One-dimensional silver(I) 5,5-diethylbarbiturato coordination polymers with N-piperidineethanol and 1,3-bis(4-piperidyl)propane: Syntheses, crystal structures, spectroscopic and thermal properties

Article abstract of DOI:10.1016/j.poly.2009.10.029

Two new coordination polymers, [Ag₂(barb)(pipet)]_n (1) and {Na₃[Ag₂(barb)₂](pippr)·2H₂O}_n (2) (where H₂barb, pipet and Hpippr are 5,5-diethylbarbituric acid, N-piperidineethanol and 1,3-bis(4-piperidyl)propane, respectively) have been synthesized and characterized by elemental analysis, IR, thermal analysis and X-ray single-crystal diffraction techniques. Silver(I) ions in complexes 1 and 2 are bridged by barb dianions, leading to one-dimensional coordination polymers. In 1, the barb ligand acts as a tetradentate bridging ligand, while in 2 as a bidendate bridging ligand. The pipet ligand behaves as a bidentate chelating donor, whereas the pippr anion is not involved in coordination and remains as a counter-ion. The one-dimensional chains of 1 and 2 are further extended into supramolecular networks. Spectral and thermal analysis data for 1 and 2 are in agreement with the crystal structures.

Full text of DOI:10.1016/j.poly.2009.10.029

Polyhedron 29 (2010) 920–924
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
One-dimensional silver(I) 5,5-diethylbarbiturato coordination polymers
with N-piperidineethanol and 1,3-bis(4-piperidyl)propane: Syntheses,
crystal structures, spectroscopic and thermal properties
Veysel T. Yilmaz , Eda Soyer , Orhan Büyükgüngör b
a,*
a
a
Department of Chemistry, Faculty of Arts and Sciences, Uludag University, 16059 Bursa, Turkey
Department of Physics, Faculty of Arts and Sciences, Ondokuz Mayis University, 55139 Samsun, Turkey
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Two new coordination polymers, [Ag (barb)(pipet)]n (1) and {Na [Ag (barb) ](pippr)Á2H O} (2) (where
2
3
2
2
2
n
Received 1 October 2009
Accepted 29 October 2009
Available online 3 November 2009
2
H barb, pipet and Hpippr are 5,5-diethylbarbituric acid, N-piperidineethanol and 1,3-bis(4-piperidyl)pro-
pane, respectively) have been synthesized and characterized by elemental analysis, IR, thermal analysis
and X-ray single-crystal diffraction techniques. Silver(I) ions in complexes 1 and 2 are bridged by barb
dianions, leading to one-dimensional coordination polymers. In 1, the barb ligand acts as a tetradentate
bridging ligand, while in 2 as a bidendate bridging ligand. The pipet ligand behaves as a bidentate che-
lating donor, whereas the pippr anion is not involved in coordination and remains as a counter-ion.
The one-dimensional chains of 1 and 2 are further extended into supramolecular networks. Spectral
and thermal analysis data for 1 and 2 are in agreement with the crystal structures.
Keywords:
5
,5-Diethylbarbiturate
N-Piperidineethanol
,3-Bis(4-piperidyl)propane
1
Coordination polymers
Silver(I)
Ó 2009 Elsevier Ltd. All rights reserved.
1
. Introduction
Barbituric acid is not pharmacologically active and its deriva-
interest in the coordination chemistry of 5,5-diethylbarbiturate, in
this paper, we report the synthesis and characterization of two
coordination polymers of this ligand with other co-ligands,
tives possess very interesting pharmaceutical properties and con-
stitute an important group of nervous system depressants and
sedative-hypnotics. The coordination chemistry of barbiturates
has been developed, due to their use in the detection and identifi-
cation of these drugs as metal complexes [1,2]. The presence of
several potential donor atoms such as two amine nitrogen and
three carbonyl oxygen atoms makes barbituric acids polyfunction-
al ligands. They readily deprotonate in solutions, forming corre-
sponding anions, which usually coordinate in a monodentate
fashion through the negatively charged N atoms [3–7], but in some
cases, the carbonyl O atoms [8,9] and the C atoms [9,10] are in-
volved in coordination depending on the type of metal ions.
We prepared a number of metal complexes of 5,5-diethylbarbi-
N-piperidineethanol (pipet) and 1,3-bis(4-piperidyl)propane
2 n 3 2 2
(Hpippr), namely [Ag (barb)(pipet)] (1) and {Na [Ag (barb) ](pip-
pr)Á2H
2
O} (2). Thermal decomposition behavior of complexes 1
and 2 is studied, and their molecular and structural properties
n
were established by single-crystal X-ray diffraction studies.
