The new helical zigzag chain {[Ag(Pepy)(NO3)]}∞ and mononuclear [HPepy(FeCl4)] with 3D network based on hydrogen bonds as well as π-π interactions

Article abstract of DOI:10.1016/j.ica.2005.09.002

The title complexes, {[Ag(Pepy)(NO₃)]}_∞ (1) and [HPepy(FeCl₄)] (2) (Pepy = trans-2-(2-phenylethyleneyl)pyridine), had been synthesized and characterized structurally by single-crystal X-ray diffraction analysis, FTIR as well as thermal analysis. The geometrical structure of complex 1 is a one-dimensional helical zigzag chain. Each Ag ^I center is five-coordinated by two NO3- anions and one Pepy ligand while the NO3- anion is an uncommon tetra-dentate coordinating to two Ag ^I by O atoms, respectively. The NO3- anions connecting with Ag ^I as bridge blocks resulted in the formation of crystalline of helical polymeric chain. In the mononuclear complex 2, the Fe^III center is four-coordinated by four Cl^- as [FeCl₄] ^- anion, which connected with hydrogen atoms from the protonated N atom and the C atoms from HPepy⁺ to form multivalent hydrogen bonded network through N-H?Cl and C-H?Cl interactions. The two frameworks can be both considered as a 3D structure driven by diverse hydrogen bonds as well as π-π stacking interactions.

Full text of DOI:10.1016/j.ica.2005.09.002

Inorganica Chimica Acta 359 (2006) 603–608
www.elsevier.com/locate/ica
The new helical zigzag chain {[Ag(Pepy)(NO3)]} and
1
mononuclear [HPepy(FeCl4)] with 3D network based on
hydrogen bonds as well as p–p interactions
a
a
a,
*
Xue-Fang Shi a,b, Zhi-Yong Xing , Li Wu , Wen-Qin Zhang
a
Department of Chemistry, Tianjin University, Tianjin 300072, PR China
Department of Chemistry, Tianjin Normal University, Tianjin 300074, PR China
b
Received 9 July 2005; received in revised form 8 September 2005; accepted 8 September 2005
Available online 13 October 2005
Abstract
The title complexes, {[Ag(Pepy)(NO3)]} (1) and [HPepy(FeCl4)] (2) (Pepy = trans-2-(2-phenylethyleneyl)pyridine), had been synthe-
1
sized and characterized structurally by single-crystal X-ray diffraction analysis, FTIR as well as thermal anꢀalysis. The geometrical struc-
ture of complex 1 is a one-dimensional helical zigzag chain. Each AgI center is five-coordinated by two NO3 anions ꢀand one Pepy ligand
while the NO3 anion is an uncommon tetra-dentate coordinating to two AgI by O atoms, respectively. The NO3 anions connecting
ꢀ
with AgI as bridge blocks resulted in the formation of crystalline of helical polymeric chain. In the mononuclear complex 2, the FeIII
center is four-coordinated by four Clꢀ as [FeCl4]ꢀ anion, which connected with hydrogen atoms from the protonated N atom and
the C atoms from HPepy+ to form multivalent hydrogen bonded network through N–Hꢁ ꢁ ꢁCl and C–Hꢁ ꢁ ꢁCl interactions. The two frame-
works can be both considered as a 3D structure driven by diverse hydrogen bonds as well as p–p stacking interactions.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: X-ray crystal structures; Helical zigzag chain; Silver coordination polymer; Iron complex; Pyridine derivative
1. Introduction
for the construction of coordination polymers owing to its
coordination diversity and flexibility. The polydentate li-
gands containing pyridine moiety are popular choices in
this field as a result of the strong interactions happened be-
tween the N atom of pyridine ring and transition metal ions
[20]. However, recently we synthesized one AgI helical
coordination polymer using monodentate ligand of trans-
2-(2-phenylethyleneyl)pyridine (Pepy) together with nitrate
anion bridge block instead of polydentate ligands. Pepy is
one of the pyridine derivatives and heterocyclic styryl
photochemistry materials that our group has worked on
[21–24]. To our best knowledge, there are few reports on
heterocyclic styryl derivatives crystallography and their
coordination with transition metals. As a continuation of
our work, we have extended our work to use heterocyclic
styryl compounds as a new kind of ligands. Herein we
report the synthesis and structural characterization
The supramolecular chemistry has generated consider-
able interesting due to the attractive applications [1–8] of
various supramolecular structures [9–11] through self-
assembly of organic compounds with metal ions. The
induction of naturally occurring helical motifs is now of
great significance since the motif has been found to be a
fundamental structure of proteins [12–14] as well as their
potential application in asymmetric catalysis, non-linear
optical materials and biomimetic chemistry [15–19]. The
designing and controlling of molecular arrangements to
form helical coordination polymers is normally relying on
the nature of metal ion and the backbone of organic li-
gands. AgI is a favorable and fashionable connecting node
*
Corresponding author. Tel.: +86 22 27407999; fax: +86 22 27403475.
