Helical and zigzag coordination polymeric chains derived from di-3-pyridyl ketone and silver(I) salts

Article abstract of DOI:10.1016/j.molstruc.2005.02.013

A series of silver(I) complexes [AgL(X)]_∞ (X=BF ₄, ClO₄, NO₃, CF₃SO₃, PF₆; L=di-3-pyridyl ketone) have been characterized by X-ray crystallography. Argentophilic interaction, π-π stacking, Ag?X interaction, C-H?X (X=F, O) and C-H?O=C hydrogen bonding contribute to different extents in the construction of helical or zigzag infinite chains.

Full text of DOI:10.1016/j.molstruc.2005.02.013

Journal of Molecular Structure 743 (2005) 1–6
www.elsevier.com/locate/molstruc
Helical and zigzag coordination polymeric chains derived from
di-3-pyridyl ketone and silver(I) salts
*
Xu-Dong Chen, Thomas C.W. Mak
Department of Chemistry, The Chinese University of Hong Kong, New Territories, Hong Kong SAR, People’s Republic of China
Received 17 December 2004; revised 14 February 2005; accepted 16 February 2005
Available online 22 March 2005
Abstract
A series of silver(I) complexes [AgL(X)]N (XZBF4, ClO4, NO3, CF3SO3, PF6; LZdi-3-pyridyl ketone) have been characterized by X-ray
crystallography. Argentophilic interaction, p–p stacking, Ag/X interaction, C–H/X (XZF, O) and C–H/OZC hydrogen bonding
contribute to different extents in the construction of helical or zigzag infinite chains.
q 2005 Elsevier B.V. All rights reserved.
Keywords: Silver; Di-3-pyridyl ketone; Di-3-pyridinylmethanone; Coordination polymer; Helical chain
1. Introduction
Here we report our studies on five silver(I) complexes
generated from di-3-pyridyl ketone (L) together
with various monoanions, namely [AgL(BF4)]N (1),
[AgL(ClO4)]N (2), [AgL(NO3)]N (3), [AgL(CF3SO3)]N
(4), [AgL(PF6)]N (5), which were shown by X-ray analysis
to exhibit two kinds of polymeric chains in the solid state.
During the past 15 years, rapid development in the
construction of supramolecular architectures based on metal
centers and organic building blocks has continuously
produced coordination polymers with interesting compo-
sitions and diverse topologies, along with their potential
applications in the fields of host–guest chemistry, catalysis,
electrical conductivity, and magnetic materials [1–7]. In the
development of both solution-based supramolecules and
solid-state infinite polymers and networks, the coordination
motif has been recognized as an effective ingredient in the
design and self-assembly of a wide variety of supramole-
cular aggregates [1,8]. It is noteworthy that anions also play
very important roles in supramolecular assembly [9–11] and
crystal engineering [12]. As is well known, di-2-pyridyl
ketone is an extraordinary ligand within the family of basic
building blocks for the construction of metal–organic
complexes with intriguing architectures and potential
applications as catalysts and advanced materials [13–17].
In contrast, the ligand behavior of its positional isomer di-3-
pyridyl ketone (di-3-pyridinylmethanone) remains unex-
plored to this date (Scheme 1).
2. Experimental
2.1. Materials and general methods
Diethyl ether was purchased from Aldrich and further
refluxed over sodium and benzophenone. All other chemi-
cals were purchased from Aldrich and used without further
purification.
Elemental analyses of C, H and N were performed by the
MEDAC LTD Vrunel Science Center, United Kingdom. IR
spectra were recorded with a Nicolet Impact 420 FT-IR
spectrometer using KBr pellets. 1H NMR spectra were
measured at 300 Hz with a Bruker-300 spectrometer using
CDCl3 as solvent. Mass spectrometry was conducted on a
ThermoFinnigan MAT 95 XL spectrometer.
2.2. Synthesis
*
Corresponding author. Tel.: C852 2609 6279; fax: C852 2603 5057.
E-mail address: tcwmak@cuhk.edu.hk (T.C.W. Mak).