O
O
OH
HN
NH
N
HN
NH
O
H
2
barb
pipet
Hpippr
2
turatic acid (barbH ), also known as barbital or veronal [11–18].
We found that in these complexes, this ligand exist in the form
of mono- or dianion, and displays different coordination modes
such as monodentate (N), bidentate chelating (N, O), bidentate
bridging (N, O) and tridentate bridging (N, O, O). Moreover, simul-
taneous coordination modes (one barb is N-coordinated and the
second barb bidentate or one barb is N-coordinated and the second
barb is a counter-ion) are also observed. As part of our continuing
2
. Experimental
.1. Materials and measurements
All commercial reagents were purchased and used as supplied.
2
Elemental analyses for C, H, and N were performed using a Costech
elemental analyzer. IR spectra were recorded with a Thermo Nico-
let 6700 FT-IR spectrophotometer with samples as KBr pellets in
*
Corresponding author.
E-mail address: vtyilmaz@uludag.edu.tr (V.T. Yilmaz).
0
277-5387/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2009.10.029

V.T. Yilmaz et al. / Polyhedron 29 (2010) 920–924
921
À1
the 4000–400 cm range. Thermal analysis curves (TGA and DTA)
were obtained using a Seiko Exstar 6200 thermal analyzer in a dy-
Mo Ka radiation (k = 0.71073). The structures were solved by direct
2
methods and refined on F with the SHELX-97 program [19]. All non-
hydrogen atoms were found from the difference Fourier map and
refined anisotropically. All C hydrogen atoms were included using
a riding model. The H atoms of the OH group of pipet in 1 and
water molecules in 2 were refined freely. The details of data collec-
tion, refinement and crystallographic data are summarized in
Table 1.
À1
namic air atmosphere with a heating rate of 10 °C min and a
sample size of ca. 10 mg.
2
.2. Synthesis of the silver(I) complexes
A 10 ml aqueous solution of Na(barbH) (5,5-diethylbarbituric
acid sodium salt) (0.21 g, 1 mmol) was added to a 10 ml aqueous
solution of AgNO (0.17 g, 21 mmol) with stirring at room temper-
3
ature. The solution immediately became milky. The addition of N-
piperidineethanol (pipet) (0.13 ml) together with a mixture of 2-
propanol (PrOH) and acetonitrile (MeCN) (1:1) (10 mL) to the
milky suspension resulted in a clear solution. The resulting solu-
tion was allowed to stand in darkness at room temperature and
3. Results and discussion
3.1. Synthesis and characterization
Complexes 1 and 2 were synthesized by the direct reaction of
colorless prisms of Ag
2
(barb)(pipet)]
days. Yield 62%. M.p. 142–145 °C (decomp). Anal. Calc. for
: C, 34.2; H, 4.8; N, 8.0. Found: C, 34.4; H, 4.6; N,
n
(1) were obtained after
3
Na(Hbarb) with AgNO in the aqueous solution in the presence of
3
C
8
2
1
7
the pipet and Hpippr ligands. They were obtained in moderate
yields (over 60%). Both complexes are air stable and soluble in a
mixture of water, EtOH and MeCN (1:1:1).
15 2 3 4
H25Ag N O
À1
.2%. IR (cm ): 3408sb, 3179mb, 3052vw, 2974w, 2934vw,
876w, 1695s, 1671vs, 1634s, 1585s, 1556vs, 1458sh, 1422vs,
381vs, 1344m, 1311vs, 1262s, 1181vw, 1033vw, 939w, 854m,
92w, 764w, 694w, 653vw, 551w, 445w.
Selected FT-IR spectroscopic data are listed in Table 2. The IR spec-
tra of both complexes display strong and broad absorption bands at
À1
around 3400 cm , due to the OH group vibrations. The absorption
À1
{
Na
way, replacing pipet with Hpippr. Yield 65%. M.p. 150 °C (decomp).
