Facile synthesis and structures of infinite one-dimensional silver(I) coordination polymers

Article abstract of DOI:10.1016/j.poly.2004.06.002

The synthesis and characterization of the isolated, infinite tubular coordination polymers {[Ag(cis-tach)]ClO₄}_∞ (1), {[Ag(trans-tach)]ClO₄}_∞ (2) and {[Ag(cis-tach)] BF₄}_∞ (3) has been achi

Full text of DOI:10.1016/j.poly.2004.06.002

Polyhedron 23 (2004) 2075–2079
www.elsevier.com/locate/poly
Facile synthesis and structures of infinite one-dimensional
silver(I) coordination polymers
*
Alexandra L. Pickering, Geoffrey J.T. Cooper, De-Liang Long, Leroy Cronin
Department of Chemistry, Joseph Black Building, University of Glasgow, University Avenue, Glasgow G12 8QQ, UK
Received 17 March 2004; accepted 7 June 2004
Available online
Abstract
The synthesis and characterization of the isolated, infinite tubular coordination polymers {[Ag(cis-tach)]ClO4}1 (1), {[Ag(trans-
tach)]ClO4}1 (2) and {[Ag(cis-tach)]BF4}1 (3) has been achieved with the isomers cis,cis-1,3,5-triaminocyclohexane and cis,trans-
1,3,5-triaminocyclohexane. Each new material has been fully characterized by single crystal X-ray diffraction, NMR, IR and
elemental analysis. Compounds 1–3 form definite channels by the trigonal planar coordination of silver(I) metal centres to rigid,
aliphatic triamino ligands, forming 42 ꢀ 6 topological networks.
Ó 2004 Elsevier Ltd. All rights reserved.
Keywords: One-dimensional; Silver(I); Aliphatic amino ligands; Coordination polymers; Tubes; Topology; Supramolecular chemistry; Self assembly;
Nanotubes
1. Introduction
build-up networks of specific topologies, and has been
successful in creating a great number of functional ma-
terials that contain channels within a higher dimen-
sionality array [10–13], and a much smaller number that
exist as isolated one-dimensional polymers [14–16]. We
have recently published the first synthesis of infinite,
isolated silver(I) coordination tubes by incorporating a
pre-organized, tridentate ligand system that is flexible
enough to ‘wrap’ its number of arms to form a tubular
network [17].
We herein report the extended synthesis of a variety
of silver(I) nanotubes using the isomerically related li-
gands cis,cis-1,3,5-triaminocyclohexane (cis-tach) and
cis,trans-1,3,5-triaminocyclohexane (trans-tach) (Fig. 1).
The ligand system in each case has combined rigidity
due to the cyclohexane backbone and flexibility due to
the primary aliphatic amino groups. The formation of
the tubular networks appears to be a function of the
nitrogen donor geometry combined with anion effects,
and as such comprise a novel synthetic route to the
construction of the isolated nanotubes {[Ag(cis-
tach)]ClO4}1 (1), {[Ag(trans-tach)]ClO4}1 (2) and
{[Ag(cis-tach)]BF4}1 (3).
Since their discovery in 1991 [1], carbon nanotubes
have become of increasing interest due to their unique-
ness in size, shape and extraordinary physical properties.
Experiments are emerging that investigate the properties
of carbon nanotubes, whose structural properties are
determined by such features as length, diameter and
chirality. Such studies have shown carbon nanotubes to
be extremely robust materials, and research into the
construction of fibre-composite materials using carbon
nanotubes is underway [2]. However, production of
single (SWNT) [3–6] and multiple (MWNT) [7] walled
carbon nanotubes is both expensive and challenging.
Coordination polymers are attractive alternatives as the
self-assembly of polynuclear, functional materials pro-
vides a flexible and facile route to systems more tradi-
tionally formed using a covalent approach [8,9]. This
methodology uses coordinative or weaker forces to
* Corresponding author. Tel.: +44-141-330-6650; fax: +44-141-330-
4888.
E-mail address: L.Cronin@chem.gla.ac.uk (L. Cronin).
0277-5387/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2004.06.002

