Synthesis, structural characterization and properties of Ag(i)-complexes based on double-armed 1,3,4-oxadiazole bridging ligands

Article abstract of DOI:10.1039/c1ce05718a

Four semirigid symmetric double-armed oxadiazole bridging ligands L1-L4 were designed and synthesized in good yields by reactions of 2,5-bis(2-hydroxyphenyl)-1,3,4-oxadiazole and 2,5-bis(3-hydroxyphenyl)-1,3,4- oxadiazole with 3-(bromomethyl)benzonitrile

Full text of DOI:10.1039/c1ce05718a

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PAPER
Synthesis, structural characterization and properties of Ag(I)-complexes
based on double-armed 1,3,4-oxadiazole bridging ligands†
*
Gui-Ge Hou, Yan Wu, Jian-Ping Ma and Yu-Bin Dong
Received 13th June 2011, Accepted 6th August 2011
DOI: 10.1039/c1ce05718a
Four semirigid symmetric double-armed oxadiazole bridging ligands L1–L4 were designed and
synthesized in good yields by reactions of 2,5-bis(2-hydroxyphenyl)-1,3,4-oxadiazole and 2,5-bis(3-
hydroxyphenyl)-1,3,4-oxadiazole with 3-(bromomethyl)benzonitrile and 4-(bromomethyl)benzonitrile,
respectively. The coordination chemistry of these four ligands with various Ag(I) salts has been
investigated. Eleven discrete, one- and two-dimensional polymeric Ag(I) complexes (1–11) were
prepared by solution reactions and characterized by infrared spectroscopy, elemental analysis, and
single-crystal X-ray diffraction. Compared to our reported ligands of this type, L1–L4 are more
flexible. The ligand conformation and polyatomic anion templating effect play a key role in
determining the final supramolecular structures. Compound 6 contains 3D intersecting channels with
different interior microenvironments. It can absorb two different types of guest molecules (benzene and
THF) independently or take them up simultaneously from a mixture of two kinds of guests.
Furthermore, it can completely separate THF/furan and benzene/toluene guest substrates in liquid
phase, respectively.
Ag(I) metal ions would allow the formation of MOFs pos-
Introduction
sessing fascinating architectures and novel topologies. Besides
the ligand and metal centre,8 the counter ion, often as
a template, is capable of directing the formation of certain
networks. Additionally, the counter ion is able to bind and
stabilize the encapsulated guest species through hydrogen
bonding interactions. Recently, the role of the polyatomic
anions in the self-assembly process has emerged as an
increasing interest.9 Thus, when designing the coordination-
driven architectures, the roles of the metal centre, anion and
ligand all need to be considered.
Metal–organic frameworks (MOFs)1–3 are a very attractive and
interesting class of porous materials due to their applications
for gas storage and organic molecule separation, catalysis,
luminescent and magnetic properties.4–6 Previous studies
demonstrate that their structure and pore size can be tuned by
changing organic ligands. Thus, the length, shape, conforma-
tion and coordinating orientation of organic ligands are
dominant in affecting the structures of the supramolecular
aggregates. For example, bent semirigid double-armed organic
ligands with long side spacers favor the variational confor-
mation (cis-, trans- or any intermediary conformations between
them),7 and would provide us with an alternative approach for
the construction of frameworks with novel patterns that are
not achievable easily by simple linear rigid ligands. On the
other hand, Ag(I), as a soft Lewis acid, may adopt various
coordination modes such as linear, trigonal planar, trigonal
pyramidal and tetrahedral coordination geometries. So, the
combination of semirigid double-armed organic spacers and
We have been exploring the coordination chemistry of 1,3,4-
oxadiazole or 4-amino-1,2,4-triazole bridging double-armed
ligands with acetylenylphenyl, pyridyl, cyano, aminophenyl,
Schiff-base or carboxylate as the terminal coordination sites. A
series of discrete and polymeric complexes based on the ligands
of this type have been reported.10 Some of them do display
interesting molecular recognizing, isomer separating and tunable
luminescent properties.10 As a part of our systematic study of
MOFs based on the ligands of this type, we present herein
a new set of semirigid double-armed oxadiazole bridging
ligands, namely 2,5-bis(2-(4-cyanobenzyloxy)phenyl)-1,3,4-oxa-
diazole (L1), 2,5-bis(2-(3-cyanobenzyloxy)phenyl)-1,3,4-oxadia-
zole (L2), 2,5-bis(3-(4-cyanobenzyloxy)phenyl)-1,3,4-oxadiazole
(L3) and 2,5-bis(3-(3-cyanobenzyloxy)phenyl)-1,3,4-oxadiazole
(L4), and eleven novel Ag(I) complexes based on L1–L4 and
College of Chemistry, Chemical Engineering and Materials Science, Key
Laboratory of Molecular and Nano Probes, Engineering Research Center
of Pesticide and Medicine Intermediate Clean Production, Ministry of
Education, Shandong Provincial Key Laboratory of Clean Production of
Fine Chemicals, Shandong Normal University, Jinan 250014, People’s
Republic of China. E-mail: yubindong@sdnu.edu.cn
ꢀ
various Ag(I)X salts (X ¼ PF6ꢀ, SbF6ꢀ, ClO4 and SO3CF3ꢀ),
† Electronic supplementary information (ESI) available. CCDC
reference numbers 791137–791147. For ESI and crystallographic data
in CIF or other electronic format see DOI: 10.1039/c1ce05718a
respectively (Scheme 1). In addition, the host–guest chemistry of
complex 6 was investigated primarily.
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Scheme 1 Synthesis of 1–11.
polar organic solvents such as CH2Cl2, acetone and THF, which
potentially facilitates the solution reactions between the ligands
and inorganic metal salts.
Results and discussion
Ligand synthesis
L1–L4 were synthesized by the reactions of 2,5-bis(2-hydroxy-
phenyl)-1,3,4-oxadiazole and 2,5-bis(3-hydroxyphenyl)-1,3,4-
oxadiazole with 3-(bromꢁomethyl)benzonitrile and 4-(bromo-
methyl)benzonitrile at 60 C in the presence of the strong base
(KOH) in good yields, respectively. The results herein demon-
strate that the 1,3,4-oxadiazole heterocycle is stable under the
experimental conditions. It is noteworthy that two terminal
moieties are connected via two exo-oxadiazole C–C single bonds
at 2,5-positions to create the bent spacer, in which two long arms
can freely rotate around the C–C bonds. Scheme 2 presents some
possible typical conformations of these new ligands. Compared
to our previously reported ligand of bis(3-acetylenylphenyl-(4-
cyanophenyl))oxadiazole,10g the two terminal cyanophenyl
groups herein are symmetrically connected to the phenyl rings via
two flexible –O–CH2– linkages instead of rigid –ChC– moieties,
which makes the ligands of L1–L4 more flexible. In addition, the
ether linkage would be an additional coordinating site to bind the
soft Ag(I) centre. Notably, L1–L4 are very soluble in common
Scheme 2 Typical possible conformations of L1–L4.