2.2.1. Synthesis of di-3-pyridyl ketone (L)
Under the protection of N2, 3-bromopyridine (1.58 g,
10 mmol) in 10 ml anhydrous diethyl ether was added
0022-2860/$ - see front matter q 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2005.02.013

2
X.-D. Chen, T.C.W. Mak / Journal of Molecular Structure 743 (2005) 1–6
CH3OH with stirring at room temperature. The solution was
stirred overnight in the dark, filtered, and allowed to stay in
the dark for two weeks to give light-yellow crystals of 3.
Yield: 77%. Anal. for C11H8N3O4Ag: Calcd. C 37.31, H
2.28, N 11.86; Found C 37.23, H 2.25, N 11.82. IR (KBr):
1651s, 1583s, 1416s, 1383vs, 1294s, 1193w, 1115w,
1020w, 930w, 841w, 823w, 729m, 698m, 669w,
Scheme 1. Structure and atom labeling of di-3-pyridyl ketone.
621w cmK1
.
slowly into 6.3 ml (10 mmol) n-butyllithium (15% in
hexane) in 15 ml anhydrous diethyl ether at K78 8C. The
resulting solution was kept at K78 8C for 30 min, and then
1.37 g (10 mmol) methyl nicotinate in 15 ml anhydrous
diethyl ether was added slowly within 20 min with vigorous
stirring. After stirring at K78 8C for another 30 min, the
solution was allowed to warm slowly to K20 8C over 3 h,
after which it was further quenched with 15 ml HCl solution
in water and methanol (water/methanol/conc. HClZ5:5:1).
The mixture was extracted with dichloromethane, and the
combined organic extract was dried over anhydrous sodium
sulfate and finally concentrated in vacuo to give an orange–
yellow solid. Purification by chromatography on silica-gel
using ethyl acetate/hexane as the eluent gave 1.4 g L as a
2.2.5. Synthesis of [AgL(CF3SO3)]N (4)
This complex was synthesized in the same way as for 1
by the reaction of AgSO3CF3 with L. Yield: 63%. Anal. for
C12H8F3N2O4SAg: Calcd. C 32.67, H 1.83, N 6.35; Found C
32.82, H 1.83, N 6.32. IR (KBr): 1653s, 1585s, 1475w,
1417m, 1333m, 1294brs, 1174m, 1117w, 1082w, 1034s,
935m, 843w, 813w, 760w, 729m, 698m, 646m, 575w,
519w cmK1
.
2.2.6. Synthesis of [AgL(PF6)]N (5)
This complex was prepared using the same method as for
1 by the reaction of L with AgPF6 in 1:1 molar ratio. Yield:
82%. Anal. for C11H8F6N2OPAg: Calcd. C 30.23, H 1.85, N
6.41; Found C 30.26, H 1.88, N 6.30. IR (KBr): 1655s,
1585s, 1477w, 1419s, 1335m, 1298s, 1250w, 1203w,
1117w, 1022w, 937m, 835brs, 731s, 698m, 671w, 621w,
1
white solid in 76% yield, m.p. 115.8–116.3 8C. H NMR
(300 MHz, CDCl3): d 9.01 (d, JZ1.5 Hz, 2H), 8.85 (dd,
J1Z1.2, J2Z4.8 Hz, 2H), 8.14 (dt, J1Z7.8, J2Z1.8 Hz,
2H), 7.49 (dd, J1Z4.8, J2Z7.8 Hz, 2H), IR (KBr): 1651s,
1581s, 1473w, 1416s, 1333m, 1294s, 1193w, 1143w,
1113w, 1083w, 1018w, 931m, 845w, 812w, 729s, 696m,
667w, 621w, 567w cmK1; MS m/z: 184.06 ([MH]C, 100%
relative abundance); Anal. for C11H8N2O: Calcd. C 71.73,
H 4.38, N 15.20; Found C 71.69, H 4.34, N 15.19.
559s cmK1
.
