Flexibility in the self-assembly of silver complexes: Coordination polymers from multi-armed pyridylmethyleneoxy ligands

Article abstract of DOI:10.1071/CH12464

The syntheses of new silver complexes of five isomeric bis(pyridylmethyleneoxy)benzenes, differing in the position of substitution on the benzene and pyridine rings, and three isomeric 1,3,5- tris(pyridylmethyleneoxy)benzenes, differing in the position of

Full text of DOI:10.1071/CH12464

RESEARCH FRONT
CSIRO PUBLISHING
Aust. J. Chem. 2013, 66, 443–451
Full Paper
http://dx.doi.org/10.1071/CH12464
Flexibility in the Self-Assembly of Silver Complexes:
Coordination Polymers from Multi-Armed
Pyridylmethyleneoxy Ligands
A
A B
,
Peter J. Steel and Christopher M. Fitchett
A
Department of Chemistry, University of Canterbury, Christchurch 8140, New Zealand.
Corresponding author. Email: chris.fitchett@canterbury.ac.nz
B
The syntheses of new silver complexes of five isomeric bis(pyridylmethyleneoxy)benzenes, differing in the position of
substitution on the benzene and pyridine rings, and three isomeric 1,3,5-tris(pyridylmethyleneoxy)benzenes, differing in
the position of substitution on the pyridine ring, are described. The structures of six of these complexes were characterised
using X-ray crystallography, showing the formation of coordination polymers for 3-pyridyl- and 4-pyridyl-armed ligands
and discrete complexes for 2-pyridyl-armed ligands. The precise nature of the structure was further determined by the
relative orientation of the pyridine rings in each case.
Manuscript received: 10 October 2012.
Manuscript accepted: 9 December 2012.
Published online: 22 January 2013.
Introduction
In this paper, we report our studies of the silver complexes
formed from a range of bis- and tris-armed ligands (L1–L8), as
shown in Scheme 1. These differ in the position and number of
coordinating arms of the central benzene ring, and the point of
attachment on the pyridyl ring. Previously, several ligands with
The self-assembly of suitably designed organic ligands with
metal fragments to construct discrete and polymeric metallosu-
pramolecular assemblies represents a well-developed route to
diverse architectures.[1] This approach has been used to form
coordination polymers and networks that are magnetically,[2]
photochemically[3] orcatalytically active,[4] and frameworks that
are able to absorb gases and small molecules.[5] Functional sec-
tions can be included as part of ligands, from the metal con-
nectors, or arise from the network.[6] However, an understanding
of the self-assembly processes is required in order to allow
controlled formation of desired architectures. Controlled self-
assembly using rigid ligands based on N-heterocyclic and
carboxylate ligands with defined geometric bridging potential
has proved an excellent method for the formation of polygons,
polyhedra, andextendednetworks.[6a,7] However, for many years
we,[8] and others,[9] have investigated ligands that have included
a degree of flexibility, and have had success in the formation of
architectures that would be unavailable to more rigid ligands.
In particular, we have concentrated on synthesising ligands
with pyridine groups appended to an aromatic core by flexible
linkers.[8b,10] This allows the conformational flexibility of the
ligand to orient the coordinating groups towards metal atoms in
ways that are unavailable to more rigid ligands. Thus, multi-
armed ligands of this type have given rise to one-, two-, and
three-dimensional metallosupramolecular helicates,[8e,11]
cages,[12] and networks.[11,13] In combination with weakly
coordinating metals, such as acidic silver cations, which can
attain varying coordination number and geometry, the formation
of a variety of different structures is possible.[14] The fluid
nature of interaction between silver and ligand allows weaker
interactions, such as weak hydrogen bonds[15] or interaction
with non-coordinating anions,[16] to dominate the formation of
the product structures.
N
N
O
O
O
O
N
N
L1
L3
L2
N
O
O
O
O
O
O
O
N
N
N
N
N
L6
O
O
O
O
N
N
N
N
L4
L5
L7
O
N
O
O
O
N
N
N
N
L8
Scheme 1.
Journal compilation Ó CSIRO 2013
www.publish.csiro.au/journals/ajc

444
P. J. Steel and C. M. Fitchett
2-pyridylmethyleneoxy arms attached to benzene rings have
demonstrated ability to form macrocycles,[17] and one- and
two-dimensional networks in the case of 1,4-disubstituted
benzene rings.[18] Three-dimensional networks are formed
in the reactions of 1,3,5-trisubstituted benzene rings with
both 2-pyridylmethyleneoxy and 3-pyridylmethyleneoxy
derivatives.[19]
of the backbone, the independent pyridine rings are free to
rotate, and orient themselves at almost identical angles of
70.4(1)8 and 70.2(1)8 to the central benzene ring. The pyridine
rings are almost coplanar, with their respective mean planes
having an angle of 2.3(1)8 to one another.
The polymeric chains of 1 propagate perpendicularly to the
˚
a-unit cell edge, and stack with the silver atoms 5.465(2) A
apart. They are staggered, such that each benzene ring is held by
edge-to-face p–p interactions from pyridine rings on either side.
