Synthesis, IR spectra, thermal analysis and crystal structure of a one-dimensional coordination polymer containing both three- and four-coordinate silver(I) centers bridged by both saccharinate and N-(2-hydroxyethyl)piperazine ligands

Article abstract of DOI:10.1016/j.molstruc.2004.09.023

A novel [Ag₂(μ-sac)₂(μ-hep)₂] _n [sac=saccharinate and hep={N-(2-hydroxyethyl)piperazine}] was synthesized and characterized. [Ag₂(μ-sac)₂(μ-hep) ₂]_n consists of dimeric [Ag₂(μ-sac) ₂] units bridged by the hep ligands, resulting a one-dimensional coordination polymer. [Ag₂(μ-sac)₂(μ-hep) ₂]_n contains two different silver(I) centers with a Ag-Ag separation of 3.492(2) A?. One of the silver(I) ion is trigonal planar to the imino N and carbonyl O atoms of two sac ligands and one of the N atom of hep, while the other silver(I) ion is tetrahedrally coordinated by the N and carbonyl O atoms of two sac ligands and the N and O chelating hep ligand.

Full text of DOI:10.1016/j.molstruc.2004.09.023

Journal of Molecular Structure 734 (2005) 191–195
www.elsevier.com/locate/molstruc
Synthesis, IR spectra, thermal analysis and crystal structure of a
one-dimensional coordination polymer containing both three- and
four-coordinate silver(I) centers bridged by both saccharinate
and N-(2-hydroxyethyl)piperazine ligands
a
Sevim Hamamci , Veysel T. Yilmaz , William T.A. Harrison
a,
b
*
aDepartment of Chemistry, Faculty of Arts and Sciences, Ondokuz Mayis University, 55139 Kurupelit, Samsun, Turkey
bDepartment of Chemistry, University of Aberdeen, Meston Walk, Aberdeen AB24 3UE, Scotland, UK
Received 2 September 2004; accepted 29 September 2004
Available online 10 November 2004
Abstract
A novel [Ag2(m-sac)2(m-hep)2]n [sacZsaccharinate and hepZ{N-(2-hydroxyethyl)piperazine}] was synthesized and characterized.
[Ag2(m-sac)2(m-hep)2]n consists of dimeric [Ag2(m-sac)2] units bridged by the hep ligands, resulting a one-dimensional coordination polymer.
˚
[Ag2(m-sac)2(m-hep)2]n contains two different silver(I) centers with a Ag–Ag separation of 3.492(2) A. One of the silver(I) ion is trigonal
planar to the imino N and carbonyl O atoms of two sac ligands and one of the N atom of hep, while the other silver(I) ion is tetrahedrally
coordinated by the N and carbonyl O atoms of two sac ligands and the N and O chelating hep ligand.
q 2004 Elsevier B.V. All rights reserved.
Keywords: Silver(I); Saccharin; N-(2-hydroxyethyl)piperazine; One-dimensional polymer
1. Introduction
characterized by Weber et al. [7], and Baran and Wagner
[8] studied its vibrational spectra. Recently, we reported the
crystal structure, spectroscopic and thermal analyses of
Na[Ag(sac)2] [9] and as a part of our current research on
the syntheses and characterizations of mixed-ligand metal
complexes of sac with ligands containing hydroxyalkyl
groups, in this communication, we report a novel
one-dimensional silver(I) coordination polymer, [Ag2(m-
sac)2(m-hep)2]n, which is also the first example
Saccharin (C7H5NO3S; also named o-benzosulfimide) is
currently the most widely used non-caloric artificial sweet-
ener in the world and is commercially available as water
soluble alkali salts. Although no metal complexes of neutral,
molecular saccharin are known, the corresponding deproto-
nated saccharinate anion [sacZ(C7H4NO3S)K] behaves as a
versatile, polyfunctional, ligand due to the presence of the
negatively charged imino nitrogen atom and the carbonyl and
sulfonyl oxygen atoms and forms a number of complexes
with different metal ions rather easily. The most common
coordination mode of sac is ligation through the negatively
charged nitrogen atom, typically observed in the aquabis
(saccharinato) complexes of transition metals [1–6].
of
{N-(2-hydroxyethyl)piperazine}].
a
mixed-ligand silver(I)–sac complex [hepZ
2. Experimental
Silver(I) complexes of sac is very rare and the first
silver(I) complex of sac, [Ag(sac)], was structurally
2.1. Materials and instrumentation
All chemical were purchased commercially and used
without further purification.
* Corresponding author. Tel.: C90 362 457 6020; fax: C90 362 457
6081.
IR spectra were obtained with a Shimadzu FTIR-8900
spectrophotometer (KBr pellets) in the 4000–400 cmK1
E-mail address: vtyilmaz@omu.edu.tr (V.T. Yilmaz).
0022-2860/$ - see front matter q 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2004.09.023

