from CCDC upon request.
b
c
a
2
Fig. 4. Packing in Ni(Hpdc),4H O complex.
3
.2.3. Barium complex
Single crystals of the barium complex were grown and
their structural investigation yielded an interesting feature
as described by atomic positions presented in Table 6:
one Ba is found in a general position with a 50% occupancy
factor, and two independent ligands, hereafter A and
B, complete the structure: A displays a planar pyrazole
central ring and two regular carboxylic ending groups:
Table 5
Table 6
Atomic coordinates and isotropic thermal parameters for Ni(Hpdc),4H
2
O
Atomic coordinates and isotropic thermal parameters for Ba(H
pdc)
2 2
pdc)
(
H
3
2
˚
2
Atom
x
y
z
U(eq)[A ]
˚
2
Atom
x
y
z
U(eq)[A ]
Ni1
O1
O2
O3
O4
O5
O6
O7
O8
N1
N2
C1
C2
C3
C4
C5
HO51
HO52
HO61
HO62
HO71
HO72
HO81
HO82
HN2
HC3
0.85831(5)
0.7655(2)
0.8273(2)
0.6653(3)
0.6743(3)
0.8376(3)
0.9021(3)
0.8772(2)
0.9538(3)
0.6649(3)
0.5657(3)
0.4565(3)
0.6674(3)
0.4861(3)
0.7111(4)
0.6178(3)
0.80475
0.78747
0.96328
0.85487
0.88099
0.82400
1.06807
1.08627
0.57962
0.73945(7)
0.2094(4)
0.6382(4)
1.0361(4)
0.5367(5)
0.4954(4)
0.9839(4)
0.8467(4)
0.3135(4)
0.7746(4)
0.8370(4)
0.7947(5)
1.1461(5)
0.7012(5)
0.6130(5)
0.6925(5)
0.41821
0.49010
1.02873
1.05828
0.78005
0.91958
0.57925
0.73786
0.92225
ꢀ0.22131(9)
0.0468(5)
0.1266(5)
0.3534(5)
0.4109(5)
ꢀ0.2913(5)
ꢀ0.1879(6)
ꢀ0.5695(5)
0.2562(6)
ꢀ0.1417(6)
ꢀ0.2400(6)
ꢀ0.0994(6)
0.1725(7)
0.1031(7)
0.2164(7)
0.0686(6)
ꢀ0.17793
ꢀ0.37713
ꢀ0.25803
ꢀ0.12825
ꢀ0.66278
ꢀ0.60761
ꢀ0.23997
ꢀ0.22845
ꢀ0.39196
0.25304
0.0163(1)
0.0226(8)
0.0215(8)
0.0342(10)
0.0379(10)
0.0249(8)
0.0388(10)
0.0229(8)
0.0289(10)
0.0203(9)
0.0216(9)
0.0191(10)
0.0189(10)
0.0205(10)
0.0219(11)
0.0180(10)
0.0299
0.0299
0.0463
0.0463
0.0275
0.0275
0.0347
0.0347
0.0260
Ba1
O1a
O1b
O2a
O2b
O3a
O3b
O4a
O4b
N1a
N1b
N2a
N2b
C1a
C1b
C2a
C2b
C3a
C3b
C4a
C4b
C5a
C5b
H1a
H1b
0.45450(5)
0.5439(4)
0.3216(4)
0.7458(5)
0.0756(4)
0.6795(4)
0.1511(4)
0.8550(5)
ꢀ0.1052(4)
0.5694(4)
0.2603(4)
0.5413(4)
0.2983(4)
0.6456(5)
0.1808(5)
0.7443(5)
0.0623(5)
0.6914(5)
0.1188(4)
0.6402(5)
0.2003(5)
0.7424(5)
0.0507(5)
0.835(5)
ꢀ0.00129(4)
0.7418(3)
ꢀ0.7247(3)
0.7306(3)
ꢀ0.7032(3)
0.0188(3)
0.0034(3)
0.1348(3)
ꢀ0.0703(3)
0.2914(3)
ꢀ0.2655(3)
0.4359(3)
ꢀ0.4123(3)
0.5092(4)
ꢀ0.4823(4)
0.4101(4)
ꢀ0.3777(4)
0.2738(4)
ꢀ0.2417(3)
0.6715(4)
ꢀ0.6483(4)
0.1297(4)
ꢀ0.0909(3)
0.424(4)
0.37716(4)
0.2220(3)
0.4891(3)
0.0143(3)
0.6674(3)
0.0711(3)
0.6205(3)
0.0253(1)
0.0420(9)
0.0379(8)
0.0512(10)
0.0383(8)
0.0483(10)
0.0432(9)
0.0535(10)
0.0382(8)
0.0323(9)
0.0310(8)
0.0318(8)
0.0309(8)
0.0292(9)
0.0275(9)
0.0315(10)