of a helical zigzag chain {[Ag(Pepy)(NO3)]} (1), and a
E-mail address: wqzhang_tju@126.com (W.-Q. Zhang).
1
0020-1693/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2005.09.002

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X.-F. Shi et al. / Inorganica Chimica Acta 359 (2006) 603–608
mononuclear complex [HPepy(FeCl4)] (2), as well as the
FTIR and thermal analysis of them.
(w), 2369 (w), 1610 (s), 1537 (m), 1459 (s), 1388 (m), 1299
(m), 1237 (m), 1205 (m), 1168 (m), 1075 (w), 964 (s), 767
(s), 523 (s). Anal. Calc. for C13H12Cl4FeN: C, 41.10; H,
3.19; N, 3.69. Found: C, 41.31; H, 3.29; N, 3.56%.
2. Experimental
2.1. Materials and general methods
2.3. X-ray crystallographic study of complex
All chemical reagents are commercially available and
purified by standard methods prior to use. FT-IR spectra
(KBr pellets) were measured on a BIO-RAD FTS 3000
Infrared spectrometer. The melting points were measured
on a Yanagimoto MP-500 apparatus (uncorrected). C, H
and N elemental analysis were carried out on a Perkin–
Elmer 240C elemental analyzer. Thermal stability (TG-
DTA) studies were performed on a NETZSCH TG 209
thermal analyzer.
A single crystal of the title complex 1 with dimensions of
0.45 mm · 0.15 mm · 0.05 mm and the complex 2 with
dimensions of 0.40 mm · 0.19 mm · 0.06 mm were moun-
ted on a Bruker Smart 1000 CCD diffractometer equipped
˚
with a graphite-monochromated Mo Ka (k = 0.71073 A)
radiation at 293(2) K. Semi-empirical absorption correc-
tions were applied using SABABS program. The structure
was solved by direct methods (SHELXL-97) [25] and succes-
sive difference Fourier syntheses (SHELXS-97), and refined
by full-matrix least-squares procedure on F2 with aniso-
tropic thermal parameters for all non-hydrogen atoms.
The hydrogen atoms were generated geometrically and re-
fined with displacement parameters riding on the con-
cerned atoms. Crystallographic data and experimental
details for structural analyses are summarized in Table 1.
The selected bond lengths and angles are presented in
Tables 2 and 3.
2.2. Preparations
The ligand Pepy was synthesized as follows: under an
atmosphere of nitrogen, the mixture of benzaldehyde
(1.60 g, 15 mmol) and 2-methylpyridine (0.93 g, 10 mmol)
was added dropwise to a solution of KOH (1.15 g,
20 mmol) in DMSO (15 ml) at 60 ꢁC for two hours. The
colorless solution turned into yellow gradually. The solu-
tion was allowed to reflux for another two hours and then
cooled down prior to pouring into 100 ml cold water. The
precipitate was filtrated and recrystallized by using metha-
nol/water to give white crystals (yield 76%, m.p. 363 K).