192
S. Hamamci et al. / Journal of Molecular Structure 734 (2005) 191–195
Table 2
Selected IR spectral dataa for [Ag2(m-sac)2(m-hep)2]n
range. The elemental analyses for C, H, N and S were
performed using a Carlo Erba 1106 microanalyser. Thermal
analysis curves (TG and DTA) were obtained using a
Rigaku TG8110 thermal analyzer in a static atmosphere of
air. A sample size of about 10 mg was used.
Assignment
[Ag2(m-sac)2(m- Na[Ag(sac)2]
hep)2]n
[Ag(sac)]
nOH)
n(NH)
3435 s, br
–
–
–
3210m, br
n(CH)
nCO)
2936–2822vw
1622vs
3080w, 3020vw 3144sh, 3087w,
2.2. Synthesis of [Ag2(m-sac)2(m-hep)2]n
1650vs, 1630vs
1583vs
1640sh, 1612vs
1577vs
n(CC)
n(CC)
1582 s
[Ag2(m-sac)2(m-hep)2]n was prepared by the following
method: Na(sac)$2H2O (1 mmol) was added to an aqueous
solution (30 ml) of AgNO3 (1 mmol) with stirring. Then, a
suspension with a white precipitate formed and the addition
of hep (1 mmol) to the suspension resulted in a clear
solution, which was kept in darkness at room temperature
and colorless single crystals of [Ag2(m-sac)2(m-hep)2]n were
obtained after 2 days. Yield 81%. Anal. Calcd for C20H22-
N4O7S2Ag2 (%) C, 33.82; H, 3.12; N, 7.89; S, 9.03. Found:
C, 33.75; H, 3.10; N, 7.92; S, 9.00%.
1458 s
1458 s
1458 s, 1434sh
1338sh
ns(CNS)
nas?(SO2)
ns(SO2)
nas(CNS)
1337 s
1335 s
1273/1250 vs
1151 vs
1300vs, 1250vs
1150vs
1284vs, 1258vs
1150vs
955 vs/964 sh
953 s, 975 s
946vs
a
aFrequencies in cmK1. b, broad; v, weak; vw, very weak; vs, very
strong; s, strong.
out with SHELXL-97 [11]. All non-hydrogen atoms were
refined with anisotropic parameters. All hydrogen atoms
were placed in idealised locations and refined by riding
on their carrier atoms. Details of crystal data, data
collection, structure solution and refinement are given in
Table 1.
2.3. X-ray crystallography
Intensity data for complex [Ag2(m-sac)2(m-hep)2]n were
collected using a Enraf KappaCCD area detector with
graphite monochromated Mo Ka radiation (lZ
˚
0.71073 A) at 120(2) K. The structures were solved by
direct-methods using SHELXS-97 [10] and full-matrix
3. Results and discussion
non-linear least-squares refinement against F2 was carried
3.1. IR spectra
Table 1
Crystallographic data for [Ag2(m-sac)2(m-hep)2]n
The spectral data of [Ag2(m-sac)2(m-hep)2]n are given
in Table 2, together with the data of [Ag(sac)] [8] and
Formula
C20H22N4O7S2Ag2
710.28
Na[Ag(sac)2] [9]. The FT-IR spectrum (400–4000 cmK1
)
Molecular weight
Temperature (K)
120(2)
of the title complex exhibits absorption bands of all the
important functional groups of both sac and hep ligands.
The strong and broad absorption bands centred at 3435
and 3210 cmK1 are attributed to the n(OH) and n(NH)
˚
Wavelength (A)
0.71073
Crystal system
Space group
Monoclinic
P21/c
Unit cell dimensions
˚
aZ11.8773(2) A
˚
bZ22.2747(4) A
˚
cZ9.15840(10) A
bZ107.1404(9)8
2315.36(6)
3
˚
Volume (A )
Z
4
Calculated density (Mg/m3)
2.038
f (mmK1
F(000)
Crystal size (mm3)
)
1.923
1408
0.40!0.20!0.13
2.96–27.51
q range (8)
Index ranges
K14!Zh!Z15; K28!Z
k!Z28; K11!Zl!Z11
26,334
Reflections collected
Reflections observed (O2sigma)
Absorption correction
4724
Multi scan
Max. and min. transmission
Refinement method
0.513 and 0.788
Full-matrix least-squares on F2
2785/0/204
Data/restraints/parameters
Goodness-of-fit on F2
1.049
Final R indices [IO2sigma(I)]
R indices (all data)
˚
Largest diff. peak and hole (e A
R1Z0.0215, wR2Z0.0463
R1Z0.0269, wR2Z0.0482
0.434 and K0.624
Fig. 1. Asymmetric unit of [Ag2(m-sac)2(m-hep)2]n with labeling scheme
and thermal ellipsoids at the 50% probability level. All C–H hydrogen
atoms omitted for clarity.
K3
)