0.0279(9)
0.0294(9)
0.0258(8)
0.0308(9)
0.0271(9)
0.0320(10)
0.0278(9)
0.025(9)
ꢀ0.1082(3)
0.7382(3)
0.1984(3)
0.4897(3)
0.2257(3)
0.4683(3)
0.1204(4)
0.5659(4)
0.0221(4)
0.6526(4)
0.0757(4)
0.6011(3)
0.1243(4)
0.5690(3)
0.0136(4)
0.6565(3)
ꢀ0.058(4)
0.740(4)
0.43269
0.66151
0.0247
ꢀ0.035(6)
ꢀ0.397(4)
0.032(10)

P. Roussel et al. / Journal of Molecular Structure 798 (2006) 134–140
139
˚
˚
O1b = 1.21 A; C4b–O2b = 1.31 A; the second one showing
c
a
O3a
C5a
˚
two nearly identical bond lengths: C5b–O3b = 1.260 A;
C5b–O4b = 1.266 A. Thus A and B can be identified as
H pdc) and (H pdc), respectively, and the barium complex
can be given the composition Ba(H pdc) (H pdc) , in
good agreement with the T.G. analysis.
Each one of the disordered Ba position is 9th coordinated
to 7 ligands: firstly through a bonding scheme implying 4
oxygen and two nitrogen atoms from 4 ligands organized
in a planar, slightly distorted hexagonal ring: one A and
one B entities are involved as bidendate ligands via one ter-
minal O atom and one nitrogen of their central ring, while
the two others (one A and one B) are acting as monodendate
ligands, thus developing a planar, polymeric type ribbon
[Ba0.5(H pdc)(H pdc)] along the [010] direction. The Ba
th fold coordination is completed on one side of the mean
plane by two atoms O1b and O3b from carboxylic groups
belonging to two B-type H pdc, from the equivalent centro-
symmetric ribbon, and finally on the opposite side of the
mean plane, by a single O4b atom from a B-type H pdc, as
the apex of a slightly distorted hexagonal pyramid on this
side. The centrosymmetric equivalent Ba position, with a
b
˚
O4a
C3a
C2a
(
3
2
N1a
2
2
3
2
A
H1a
N2a
C1a
C4a
O1a
B
O2a
O1b
O4b
Ba1
O3b
O1b
O2b
C4b
A
2
3
1
C1b
N2b
9
C2b
H1b
B
2
C3b
N1b
C5b
O3b
2
O4b
2 3
Fig. 5. Ba coordination scheme in [Ba0.5(H pdc)(H pdc)].
50% occupancy, displays an equivalent centrosymmetric
coordination scheme, obtained through the center of
symmetry located midway between the two Ba disordered
atomic positions. The structure is organized in double
˚
˚
(
C4a–O1a = 1.22 A;
C4a–O2a = 1.31 A
and
C5a–
˚
˚
O3a = 1.23 A; C5a–O4a = 1.30 A) while in B only one end-
ing carboxylic group displays such a geometry: C4b–
[Ba0.5(H
2
pdc)(H
3
pdc)]
1
planar ribbons stacked parallel to
a
c
C
H
O
Ba
N
2 2 3 2 1
Fig. 6. Stacking of [Ba(H pdc) (H pdc) ] layers parallel to (001).

140
P. Roussel et al. / Journal of Molecular Structure 798 (2006) 134–140
(
101), building [Ba(H pdc) (H pdc) ] entities linked to each
[2] D.W. Capone, D.G. Hinks, J.D. Jorgensen, K. Zhang, Appl. Phys.