FTIR (KBr, cmꢀ1): 3048 (m), 1950 (m), 1811 (w), 1750
(w), 1635 (s), 1598 (vs), 1559 (s), 1494 (s), 1472 (vs), 1448
(vs), 1320 (s), 1315 (m), 1250 (m), 1216 (m) 1156 (s), 959
(vs), 770 (vs), 729 (s), 688 (vs), 531 (s). Anal. Calc. for
C13H11N: C, 86.14; H, 6.13; N, 7.73. Found: C, 86.33; H,
6.28; N, 7.52%.
3. Results and discussion
3.1. Crystal structures of the complexes
{[AgPepy](NO3)} (1). X-ray crystallography has
1
established that the crystal structure of polymeric complex
Table 1
Crystal data and structure refinement summary for complex 1 and 2
{[AgPepy](NO3)}
(1)
[HPepy(FeCl4)]
(2)
1
{[AgPepy](NO3)} (1). It was prepared as follows: the
1
Empirical formula
Formula weight
Crystal system
Space group
C
351.11
monoclinic
P21/c
10.798(10)
7.324(7)
16.919(16)
107.748(13)
1274(2)
1.830
1.586
696
4
0.45 · 0.15 · 0.05
1.98–25.03
13H11AgN2O3
C13H12C14FeN
379.89
monoclinic
P21/c
6.7944(18)
16.324(4)
14.720(4)
92.614(4)
1630.9(7)
1.547
1.564
764
4
0.4 · 0.19 · 0.06
2.77–20.05
mixture of Pepy (0.36 g, 2 mmol) in acetonitrile (10 ml) and
AgNO3 (34 mg, 0.20 mmol) in methanol (10 ml) was stirred
at room temperature for 20 min and then filtered. The fil-
trate was allowed to evaporate the solvent slowly at ambi-
ent temperature for one week to give colourless column
single crystals of 1 suitable for X-ray analysis, yield: 32%,
m.p. 495–496 K. FTIR (KBr, t, cmꢀ1): 3426 (m), 3055
(w), 2438 (w), 1752 (w), 1633 (m); 1595 (s), 1563 (m),
1494 (s), 1419 (vs), 1359 (vs), 1291 (vs), 1156 (w),
1024(w), 962 (s), 768 (s), 728 (m), 692 (s), 532 (m). Anal.
Calc. for C13H11AgN2O3: C, 44.47; H, 3.16; N, 7.98.
Found: C, 44.62; H, 3.28; N, 7.81%.
˚
a (A)
˚
b (A)
˚
c (A)
b (ꢁ)
3
˚
Volume (A )
Dcalc (g/cm3)
l (mmꢀ1
F(000)
Z
)
Crystal size (mm3)
h Range (ꢁ)
[HPepy(FeCl4)] (2). Hydrochloric acid (10%) was
added to the mixture of Pepy (0.36 g, 2 mmol) in methanol
(10 ml) and FeCl3 Æ 6 H2O (0.34 g, 2 mmol) in ethanol
(10 ml) until the pH was 3, during which the colorless solu-
tion turned yellow. The solution was stirred at room temper-
ature for 30 min and then filtered. The filtrate was allowed to
evaporate slowly at ambient temperature to give single yel-
low crystals of 2 suitable for X-ray analysis, yield: 39%, m.p.
425–426 K. FTIR (KBr, t, cmꢀ1): 3263 (m), 3173 (m), 2980
Range of h,k,l
ꢀ10/12, ꢀ8/8, ꢀ20/18 ꢀ8/8, ꢀ15/19,
ꢀ17/16
Reflections collected/unique 6555/2254
8678/2875
Data/restraints/parameters
Ra and wRb
Goodness-of-fit on F2
Maximum residual
peak and hole (e Æ A
2254/0/173
2875/1/177
0.0516 and 0.0996
1.032
0.0781 and 0.1566
1.082
0.363 and ꢀ0.569
0.706 and ꢀ0.394
ꢀ3
˚
)
P
P
a
R= ðjjF oj ꢀ jF cjjÞ= jF oj.
P
P
2
2
2
1=2
b
wR ¼ ½ wðjF oj ꢀ jF cj Þ = wðF 2oÞꢂ
.