These interactions are characterised by the close approach
between hydrogen atoms of the benzene rings to the plane of
Results and Discussion
The ligand series for this investigation was drawn from several
literature compounds, combined with new ligands synthesised
by us. Ligands L1,[20] L2,[21] L3,[22] and L6–L8[23] were syn-
thesised using literature procedures. The remaining ligands
were synthesised using modified literature procedures. Catechol
or resorcinol was combined with the appropriate chloro-
methylpyridine hydrochloride and potassium carbonate in
DMF. This mixture was then heated to 1108C overnight, and the
product purified by column chromatography and recrystallisa-
tion, providing the ligands in low yield (L4, 24 %, and L5,
22 %). The ligands were characterised by 1H NMR, 13C NMR,
HR-ESMS and elemental analysis.
Initially, we decided to investigate the effect changing the
substitution of the pyridine rings system would have on the
structures formed. Thus, L1 and L2, which correspond to a
change in substitution position of the pyridine to 3- and
4-substituted, were reacted with silver nitrate. The complexes
1 and 2 were isolated as crystalline powders from their respec-
tive solutions. Analysis of the complexes by NMR showed only
the presence of ligand, indicating the complexes formed were
not stable in typical NMR solvents, as observed by us in previous
investigations.[17] The crystalline solids of 1 and 2 both showed
a 1 : 1 metal-to-ligand stoichiometry, but only 1 could be
induced to form single crystals, despite numerous attempts.
The structure of 1 was determined from crystals grown by the
slow evaporation of a solution of 1 in acetonitrile.
˚
the pyridine ring (2.76(8) and 2.81(8) A). The solvate water
molecules and nitrate counterions occupy the spaces between
the polymeric chains, and form a hydrogen-bonded polymer
perpendicular to the direction of the coordination polymer. The
nitrate ion is involved in hydrogen-bonding interactions with
water molecules through different oxygen atoms, with distances
˚
˚
of O20AꢀꢀꢀO13 2.849(4) A and O20BꢀꢀꢀO12 2.861(5) A, and
donor-hydrogen-acceptor (DHA) angles of 166(4)8 and
174(5)8, respectively.
The reaction of the three ortho-substituted ligands L3, L4,
and L5 with silver nitrate gave complexes 3, 4, and 5. Pleasingly,
crystals of all three complexes could be formed, by diffusion of
diethyl ether into the reaction mixture in the case of 3, and into
an acetonitrile solution of the complex in the case of complexes
4 and 5. We expected that ligand L3 would likely form a
tetradentate mononuclear complex with silver, a structural motif
that had already been observed for this ligand in an iron(II)
complex.[22] The structure of the silver nitrate complex 3 was
unusual, in that it contained four discrete ligand–metal units, all
with very similar structures. Fig. 2 illustrates both the structures
of the units and their similarity by overlaying the four indepen-
dent ligand–metal units. In each of the units, the silver forms
strong bonds to the pyridine nitrogen atoms, with lengths
˚
ranging between 2.192(2) and 2.265(2) A, with N–Ag–N bond
The structure of 1, shown in Fig. 1, was found to be a one-
dimensional polymer. The structure contains two independent
half molecules, which are arranged around a centre of inversion
at the centre of the benzene ring. This orients the coordinating
pyridine nitrogens away from one another, while the ether
oxygen atoms are non-coordinating. The silver atoms have a
slightly distorted linear coordination geometry with an N–Ag–N
angle of 176.7(1)8, and Ag–N bond lengths of 2.134(3) and
2.137(3) A, giving the polymer a zig-zag shape. The silver is
also weakly interacting with an adjacent nitrate counterion lying
˚
above the polymer (Ag–O 3.061(3) A), which accounts for the
slight distortion fromlinearity. Owing to the enhanced flexibility
angles in the range 156.7(2)–163.3(2)8. However, despite our
initial assumptions about the potential for the ligand to be
tetradentate, the silver formed only relatively weak interactions
with the ligand oxygen atoms, with AgꢀꢀꢀO distances between
˚
2.611(2) and 2.679(2) A. The nitrate counterions occupy spaces
between the mononuclear units, with each of the counterions
interacting with a silver atom through an oxygen. Three of these
˚
interactions are in the range 2.883(2)–2.993(2) A. The fourth is
˚
˚
considerably closer, with an AgꢀꢀꢀO distance of 2.678(2) A,
which, in part, destroys any higher-symmetry relationships
between the mononuclear units. The oxygen atoms of the nitrate
counterions are also involved in C–HꢀꢀꢀO interactions with the
O11
N10
O12
O13
O8Ј
N1Ј
Ag1
O20
N1
O8
0
˚
Fig. 1. Perspective view of the structure of 1, with part of the asymmetric unit labelled. Selected bond lengths (A) and bond angles (8): Ag1–N1
2.134(3), Ag1–N1 2.137(3), N10–Ag1–N1 176.71(9).

Coordination Polymers
445
˚
ligand, with HꢀꢀꢀO distances between 2.405(4) and 2.939(4) A
parallel to the bc-face of the unit cell, with the nitrate counter-
ions occupying spaces between molecules in each layer. This
arrangement maximises face-to-face p–p interactions involv-
ing off-set rings, with distances between planes of 3.4–4.8 A,
and precludes any edge-to-face interactions.