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Synthesis of Ag(I)-based complexes
along the crystallographic c axis, in which benzene solvent
ꢀ
molecules and non-coordinating PF6 counter ions are alterna-
The slow diffusion of an organic solution (THF or CH2Cl2) of
ꢀ
tively located (Fig. 1). The other set of benzene molecules are
located between layers.
L1–L4 into a THF or benzene solution of Ag(I)X (X ¼ PF6
,
ꢀ
SbF6ꢀ, SO3CF3 and ClO4ꢀ), respectively, afforded the 1 : 1 or
2 : 1 metal–organic adducts with various coordination struc-
tures. Crystals formed within half a month in satisfactory yields.
It is worthwhile to point out that, in these specific reactions, the
products do not depend on the ligand-to-metal ratio. Their
assembled structures, however, are determined by the various
ligand conformations (cis-, trans- or any intermediary confor-
mations between them)7 by changing either the polyatomic
anions or solvent template. L1–L4 show various conformations
in the compounds of 1–11. For example, ligands L1 and L2 in 1,
2, 4 and 5 adopt cis-conformation I (Scheme 2) to link Ag(I) ions
into discrete or polymeric complexes, while L1 in 3 adopts trans-
conformation III (Scheme 2) into a 1D double-chain. L3 and L4
in 6–11 adopted cis-conformation IV (Scheme 2) to bind Ag(I)
ions into 1- and 2D complexes. On the other hand, the anions
also caused the change in the structures of the Ag(I)-based
complexes. For instance, the reaction of AgPF6, AgSbF6 and
AgSO3CF3 with L1 in CH2Cl2/benzene system produced three
kinds of complexes, that is, discrete complex (1) and 1D poly-
meric complexes (2 and 3). Although similar 1D zigzag chains are
found in 4 and 5 after the coordination of L2 to Ag(I) ions,
greatly different crystal stacking fashions are observed due to the
different coordinating natures of the SbF6ꢀ and SO3CF3ꢀ anions.
Again, the self-assembly of L4 with AgPF6, AgSbF6 and AgClO4
yields in each case a 1D chain motif, however, the non-coordi-
Differently to 1, 2 presents a 1D double-chain. As shown in
Fig. 2, the Ag(I) coordination sphere changes from {AgN2O2} in
1 to {AgN3O2} in 2 due to one of the two terminal –CN donors
becoming involved. The {Ag2N4} dinuclear core also exists in 2
ꢀ
with a Ag/Ag contact of ca. 3.56 A. The chains extend along the
crystallographic a axis and are further reinforced by the weak
intra-ligand p–p interactions (centroid-to-centroid distance
ꢀ
ꢀ
between benzene groups ca. 3.7 A and ca. 3.9 A) (Fig. 3). All the
chains are parallel and arrange in the crystallographic bc plane.
Inter-chain p–p interactions between the oxadiazole-phenyl
fragments link these 1D chains into a 3D network. The non-
ꢀ
coordinating PF6 anions fill in the space between chains in an
ordered way.
In a different way from 2, the Oether donors in 3 are uncoor-
dinated (Fig. 4). The trigonal pyramidal {AgN3O} coordination
sphere consists of two Noxadiazole donors, one NCN donor and one
Om-OTf donor. The orientation of the two terminal 4-benzoni-
trilephenyl arms are oriented in the reverse directions, so L1
herein shows a trans-conformation III (Scheme 2), which is
markedly different from its cis-conformation in 1 and 2.
As shown in Fig. 5, the {Ag2N4} units are bridged by the ‘‘S-
shaped’’ L1 ligands to form a 1D double-chain along the crys-
tallographic c axis. Again, the weak intra-chain p–p interactions
ꢀ
(3.9 A) and inter-chain p–p interactions (3.8 A) exist, and the
ꢀ
benzene guests are located between the chains.
ꢀ
ꢀ
nating PF6 and SbF6 yield a single chain motif, whereas the
ꢀ
weakly coordinated ClO4 yields a 1D double-chain pattern.
The PF6ꢀ, SbF6ꢀ and ClO4ꢀ counterions, however, do not affect
the self-assembly of L3 and the Ag(I) cation, and compounds 6–8
are isostructural with the same 2D networks. All the obtained
complexes were photostable during our experimental process.
Ag(I)-complexes based on L2
Crystallization of L2 with AgSbF6 and AgSO3CF3 (metal-to-
ligand ratio 2 : 1) in a CH2Cl2/THF mixed-solvent system at
room temperature, respectively, afforded compounds 4 and 5
with infinite 1D zigzag double-chain motifs.
Structural analysis
In 4 ([Ag2(L2)](SbF6)2), two crystallographically independent
Ag(I) centres adopt a three-coordinate {AgN2O} coordination
Ag(I)-complexes based on L1
sphere that consists of one N,O-chelating group and one NCN
-
Crystallization of L1 with AgPF6, AgSbF6 and AgSO3CF3
(metal-to-ligand ratio 2 : 1) in a CH2Cl2/C6H6 mixed solvent
system at room temperature afforded 1–3 as colourless crystals.
Single-crystal X-ray analysis reveals that 1 ([Ag(L1)](PF6)$1.5
(C6H6)) is a discrete Ag2L2 molecular complex, while 2 ([Ag(L1)]
(SbF6)) and 3 ([Ag2(L1)2](SO3CF3)2$(C6H6)) are 1D polymers.
In 1, two cis-L1 ligands (cis-conformation I, Scheme 2) link
two Ag(I) centres into a discrete molecular complex. Ag(I) adopts
a distorted tetrahedral {AgO2N2} coordination sphere that
consists of two N,O-chelating groups.10 As shown in Fig. 1, the
Ag1 atom lies on the two fold axis of rotation parallel to the
donor (Fig. S1†). In the solid state, the cis-conformational L2
(cis-conformation I, Scheme 2) acts as a ‘‘doubling up’’ spacer to
link Ag(I) atoms into a 1D zigzag double-chain extended along
the crystallographic b axis. As indicated in Fig. 6, all the zigzag
ꢀ
double-chains are parallel and the SbF6 anions are located
ꢀ
between the chains. It is worth pointing out that one of the SbF6
anions is weakly coordinated to the Ag(I) centre with a long F/
ꢀ
Ag bond distance of 2.86 A. The weak F/M interactions often
ꢀ
occur in the supramolecular complexes that contain Fꢀ, BF4
PF6ꢀ, SbF6ꢀ or SO3CF3 counterions.11
,
ꢀ
In 5 ([Ag(L2)](SO3CF3)2), however, the Ag(I) centre lies in
ꢀ
a axis and the P atoms of the two independent PF6 ions are at
a five coordinated {AgN2O3} sphere because of the involved
ꢀ
sites with 222 symmetry. Two Ag(I) atoms are bridged by four
coordinated H2O molecule (dAg(1)-O(3) ¼ 2.475(4) A) and
SO3CF3ꢀ anions (dAg(1)-O(4) ¼ 2.655(5) A) (Fig. 7 and S2†). Two
ꢀ
N
oxadiazole atoms into an {Ag2N4} cluster core with a short Ag/
ꢀ
Ag distance (ꢂ3.52 A), which is slightly longer than the sum of
neighbouring Ag(I) atoms are bridged by a bridging m-OH2
molecule, two Noxadiazole-donors and a m2-O3SCF3ꢀ anion into an
{Ag2O3N2} cluster core.