S. Hamamci et al. / Journal of Molecular Structure 734 (2005) 191–195
193
vibrations of hep. The relatively weak bands at around
2900 are due to absorption of the CH2 groups in hep.
The n(CaO) vibration of the sac ions is observed at
1622 cmK1 as a strong band adjacent to the NH band at
1650 cmK1. The position of the carbonyl band in the
spectrum of the title complex is comparable to the
corresponding band in [Ag(sac)] as a consequence of its
coordination with silver(I). However, the carbonyl band
of Na[Ag(sac)2] occurs at higher frequency region, since
there is not any interaction between the carbonyl
O and the Ag(I) ion in the complex [9]. The stretching
and 955 cmK1 may be assigned to nsym(CNS) and
asym(CNS) stretches of the sac ligand, respectively.
n
The positions of these bands are similar to those found in
[Ag(sac)] [8] and Na[Ag(sac)2] [9].
3.2. Thermal analysis
Thermal behaviour of [Ag2(m-sac)2(m-hep)2]n was
investigated in the static atmosphere of air. [Ag2(m-
sac)2(m-hep)2]n does not melt and exhibits three distinct
decomposition stages. In the first stage, endothermic
removal of hep occurs between 80 and 350 8C with a
mass loss of 17.8% (calcd 18.3%). The degradation of a
sac ion takes place in the second stage in the temperature
vibrations of
n
asym(SO2) and
nsym(SO2) appear
characteristically at ca. 1273 and 1151 cmK1, respect-
ively, as very strong bands. Additional bands at ca. 1337
Fig. 2. (a) A fragment of the one-dimensional [001] polymeric chain of [Ag2(m-sac)2(m-hep)2]n. Symmetry codes: (i) x, y, zK1 and (ii) x, y, zC1. (b) Packing of
polymeric chains viewed down the a-axis. All C–H hydrogen atoms omitted for clarity.