(see Supplementary Information).
The mononuclear units are planar, with the angle of each
pyridine ring mean plane to its attached benzene ring between
4.9(1)8 and 17.0(1)8. These units are arranged in layers that stack
˚
Unlike L3, the ligand in 4 was not expected to be planar, as it
was less likely to chelate a metal atom, although large chelate
rings have been observed for flexible ligands.[24] The silver
nitrate complex 4 required recrystallisation from the original
sample, which showed an intriguing 2 : 3 ligand-to-metal ratio
on analysis, to give crystals suitable for single-crystal structural
analysis. The recrystallised complex forms in the monoclinic
space group P21/c, with an asymmetric unit containing one
silver nitrate, one molecule of L4 and one acetonitrile solvate
molecule. This 1 : 1 metal–ligand stoichiometry represents a
reorganisation of the structure during crystal growth in the
donating acetonitrile solvent. The complex has a one-
dimensional structure, with the L4 molecule bridging two silver
˚
atoms at a distance of 11.674(2) A, as shown in Fig. 3. The
pyridine rings of the ligand bridge the metal atoms, are signifi-
cantly twisted away from each other (71.6(2)8), and have quite
different angles to the mean plane of the benzene ring (14.6(2)8
and 64.0(2)8). The silver atom has a linear geometry, with an
angle of 171.35(9)8 between the nitrogen atoms, and with Ag–N
Fig. 2. Perspective view overlaying the four independent ligand–metal
units of 3.
˚
bond lengths of 2.184(3) and 2.188(3) A. Combined with the
twist of the ligand, which gives an angle between the Ag–N
bonds of 108.0(9)8, the polymer has an undulating structure. The
silver atom is also weakly interacting with the oxygen atoms of
two nitrate counterions, with AgꢀꢀꢀO distances of 2.698(3) and
˚
2.709(3) A. The nitrate counterions bridge two metal atoms,
˚
which are 3.263(3) A apart. Such a close approach implies an
O8A
O8B
interaction between the two metal atoms, being within the van
der Waals radius for the atoms. This has the effect of forming a
two-dimensional brick-wall structure, with the silver–silver
interactions making the silver atoms into T-shaped connectors,
with N–AgꢀꢀꢀAg angles of 77.25(7)8 and 42.07(7)8, as shown in
Fig. 4. The close approach of the interacting silver atoms is also
aided by face-to-face p–p interactions between the pairs of
coordinated pyridine rings, which are coplanar (9.3(2)8) and
N1A
Ag1
O12
N1B
N10
O13
˚
slightly offset, so that the closest approach is 3.47(1) A. The
pyridine rings across the centre of the ‘bricks’, which are related
by a centre of inversion, are slightly closer with the mean planes
Ag1
O11
˚
3.39(1) A apart. The twisting of the ligand orients the edges of
Fig. 3. Perspective view of the structure of 4, showing the asymmetric unit
˚
as part of the polymeric chain. Selected bond lengths (A) and bond angles (8):
Ag1–N1A 2.184(3), Ag1–N1BA 2.188(3), N1A–Ag1–N1BA 171.35(9).
pyridine rings and the central benzene rings towards faces of
adjacent aromatic systems, but these are not oriented close
Fig. 4. Perspective view of a section of the two-dimensional brick-wall structure of 4.

446
P. J. Steel and C. M. Fitchett
˚
Fig. 5. Perspective view of a section of the polymeric chain of 5, with the atomic labelling shown. Selected bond length (A): Ag1–N1
2.151(3).
enough for edge-to-face p–p interactions.[25] The acetonitrile
solvate molecules are found between the two-dimensional
layers.
The silver nitrate complex 5 also formed a one-dimensional
polymeric structure, as shown in Fig. 5. The complex crystal-
lises in the monoclinic space group C2/c, with half silver atoms
and half-molecules of L5 occupying a centre of inversion and a
two-fold axis (through the centre of the benzene ring), respec-
tively. The ligand is arranged with the pyridine rings oriented in
the same direction, bridging strictly linear silver atoms (Ag–N
˚
bond length 2.151(3) A) at an angle of 17.8(2)8 (angle subtended
by the Ag–N bonds) to give a zig-zag polymer.
The polymer chains of 5 are remarkably planar, with the
˚
ligand having a mean deviation of only 0.052(7) A from the
mean plane of all non-hydrogen atoms. The silver atom deviates
˚
only slightly from the plane of the pyridine ring (0.011(7) A).
The polymeric chains of 5 are planar, and propagate along the
ac-diagonal, with the distance between the silver atoms of the
˚
chain 7.715(2) A. The nitrate counterions are found in the plane
of the polymer, and are non-coordinating (closest approach O12
˚
3.037(3) A), occupying the spaces between the silver atoms. The
Fig. 6. Perspective view of the macrocyclic structure of 6, showing the
face-to-face overlap of the central benzene rings. The hydrogen atoms have
˚
been omitted for clarity. Selected bond lengths (A) and bond angles (8):
planar chains stack to form a sandwich of layers, with the
polymeric chains offset so that the benzene of one chain lies
above the silver atom of an adjacent chain. This offset means
that the aromatic rings of the chains do not overlap, which is
required for any p–p face-to-face interactions.