ꢀ
the van der Waals radii of two silver atoms (3.44 A). Notably,
two terminal –CN groups are not coordinated to an Ag(I) centre
probably due to the steric hindrance. In the solid state, the Ag2L2
discrete molecular complexes stack offset to generate rectan-
ꢀ
Therein, the SO3CF3 anion acts as a m2-k2-OO’ bridging
ꢀ
ligand12 rather than showing the terminal m-O3SCF3 bridging
coordination mode observed in 3 or reported Ag-OSO2CF3
2
ꢀ
gular-like channels (effective cross section of ca. 5.4 ꢃ 7.3 A )
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Fig. 1 Coordination environment of Ag(I) in 1 (left, displacement ellipsoids drawn at the 30% probability level, A ¼ ꢀx + 3/2, ꢀy + 1/2, z; B ¼ x, ꢀy +
1/2, ꢀz + 1; C ¼ ꢀx + 3/2, y, ꢀz + 1) and its crystal packing view down the crystallographic c axis (right, benzene guest molecules are marked in yellow
for clarity).
Fig. 2 ORTEP figure of 2 (displacement ellipsoids drawn at the 30%
probability level. A ¼ ꢀx + 1, ꢀy, ꢀz + 1).
complexes.10 The united coordinating mode results in the rela-
ꢀ
tively short Ag/Ag distance (3.52 A). As indicated in Fig. 7, the
{Ag2O3N2} cluster cores are linked to each other by cis-confor-
mational L2 ligands into a 1D zigzag double-chain, which is
similar to those of 4. Furthermore, these zigzag double chains
stack offset to generate elliptical-like channels, in which the non-
Fig. 4 Coordination environment of Ag(I) in 3 (displacement ellipsoids
ꢀ
coordinating SO3CF3 anions are located and fixed by two sets
drawn at the 50% probability level. A ¼ ꢀx, ꢀy + 2, ꢀz; B ¼ x, y, z ꢀ 1).
of O(7)/H(3A)-O(3) hydrogen bonds between water and the
Fig. 3 1D double-chain (left) and crystal packing (right) of 2.
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Fig. 5 1D double-chain and the crystal packing driven by p–p interactions in 3.
SO3CF3ꢀ anion (Fig. 8). The corresponding O(7)/H(3A) and O
(7)/O(3) bond distances are 2.33 A and 3.19(2) A, and the O
(7)/H(3A)-O(3) angle is 145.1ꢁ, respectively.
the host framework. Notably, L3 adopts cis-conformation IV in
6 (Scheme 2).
ꢀ
ꢀ
Upon close inspection of the structures, we found that the
encapsulated guests are stabilized in the cavities through
a complicated host(D–H)/SbF6ꢀ(A)/guest(D–H) hydrogen
bonding system. As shown in Fig. 9, two THF molecules are
fixed in the cavity by four equivalent sets of C(21)–H(21A)/F
(3) hydrogen bonds. The corresponding C(21)/F(3) and H
Ag(I)-complexes based on L3
Complexes 6 ([Ag(L3)](SbF6)$0.5(C6H6)(THF)), 7 ([Ag(L3)]
PF6$0.5(C6H6)) and 8 ([Ag(L3)]ClO4$0.5(C6H6)) were obtained
as 2D networks by the combination of L3 with the corresponding
Ag(I) salts (metal-to-ligand ratio 2 : 1) in a THF/C6H6 mixed
solvent system. The single-crystal X-ray crystal structure analysis
revealed that 6–8 are isostructural (Fig. S3–5†). Therefore, only
the structure of 6 is described in detail herein. As shown in Fig. 9,
The Ag(1) atom lies on the two fold axis of rotation parallel to
the c axis. The ligand and the SbF6ꢀ ion are both bisected by the
crystallographic mirror plane perpendicular to the b axis. The Ag
(I) centre in 6 is surrounded by two Noxadiazole and two –CN
groups. The corresponding Ag(I)-Noxadiazole and Ag(I)-NCN
ꢀ
ꢀ
(21A)/F(3) distances are 3.511(32) A and 2.71 A, respectively,
ꢀ
and :C(21)–H(21A)/F(3) is 139.5ꢁ. Meanwhile, the SbF6
anion still connects to the host framework by a series of F/H–
phenyl hydrogen bonds. The F/H and F/C bond distances
ꢀ
are in the ranges of 2.5–2.7 and 3.1–3.6 A, respectively. Fig. 10
shows that the benzene guest is fixed by the C–H/F hydrogen
bonds. The H(18)/F(1), H(18)/F(4) and H(16)/F(4)
ꢀ
ꢀ
ꢀ
distances are 2.310(13) A, 3.001(7) A and 3.172(7) A, respec-
tively, and the corresponding :C(18)–H(18)/F(1), :C(18)–H
(18)/F(4) and :C(16)–H(16)/F(4) are 178.2ꢁ, 125.9ꢁ and
119.0ꢁ respectively. In addition, the weak interaction between
the H(17) atom and {Ag2N4} bimetallic ring occurs in the
ꢀ
ꢀ
bonding distances are 2.275(4) A and 2.392(6) A, respectively.
Two central oxadiazole groups bind two Ag(I) atoms to generate
a {Ag2N4} bimetallic ring, in which the Ag/Ag distance is 3.58
ꢀ
host–guest framework with a short distance of ca. 1.98 A
ꢀ
A, which is slightly longer than the sum of the van der Waals
(Fig. 10).
radii of two silver atoms. Four {Ag2N4} moieties are doubly
connected to each other by the 4-benzonitrilephenyl arms of L3
to generate a rhombus-like macrocycle, in which the two pairs of
opposite Ag/Ag distances are ca. 1.6 and 3.0 nm, respectively.