2076
A.L. Pickering et al. / Polyhedron 23 (2004) 2075–2079
NH2
H2N
H2N
NH2
H2N
H2N
cis,cis-1,3,5-triaminocyclohexane
cis,trans-1,3,5-triaminocyclohexane
Fig. 1. Ligand geometry facilitating network formation.
2. Experimental
evaporation over two months. Yield: 41 mg (0.12 mmol,
48%). [Ag(C6H15N3)]ClO4; Found (Calc.)%: C 21.38
(21.49), H 4.69 (4.55), N 11.65 (11.72); H NMR (ppm)
1
2.1. Materials and physical measurements
1.15 (q, 1H, J 11.60 Hz), 1.42 (tt, 2H, J 3.93, 12.81 Hz),
1.88 (d, 2H, J 13.61 Hz), 2.17 (dt, 1H, J 1.80, 11.86 Hz),
3.23 (tt, 2H, J 3.83, 11.68 Hz), 3.47 (quin, 1H, J 3.41
Hz); 13C NMR (ppm) 37.96 (CH2), 44.53 (CH2), 45.19
(CH), 45.73 (CH); FTIR (wavenumbers in cmꢁ1) 3332
(m), 3282 (m), 2904 (w), 2389 (w), 1716 (m), 1579 (m),
1454 (w), 1365 (m), 1351 (m), 1211 (w), 1187 (w), 1068
(s), 993 (s), 970 (s), 875 (m), 844 (m), 806 (m).
Ligands cis,cis- and cis,trans-1,3,5-triaminocyclohex-
ane were synthesized according to literature methods
[18]. All other solvents and reagents were used as pur-
chased without further purification. NMR spectra were
1
measured in D2O on a Bruker DPX-400 (400 MHz H,
100 MHz 13C). Infrared spectra were obtained from
samples prepared as KBr discs in the 650–4000 cmꢁ1
range using a Jasco FTIR-410 spectrometer. Elemental
analyses were performed on a CE-440 Elemental
Analyser.
2.2.3. Synthesis of [Ag(cis-tach)]BF4 (3)
Silver(I) tetrafluoroborate (75 mg, 0.39 mmol) in
water (3 ml) was added dropwise to a solution of cis,cis-
1,3,5-triaminocyclohexane (100 mg, 0.78 mmol) in
methanol (2 ml) and the solution stirred for 1 h. The
resulting clear, colourless solution was filtered and single
crystals suitable for X-ray diffraction were grown by
diffusion of ether. Yield: 116 mg (0.358 mmol, 46%).
[Ag(C6H15N3)]BF4; Found (Calc.)%: C 22.32 (22.25),
2.2. Synthesis of compounds 1–3
2.2.1. Synthesis of [Ag(cis-tach)]ClO4 (1)
Silver perchlorate (40 mg, 0.19 mmol) in methanol
(3 ml) was added dropwise to a methanolic solution of
cis,cis-1,3,5-triaminocyclohexane (50 mg, 0.39 mmol)
and stirred at room temperature for 1 h, during which
white precipitate occurred. Water (5 ml) was added and
the mixture stirred for a further 30 min. The resulting