Ag1–N1A 2.218(3), Ag1–O22 2.347(3), Ag1–O13 2.459(3), Ag1–O12
2.573(3), Ag2–N1B 2.188(3), Ag2–N1CA 2.189(3), N1A–Ag1–O22
142.2(1), N1A–Ag1–O13 133.3(1), O22–Ag1–O13 82.9(1), N1A–Ag1–
O12 113.60(9), O22–Ag1–O12 97.6(1), N1B–Ag2–N1CA 170.6(1).
We next decided to investigate the effect of adding another
coordinating arm to the central benzene ring. We choose to
maximise symmetry of the ligands by using phloroglucinol as
the parent alcohol, giving 1,3,5-trisubstituted benzene cores.
The ligands differ in the substitution pattern of the pyridine ring.
The reaction of L6 with silver nitrate gave a crystalline precipi-
tate of complex 6 in quantitative yield (98 %). Crystals of 6
suitable for X-ray single-crystal structure determination were
grown by diffusion of pentane into an acetonitrile solution of 6.
The reaction of L7 and L8 with silver nitrate gave only products
that discoloured quickly on isolation from the solvent, possibly
indicating reduction of the silver cation. Alternatively, L7 and
L8 were reacted with silver tetrafluoroborate in acetonitrile to
give 7 and 8, which were isolated by diffusion of pentane into the
reaction mixtures. Complex 7 was isolated as crystals suitable
for structure determination, whereas suitable crystals of 8 could
not be grown despite numerous attempts.
The silver nitrate complex 6 forms a macrocyclic structure
consisting of two molecules of 6 bridged by two silver atoms,
giving a 24-membered dimetallomacrocycle, as shown in Fig. 6.
As for the structure of 3 above, the potentially chelating ability
of the arms of L6 is not observed in this structure. The silver
atoms are only coordinated to the ligand through the pyridine
nitrogens, which are twisted away from the ether oxygens. The
silver atoms that are part of the 24-membered macrocycle have a
slightly distorted linear coordination geometry, with Ag–N bond
˚
lengths of 2.188(3) and 2.189(3) A. The remaining silver atom is
coordinated by one pyridine, with an Ag–N bond length of
˚
2.218(3) A, and three oxygen atoms of two nitrate anions. One of
the nitrate anions chelates the silver through two oxygen atoms
˚
with bond lengths 2.459(3) and 2.573(3) A, whereas the other is
˚
monodentate with an Ag–O bond length of 2.347(3) A, giving
the silver atom a distorted tetrahedral geometry.

Coordination Polymers
447
˚
Fig. 7. Perspective view of a section of polymeric chain of the structure of 7. Selected bond lengths (A) and bond angles (8): Ag1–N1B 2.183(2), Ag2–N1A
2.146(2), Ag2–N1CA 2.152(2), N1A–Ag2–N1CA 174.27(9).
The pyridine rings of the ligand molecules are slightly
tilted relative to the central benzene ring at angles of 23.9(7)8,
18.4(7)8, and 40.7(7)8. This, combined with the flexibility of
the spacer groups, allows the ligands to form a macrocyclic
structure with the remaining pyridine rings pointed in opposite
directions, or anti to one another. The structure forms in the
triclinic space group P-1, with a centre of inversion in the
middle of the macrocycle making the opposite benzene rings
necessarily coplanar. These rings overlap, with the centre of the
chains to be involved in p–p face-to-face interactions. The
closest of these interactions occurs between one of the pyridine
rings and a benzene ring of an adjacent chain. These rings are
almost coplanar (7.1(2)8) and slightly offset, with C2A
˚
3.34(4) A above the centre of the benzene ring.
The planarity and proximity of the chains also allow an
Agꢀꢀꢀp interaction to occur between Ag1 and the C2–C3 bond of
an adjacent benzene ring. This interaction is not symmetrical,
˚
with distances of 3.339(3) and 3.378(3) A between the silver
atom and C2 and C3 respectively. The interaction is quite weak
compared with other silver–arene complexes, which typically
˚
C1–C2 bond 3.49(1) A above the adjacent ring, indicating p–p
face-to-face stacking.
˚
The macrocyclic units pack with numerous interactions
between adjacent units. The benzene cores arrange with the
have bonding distances of ,2.6 A. The distance from the silver
atom to the midpoint of the double bond is 3.286(4) A, which is
˚
˚
edges overlapped and 3.385(5) A apart, indicating a p–p inter-
shorter than the proposed silver to double-bond van der Waals
[26]
˚
interaction distance of 3.42 A.
action. The non-coordinated oxygen atom of the chelating
nitrate anion interacts with the bridging silver atom (AgꢀꢀꢀO
The one-dimensional polymeric chain of ‘loops and rods’
topology of 7, although rare, has been described on various
occasions. These polymers usually involve flexible bidentate
ligands and metals atoms that bridge three ligand molecules.