Lett. 50 (1987) 543.
2
2
3
2
others via the Ba coordination scheme (i.e., through the
Ba–O4b link described previously) along the a axis of
the unit cell, and designing an overall stacking of
Ba(H pdc) (H pdc) layers parallel to (001) (Figs. 5 and 6).
[
[
3] F. Mahloozchi, F.R. Sale, Ceramics Int. 14 (4) (1988) 229.
4] K. Bernhard, G. Gritzner, X.Z. Wang, D. Bauerie, J. Solid State
Chem. 86 (1990) 293.
2
2
3
2
[5] C.Y. Shei, R.S. Liu, C.T. Chang, P.T. Wu, Inorg. Chem. 29 (1990)
117.
3
[
6] J. Fransaer, J.R. Roos, L. Delaey, O. Van Der Biest, O. Arkens,
J.P. Celis, J. Appl. Phys. 65 (1989) 3277.
4
. Conclusion
H pdc is a versatile ligand that can be useful in metal
[7] A. Pebler, R.G. Charles, Mater. Res. Bull. 24 (1989) 1069.
3
[8] A. Patnak, D.K. Mukhopadhyay, P. Pramanik, Mater. Res. Bull. 27
(1992) 155.
sequestering processes. H pdc is also potentially a tetrache-
3
lating ligand; the rigidity of the NAN bonding, and the
positioning of the two carboxyl groups may allow simulta-
neous complexation to two metal atoms leading to polynu-
clear complexes. The use of pdc complexes as corrosion
inhibiting agent and as anticorrosive coating agents is
under investigation.
[9] R.D. Gillard, S.H. Laurie, F.S. Phens, J. Chem. Soc. (A) (1968)
2
588.
[
10] S. Sobanska, J.P. Wignacourt, P. Conflant, M. Drache, M. Lagren e´ e,
E.M. Holt, New J. Chem. 23 (4) (1999) 393.
11] M. Wenkin, R. Touillaux, M. Devillers, New J. Chem. 22 (1998)
973.
[12] M.A.R. Dakers, M.N.S. Hill, J.C. Lockhart, D.J. Rushton, J. Chem.
Dalton Trans. (1994) 209.
[
The crystallographic data have been deposited and can
be obtained through the CCDC data bank, under the refer-
ence CCDC 286900, CCDC 286901, CCDC 286902 and
CCDC 286903 for Ba(H pdc) (H pdc) , H pdc-b,
[
13] B. Mernari, F. Abraham, M. Lagren e´ e, Adv. Mater. Res. 1–2 (1994)
24.
3
[
14] P. Fung, R. Clerac, C.E. Anson, C. Coulon, A. Powell, Inorg. Chem.
42 (2003) 3492.
2
2
3
2
3
[15] F. Bentiss, P. Roussel, M. Drache, P. Conflant, M. Lagrene
´
e,
H pdc,H O and Ni(Hpdc),4H O, respectively.
3
2
2
J.P. Wignacourt, J. Mol. Struct. 707 (2004) 63.
[
[
16] F. Bentiss, M. Traisnel, L. Gengembre, M. Lagren e´ e, Appl. Surf. Sci.
52 (1999) 237.
17] M. Lebrini, M. Lagren e´ e, H. Vezin, L. Gengembre, F. Bentiss,
Corros. Sci. 47 (2) (2005) 485.
Acknowledgments
1
The ‘‘Fonds Europ e´ en de D e´ veloppement R e´ gional
FEDER)’’, ‘‘CNRS’’, ‘‘R e´ gion Nord Pas-de-Calais’’ and
`
(
[18] S. Nadir, These de Doctorat, Lille, France (1996).
[
19] B. Mernari, F. Abraham, M. Lagren e` e, Adv. Mater. Res. 1–2 (1994)
17.
‘
‘Minist e` re de l’Education Nationale de l’Enseignement
3
Sup e´ rieur et de la Recherche’’ are acknowledged for fun-
dings of X-ray diffractometers.
[
20] V. Petricek, M. Dusek, L. Palatinus. JANA2000, Institute of Physic,
Academy Of Sciences of the Czech Republic, Praha, Czech Republic,
2
005.
References
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[
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