cloudy solution was filtered and the clear colourless fil-
trate yielded colourless needle-like crystals suitable for
diffraction by diffusion with ethanol. Yield: 20 mg
(0.06 mmol, 32%) [Ag(C6H15N3)]ClO4 (334.98); Found
(Calc.)%: C 20.99 (21.49), H 4.32 (4.49), N 11.98 (12.48);
1H NMR (ppm) 0.96 (q, 3H, J 11.62 Hz), 2.19 (dt, 3H,
J 3.83, 11.42 Hz), 3.12 (m, 3H); 13C NMR (ppm) 40.154
1
H 4.65 (4.66), N 12.74 (12.97); H NMR (ppm) 1.03 (q,
3H, J 11.60 Hz), 2.17 (dt, 3H, J 3.53, 11.34 Hz), 3.15 (tt,
3H, J 3.73, 11.05 Hz); 13C NMR (ppm) 39.195 (CH2),
47.096 (CH); FTIR (wavenumbers in cmꢁ1) 3372 (w),
3347 (m), 3301 (w), 2923 (m), 2852 (m), 2237 (w), 1587
(s), 1459 (s), 1382 (m), 1359 (m), 1290 (w), 1261 (w),
1201 (s), 1074 (s), 948 (m), 923 (m), 856 (w), 806 (m).
2.3. X-ray crystallography
(CH2), 47.124 (CH); FTIR (wavenumbers in cmꢁ1
)
Suitable single crystals of 1–3 were prepared and the
crystals were mounted on a thin glass fibre using Fom-
blin oil. X-ray intensity data were measured at 150 K on
a Nonius Kappa-CCD diffractometer [kðMo KaÞ ¼
3332 (m), 3284 (m), 2919 (w), 2850 (w), 1581 (m),
1457 (w), 1378 (m), 1199 (m), 1074 (s), 1047 (s), 948 (m),
921 (m), 856 (w).
ꢀ
0:7107 A]. Structure solution and refinement for 1–3 was
2.2.2. Synthesis of [Ag(trans-tach)]ClO4 (2)
carried out with SHELXS-97 [19] and SHELXL-97 [20] via
WinGX [21]. Corrections for incident and diffracted
beam absorption effects were applied using empirical
[22] and numerical methods [23]. None of the crystals
showed evidence of crystal decay during data collection.
Compounds 1–3 crystallized in the space group P21=c,
as determined by systematic absences in the intensity
data, intensity statistics and the successful solution and
refinement of the structures. All structures were solved
Silver perchlorate (53 mg, 0.25 mmol) in methanol (3
ml) was added dropwise to a methanolic solution of
cis,trans-1,3,5-triaminocyclohexane (65 mg, 0.51 mmol)
and stirred at room temperature for 1 h, during which a
small amount of white precipitate occurred. The cloudy
solution was filtered through a cotton wool plug until
clear. The clear colourless filtrate yielded pale brown,
block-like crystals suitable for diffraction by slow