The silver nitrate and zinc nitrate complexes of 1,4-bis(1-
imidazolylmethyl)benzene have similar structures, which are
slightly more complex owing to interpenetration of the poly-
˚
2.727(3) A), and this interaction distorts the silver atom from a
linear geometry. The non-coordinated oxygen atoms of the
nitrate anions also interact with numerous hydrogen atoms,
˚
the closest of which has an OꢀꢀꢀH distance of 2.30(5) A.
The silver tetrafluoroborate structure 7 was also found to
form a macrocyclic structure, with the remaining pyridine ring
bridging two ligands to from a one-dimensional polymer of
rings, as shown in Fig. 7. The structure forms in the triclinic
space group P-1 with an asymmetric unit comprising one
molecule of L7 and one-and-a-half silver tetrafluoroborates
with two acetonitrile solvate molecules. This corresponds to
the M3L2 stoichiometry found in the elemental analysis, assum-
ing that the acetonitrile molecules were lost during sample
preparation. As with the structure of 6, the complex forms a
macrocycle surrounding a centre of inversion, which relates the
two halves of the macrocycle. The silver atoms of the
28-membered macrocycle are coordinated by two pyridine
nitrogen atoms, with Ag–N bond lengths of 2.146(2) and
meric strands to form
a two-dimensional polyrotaxane
network[27] and a polyrotaxane column,[28] respectively. There
are also examples of structures with this topology using rigid
bidentate ligands such as the silver hexafluorophosphate com-
plex of 1,4-bis(3-pyridyl)1,2,4,5-tetrazine.[29] However, the
structure of 7 represents the first example of this topology
type where the roles of the components have been reversed;
here the flexible ligand L7 is tridentate and the silver atoms
each bridge two ligand molecules, giving an M3L2, rather than
an M2L3, stoichiometry for the polymer.
The polymers of 7 are arranged with coplanar chains stacked
offset by half a ligand unit. This offset gives the structure a
‘honeycomb’ appearance, with columnar channels, as shown in
Fig. 8. These channels contain the tetrafluoroborate counterions
and acetonitrile solvate molecules. One of the tetrafluoroborate
counterions resides on a centre of inversion, and is therefore
disordered over two orientations. Both of the tetrafluoroborate
counterions are involved in numerous CHꢀꢀꢀF interactions with
˚
2.152(2) A, and have a slightly distorted linear coordination
geometry (N–Ag–N 174.27(9)8). The silver atoms that link the
macrocyclic units to form the polymeric chain reside on centres
˚
of inversion, with an Ag–N bond length of 2.183(2) A and a
strictly linear coordination geometry.
The ligand molecules are remarkably planar, with the pyri-
dine rings of the macrocycle tilted by 7.1(2)8 and 5.7(2)8 to the
benzene ring, and the linking pyridine tilted at an angle of
11.1(2)8 to the benzene ring. The macrocycle is also quite planar,
˚
HꢀꢀꢀF distances between 2.30 and 3.00 A. The majority of their
interactions occur between the tetrafluoroborate counterions
and the acetonitrile solvate molecules, which in turn weakly
interact with the silver atoms of the polymeric chains, with
˚
with a mean deviation of only 0.112(5) A from planarity for its
28 atoms. The planarity of the polymer allows the adjacent
˚
AgꢀꢀꢀN distances in the range 2.78–2.96 A.

448
P. J. Steel and C. M. Fitchett
Fig. 8. Perspective view of the offset co-planar chains of 7 down the bc-diagonal, showing the channels filled with
tetrafluoroborate counterions (fluorine atoms as spheres). The solvate molecules and hydrogen atoms have been
removed for clarity.
Conclusions
chromatography (20 g silica, 90 : 10 EtOAc/MeOH) and
recrystallisation from 1 : 1 light petroleum/EtOAc gave L7 as a
white crystalline solid. Yield 0.36 g (24 %), mp 76–778C. Anal.
calc. for C18H16N2O2: C 73.95, H 5.52, N 9.58. Found: C 73.77,
H 5.58, N 9.72 %. dH (500 MHz, CDCl3) 8.67 (2H, s, H20), 8.57
(2H, d, H60), 7.78 (2H, d, H40), 7.29 (2H, m, H50), 6.96 (4H, m,
H2,H3,H4,H5), 5.14 (4H, s, CH2). dC (75 MHz, CDCl3) 149.33
(C20), 148.84 (C60), 148.56 (C1,C6), 135.17 (C40), 132.58 (C30),
123.44 (C50), 122.14 (C3,C4), 115.85 (C2,C5), 68.89 (CH2). m/z
(EI-MS) 292.1219, C18H16N2O2 requires [Mþ] 292.1212.
The six crystal structures presented here show that two- and
three-armed flexible ligands based on pyridylmethyleneoxy
substituents are able to form both discrete and polymeric com-
plexes with silver. The formation of coordination polymers was
shown to be more likely with 3- and 4-substituted pyridine-
based ligands, but the precise complex formation was driven by
the relative conformation of the pyridine rings. We believe that
these ligands represent useful additions to the library of multiply
armed molecules available for use in the formation of coordi-
nation polymers.