X.-F. Shi et al. / Inorganica Chimica Acta 359 (2006) 603–608
605
Table 2
˚
Selected bond lengths (A) and angles (ꢁ) for complex 1
Ag1–N1
Ag1–O3
Ag1–O1
Ag1–O2
O1–N2
O2–N2
O3–N2
2.196(3)
2.438(3)
2.599(4)
2.635(4)
1.232(4)
1.231(4)
1.263(4)
N1–Ag1–O2A
N1–Ag1–O3
N1–Ag1–O1
98.12(10)
142.02(10)
127.43(12)
50.42(9)
O3–Ag1–O1
N1–Ag1–O3A
O1–Ag1–O2A
O3–Ag1–O2A
O3A–Ag1–O2A
O3–Ag1–O3A
O1–Ag1–O3A
N2–O1–Ag1
120.66(10)
134.37(7)
97.72(11)
48.31(11)
95.37(7)
97.12(11)
91.7(2)
N2–O3–Ag1
98.6(2)
N2–O3–Ag1B
Ag1–O3–Ag1B
97.0(2)
164.27(11)
Symmetry codes: A: ꢀx + 2, y + 1/2, ꢀz + 1/2, B: ꢀx + 2, y ꢀ 1/2,
ꢀz + 1/2.
Table 3
˚
Selected bond lengths (A) and angles (ꢁ) for complex 2
Fe1–Cl1
Fe1–Cl4
Fe1–Cl2
Fe1–Cl3
N1–C5
2.1577(17)
2.1648(19)
2.1774(17)
2.2026(18)
1.340(6)
N1–C1
1.341(6)
Cl1–Fe1–Cl4
Cl1–Fe1–Cl2
Cl4–Fe1–Cl2
Cl1–Fe1–Cl3
Cl4–Fe1–Cl3
Cl2–Fe1–Cl3
109.34(8)
109.75(8)
108.81(9)
108.41(8)
111.46(9)
109.06(7)
1 consists of a one-dimensional helical chain, which dis-
plays a zigzag coordination geometry comprised N atoms
from Pepy ligands and O atoms from nitrate bridge li-
gands. The drawing and atomic labeling of the fragment
of complex 1 are shown in Fig. 1(a).
Fig. 1. (a) Coordination environment of the metal AgI in complex 1. (b)
Showing the helical zigzag chain along a axis.
In oneꢀcrystallographic unit there is one Pepy ligand and
ꢀ
two NO3 anions, while the NO3 anion is an uncommon
from 48.32(11)ꢁ to 134.33(7)ꢁ in which the angle of O3A–
Ag1–O2A bonds is the smallest due to the nitrate adopting
a tetra-dentate coordination mode.
l4-bridge ligand (l4- O1, O2, O3, O3) coordinating to two
AgI by O atoms, respectively. Each AgI center is five-
coordinated in a heavily distorted square pyramid geometry
formed by one Ag–N bond with N atom from Pepy ligand
and four Ag–O bonds with O atoms from two different ni-
Along with b axis each AgI cation connects two NO3
ꢀ
anion ligands in two different directions. The adjacent
AgI centers are linked together by O3 atoms that act as
l2-coordinated bridges. The adjacent Pepy ligands adopt
W-style configurations along with c-axis. The two pyridine
groups are inclined to the AgꢀI center with a dihedral angle
of 49.4ꢁ while the Pepy, NO3 and AgI center three motifs
constructed a zigzag helix in the b axis (Fig. 1(b)). It is
noteworthy that the period of the helices and the transla-
I
˚
trate anions. The Ag is situated 1.257(3) A above the cen-
ter of the distorted square consisting of O1, O3, O2A and
O3A atoms, and the N1 atom of ligand at the apex of the
distorted square pyramid coordinates with the AgI center
˚
with Ag–N bond distance of 2.196(3) A and the distances
˚
of Ag–O bonds vary from 2.438(3) to 2.635(4) A. All the
˚
Ag-donor bond distances and angles are within the ex-
pected range [6,10,11,26]. The angles around AgI range
tion vector in the columns is 7.324(1) A, while the distances
of neighboring adjacent AgI centers are separated by

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X.-F. Shi et al. / Inorganica Chimica Acta 359 (2006) 603–608
˚
4.990(1) A. Both of the distances are far longer than the
sum of van der Waals radii of two free silver atoms
˚
(3.44 A) [1] indicating the absence of ligand-supported
Agꢁ ꢁ ꢁAg interactions.