Anal. Calc. for C29 Na : C, 38.8; H, 5.8; N, 9.4. Found: C,
3
[Ag
2
(barb)
2
](pippr)Á2H
2
O}
n
(2) was synthesized in a similar
bands of the amine groups appear at 3179 cm
in 1, and
À1
3260 cm
in 2. Medium and weak bands between 2848 and
3052 cm correspond to the CH stretching vibrations. Since the
barbH2 ligand contains three carbonyl groups, the coordination of this
À1
H
29Ag
2
N
6
3
O
8
À1
3
2
1
8
8.7 H, 5.6; N, 9.5%. IR (cm ): 3403sb, 3260m, 2966sh, 2917s,
848s, 1708m, 1671s, 1630s, 1601vs, 1548vs, 1446s, 1418s,
360s, 1311vs, 1279m, 1181vw, 1156vw, 1103w, 1033w, 952w,
58w, 805w, 756w, 633vw, 613vw, 539vw, 478vw.
ligand is easily deduced from the IR spectra. Complexes 1 and 2 pres-
À1
ent three absorption bands in the frequency range 1610–1708 cm
,
which are indicative of the unequal coordination of the carbonyl
À1
groups. The bands below 1600 cm are due to the CC stretching,
2.3. X-ray crystallography
CH deformation and CN stretching vibrations as given in Table 2.
The intensity data of the complexes 1 and 2 were collected
using a STOE IPDS 2 diffractometer with graphite-monochromated
3.2. Crystal structures
A view of the coordination environment around silver(I) in 1 is
Table 1
Crystallographic data and structure refinement for 1 and 2.
shown in Fig. 1a, together with the atom numbering scheme. Se-
lected bond distances and angles are listed in Table 3. Single X-
ray crystal analysis reveals that the complex crystallizes in triclinic
1
2
Formula
C
15
2
H25Ag N
3
O
4
C
29
H
29Ag
2
N
6
3
Na O
8
ꢀ
space group P1 and is a one-dimensional neutral metallopolymer.
Molecular weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
527.12
298(2)
0.71073
triclinic
P1ꢀ
894.45
296(2)
0.71073 Å
monoclinic
P2 /c
In 1, the barb ligands are in the form of dianions, acting as a tetra-
dentate bridging ligand between four silver(I) centers through two
negatively charged N and two carbonyl O atoms, forming centro-
symmetric tetranuclear units. To the best of our knowledge, the
tetradentate coordination mode of the barb dianion was observed
for the first time in this complex. The tetranuclear units are linked
by the N(barb)–Ag–N(barb) bridges, leading to a linear polymeric
chain propagating along the c axis (Fig. 1b). The present coordina-
tion polymer has three non-equivalent silver(I) ions. The coordina-
1
7.3494(5)
14.4356(12)
15.1833(7)
22.3716(19)
90
127.298(5)
90
3900.6(6)
4
1.523
b (Å)
c (Å)
11.3548(8)
11.3832(7)
77.624(5)
76.630(5)
88.814(6)
902.30(11)
2
a
(°)
b (°)
(°)
c
3
tion geometry around the Ag1 atom is
tetrahedron with an AgNO chromophore, whereas Ag2 and Ag3
atoms have distorted linear coordination geometry of AgN . The
a highly distorted
Volume (Å )
Z
Calculated density (g/cm )
3
3
1.940
2.194
2
À1
l
(mm
)
1.088
1824
tetranuclear unit exhibits Ag–Ag interactions with a AgÁÁÁAg sepa-
F(0 0 0)
Crystal size (mm )
h Range (°)
524
ration of 2.9283(3) Å, being much smaller than twice the van der
3
0.58 Â 0.24 Â 0.07 0.50 Â 0.26 Â 0.03
2.33–26.50
À9/9; À14/14;
À14/14
1.76–27.00
Table 2
Index ranges (h, k, l)
À17/18; À19/19;
a
Selected FT-IR spectral data for 1 and 2.
À28/28
Reflections collected
12 574
34 104
Assignment
1
2
Independent reflections
3739
8518 [Rint = 0.1134]
m
m
m
m
m
(OH)
(NH)
(CH)
(CO)
(CC)
3408sb
3179mb
3403sb
3260m
[Rint = 0.0489]
Reflections observed (>2
Absorption correction
Data/parameters
r
)
3475
4539
3052vw, 2974w, 2934vw, 2876w
1695s, 1671vs, 1634s
1585s, 1556vs
1422vs, 1381vs, 1344m, 1311vs
1262s
2966sh, 2917s, 2848s
1708m, 1671s, 1630s
1601vs, 1548vs
1418s, 1360s, 1311vs
1279m
numerical
3739/223
1.156
numerical
8518/413
0.988
2
Goodness-of-fit (GOF) on F
Final R indices [I > 2 (I)]
d(CH)
r
R
1
= 0.0294
wR = 0.0705
0.611 and À1.102 1.309 and À1.928
R
1
= 0.0672
m(CN)
2
wR = 0.1436
2
Largest differences in peak and
b = broad; m = medium; w = weak; vw = very weak; vs = very strong; s = strong.