2.3. X-Ray crystallography
Crystals mounted inside Lindemann glass capillaries
were used for data collection on a Bruker SMART 1000
CCD diffractometer operating at 50 KV and 30 mA using
˚
2.2.2. Synthesis of [AgL(BF4)]N (1)
Mo Ka radiation (lZ0.71073 A) at 293 K. Data collection
AgBF4 (40 mg, 0.2 mmol) and L (37 mg, 0.2 mmol)
were dissolved in 5 ml CH3OH with stirring at room
temperature. A white precipitate formed immediately,
which was dissolved by the addition of CH3CN. After
filtration, the solution was placed in the dark for a week
to give light yellow crystals of 1. Yield: 73%. Anal. for
C11H8BF4N2OAg: Calcd. C 34.87, H 2.13, N 7.39; Found C
35.03, H 2.16, N 7.42. IR (KBr): 1653s, 1585s, 1477w,
1419m, 1333m, 1298s, 1196w, 1119s, 1080s, 1034s, 931m,
and reduction were performed using the SMART and
SAINT software [18]. An empirical absorption correction
was applied using the SADABS program [19]. All five
structures were solved by direct methods and refined by full-
matrix least squares on F2 using the SHELXTL program
package [20]. Crystallographic data of complexes 1–5 are
listed in Table 1.
843w, 814w, 721m, 698m, 671w, 623w, 525w cmK1
.
3. Results and discussion
2.2.3. Synthesis of [AgL(ClO4)]N (2)
The known ligand di-3-pyridyl ketone (L) was syn-
thesized by a procedure similar to that for 2-pyridinyl-3-
pyridinylmethanone as reported by Mikhura, et al. [21,22].
Ligand L readily gives rise to silver(I) complexes upon
reaction with various silver salts, which can be crystallized
by slow evaporation of the solvent. This family of
coordination polymers exhibits two structural types in the
crystalline state, namely helical and zigzag chain, due to
the different linkage modes that L may take. Changing of the
reaction ratio between ligand L and the Ag(I) salts does not
affect the structure of the polymers and leads to the same
product in each case.
This complex was obtained as light-yellow crystals in a
similar manner as for 1 by the reaction of AgClO4 with L.
Yield: 80%. Anal. for C11H8ClN2O5Ag: Calcd. C 33.75, H
2.06, N 7.15; Found C 33.80, H 2.05, N 7.17. IR (KBr):
1653s, 1585s, 1477w, 1419m, 1333w, 1298s, 1143s, 1113s,
1088s, 1022w, 933w, 842w, 814w, 729m, 698m, 671w,
627m, 571w cmK1
.
2.2.4. Synthesis of [AgL(NO3)]N (3)
AgNO3 (34 mg, 0.2 mmol) and L (37 mg, 0.2 mmol)
were dissolved in a mixed solvent of 3 ml CH3CN and 3 ml

X.-D. Chen, T.C.W. Mak / Journal of Molecular Structure 743 (2005) 1–6
3
Table 1
Crystallographic data of complexes 1–5
Complexes
1
2
3
4
5
Empirical formula
Formula weight
Crystal size
C11H8BF4N2OAg
378.87
C11H8ClN2O5Ag
391.51
C11H8N3O4Ag
354.07
C12H8F3N2O4SAg
441.13
C11H8F6N2OPAg
437.03
0.60!0.45!0.29
Monoclinic
P21/c (No. 14)
10.9257(8)
8.3727(6)
14.243(1)
90
0.58!0.46!0.37
Monoclinic
P21/c (No. 14)
10.8435(7)
8.4137(5)
14.4632(9)
90
0.65!0.51!0.20
Monoclinic
P21/c (No. 14)
11.521(1)
7.4031(7)
13.856(1)
90
0.65!0.54!0.42
Orthorhombic
Pbca (No. 61)
12.2360(6)
13.5248(7)
17.1609(9)
90
0.45!0.38!0.23
Monoclinic
P2/c (No. 13)
8.358(2)
6.273(2)
13.643(3)
90
Crystal system
Space group
˚
a (A)
˚
b (A)
˚
c (A)
a (8)
b (8)
g (8)
98.685(1)
90
96.551(1)
90
97.322(2)
90
90
106.049(5)
90
90
3
˚
V (A )
1287.9(2)
4
1310.9(1)
4
1172.1(2)
4
2839.9(3)
8
687.4(3)
2
Z
D
calc (g/cm3)
1.954
1.984
2.006
2.063
2.112
m(Mo Ka) (mmK1
F(000)
)
1.607
1.761
1.734
1.622
1.653
736
768
696
1728
424
Reflections collected
Independent reflec-
6644
6784
5968
14261
3513
2266 (0.0511)
2310 (0.0293)
2058 (0.0351)
2492 (0.0311)
1220 (0.0377)
tions (Rint
)
Observed reflections
[IO2s(I)]
Parameters
1936
1965
1831
2107
1006
217
217
172
208
104
Goodness-of-fit
1.198
1.133
1.232
1.149
1.128
R1 [
IO2s(I)]a
wR2 (all data)b
0.0612
0.1512
0.0462
0.1195
0.0574
0.1307
0.0389
0.0910
0.0487
0.1336
a
R1ZSjjFojKjFcjj/SjFoj.
b
1=2
2
2
wR2 ZfS½wðFo2 KFc2Þ Š=S½wðFo2Þ Šg
.