1,2-Bis(4-pyridylmethoxy)benzene, L5
Catechol (0.60 g, 5.5 mmol), 4-chloromethylpyridine hydro-
chloride (1.81 g, 11.0 mmol), and K2CO3 (3.41 g, 25 mmol)
were stirred at 1008C in dry DMF (10 mL) under nitrogen for
21 h. The resulting suspension was poured onto H2O (50 mL)
and extracted with CH2Cl2 (2 ꢁ 75 mL). The organic extracts
were washed (2 ꢁ 50 mL H2O, 50 mL brine), dried (Na2SO4)
and reduced under vacuum to a brown solid. Flash chromatog-
raphy (20 g silica, 90 : 10 EtOAc/MeOH) and recrystallisation
from 1 : 1 light petroleum/EtOAc gave L8 as a white crystalline
solid. Yield 0.35 g (22 %), mp 101–1028C. Anal. calc. for
C18H16N2O2: C 73.95, H 5.52, N 9.58. Found: C 74.12, H 5.59,
N 9.69 %. dH (500 MHz, CDCl3) 8.61 (4H, s, H20,H60), 7.37 (4H,
d, H30,H50), 6.92 (4H, m, H2,H3,H4,H5), 5.18 (4H, s, CH2). dC
(75MHz, CDCl3) 149.86 (C20,C60), 148.18 (C1,C6), 146.22
(C40), 122.03 (C30,C50), 121.29 (C3,C4), 114.66 (C2,C5), 69.25
(CH2). m/z (EI-MS) 292.1219, C18H16N2O2 requires [Mþ]
292.1212.
Experimental
Materials and Methods
NMR spectra were recorded on Varian Unity 300 or Varian
1
INOVA 500 spectrometers at 300 or 500 MHz for H respec-
tively, and 75 MHz for 13C. 1H NMR and 13C NMR spectra were
recorded in CDCl3 and referenced relative to TMS. Electrospray
mass spectra were recorded using a Micromass LCT time-of-
flight mass spectrometer, with a probe operating at 3200 V and
cone voltage of 30 V. Melting points were determined using an
Electrothermal melting point apparatus and are uncorrected.
The Campbell microanalytical laboratory, University of Otago,
Dunedin, performed elemental analyses.
1,2-Bis(3-pyridylmethoxy)benzene, L4
Catechol (0.56 g, 5.1 mmol), 3-chloromethylpyridine hydro-
chloride (1.72 g, 10.4 mmol), and K2CO3 (3.61 g, 26 mmol)
were stirred at 1008C in dry DMF (10 mL) under nitrogen for
27 h. The resulting suspension was poured onto H2O (50 mL)
and extracted with CH2Cl2 (2 ꢁ 75 mL). The organic extracts
were combined, washed (2 ꢁ 50 mL H2O, 50 mL brine), dried
(Na2SO4) and evaporated under vacuum to a brown solid. Flash
Complex 1
Reaction of L1 (14.6 mg, 0.05 mmol) dissolved in hot acetone
with silver nitrate (17.0 mg, 0.10 mmol) dissolved in hot meth-
anol gave a colourless solution. A crystalline product appeared

Coordination Polymers
449
Table 1. Crystal data and X-ray experimental details for 1 and 3 7
]
Compound
1
3
4
5
6
7
Empirical formula
Formula weight
Temperature [K]
Crystal system
C
18H18N3O6Ag
C18H16N3O5Ag
462.21
C20H19N4O5Ag
503.26
C18H16N3O5Ag
462.21
C48H42N10O18Ag4 C56H54B3N10O6F12Ag3
480.22
168.15
Triclinic
P-1
1478.40
168.15
Triclinic
P-1
1547.13
168.15
Triclinic
P-1
168.15
168.15
168.15
Triclinic
P-1
Monoclinic
P21/c
Monoclinic
C2/c
Space group
Unit cell dimensions:
˚
a [A]
˚
b [A]
5.465(5)
6.931(6)
23.47(2)
84.090(10)
85.770(11)
89.558(13)
882.0(13)
2
14.141(5)
15.131(5)
16.909(6)
90.117(4)
110.099(5)
94.830(5)
3384(2)
8
11.827(5)
22.938(9)
8.104(3)
90.00
11.560(4)
17.727(6)
8.641(3)
90.00
8.297(6)
10.520(8)
14.946(11)
78.690(10)
75.663(9)
84.997(10)
1238.3(16)
1
11.151(3)
11.553(3)
12.764(3)
75.628(4)
82.693(3)
68.782(3)
1483.5(7)
1
˚
c [A]
a [8]
b [8]
g [8]
108.133(5)
90.00
98.569(5)
90.00
3
˚
Volume [A ]
2089.5(14)
4
1751.0(11)
4
Z
Density (calculated)
[Mg mꢂ3
1.808
1.815
1.600
1.753
1.982
1.732
]
Absorption coefficient
[mmꢂ1
F(000)
1.186
484.0
1.229
1.004
1.187
928.0
1.647
732.0
1.078
772.0
]
1856.0
1016.0
Crystal size [mm]
Theta range for data
collection [8]
0.55 ꢁ 0.46 ꢁ 0.16 0.31 ꢁ 0.25 ꢁ 0.05 0.59 ꢁ 0.57 ꢁ 0.07 0.34 ꢁ 0.24 ꢁ 0.17 0.29 ꢁ 0.25 ꢁ 0.19 0.61 ꢁ 0.52 ꢁ 0.24
5.24 to 518
3.78 to 518
4.04 to 528
4.6 to 52.728
3.96 to 50.248
4.46 to 50.58
Reflections collected
Independent reflections
[R(int)]
10066
39367
25399
6083
9267
17683
3262 [0.0413]
12411 [0.0382]
4078 [0.0432]
1778 [0.0317]
4350 [0.0220]
5334 [0.0198]
Observed reflections
3103
8419
3419
1422
3942
5032
[I . 2s(I)]
Data/restraints/parameters 3262/0/259
12411/0/973
1.011
4078/0/272
1.100
1778/0/125
1.026
4350/0/361
1.153
5334/0/427
1.071
Goodness-of-fit on F2
1.252
R1 [I . 2s(I)]
wR2 (all data)
0.0323
0.0829
0.0305
0.0366
0.0413
0.0278
0.0322
0.0744
0.0871
0.0905
0.0733
0.0804
on standing for 30 min. Yield 15.0 mg (64 %), mp 224–2288C.