A.L. Pickering et al. / Polyhedron 23 (2004) 2075–2079
2077
Table 1
Crystallographic data for compounds 1–3a
listed in Table 1. Relevant interatomic bond distances
and bond angles for 1–3 are given in Table 2.
1
2
3
Empirical formula
C6H15Ag-
ClN3O4
336.53
C6H15Ag-
ClN3O4
336.53
C6H15AgB-
F4N3
3. Results and discussion
Formula weight
Crystal system
323.89
monoclinic
8.4228(4)
7.6234(4)
16.4719(8)
90
monoclinic
8.4778(5)
7.6947(3)
monoclinic
7.3136(8)
8.0334(13)
3.1. Structural analysis of compounds 1–3
ꢀ
a (A)
ꢀ
b (A)
ꢀ
Crystallization of a methanolic mixture of cis,cis-
1,3,5-triaminocyclohexane with AgClO4 and AgBF4 and
cis,trans-1,3,5-triaminocyclohexane with AgClO4 results
in the formation of infinite one-dimensional coordina-
tion polymers. Each structure contains a metal to ligand
ratio of 1:1 and the asymmetric unit in each case consists
of one ligand, one silver(I) ion and one counter ion.
None of the structures presented here contain solvent
molecules (see Fig. 2).
Both the trigonal planar silver(I) ions and the tri-
dentate amino ligands can be seen as three-coordinate
units, which self-assemble to form 42 ꢀ 6 topological
networks. The macrocycles formed upon coordination
facilitate a tubular structure with a definite channel. The
channels found in compounds 1, 2 and 3 are not large
enough to encapsulate a further molecule, having di-
c (A)
16.6640(12) 8.9245(12)
90
a (°)
b (°)
90
101.289(8)
90
96.803(2)
90
97.792(3)
90
c (°)
Space group
P21=c P21=c
1079.41(11) 514.20(12)
P21=c
1047.90(9)
3
ꢀ
V (A )
Z value
4
2
4
2.053
qcalc (g/cm3)
2.071
2.114
150(2)
2.174
2.219
150(2)
1559
l (cmꢁ1
T (K)
)
1.950
150(2)
2061
Number of observations 2121
Residuals: R; Rw
0.0295;
0.0578
0.0590;
0.1041
0.0308;
0.0500
P
P
a R1 ¼ kFoj ꢁ jFck= jFoj.
n
.
o
1=2
P
P
2
2
wR2 ¼
½wðFo2 ꢁ Fc2Þ ꢂ
½wðFo2Þ ꢂ
.
ꢀ
Table 2
Bond lengths and angles for compounds 1–3
mensions of 5.4, 5.3 and 5.6 A, respectively. The isolated
one-dimensional polymers together form an extensive
three-dimensional hydrogen-bonded network linked via
interactions between the coordinating amino groups and
the counter ions (Fig. 3).
ꢀ
Bond lengths (A)
Compound
Bond angles (°)
1
Ag–N(1) 2.403(3) N(1)–Ag–N(2)
98.15(10)
Ag–N(2) 2.222(3) N(1)–Ag–N(3) 111.44(11)
Ag–N(3) 2.224(3) N(2)–Ag–N(3) 150.28(11)
The manner in which these rigid ligands facilitate the
formation of tubular networks is dependent upon their
coordination geometry. The molecule cis-tach is a tri-
podal ligand, where the three equatorial amino residues
can wrap around the walls of the channel (Fig. 4(a)).
trans-Tach, on the other hand, has the ability to coor-
dinate in a linear polymer via the two equatorial groups
along a chain (Fig. 4(b)), and further coordination via
the axial amino group connects to a silver(I) centre of a
second chain and forms the tubular structure (Fig. 4(c)).
The macrocyles formed in each case by two silver(I) ions
and two ligands consist of 12 atoms and have an in-
version centre.
2
3
Ag–N(1) 2.273(11) N(1)–Ag–N(2) 133.5(4)
Ag–N(2) 2.276(10) N(1)–Ag–N(3) 108.4(4)
Ag–N(3) 2.345(11) N(2)–Ag–N(3) 118.1(4)
Ag–N(1) 2.227(3) N(1)–Ag–N(2) 150.33(11)
Ag–N(2) 2.227(3) N(1)–Ag–N(3) 111.71(11)
Ag–N(3) 2.391(3) N(2)–Ag–N(3)
97.89(10)
by a combination of direct methods and difference
Fourier syntheses and refined against F 2 by the full-
matrix least-squares technique. Crystal data, data col-
lection parameters and refinement statistics for 1–3 are
Fig. 2. Asymmetric unit of 1 (a), 2 (b) and 3 (c). Note the coordination environment of the silver ion lies between T-shaped planar and trigonal
planar, with the Ag ion being ligated to three amino groups of different tach ligands.

2078
A.L. Pickering et al. / Polyhedron 23 (2004) 2075–2079
Fig. 3. Three-dimensional hydrogen bonded networks of (a) compound 1, (b) compound 2 and (c) compound 3 showing isolated coordination
polymers. The anions are shown by the black tetrahedra and the nitrogen atoms of the tach-based ligands are shown as spheres.
compound 1, CCDC No. 233832 for compound 2 and
CCDC No. 233833 for compound 3. Copies of this in-
formation may be obtained from the Director, CCDC,
12 Union Road, Cambridge, CB21EZ, UK (fax: +44-
1223-336033; e-mail: deposit@ccdc.cam.ac.uk or http://
www.ccdc.cam.ac.uk).
Acknowledgements
Fig. 4. (a) Ligand motifs of cis- and trans-tach shown as black dots
The authors are grateful to the EPSRC and the
University of Glasgow for financial support.
with arrows. (b) Macrocycle formation utilizing the different ligand
geometries with the silver ions show as black dots. (c) End-on view of
tubes showing channels.
3.2. Conclusions
References
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