The macrocyclic unit of 6 propagates along two dimensions,
resulting in 2D layers arranged in the crystal in an –AA– stacking
fashion along the crystallographic c axis to generate rhombic
channels. These are further reinforced by inter-ligand p–p
interactions (Fig. 9). An inspection of Fig. 9 and 10 reveals that
the overall array contains a 3D intersecting channel system and
large open windows, with an approximate effective cross section
Compared to 6, compounds 7 and 8 have the same size of
rhombus-like channels (Fig. S6†). There are no THF guest
molecules, however, found in the cavities of 7–8. Such a change
might again result from the different anion templates. Compared
to the SbF6ꢀ anion, the ClO4ꢀ and PF6ꢀ anions might be not be
suitable to form the anion-THF hydrogen bonding systems,
which could be the rational explanation for the host framework
showing no affinity for the THF guest.
Ag(I)-complexes based on L4
ꢀ
ꢀ
ꢀ
ꢀ
of ca. 16 ꢃ 12 A (down c), 6 ꢃ 8 A (down a), and 7 ꢃ 8 A (down
The combination of L4 with AgSbF6, AgPF6 and AgClO4
(metal-to-ligand ratio 2 : 1) produced the polymeric complexes 9
([Ag(L4)](SbF6)), 10 ([Ag(L4)](PF6)ꢄ(THF)) and 11 ([Ag(L4)]
(ClO4)$0.5(CH2Cl2)$0.5(H2O)), respectively, with novel one-
dimensional chain motifs.
[101]). Benzene, THF and SbF6 are found in the different
channel spaces with different orientations. Interestingly, in 6, two
distinct different organic species, that is, ether and aromatics, are
stored within the same crystals and separated from each other by
Fig. 6 1D chain along the crystallographic b axis of 4 (A ¼ ꢀx + 1, ꢀy + 1, ꢀz).
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Fig. 7 Ag(I) coordination sphere and zigzag double-chain in 5 (A ¼ ꢀx + 2, ꢀy + 1, ꢀz + 1; B ¼ x + 1, y, z).
nets to a 1D chain in 9, indicating the remarkable influence of the
different nitrogen donor orientations. In the solid state, all the
ꢁ
one-dimensional chains stack together along the [101] direction
to generate honeycomb-like channels (Fig. 11). Therein, the
ꢀ
dimensions of the honeycomb-like channel is about 8 ꢃ 9 A.
ꢀ
Inside the channels, non-coordinating SbF6 counter ions are
located.
Compared to 9, 10 (Fig. S8 †) exhibits the same macrocycle-
containing one-dimensional chain and the same honeycomb-like
channels (Fig. 12). It is different from 9, however, as the
ꢀ
honeycomb-like channels contain both PF6 anions and guest
ꢀ
THF molecules. The PF6 anion and the guest THF molecule
form a hydrogen bonded pair with a F/H bond length of
ꢀ
2.658 A.
By simply changing the anions from the non-coordinating
ꢀ
PF6 to the weakly coordinating ClO4ꢀ, complex 11 was
obtained as an infinite one-dimensional chain but containing
different ring unit. It is different from 9–10. The Ag(I) centre in
11 lies in a distorted trigonal {AgN3} coordination sphere
(Fig. 13 and Fig. S9†). L4 in 11 also takes a cis-conformation of
IV (Scheme 2). Fig. 13 indicates that the two 3-benzoni-
trilephenyl arms on each L4 bend inward and converge at the Ag
(I) centre to give rise to a monometallic metallocycle. This is
further connected to other metallocycles through the Noxadiazole
donors to form a one-dimensional chain along the crystallo-
Fig. 8 Crystal packing of 5 showing channels along the crystallographic
a axis (i ¼ x, ꢀy + 3/2, z).
In 9, the Ag(1) atom lies on the two fold axis of rotation
ꢀ
parallel to the c axis. The ligand and the SbF6 ion are both
bisected by the crystallographic mirror plane perpendicular to
the b axis. The cis-conformational L4 (cis-conformation IV,
Scheme 2) links the four coordinated Ag(I) centres (Fig. S7†) into
a 27-membered macrocycle-containing 1D chain along the
ꢀ
graphic b axis. It is worth pointing out that the ClO4 anion is
near to the Ag(I) centre and is weakly coordinated to the Ag(I)
ꢀ
ꢀ
crystallographic c axis (Fig. 11). The non-coordinating SbF6
atom with a long O/Ag bond distance of 2.782(8) A. The chains
anions are located in the macrocycles. In 9, the Ag/Ag contact
stack along the crystallographic [101] direction in a –ABAB–
fashion into a two-dimensional network, which is assisted by the
inter-chain p–p interactions between parallel phenyl rings on
ꢀ
in the {Ag2N4} ring is 3.65 A, which is slightly longer than those
of 6–8. Compared to 6–8, the polymer patterns change from 2D
Fig. 9 Ag(I) coordination environment, molecular Ag(I)-L3 macrocyclic unit and crystal packing pattern of 6. The encapsulated benzene and THF
molecules are shown in bright yellow and deep yellow colours, respectively (i ¼ 1 ꢀ x, y, 1 ꢀ z; ii ¼ 0.5 ꢀ x, 0.5 ꢀ y, 2 ꢀ z; iii ¼ 0.5 + x, 0.5 ꢀ y, ꢀ1 + z).
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Fig. 10 Views (down a (left) and down [101] (right)) of the crystal packing of 6. The encapsulated benzene and THF molecules are shown in bright
yellow and deep yellow colours, respectively (i ¼ ꢀx + 1, y, ꢀz + 2; ii ¼ x + 0.5, y + 0.5, z; iii ¼ x + 0.5, ꢀy + 0.5, z; iv ¼ x + 0.5, y + 0.5, z).
neighboring chains. Disordered water and CH2Cl2 molecules are
ꢀ
sample in DMSO-d6 indicates both benzene (d ¼ 7.33 ppm) and
THF (d ¼ 1.75 and 3.59 ppm) guest molecules were re-absorbed
into the framework to result in [Ag(L3)]$0.5(C6H6)(THF) (6d).
This indicates the host/guest complex of 6 is restored under
experimental conditions. The XRPD patterns based on the
regenerated samples of 6a–d confirm that the AgL3 framework is
stable during these reversible adsorption processes (Fig. 14).
Since 6a is insoluble in benzene and THF, the possibility of
a dissolution-recrystallization mechanism to explain the solvent
re-absorption is unlikely.
located in the honeycomb-like channels (ca. 7 ꢃ 8 A, Fig. 13).
Host–guest chemistry of compound 6.