À3
hole (e Å
)
a
À1
Frequencies in cm
.

9
22
V.T. Yilmaz et al. / Polyhedron 29 (2010) 920–924
Fig. 1. (a) Coordination environment around silver(I) ions in 1, (C–H hydrogen atoms were omitted for clarity). (b) A perspective view of the one-dimensional chain in 1.
compared to Ag–N(barb) bond distances. On the other hand, the pi-
pet ligand is neutral and behaves as a bidentate chelating ligand
via the N atom and hydroxyl O atoms. The Ag–N(pipet) and Ag–
O(pipet) bond distances are comparable to those found in [Ag(sa-
c)(hepip)] [20].
The pyrimidine ring of the barb ligand is essentially planar and
the three carbonyl groups are not significantly displaced from the
mean planes of their attached pyrimidine ring, whereas the piper-
idine moiety of pipet exhibits a chair conformation. A packing dia-
gram of complex 1 is shown in Fig. S1. The individual chains show
a two-dimensional array along the ac plane.
Table 3
Selected bond and hydrogen bonding geometry for 1.
Bonds lengths (Å) and angles (°)
Ag1–N1
Ag2–N2
Ag3–N3
Ag1–O1
Ag1–O2
Ag1–O3
Ag1–Ag2
2.321(3)
2.085(2)
2.090(2)
2.546(3)
2.459(3)
2.262(2)
2.9283(3)
N1–Ag1–O1
N1–Ag1–O2
N1–Ag1–O3
O1–Ag1–O2
O1–Ag1–O2
O2–Ag1–O3
74.92(12)
95.15(11)
133.69(11)
81.99(9)
120.74(9)
128.36(10)
Hydrogen bonds
D–HÁÁÁA
O1–H1ÁÁÁO4
D–H (Å)
0.82(6)
HÁÁÁA (Å)
2.09(4)
DÁÁÁA (Å)
2.835(4)
D–HÁÁÁA (°)
149(6)
The asymmetric unit of complex 2 is shown in Fig. 2a and se-
lected bond length and angles are listed in Table 4. Complex 1 con-
sist of a [Ag (barb) ] , three Na and a deprotonated pippr ions,
2 2
2À
+
and two lattice water molecules. As shown in Fig. 2a and b, the
complex is a coordination polymer, in which the barb dianions
bridge the silver(I) cations giving rise to a one-dimensional zig-
zag chain. All silver(I) ions are linearly coordinated by both nega-
tively charged N atoms of the barb ions and all Ag–N bond dis-
tances are almost identical, being slightly longer than those
found in complex 1. The pippr monoanion is not involved in coor-
dination with silver(I) and remains a counter-ion.
The complex contains three different sodium(I) ions. The barb
anions also act as a bridge between two sodium(I) cations (Na1
and Na2) through their carbonyl groups, while the Na3 atom are
linearly coordinated by the deprotonated N atom of pippr and
Waals radius of silver (3.44 Å), indicating a strong interaction be-
tween the silver(I) ions.
The Ag–N(barb) bond distances are 2.085(2) and 2.090(2) Å are
practically similar to those found in [Ag(barb)(
somewhat longer than those found Na [Ag
[Ag -barb) ][Ag -en) O} [12], while they are signifi-
]Á5H
cantly shorter than the corresponding distances found in [Ag(-
barb)(bpy)] [15], [Ag(barb)(pypr)] [15], [Ag(barb)(pym)]ÁH O [18]
O [18]. Again, the coordination of the
l-bpe)]
n
[12], but
3
3
(l-barb) ]
6
[12],
{
2
(l
2
2
(l
2
2
n
2
and [Ag(barb)(dmpy)]Á1.5H
2
barb ligand to silver(I) ion via the carbonyl O atoms was observed
for the first time. The Ag–O(barb) bond distances are much longer,

V.T. Yilmaz et al. / Polyhedron 29 (2010) 920–924
923
Fig. 2. (a) Coordination environment around silver(I) and sodium(I) ions in 2, (C–H hydrogen atoms were omitted for clarity). (b) A fragment of the one-dimensional chain
in 2.
Table 4
angle between the mean planes of the pyrimidine rings of
two neighboring barb ligands is 15.93(5)°. The polymeric
chains run parallel to the c axis and are further cross-linked
by the OW–H–O(barb) type intermolecular hydrogen bonds,
Selected bond and hydrogen bonding geometry for 2.