Anal. calc. for C18H16N3O5Agꢀ1/2H2O: C 45.88, H 3.64, N 8.92.
Found: C 45.87, H 3.67, N 8.85 %. Crystals suitable for X-ray
diffraction were obtained by slow evaporation of an acetonitrile
solution of 1.
C36H32N7O13Ag3ꢀ(CH3)2CO: C 40.65, H 3.32, N 8.51. Found:
C 40.70, H 3.39, N 8.78 %. Crystals suitable for X-ray diffrac-
tion were obtained by diffusion of ether into an acetonitrile
solution of 4.
Complex 5
Complex 2
Reaction of L5 (14.4 mg, 0.05 mmol) in acetone with silver
nitrate (17.4 mg, 0.10 mmol) in methanol gave a light brown
precipitate immediately. Yield 19.2 mg (84 %), mp 164–1658C.
Anal. calc. for C18H16N3O5Ag: C 46.76, H 3.49, N 9.09. Found:
C 46.80, H 3.50, N 9.09 %. Crystals suitable for X-ray diffrac-
tion were obtained by diffusion of ether into an acetonitrile
solution of 5.
Reaction of L2 (14.7 mg, 0.05 mmol) dissolved in hot aceto-
nitrile with silver tetrafluoroborate (20.1 mg, 0.10 mmol) dis-
solved in hot acetonitrile gave
A crystalline powder formed on diffusion of diethyl ether into
the mother liquor. Yield 19.2 mg (70 %), mp 190–1918C. Anal.
calc. for C18H16N2O2BF4Agꢀ1½CH3CN: C 45.98, H 3.77, N
8.94. Found: C 45.88, H 3.73, N 8.73 %.
a colourless solution.
Complex 6
Complex 3
Reaction of L6 (19.8 mg, 0.05 mmol) in methanol with silver
nitrate (26.2 mg, 0.16 mmol) in methanol gave a colourless
solution. A crystalline product precipitated in standing for
30 min. Yield 36.0 mg (98 %), mp 199–2008C. Anal. calc. for
C24H21N5O9Ag2: C 39.00, H 2.86, N 9.47. Found: C 39.07,
H 2.76, N 9.35 %. Crystals suitable for X-ray diffraction
were obtained by diffusion of pentane into an acetonitrile
solution of 6.
Reaction of L3 (14.6 mg, 0.05 mmol) in acetone with silver
nitrate (17.3 mg, 0.10 mmol) in methanol gave a colourless
solution. Crystals suitable for X-ray diffraction were obtained
by diffusion of ether into the reaction mixture. Yield 12.1 mg
(52 %), mp 134–1358C. Anal. calc. for C18H16N3O5Ag: C 46.77,
H 3.49, N 9.09. Found: C 46.39, H 3.45, N 8.79 %.
Complex 4
Complex 7
Reaction of L4 (14.6 mg, 0.05 mmol) in acetone with silver
nitrate (17.4 mg, 0.10 mmol) in methanol gave a colourless
solution. A crystalline product appeared on standing overnight.
Yield 22.9 mg (79 %), mp 197–1998C. Anal. calc. for
Reaction of L7 (20.0 mg, 0.05 mmol) in acetonitrile with silver
tetrafluoroborate (31.2 mg, 0.16 mmol) in acetonitrile gave a
colourless solution. Crystals suitable for X-ray crystallography

450
P. J. Steel and C. M. Fitchett
were obtained from diffusion of pentane into this solution.
Yield 25.4 mg (73 %), mp .2608C (dec.). Anal. calc. for
C48H42N6O6Ag3B3F12: C 41.72, H 3.06, N 6.08. Found:
C 41.51, H 3.41, N 5.88 %.