Metal–organic hosts with well-defined inner cavities have
provided an alternative approach for molecular adsorption and
separation.13 We have been exploring the adsorption and sepa-
ration of aromatics, including alkyl- and active functional group-
substituted aromatic isomers, on porous MOFs.10i–j As a porous
framework, we wondered if compound 6 herein is robust and
could reversibly adsorb guest species such as benzene and THF
molecules. Thermogravimetric analyses (TGA, Fig. S10,† the
calculated and experimental weight loss percentage values at
As shown above, compound 6 herein exhibits 3D intersecting
channels. It contains different channels with different interior
microenvironments extended along the different directions and is
able to absorb different types of guest molecules independently,
or take them up simultaneously from a mixture of different guest
species.14
ꢁ
1
100ꢂ180 C are 11.4% and 9.7%, respectively) together with H
NMR spectra indicate that all benzene and THF guest molecules
can be removed at 100ꢂ180 ꢁC (Fig. 14). The desolvated sample
Interestingly, when the desolvated solid 6a is immersed in
1
furan for 12 h at room temperature, the H NMR (DMSO-d6)
ꢁ
of 6a was obtained by heating crystals of 6 at 110 C for about
1
12 h. The H NMR spectrum and TGA trace indicate the guest
spectrum indicates that furan molecules (d ¼ 6.47 and 7.59 ppm)
can also be absorbed into the framework to generate the corre-
sponding host–guest system furan3AgL3 (6e) with a host/guest
ratio of 1 : 1 (Fig. 15). As we know, the major hurdle in molec-
ular recognition is selectivity, that is, preparing a host-pocket
that responds only to the specific substrate in the presence of
other potential competitors. To explore the molecular selectivity
of AgL3 towards THF and furan, a designed experiment was
performed. The desolvated solid 6a was immersed in a mixed
solvent system consisting of equivalent molar amounts of THF
and furan (1 : 1) for 12 h at room temperature (no change in
binding was observed after 12 h, suggesting that the system
reached an equilibrium by 12 h). The 1H NMR (DMSO-d6)
spectrum indicates that only THF (d ¼ 1.75 and 3.59 ppm)
molecules were selectively absorbed in the channels (6f) (Fig. 15).
Such a rigorous selectivity might be attributed to the different
molecular geometrical shapes of THF and furan. Moreover, 6a is
able to recognize and separate benzene and toluene. When 6a
molecules were completely removed to generate the corre-
sponding desolvated sample of 6a. The XRPD pattern of 6a
shows that the shapes and intensities of some reflections are
slightly changed relative to that of the original sample (Fig. 14).
This means that guest loss does not result in symmetry change or
cavity volume collapse.
As shown in Fig. 14, when samples of the desolvated solid 6a
were, respectively, immersed in benzene and THF for 12 h at
room temperature, the solid samples were then dried in air and
then dissolved in DMSO-d6 for 1H NMR measurements. The 1H
NMR spectra (d ¼ 7.33 ppm for benzene and d ¼ 1.75 and 3.59
ppm for THF) indicate the corresponding guest molecules were
re-incorporated into the framework to generate two new host–
guest systems benzene3AgL3 (6b) and THF3AgL3 (6c),
respectively. Similarly, when the desolvated solid 6a was
immersed in a benzene/THF (v:v, 1 : 1) mixed solvent system for
1
12 h, the H NMR spectrum performed on the obtained solid
Fig. 11 1D chain (left) (A ¼ 1 ꢀ x, y, ꢀz; B ¼ x, y, ꢀ1 + z; C ¼ 1 ꢀ x, y, 1 ꢀ z) and the crystal packing of 9 with honeycomb-like channels (right).
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Fig. 12 1D chain (left, A ¼ x, ꢀy, z + 0.5; B ¼ x, ꢀy, z ꢀ 0.5; C ¼ x, y ꢀ 1, 1 + z) and the crystal packing of 10 with honeycomb-like channels (right, i ¼
0.5 + x, 0.5 ꢀ y, 0.5 + z).
was immersed in a mixed solvent system consisting of benzene
and toluene (v:v, 1 : 20) for 12 h (no difference in binding was
observed at the longer exposure times), only benzene molecules
were absorbed to generate benzene3AgL3 (6h). This is
confirmed by the corresponding 1H NMR (DMSO-d6) spectrum
(Fig. 15 (6h)). In other words, 6a displays a strict selectivity for
benzene and toluene and can completely separate them under
photoluminescence quantum yields, together with the electron-
deficient nature of the oxadiazole group.18 Therefore, many
oxadiazole-based molecular wires, dendritic derivatives, conju-
gated polymers and metal–organic frameworks have been
studied as excellent luminescent materials.17
Our previous study indicates that 1,3,4-oxadiazole bridging
metal–organic frameworks do display interesting luminescence
properties.10 The results demonstrated that the emission colours
of oxadiazole-organic molecules were sometimes affected by
their incorporation into metal-containing coordination
compounds. With this in mind, the luminescent properties of L1–
L4 and their Ag(I) complexes 1–11 were investigated in the solid
state (Table 1). In the solid state, L1–L4 exhibit interesting
photoluminescence with an emission maximum in the range of
495, 484, 417 and 487 nm upon excitation at 347, 397, 365 and
413 nm, respectively. Thus, the emission colour of the free ligand
L1 was significantly affected by its incorporation into its Ag(I)-
containing complexes, as evidenced by the large blue shift (70–97
nm) for 1–3 in the emission colours (Fig. S11†). Similarly, the
emissions of compounds 9–11 are blue-shifted by 19–26 nm
compared with that of L4 (Fig. S12†). This indicates that the
emissions of 1–3 and 9–11 may originate from charge transition
between the ligand and the metal ions. In contrast to the emis-
sions of 1–3 and 9–11, the emissions of 4–8 are neither MLCT
nor LMCT in nature and might be assigned to the intraligand (n–
p* or p–p*) emission because very similar emission bands are
also observed for the free L2 and L3 ligands, respectively
(Fig. S13–14†).
mild conditions in liquid phase.13i Notably, the H NMR spec-
1
trum indicates no toluene guest can be encapsulated in the AgL3
host even without any other guest competitors (Fig. 15 (6g)). It is
different from the THF/furan mixture, the molecular size herein
might be the critical factor for this strict selectivity. The crys-
tallographic lengths of benzene and toluene molecules are ꢂ2.7
ꢀ
and ꢂ4.2 A (defined as the longest distances between the non-
hydrogen atoms on these guest molecules), respectively.
Compared to benzene, the larger toluene guest is harder to fit in
ꢀ
the channel (dimensions of ca. 6 ꢃ 8 A) along the crystallo-
graphic a axis.