In the isostructural complexes 1, 2 and 3, the bidentate
bridging ligand L and silver atom are linked alternatively to
form an infinite helical chain (Fig. 1). In each complex, five
kinds of weak interactions are involved in cross-linking
such chains into a three-dimensional network: argentophilic
interaction [23], p–p stacking [24], Ag/X interaction [25],
C–H/X (XZF in 1, XZO in 2 and 3) hydrogen bonding
and C–H/OZC hydrogen bonding [26]. Among these, the
˚
weak C–H/OZC hydrogen bonds (H/O 2.433 A, C–H/
O 154.98) occur between L ligands belonging to adjacent
chains, leading to 10-membered rings that bind the chains
together to form a two-dimensional network (Fig. 2a). In the
(1 0 0) plane, the chains are also linked together by
argentophilic and p–p stacking interactions (Fig. 2b), as
well as Ag/X interaction and C–H/X hydrogen bonding
(XZF in 1, XZO in 2 and 3). The intervening space
between adjacent repeating pitches of the helical structure is
filled by the corresponding counter anions. This suggests
that the spring-like chains in complexes 1 and 2 are in a
more relaxed state than that in 3, since the steric bulk of BFK4
or ClOK4 is much larger than that of NOK3 . Concerning the
non-bonded distance between Ag1 and Ag1B as shown in
˚
˚
˚
Fig. 1, the values are 8.373 A, 8.414 A and 7.403 A for
complexes 1, 2 and 3, respectively.
Fig. 1. Helical structure in complexes 1–3. Hydrogen atoms are omitted for
clarity. Color code: purple: silver; light gray: carbon; turquoise: nitrogen;
red: oxygen.
Complexes 4 and 5 comprise the same kind of infinite
zigzag polymeric chain (Fig. 3), whose conformation is

4
X.-D. Chen, T.C.W. Mak / Journal of Molecular Structure 743 (2005) 1–6
Fig. 2. (a) Cross-linkage of adjacent chains through hydrogen bonding in complex 3, viewed along the [111] direction. (b) Assembly of the adjacent chains by
argentophilic interaction and p–p stacking interaction, viewed along the [100] direction. Color code: purple: silver; light gray: carbon; turquoise: nitrogen; red:
oxygen.
affected by the different electron donor ability of the counter
anion. As observed in their crystal structures, the two-
coordinated silver atom in 5 takes a strictly linear
conformation, whereas in 4 the N–Ag–N bond angle is
165.58. In complex 4, besides being coordinated by the N
atoms from two independent L ligands, the silver atom also
has weak interactions with O atoms from both ligand L and
trifluoromethanesulfonate anions at distances between
˚
2.747 and 3.139 A. Furthermore, Ag/p interaction [27]
˚
with a Ag-centroid distance of 3.378 A accounts for
stacking of the zigzag chains into a two-dimensional
network (Fig. 4a), which are further consolidated by Ag/
O weak interactions and C–H/O (trifluoromethanesulfo-
nate) hydrogen bonding. In complex 5, Ag/p interaction
˚
with a Ag-centroid distance of 3.794 A, together with p–p
˚
interaction with a centroid–centroid distance of 3.739 A
(Fig. 4b), bind the zigzag chains into a two-dimensional
network. The highly symmetric PFK6 anion in 5 acts as
Fig. 4. (a) The Ag/p interactions in complex 4, which link the infinite
chains into a two-dimensional network. (b) The Ag/p and p–p
interactions in complex 5, which link the infinite chains into a two-
dimensional network. Hydrogen atoms are omitted for clarity. Color code:
purple: silver; light gray: carbon; turquoise: nitrogen; red: oxygen.
Fig. 3. The zigzag chain in complexes 4 and 5. Hydrogen atoms are omitted
for clarity. Color code: purple: silver; light gray: carbon; turquoise:
nitrogen; red: oxygen.