Between the two neighboring helical chains, O3 atoms
exist interactions with H4 of pyridine ring to form C–
˚
˚
Hꢁ ꢁ ꢁO hydrogen bonds(Oꢁ ꢁ ꢁC = 3.329 A, Hꢁ ꢁ ꢁO = 2.561 A,
C–Hꢁ ꢁ ꢁO = 140.2ꢁ). These hydrogen bonds further extend
the 1 D helical chains spreading on bc plane and forming
quasi 2D structure as illustrated in Fig. 2.
In addition, the Pepy ligands of two adjacent helical
chain staggered antiparallel with centroid–centroid separa-
Fig. 3. Showing the Pepy ligands of two adjacent helical chain staggered
and the p–p stacking interactions down b axis.
˚
tion of pyridine rings to phenyl ring by 3.590(2) A perpen-
˚
dicular and 1.245(2) A offset distances indicating the
presence of face-to-face p–p stacking interactions which
further packs the crystal as 3D structure viewing down
the b axis in Fig. 3.
[HPepy(FeCl4)] (2). In the mononuclear complex,
there is one tetrachloroiron(III) anion and one Pepy ligand
in which the N atom is protonated with H1A. The Cl3
atom of the [FeCl4]ꢀ anion interacts with H1A and H1
through N1–H1Aꢁ ꢁ ꢁCl3 and C1–H1ꢁ ꢁ ꢁCl3 while the Cl4
atom interacts with H13 from phenyl ring to form C13–
H13ꢁ ꢁ ꢁCl4 hydrogen bonds as illustrated in Fig. 4.
In addition, there also exist other kinds of hydrogen
bonding interactions between adjacent mononuclear com-
plexes. The Cl1 atom links with H1AA, H2A, H11C and
H12C which come from the phenyl ring or pyridyl ring
of another two mononuclear complexes and Cl2 links
H2B and H3B which come from the pyridyl ring of a
fourth mononuclear complex through C–Hꢁ ꢁ ꢁCl hydrogen
bonds to form 2D network (see Fig. 5 and Table 4).
The Pepy ligand is quasi-plane with the dihedral angle
between the pyridinyl ring and the phenyl ring being 3.4ꢁ.
In the unit-cell packing of 1, viewing along the a axis, we
can see that there are p–p stacking interactions between
pyridinyl and phenyl ring of the ligand. The centroids of
Fig. 4. ORTEP drawing of complex 2 showing the atomic numbering
scheme with 30% displacement ellipsoids probability.
˚
the phenyl and pyridine rings is separated by 3.347(2) A
Fig. 5. Showing hydrogen bonds between [FeCl4]ꢀ anion and aromatic
rings from different complexes. These interactions organized complex 2 as
2D network.
Fig. 2. The 2D structure of complex 1 formed by C–Hꢁ ꢁ ꢁO hydrogen
bonds between adjacent helical zigzag chains.