Luminescent properties of L1–L4 and their Ag(I)
complexes
MOFs have been investigated for fluorescence properties and for
potential applications as luminescent materials.15 Owing to the
higher thermal stability of inorganic–organic coordination
polymers and the ability to affect the emission wavelength of
organic materials, the syntheses of coordination polymers by the
judicious choice of conjugated organic spacers and transition
metal centres can be an efficient method for obtaining new types
of electroluminescent materials, especially for d10 or d10–d10 co-
systems16 and oxadiazole-based complexes.17 The oxadiazole ring
is electron deficient, resulting in poor hole transport but good
electron transport properties as electron-accepting materials. In
the past two decades, 2,5-diaryl-1,3,4-oxadiazole derivatives
have been among the most widely employed electron-trans-
porting/hole-blocking materials. This is due to their good
Conclusions
In this study, four semirigid double-armed oxadiazole bridging
ligands L1–L4 were designed and synthesized by the reaction of
2,5-bis(2-hydroxyphenyl)-1,3,4-oxadiazole
and
2,5-bis(3-
hydroxyphenyl)-1,3,4-oxadiazole with 3-(bromomethyl)benzo-
nitrile and 4-(bromomethyl)benzonitrile, respectively. Eleven Ag
(I) discrete and polymeric coordination complexes have been
thermal
and
chemical
stabilities
and
their
high
Fig. 13 1D chain (left, A ¼ x, y + 1, z) and crystal packing pattern (right) of 11.
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Fig. 14 1H NMR spectra (DMSO-d6) and corresponding XRPD patterns recorded at room temperature: (6) The as-synthesized sample of 6. (6a) The
solid sample of 6 was heated at 110 ꢁC for 12 h. (6b) The desolvated solid 6a was immersed in benzene for 12 h and dried at room temperature for 12 h.
(6c) The desolvated solid 6a was immersed in THF for 12 h and dried at room temperature for 12 h. (6d) The desolvated solid 6a was immersed in
benzene and THF (v: v, 1 : 1) for 12 h and dried at room temperature for 12 h. (S6) The simulated XRPD pattern based on the single crystal of 6. The
encapsulated benzene and THF molecules are marked in the 1H NMR spectra, respectively.
successfully prepared by the reaction of these new ligands and
Experimental
various silver salts in solution. This study demonstrates that
Materials and methods
the semirigid double-armed oxadiazole-bridged organic ligands
are useful building blocks in the construction of discrete and
AgPF6, AgSbF6, AgSO3CF3, AgClO4 (Acros) were used as
polymeric complexes and the ligand isomerism and templating
obtained without further purification. Infrared (IR) samples
effect of polyatomic anions are the key factors in determining
were prepared as KBr pellets, and spectra were obtained in the
400–4000 cmꢀ1 range using a Perkin-Elmer 1600 FTIR spec-
the final structure of supramolecular complexes. Interestingly,
the framework of 6 is robust and is able to desorb and re-
trometer. Elemental analyses were performed on a Perkin-
Elmer Model 2400 analyzer. 1H NMR data were collected
absorb benzene and THF molecules. More interestingly, it can
absorb two different types of guest molecules (benzene and
using an AM-300 spectrometer. Chemical shifts are reported in
THF) independently or take them up simultaneously from
d relative to TMS. All fluorescence measurements were carried
a mixture of two kinds of guests. In addition, 6 can completely
out on a Cary Eclipse Spectrofluorimeter (Varian, Australia)
separate THF/furan and benzene/toluene substrate mixtures,
equipped with a xenon lamp and quartz carrier at room
respectively. We are currently extending this result by
temperature. Thermogravimetric analyses were carried out
preparing new rigid and semirigid symmetric and unsymmetric
using a TA Instrument SDT 2960 simultaneoꢁ us DTA-TGA
under flowing nitrogen at a heating rate of 10 C minꢀ1. XRD
five-membered heterocyclic ring bridging ligands of this type
containing different terminal coordination functional groups.
patterns were obtained on a D8 ADVANCE X-ray powder
ꢀ
The new metal–organic polymers and supramolecular
complexes based on new bent spacers of this type with novel
polymeric patterns and properties will be reported in the near
future.
diffractometer (XRD) with CuKa radiation (l ¼ 1.5405 A).
Caution! One of the crystallization procedures involves AgClO4,
which is a strong oxidizer.
Fig. 15 1H NMR spectra (DMSO-d6) and corresponding XRPD patterns recorded at room temperature: (6e) The desolvated solid 6a was immersed in
furan for 12 h and dried at room temperature for 12 h. (6f) The desolvated solid 6a was immersed in furan and THF (v:v, 1 : 1) for 12 h and dried at room
temperature for 12 h. (6g) The desolvated solid 6a was immersed in toluene for 12 h and dried at room temperature for 12 h. (6h) The desolvated solid 6a
was immersed in benzene and toluene (v:v, 1 : 20) for 12 h and dried at room temperature for 12 h. The encapsulated benzene and furan molecules are
1
marked in the H NMR spectra, respectively.
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Table 1 Luminescent properties of L1–L4 and 1–11 in the solid state
Compound
lex/lem (nm)
Compound
lex/lem (nm)
Compound
lex/lem (nm)
L1
L2
L3
L4
1
347/495
397/484
365/417
413/487
348/402
2
3
4
5
6
368/425
349/398
397/482
397/474
360/419
7
8
9
10
11
358/412
365/425
383/461
366/464
396/468
Preparation of L1
Preparation of L4.
4-(Bromomethyl)benzonitrile (2.2 g, 11.2 mmol) was added with
stirring to a solution of 2,5-bis(2-hydroxyphenyl)-1,3,4-oxadia-
zole (1.27 g, 5.0 mmol) and KOH (0.63 g, 11.2 mmol) in acetone
(40 mL) at 60 ꢁC. The mixture was refluxed for 10 h (monitored
by TLC). After removal of solvent under vacuum, the residue
was purified on silica gel by column using CH2Cl2/THF (25 : 1,
v/v) as the eluent to afford L1 as a white crystalline solid (1.80 g).
Yield, 74%. M.p. ¼ 164ꢂ166 ꢁC, IR (KBr, cmꢀ1): 3053 (ms), 3040
(ms), 2899 (ms), 2852 (ms), 2227 (s), 1605 (s), 1534 (s), 1498 (s),
1454 (s), 1317 (s), 1289 (s), 1267 (s), 1167 (s), 1144 (ms), 1059
(ms), 849 (s), 830 (s), 768 (s), 750 (s), 706 (s), 550 (ms). 1H NMR
(300 MHz, CDCl3, 25 ꢁC, TMS, ppm): 8.00 (d, J ¼ 6.6 Hz, 2H,
–C6H4), 7.70 (d, J ¼ 8.3 Hz, 4H, –C6H4CN), 7.62 (d, J ¼ 8.3 Hz,
4H, –C6H4CN), 7.55 (d, J ¼ 7.5 Hz, 2H, –C6H4), 7.14 (t, J ¼ 7.1,
8.0 Hz, J ¼ 8.3 Hz, 4H, –C6H4), 5.27 (s, 4H, –CH2). Anal. calcd
for C30H20N4O3: C 74.38, H 4.13, N 11.57. Found: C 74.26, H
4.21, N 11.45.