Bonds lengths (Å) and angles (°)
Ag1–N2
Ag1–N4
Ag2–N1
Ag2–N3
Na1–O1
Na2–O3
2.110(5)
2.104(5)
2.098(6)
2.097(6)
2.751(9)
2.764(8)
2.906(8)
2.792(9)
2.806(10)
2.903(9)
2.719(13)
N2–Ag1–N4i
N1–Ag1–N3
N6–Na3–O2W
O1–Na1–O6
O3–Na2–O4
O3–Na2–O2W
O4–Na2–O2W
175.6(2
177.4(2)
111.9(3)
100.0(3)
100.2(3)
127.7(3)
126.3(3)
i
leading to
(Fig. S2).
a
three-dimensional supramolecular network
3.3. Thermal decomposition
Na2–O4
Na1–O6
Thermal decomposition and stability of both complexes were
Na2–O2W
Na3–O2W
Na3–N6
studied by TGA and DTA at the atmosphere of air in the tempera-
ture range 25–900 °C. Thermal curves are illustrated in Fig. 3. Com-
plex 1 is stable up to 145 °C and begins to release the pipet ligand
between 145 and 212 °C. The mass loss of 23.7% in this stage is
consistent with the calculated value of 24.5%. Then, the highly exo-
thermic decomposition of the barb moiety occurs in the tempera-
ture range 215–448 °C to yield the metallic silver. Complex 2
dehydrates between 40 and 106 °C with a mass loss of 5.5% (calcd.
4.0%) and dehydrated complex is stable up to the 149 °C. Then, a
3.2% mass loss was observed between 149 and 185 °C, followed
by a continuous mass loss related to decomposition of both pippr
and barb ligands in the range of 149–467. The endothermic DTA
peak at centered at 210 °C correspond to the elimination of the ae-
pip ligand, while the violently exothermic peak at 369 °C charac-
terizes the decomposition of the barb ligands. The decomposition
ends at 467 °C to give presumably a mixture of sodium and silver
oxides.
Hydrogen bondsa
D–HÁÁÁA
D–H (Å)
HÁÁÁA (Å)
DÁÁÁA (Å)
D–HÁÁÁA (°)
142(12)
166(8)
124(12)
158(13)
148(10)
O1W–H12W–N6
0.82(13)
0.86(7)
0.83(7)
0.83(8)
0.84(9)
2.02(9)
1.95(8)
2.15(11)
1.99(6)
2.01(7)
2.717(15)
2.796(8)
2.701(10)
2.784(9)
2.760(12)
i
N5–H5ÁÁÁO2
ii
O1W–H11W–O2
O2W–H21W–O5
iii
iv
O2W–H22W–O1W
a
Symmetry codes: (i) x À 1, Ày + 1/2, z À 1/2; (ii) x, Ày + 1/2, z À 1/2; (iii) Àx + 1,
Ày + 1, Àz; (iv) Àx + 2, y + 1/2, Àz + 1/2.
one of the lattice water O atom, which acts as a bridge between the
Na2 and Na3 atoms (Fig. 2a). The Na–O(barb) bond distances range
from 2.751(9) to 2.906(8) Å, being significantly longer than those
reported for Na [Ag (barb) ] [12] and Na(Hbarb) [21].
3 3 6
Both piperidine moieties of pippr show a chair conforma-
tion. The barb ligands are essentially planar and the dihedral

9
24
V.T. Yilmaz et al. / Polyhedron 29 (2010) 920–924
Appendix A. Supplementary data
CCDC 748034 and 748035 contain the supplementary crystallo-
graphic data for 1 and 2. These data can be obtained free of charge
via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cam-
bridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: depos-
it@ccdc.cam.ac.uk. Supplementary data associated with this
article can be found, in the online version, at doi:10.1016/
j.poly.2009.10.029.
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4
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In summary, two new coordination polymers, [Ag
pet)] (1) and {Na [Ag (barb) O} (2) were synthesized
](pippr)Á2H
and structurally characterized. Although in the metal complexes,
,5-diethylbarbituric acid (H barb) usually exists in the Hbarb
monoanion, the polymeric structures were achieved by the bridg-
ing of the barb dianion. In addition, a new coordination mode (tet-
radentate) of the barb dianion is observed.
2
(barb)(pi-
n
3
2
2
2
n
[16] V.T. Yilmaz, M.S. Aksoy, O. Sahin, Inorg. Chim. Acta 362 (2009) 3703.
[
[
[
17] M.S. Aksoy, V.T. Yilmaz, O. Buyukgungor, J. Coord. Chem. 62 (2009) 3250.
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5
2
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Acknowledgements
We thank the research fund of Uludag University for the finan-
cial support given to the research project (F-2008/56).