X.-F. Shi et al. / Inorganica Chimica Acta 359 (2006) 603–608
607
Table 4
Hydrogen bonds lengths (A) and angles (ꢁ) for complex 2
˚
D–Hꢁ ꢁ ꢁA
D–H
Hꢁ ꢁ ꢁA
Dꢁ ꢁ ꢁA
D–Hꢁ ꢁ ꢁA
C1A–H1AAꢁ ꢁ ꢁCl1
C2A–H2Aꢁ ꢁ ꢁCl1
C11C–H11Cꢁ ꢁ ꢁC11
C12C–H12Cꢁ ꢁ ꢁC11
C2B–H2Bꢁ ꢁ ꢁC12
C3B–H3Bꢁ ꢁ ꢁC12
N1–H1Aꢁ ꢁ ꢁC13
C1–H1ꢁ ꢁ ꢁC13
0.930
0.930
0.930
0.930
0.930
0.930
0.900
0.930
0.930
3.250
3.065
3.115
3.059
3.205
3.116
2.396
2.505
2.779
3.760
3.665
3.753
3.724
3.820
3.778
3.261
3.268
3.614
116.6
123.8
127.4
129.9
125.4
129.7
161.4
103.2
149.9
C13–H13ꢁ ꢁ ꢁCl4
Symmetry codes: A: x, 1/2 ꢀ y, ꢀ1/2 + z, B: 1 ꢀ x, 1/2 + y, 3/2 ꢀ z, C: x,
1/2 ꢀ y, 1/2 + z.
˚
perpendicular and 1.780(2) A offset distances. These hydro-
gen bond and p–p stacking interactions connect the molec-
ular ions into a 3D structure along a axis as illustrated in
Fig. 6.
Fig. 7. TG-DTA of complex 1 and 2.
In summary, a new AgI complex helical zigzag chain
complex 1 and a FeIII complex 2 was prepared and struc-
turally characterized. The AgI complex helical polymer
had adequately exhibited that the N atoms of pyridine
rings and O atoms of nitrates have excellent coordination
ability. To our best knowledge, this AgI complex helical
chains polymer is rare for it contained inorganic nitrate
bridge blocks and organic backbone ligand with only one
N atom comprised. The multiple hydrogen bonding inter-
actions is even more important in crystal 2 for its not only
linking the HPepy+ cation and [FeCl4]ꢀ anion together as a
mononuclear structure but also arranging into 3D struc-
ture. Meanwhile complexes 1 and 2 both exist the aromatic
rings face-to-face p–p stacking interactions. This work
demonstrates that the extended structural motifs can be
constructed to build construct helical architecture through
tailored backbone of the organic ligands as well as employ-
ing inorganic nitrate as synergic ligands.
be attributed to the stretching vibration of C@N and C@C
bonds of Pepy.
The thermal analysis showed that complex 1 was stable
up to 220.5 ꢁC. The first weight loss was observed in the
temperature of 220.5–325.0 ꢁC to liberate Pepy (theoretical,
51.62%; experimental, 51.86%) with an endothermic peak
at 246.6 ꢁC. The second weight loss was gave off from
407.0 to 556.5 ꢁC due to the decomposition of the silver ni-
trate to Ag2O and NO2 (theoretical, 13.10%; experimental,
13.16%). And the thermal analysis of complex 2 showed
that it is stable up to 272.0 ꢁC. The first weight loss was ob-
served in the temperature of 272.0–403.7ꢁC to liberate HCl
and Cl2 (theoretical, 28.26%; experimental, 30.23%) with
an endothermic peak at 336.6 ꢁC. The second weight loss
was gave off from 498.0 to 636.0 ꢁC due to the decomposi-
tion of the Pepy ligands (theoretical, 47.71%; experimental,
48.62%) (see Fig. 7).
3.2. FTIR spectrum and thermal analysis
Appendix A. Supplementary data
The FTIR spectrum of 1 is remarkably characteristic of
a group of strong broad peaks at 1419–1291 cmꢀ1, which
are associated with the presence of coordinated nitrate an-
ions. Absorption peaks at 1633–1494 cmꢀ1 can be attrib-
uted to the stretching vibration of C@N and C@C bonds
of Pepy. The FTIR spectrum of 2 is remarkably character-
istic of a group of absorption peaks at 1611–1459 cmꢀ1 can
The supplementary crystallographic data for the struc-
tures analyses have been deposited with the Cambridge
Crystallographic Data Centre, CCDC Nos. 275174 and
276322. Copies of the data can be obtained free of charge
via www.ccdc.cam.ac.uk/conts/retrieving.html (or from
the Cambridge Crystallographic Data Centre, 12, Union
Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336
033). Supplementary data associated with this article can
be found, in the online version, at doi:10.1016/
j.ica.2005.09.002.
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