X.-D. Chen, T.C.W. Mak / Journal of Molecular Structure 743 (2005) 1–6
5
Table 2
Atom labeling of ligand L and torsion angles of the two pyridyl rings with
respect to the carbonyl group in complexes 1–5.
Complex
Torsion angle (8)
C2–C1–CZO
C20–C10–CZO
1
2
3
4
5
K165.0(8)
K163.4(6)
K166.1(6)
K159.4(4)
147.0(4)
K130.3(9)
K130.8(7)
K135.5(7)
K132.1(4)
147.0(4)
1651 cmK1 and complexes 1–5 show the same peak at 1653,
1653, 1651, 1653 and 1655 cmK1, respectively.
In summary, five silver(I) complexes of di-3-pyridyl
ketone (L) have been successfully synthesized and their
structures characterized by X-ray diffraction. Two kinds of
infinite chains resulting from N,N0-bridging of ligand L have
been observed in these complexes. Weak argentophilic
interactions are manifested in complexes 1–3 that comprise
helical chains, while Ag/p interaction exists in complexes
4 and 5 exhibiting zigzag chains. The structural differences
within this series of complexes illustrate the significance of
the anion effect [9–12], as well as the interplay among
various kinds of weak interactions, on the construction of
supramolecular metal–organic complexes.
Fig. 5. Three-dimensional network in complex 5 linked by PFK6 counter
anions, viewed along the b direction.
the dominent factor in the conglomeration of the layers
˚
through C–H/F hydrogen bonding (H/F 2.471 A and
˚
˚
2.494 A) [28] and Ag/F weak interaction (3.110 A) [29]
(Fig. 5).
Though the coordination mode of ligand L in complexes
1–5 remains invariant, its linking direction in complexes 4
and 5 is different from that in 1–3, resulting in two kinds of
infinite chains (Fig. 6). In accordance with this, together
with the subtle effect of the counter anions, the torsion
angles of the two pyridyl rings with respect to the carbonyl
group of ligand L are different in these complexes, as shown
in Table 2. Within each infinite chain, the silver atoms of
complex 5 are strictly co-linear, while the Ag/Ag/Ag
angle involving three consecutive, non-bond silver atoms
takes the value 75.18, 74.68, 70.08, and 166.78 for complexes
1–4, respectively, which clearly differentiate the two kinds
of chains.
4. Supplementary material
Crystallographic data of complexes 1–5 are available in
the Supplementary Information. CCDC 258514–258518 for
complexes 1–5, respectively.
In 1994, Sommerer et al. reported a silver complex of di-
2-pyridyl ketone, [Ag(C11H8N2O)(NO3)]N, which com-
prises an infinite helical chain,[30] and in 2000 Chen et al.
reported a series of related helical complexes [Ag(C11H8-
N2O)(X)]N (XZNO2, ClO3, PF6, ClO4) [31]. The present
studies on complexes 1–5 show that both positional isomers
of dipyridyl ketone exhibit analogous coordination behavior
toward silver(I) with the carbonyl group remaining intact.
The IR spectra of the present series of complexes indicate
that the coordination of ligand L with silver(I) salts affect
the vibration of ligand L only to a minor extent. As to the
v(CZO) mode, ligand L exhibits a sharp and strong peak at
Acknowledgements
This work is supported by the Hong Kong Research
Grants Council (Ref. No. CUHK 402003).
References
[1] J.-M. Lehn, Supramolecular Chemistry, VCH, Weinheim, 1995.
[2] S. Subramanian, M.J. Zaworotko, Coord. Chem. Rev. 137 (1994) 357.
[3] D. Braga, F. Grepioni, G.R. Desiraju, Chem. Rev. 98 (1998) 1375.
[4] S. Leininger, B. Olenyuk, P.J. Stang, Chem. Rev. 100 (2000) 853.
[5] O.M. Yaghi, H. Li, C. David, D. Richardson, T.L. Groy, Acc. Chem.
Res. 31 (1998) 474.
[6] P.J. Hagrman, D. Hagrman, J. Zubieta, Angew. Chem. Int. Ed. 38
(1999) 2638.
[7] S.R. Batten, R. Robson, Angew. Chem. Int. Ed. 37 (1998) 1461.