(b) L. J. Murray, M. Dinca, J. R. Long, Chem. Soc. Rev. 2009, 38, 1294.
doi:10.1039/B802256A
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2011, 44, 123. doi:10.1021/AR100112Y
(b) N. N. Adarsh, P. Dastidar, Chem. Soc. Rev. 2012, 41, 3039.
doi:10.1039/C2CS15251G
(c) S. Kitagawa, R. Matsuda, Coord. Chem. Rev. 2007, 251, 2490.
doi:10.1016/J.CCR.2007.07.009
(d) P. R. Andres, U. S. Schubert, Adv. Mater. 2004, 16, 1043.
doi:10.1002/ADMA.200306518
Complex 8
Reaction of L8 (19.8 mg, 0.05 mmol) in acetonitrile with silver
tetrafluoroborate (32.1 mg, 0.16 mmol) in acetonitrile gave a
colourless solution. A fawn precipitate appeared on diffusion of
pentane into this solution. Yield 28.7 mg (95 %), mp 185–1878C
(dec.). Anal. calc. for C24H21N3O3AgBF4ꢀH2O: C 47.09, H 3.79,
N 6.86. Found: C 46.84, H 3.52, N 6.75 %.
[7] (a) P. J. Steel, C. M. Fitchett, Coord. Chem. Rev. 2008, 252, 990.
doi:10.1016/J.CCR.2007.07.018
(b) M. Ruben, J. Rojo, F. J. Romero-Salguero, L. H. Uppadine,
J.-M. Lehn, Angew. Chem. Int. Ed. 2004, 43, 3644. doi:10.1002/
ANIE.200300636
Crystallography
[8] (a) J. Burgess, P. J. Steel, Coord. Chem. Rev. 2011, 255, 2094.
doi:10.1016/J.CCR.2011.01.024
Table 1 lists crystal data and X-ray experimental details for the
structures discussed. All measurements were made with a
Siemens CCD area detector using graphite monochromated Mo
(b) J. R. A. Cottam, P. J. Steel, Tetrahedron 2009, 65, 7948.
doi:10.1016/J.TET.2009.07.068
(c) C. M. Fitchett, P. J. Steel, Inorg. Chem. Commun. 2007, 10, 1297.
doi:10.1016/J.INOCHE.2007.07.021
(d) P. J. Steel, Acc. Chem. Res. 2005, 38, 243. doi:10.1021/
AR040166V
(e) D. A. McMorran, P. J. Steel, Angew. Chem. Int. Ed. 1998, 37,
3295. doi:10.1002/(SICI)1521-3773(19981217)37:23,3295::AID-
ANIE3295.3.0.CO;2-5
˚
Ka (l ¼ 0.71073 A) radiation at the temperature indicated in the
following table. The data reduction was performed using
SAINT.[30] Intensities were corrected for Lorentz and polarisa-
tion effects and for absorption using SADABS.[31] Space groups
were determined from systematic absences and checked for
higher symmetry. The structures were solved by direct methods
using SHELXS,[32] and refined on F2 using all data by full-matrix
least-squares procedures with SHELXL-97.[33] All non-
hydrogen atoms were refined with anisotropic displacement
parameters. Hydrogen atoms were included in calculated
positions with isotropic displacement parameters 1.3 times the
isotropic equivalent of their carrier carbons. The functions
[9] (a) P. Thanasekaran, C.-C. Lee, K.-L. Lu, Acc. Chem. Res. 2012, 45,
1403. doi:10.1021/AR200243W
(b) F. Dai, J. Dou, H. He, X. Zhao, D. Sun, Inorg. Chem. 2010, 49,
4117. doi:10.1021/IC902178C
(c) T.-F. Liu, J. Lu, R. Cao, CrystEngComm 2010, 12, 660.
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(d) J. A. Smith, J. G. Collins, F. R. Keene, Metal Complex–DNA
Interactions 2009, 319.
minimised were Sw(F2o – Fc2), with w ¼ [s2(F2o) þ (aP)2 þ bP]ꢂ1
,
where P ¼ [max(Fo)2 þ 2Fc2]/3. In all cases, final Fourier
syntheses showed no significant residual electron density in
chemically sensible positions. CCDC 903401–903406 contains
the supplementary crystallographic data for this paper. These
data can be obtained free of charge from the Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
(e) T. Basu, H. A. Sparkes, M. K. Bhunia, R. Mondal, Cryst. Growth
Des. 2009, 9, 3488. doi:10.1021/CG900195F
(f) X.-L. Wang, C. Qin, E.-B. Wang, L. Xu, Z.-M. Su, C.-W. Hu,
Angew. Chem. Int. Ed. 2004, 43, 5036. doi:10.1002/ANIE.200460758
[10] (a) M. R. A. Al-Mandhary, C. M. Fitchett, P. J. Steel, Aust. J. Chem.
2006, 59, 307. doi:10.1071/CH06116
(b) M. R. A. Al-Mandhary, P. J. Steel, Aust. J. Chem. 2002, 55, 705.
doi:10.1071/CH02128
Supplementary Material
[11] B. J. O’Keefe, P. J. Steel, CrystEngComm 2007, 9, 222. doi:10.1039/
B613689C
[12] (a) C. M. Hartshorn, P. J. Steel, Chem. Commun. 1997, 541.
doi:10.1039/A608081B
Tables of crystallographic data for all crystal structures are
available on the Journal’s website.
(b) C. M. Hartshorn, P. J. Steel, Angew. Chem. Int. Ed. 1996, 35, 2655.
doi:10.1002/ANIE.199626551
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