194
S. Hamamci et al. / Journal of Molecular Structure 734 (2005) 191–195
Table 3
has a distorted trigonal planar coordination of AgN2O, with
˚
Ag2 displaced from the N/N/O plane by 0.0880(10) A. The
Selected bond and hydrogen bonding geometry for [Ag2(m-sac)2(m-hep)2]n
˚
Bond lengths (A) and angles (8)
significant distortion in the coordination geometries are
evident from the angles around both silver ions. The Ag/
Ag1–N2
Ag1–O1
Ag1–N3
Ag1–O7
Ag2–N1
Ag2–O4
Ag2–N4i
2.1819(17) O1–Ag1–N2
2.2535(15) O1–Ag1–N3
2.4206(16) O1–Ag1–O7
2.7244(15) N2–Ag1–N3
2.1718(17) N2–Ag1–O7
2.3010(14) N3–Ag1–O7
2.3406(16) N1–Ag2–O4
150.96(6)
83.85(5)
103.03(5)
125.12(6)
87.31(5)
69.74(5)
146.01(6)
˚
Ag separation in the dimeric unit is 3.492(2) A, is greater
˚
than twice the van der Waals radius of silver (3.44 A),
indicating that there is no interaction between the two Ag
atoms. This is similar to the situation reported for the
dimeric or polymeric silver(I) complexes [12–17]. Both the
Ag–Nsac bond distances in [Ag2(m-sac)2(m-hep)2]n are
practically identical and comparable to those found in
N1–Ag2–N4i 126.06(6)
O4–Ag2–N4
87.39(5)
˚
[Ag(sac)] [2.16 A] [7] and Na[Ag(sac)2] [2.1405(11) and
˚
2.1570(11) A] [9], while the two Ag–Osac bond distances
˚
slightly longer than that of [Ag(sac)] [2.22 A] [7]. The Ag–
˚
Nhep bond distances of 2.3406(16) and 2.4206(16) A are
significantly shorter than the Ag–Ohep bond distance of
Hydrogen bonds
D–H/A
d(D–H)
0.87
d(H/A)
1.91
d(D/A)
2.775(2)
3.147(2)
3.186(2)
3.335(3)
!(DHA)
173
O7–H22/O5
N4–H21/O2ii 0.94
2.50
126
N4–H21/O6iii 0.94
2.49
131
C5–H3/O7iv
0.95
2.49
148
˚
2.7244(15) A, indicating much a weaker interaction of the
Symmetry transformations used to generate equivalent atoms: (i) x, y, zK1;
(ii) Kx, 1Ky, 1Kz; (iii)1Kx, 1Ky, 2Kz2; (iv) xK1, 1/2Ky, zK1/2.
hydroxyl O atom of hep with the silver(I) ion. Both sac
ligands are essentially planar and the rms deviations for sac1
with the N1 atom and the sac2 with the N2 atom are 0.021
range 355–466 8C, with an exothermic peak at 432 8C. A
24.9% mass loss observed in the stage is in good
agreement with the calculated mass loss of 25.6%. Over
the 470–587 8C range, the DTA curve displays an
extremely exothermic peak at 542 8C, attributed to the
removal of the second sac ion, with a mass loss of
26.2% (calcd 25.6%). As well as the elemental analysis
of the end residue, mass loss calculations show that the
final decomposition product is metallic silver.
˚
and 0.016 A, respectively, whereas the piperazine moiety of
hep exhibits a chair conformation (Table 3).
A packing diagram of [Ag2(m-sac)2(m-hep)2]n is shown in
Fig. 2b. The hydroxyl hydrogen atom of hep forms a strong
˚
intramolecular hydrogen bond (H/O 1.91 A) with one of
the sulfonyl O atoms in the dimeric unit. The individual
polymeric chains are crosslinked by the N-H/Osulfonyl type
intermolecular hydrogen bonds with an average H/O
˚
distance of 2.50 A, resulting a three-dimensional network.
3.3. Description of the crystal structure
An ORTEP drawing of the asymmetric unit of [Ag2(m-
sac)2(m-hep)2]n is shown in Fig. 1. Selected bond distances
and angles together with hydrogen bond geometry is listed
in (Table 3). Single X-ray crystal analysis reveals that the
complex crystallizes in monoclinic space group P21/c and is
a one-dimensional neutral metallopolymer. The asymmetric
unit of [Ag2(m-sac)2(m-hep)2]n contains two silver(I) ions,
two sac anions and a hep molecule. The sac anions act as a
bidentate bridging ligand between two silver(I) centers
through the imino N and carbonyl O atoms, forming
binuclear [Ag2(sac)2] units. An eight-membered, roughly
planar [root-mean-square deviation (rms) of the eight
4. Supplementary data
Crystallographic data for the structure reported in this
paper have been deposited with the Cambridge Crystal-
lographic Data Centre as the supplementary publication no.
CCDC-245991. Copies of the data can be obtained, free of
charge, on application to CCDC, 12 Union Road, Cam-
bridge CB2 1EZ, UK, (Fax: C44 1223 336033 or e-mail:
deposit@ccdc.cam.ac.uk).
Acknowledgements
˚
atomsZ0.099 A], dinuclear ring is formed by two silver(I)
ions linked by two N–C–O bridges. The dimeric units are
bridged by neutral hep ligands, leading to a linear polymeric
chain propagating along [001] (see Fig. 2a). The hep ligand
is attached to the silver(I) ion (Ag2) of the neighboring
dimeric unit as a monodentate ligand viathe amine N (N4)
atom, and also coordinated to the silver(I) ion (Ag1) of the
adjacent dimeric unit as a bidentate chelating ligand through
the hydroxyl O and the other amine N atoms, forming a five-
membered chelate ring around Ag1. The present metallo-
polymer has two nonequivalent silver(I) ions. The coordi-
nation geometry around Ag1 is a significantly distorted
tetrahedron with an AgN2O2 chromophore, whereas Ag2
This work was supported financially by the research fund
of Ondokuz Mayis University.
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