[8] G.F. Swiegers, T.J. Malefeste, Chem. Rev. 100 (2000) 3483.
´
[9] A. Bianchi, K. Bowman-James, E. Garcıa-Espan˜a, Supramolecular
Chemistry of Anions, Wiley, New York, 1997.
[10] O.-S. Jung, Y.J. Kim, Y.-A. Lee, K.-M. Park, S.S. Lee, Inorg. Chem.
42 (2003) 844.
[11] C.S. Campos-Fernandez, R. Clerac, K.R. Dunbar, Angew Chem. Int.
Ed. 38 (1999) 3477.
Fig. 6. Different linking directions of consecutive L ligand leading to a
helical chain (left, for 1–3) and a zigzag chain (right, for 4 and 5).
[12] D. Braga, F. Grepioni, Acc. Chem. Res. 33 (2000) 601.

6
X.-D. Chen, T.C.W. Mak / Journal of Molecular Structure 743 (2005) 1–6
[13] G.S. Papaefstathiou, S.P. Perlepes, Comment Inorg. Chem. 23 (2002)
249 and references therein.
[21] I.S. Popova, A.A. Formanovsky, I.V. Mikhura, Russ. Chem. Bull. 51
(2002) 540.
[14] C. Dendrinou-Samara, M. Alexiou, C.M. Zaleski, J.W. Kampf,
M.L. Kirk, D.P. Kessissoglou, V.L. Pecoraro, Angew. Chem. Int. Ed.
42 (2003) 3763.
[22] J.E. Parks, B.E. Wagner, R.H. Holm, J. Organomet. Chem. 56 (1973)
53.
¨
[23] P. Pyykko, Chem. Rev. 97 (1997) 597; M. Jansen, Angew. Chem. Int.
[15] C.J. Milios, E. Kefalloniti, C.P. Raptopoulou, A. Terzis, R. Vicente,
N. Lalioti, A. Escuer, S.P. Perlepes, Chem. Commun. (2003) 819.
[16] A.K. Boudalis, F. Dahan, A. Bousseksou, J.-P. Tuchagues,
S.P. Perlepes, Dalton Trans. (2003) 3411.
Ed. Engl. 26 (1987) 1098; X.-L. Zhao, O.-M. Wang, T.C.W. Mak,
Inorg. Chem. 42 (2003) 7872 and references therein.
[24] J.W. Steed, J.L. Atwood, Supramolecular Chemistry, Wiley, Chiche-
ster, 2000; C. Janiak, J. Chem. Soc. Dalton Trans. (2000) 3885.
[25] Y.-B. Xie, C. Zhang, J.-R. Li, X.-H. Bu, Dalton Trans. (2004) 562.
[26] H.W. Roesky, M. Andruh, Coord. Chem. Rev. 236 (2003) 91.
[27] Q.-M. Wang, T.C.W. Mak, Chem. Commun. (2002) 2682, and
references therein.
[17] C.M. Kepert, G.B. Deacon, N. Sahely, L. Spiccia, G.D. Fallon,
B.W. Skelton, A.H. White, Inorg. Chem. 43 (2004) 2818.
[18] Bruker, SMART 5.0 and SAINT 4.0 for Windows NT, Area Detector
Control and Integration Software. Burker Analytical X-Ray Systems
Inc. Madison, WI, 1998.
[28] F. Grepioni, G. Cojazzi, S.M. Draper, N. Scully, D. Braga,
Organometallics 17 (1998) 296.
[19] G.M. Sheldrick, SADABS: Program for Empirical Absorption
¨ ¨
Correction of Area Detector Data, University of Gottingen, Gottingen,
[29] Q.-M. Wang, T.C.W. Mak, Chem. Commun. (2001) 807.
[30] S.O. Sommerer, B.L. Westcott, K.A. Abboud, Acta Cryst. C50 (1994)
48.
Germany, 1996.
[20] G.M. Sheldrick, SHELXTL 5.1 for Windows NT: Structure
Determination Software Programs, Bruker Analytical X-ray Systems,
Inc., Madison, WI, 1997.
[31] G. Yang, S.-L. Zheng, X.-M. Chen, H.K. Lee, Z.-Y. Zhou,
T.C.W. Mak, Inorg. Chim. Acta 303 (2000) 86.