L4 was prepared following the procedure described for L3 except
by using 3-(bromomethyl)benzonitrile (2.2 g, 11.2 mmol) instead
of 4-(bromomethyl)benzonitrile to afford a white crystalline
solid (1.60 g). Yield, 66%. M.p. ¼ 168ꢂ170 ꢁC, IR (KBr, cmꢀ1):
2229 (s), 1699 (s), 1590 (s), 1557 (s), 1492 (s), 1454 (s), 1374 (ms),
1293 (s), 1219 (s), 1170 (s), 1098 (ms), 1046 (s), 874 (s), 787 (s),
735 (s), 681 (s). 1H NMR (300 MHz, DMSO, 25 ꢁC, TMS, ppm):
7.98 (s, 2H, –C6H4CN), 7.84 (t, J ¼ 7.6 Hz, 4H, –C6H4CN), 7.77
(d, 4H, –C6H4CN, –C6H4), 7.65 (t, J ¼ 7.7 Hz, 2H, –C6H4), 7.56
(t, J ¼ 8.2 Hz, 2H, –C6H4), 7.32 (d, J ¼ 8.1 Hz, 2H, –C6H4), 5.30
(s, 4H, –CH2). Anal. calcd for C30H20N4O3: C 74.38, H 4.13, N
11.57. Found: C 74.25, H 4.24, N 11.72.
Preparation of 1
A solution of AgPF6 (10.4 mg, 0.04 mmol) in benzene (8 mL) was
layered onto a solution of L1 (10.0 mg, 0.02 mmol) in CH2Cl2 (8
mL). The solutions were left for about two weeks at room
temperature, and colourless crystals were obtained. Yield, 55%
(based on L1). IR (KBr, cmꢀ1): 3244 (ms), 2227 (ms), 1605 (vs),
1540 (s), 1499 (s), 1294 (s), 1244 (vs), 1083 (s), 1269 (s), 1022 ꢁ(s),
Preparation of L2
L2 was prepared following the procedure described for L1 except
by using 3-(bromomethyl)benzonitrile (2.2 g, 11.2 mmol) instead
of 4-(bromomethyl)benzonitrile to afford a white crystalline
solid (1.70 g). Yield, 70%. M.p. ¼ 120ꢂ122 ꢁC, IR (KBr, cmꢀ1):
2226 (s), 1605 (s), 1592 (s), 1534 (s), 1500 (s), 1459 (s), 1380 (s),
1300 (s), 1269 (s), 1230 (s), 1065 (s), 1021 (s), 792 (s), 745 (s), 686
(s). 1H NMR (300 MHz, CDCl3, 25 ꢁC, TMS, ppm): 8.00 (d, J ¼
6.8 Hz, 2H, -C6H4CN), 7.86 (d, J ¼ 7.8 Hz, 2H, –C6H4CN), 7.77
(s, 2H, –C6H4CN), 7.55 (d, J ¼ 7.6 Hz, 4H, –C6H4), 7.45 (d, J ¼
7.7 Hz, 2H, –C6H4CN), 7.12 (t, J ¼ 8.0 Hz, 4H, –C6H4), 5.23 (s,
4H, –CH2). Anal. calcd for C30H20N4O3: C 74.38, H 4.13, N
11.57. Found: C 74.25, H 4.21, N 11.48.
1
841 (vs), 749 (vs), 557 (s). H NMR (300 MHz, DMSO, 25 C,
TMS, ppm): 7.87 (d, J ¼ 6.5 Hz, 2H, –C6H4), 7.80 (d, J ¼ 8.3 Hz,
4H, –C6H4CN), 7.74 (d, J ¼ 8.3 Hz, 4H, –C6H4CN), 7.64
(t, J ¼ 8.6, 7.3 Hz, 2H, –C6H4), 7.39 (d, J ¼ 8.5 Hz, 2H, –C6H4),
7.36 (s, 9H, C6H6), 7.15 (t, J ¼ 7.6 Hz, 2H, –C6H4), 5.39 (s, 4H,
–CH2). Anal. calcd for C39H29AgF6N4O3P (1): C 42.13, H 3.39,
N 6.55. Found: C 42.05, H 3.49, N 6.42.
Preparation of 2
A solution of AgSbF6 (14.1 mg, 0.04 mmol) in benzene (8 mL)
was layered onto a solution of L1 (10.0 mg, 0.02 mmol) in
CH2Cl2 (8 mL). The solutions were left for about two weeks at
room temperature, and colourless crystals were obtained. Yield,
58% (based on L1). IR (KBr, cmꢀ1): 2265 (ms), 1607 (vs), 1548
(m), 1499 (s), 1381 (m), 1249 (s), 1170 (s), 1002 (s), 823 (s), 753 (s),
Preparation of L3.
L3 was prepared following the procedure described for L1 except
by using 2,5-bis(3-hydroxyphenyl)-1,3,4-oxadiazole (1.27 g, 5.0
mmol) instead of 2,5-bis(2-hydroxyphenyl)-1,3,4-oxadiazole to
afford a white crystalline solid (2.10 g). Yield, 87%. M.p. ¼
220ꢂ222 ꢁC, IR (KBr, cmꢀ1): 3075 (m), 2228 (s), 1718 (ms), 1613
(ms), 1587 (s), 1556 (s), 1476 (s), 1451 (s), 1379 (m), 1300 (s), 1272
(s), 1240 (s), 1035 (m), 967 (m), 816 (s), 787 (s), 735 (s), 683 (s),
545 (s). 1H NMR (300 MHz, DMSO, 25 ꢁC, TMS, ppm): 7.90 (d,
J ¼ 7.9 Hz, 4H, –C6H4CN), 7.76 (s, 4H, –C6H4), 7.71 (d, J ¼ 7.9
Hz, 4H, –C6H4CN), 7.56 (t, J ¼ 8.3 Hz, 2H, –C6H4), 7.33 (d, J ¼
7.8 Hz, 2H, –C6H4), 5.35 (s, 4H, –CH2). Anal. calcd for
C30H20N4O3: C 74.38, H 4.13, N 11.57. Found: C 74.24, H 4.03,
N 11.70.
1
660 (vs), 553 (s). H NMR (300 MHz, DMSO, 25 ꢁC, TMS,
ppm): 7.87 (d, J ¼ 7.5 Hz, 2H, –C6H4), 7.80 (d, J ¼ 8.2 Hz, 4H,
–C6H4CN), 7.74 (d, J ¼ 8.2 Hz, 4H, –C6H4CN), 7.64 (t, J ¼ 8.2,
7.4 Hz, 2H, –C6H4), 7.37 (d, J ¼ 8.3 Hz, 2H, –C6H4), 7.15 (t, J ¼
7.5 Hz, 2H, –C6H4), 5.39 (s, 4H, –CH2). Anal. calcd for
C30H20AgF6N4O3Sb (2): C 43.47, H 2.41, N 6.76. Found: C
43.63, H 2.32, N 6.59.
Preparation of 3
A solution of AgSO3CF3 (14.1 mg, 0.04 mmol) in benzene (8 mL)
was layered onto a solution of L1 (10.6 mg, 0.02 mmol) in
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CH2Cl2 (8 mL). The solutions were left for about two weeks at
room temperature, and colourless crystals were obtained. Yield,
58% (based on L1). IR (KBr, cmꢀ1): 2226 (s), 1606 (vs), 1535 (s),
1500 (s), 1416 (s), 1258 (vs), 1164 (vs), 1032 (vs), 823 (s), 752 (s),
638 (s), 550 (s). 1H NMR (300 MHz, DMSO, 25 ꢁC, TMS, ppm):
7.86 (d, J ¼ 7.5 Hz, 2H, –C6H4), 7.78 (d, J ¼ 8.2 Hz, 4H,
–C6H4CN), 7.73 (d, J ¼ 8.2 Hz, 4H, –C6H4CN), 7.63 (t, J ¼ 8.0,
7.6 Hz, 2H, –C6H4), 7.36 (d, J ¼ 8.6 Hz, 2H, –C6H4), 7.35 (s, 3H,
C6H6), 7.14 (t, J ¼ 7.5 Hz, 2H, –C6H4), 5.37 (s, 4H, –CH2). Anal.
calcd for C68H46Ag2F6N8O12S2 (3): C 52.27, H 2.94, N 7.17.
Found: C 52.18, H 2.85, N 7.34.
Preparation of 7
A solution of AgPF6 (10.4 mg, 0.04 mmol) in benzene (8 mL) was
layered onto a solution of L3 (10.0 mg, 0.02 mmol) in THF (8
mL). The solutions were left for about two weeks at room
temperature, and colourless crystals were obtained. Yield, 60%
(based on L3). IR (KBr, cmꢀ1): 2230 (s), 1614 (s), 1589 (s), 1557
(s), 1476 (s), 1453 (s), 1303 (s), 1246 (s), 1220 (s), 1052 (s), 838
(vs), 734 (s), 681 (s), 559 (s). 1H NMR (300 MHz, DMSO, 25 ꢁC,
TMS, ppm): 7.90 (d, J ¼ 7.9 Hz, 4H, –C6H4CN), 7.77 (s, 4H,
–C6H4), 7.71 (d, J ¼ 7.9 Hz, 4H, –C6H4CN), 7.57 (t, J ¼ 8.3 Hz,
2H, –C6H4), 7.36 (t, 2H, –C6H4, 3H, C6H6), 5.36 (s, 4H, –CH2).
Anal. calcd for C33H23AgF6N4O3P (7): C 51.01, H 2.96, N 7.21.
Found: C 51.12, H 2.87, N 7.30.
Preparation of 4
A solution of AgSbF6 (14.1 mg, 0.04 mmol) in THF (8 mL) was
layered onto a solution of L2 (10.0 mg, 0.02 mmol) in CH2Cl2 (8
mL). The solutions were left for about two weeks at room
temperature, and colourless crystals were obtained. Yield, 60%
(based on L2). IR (KBr, cmꢀ1): 2267 (ms), 1605 (s), 1547 (s), 1500
(s), 1439 (m), 1244 (s), 1171 (s), 1087 (m), 1000 (m), 753 (s), 660
Preparation of 8
A solution of AgClO4 (8.5 mg, 0.04 mmol) in benzene (8 mL) was
layered onto a solution of L3 (10.0 mg, 0.02 mmol) in THF (8
mL). The solutions were left for about two weeks at room
temperature, and colourless crystals were obtained. Yield, 50%
(based on L3). IR (KBr, cmꢀ1): 2230 (s), 1610 (s), 1560 (s), 1494
(s), 1476 (s), 1452 (s), 1301 (s), 1231 (s), 1120 (vs), 818 (s), 735 (s),
623 (s), 548 (s). 1H NMR (300 MHz, DMSO, 25 ꢁC, TMS, ppm):
7.91 (d, J ¼ 7.9 Hz, 4H, –C6H4CN), 7.77 (s, 4H, –C6H4), 7.71 (d,
J ¼ 7.9 Hz, 4H, –C6H4CN), 7.57 (t, J ¼ 8.3 Hz, 2H, –C6H4), 7.36
(t, 2H, –C6H4, 3H, C6H6), 5.37 (s, 4H, –CH2). Anal. calcd for
C33H23AgClN4O7 (8): C 54.18, H 3.14, N 7.66. Found: C 54.08,
H 3.20, N 7.74.
1
ꢁ
(vs). H NMR (300 MHz, DMSO, 25 C, TMS, ppm): 7.99 (s,
2H, –C6H4CN), 7.86 (t, 2H, –C6H4CN, 2H, –C6H4), 7.78 (d, J ¼
7.6 Hz, 2H, –C6H4CN), 7.62 (t, J ¼ 7.5 Hz, 2H, –C6H4), 7.54 (t, J
¼ 7.7 Hz, 2H, –C6H4CN), 7.38 (d, J ¼ 8.5 Hz, 2H, –C6H4), 7.14
(t, J ¼ 7.5 Hz, 2H, –C6H4), 5.31 (s, 4H, –CH2). Anal. calcd for
C30H20Ag2F12N4O3Sb2 (4): C 30.72, H 1.70, N 4.78. Found: C
30.61, H 1.79, N 4.66.
Preparation of 5
Preparation of 9
A solution of AgSO3CF3 (10.6 mg, 0.04 mmol) in THF (8 mL)
was layered onto a solution of L2 (10.0 mg, 0.02 mmol) in
CH2Cl2 (8 mL). The solutions were left for about two weeks at
room temperature, and colourless crystals were obtained. Yield,
50% (based on L2). IR (KBr, cmꢀ1): 2262 (ms), 1605 (vs), 1547
(m), 1500 (s), 1438 (s), 1253 (vs), 1165 (s), 1033 (s), 799 (s), 754 (s),
A solution of AgSbF6 (14.1 mg, 0.04 mmol) in benzene (8 mL)
was layered onto a solution of L4 (10.0 mg, 0.02 mmol) in THF
(8 mL). The solutions were left for about two weeks at room
temperature, and colourless crystals were obtained. Yield, 79%
(based on L4). IR (KBr, cmꢀ1): 2871 (m), 2246 (s), 1588 (m), 1559
(s), 1491 (s), 1457 (s), 1439 (m), 1376 (m), 1321 (m), 1295 (s), 1224
(s), 1052 (s), 864 (m), 792 (s), 747 (s), 683 (s), 658 (vs). 1H NMR
(300 MHz, DMSO, 25 ꢁC, TMS, ppm): 7.99 (s, 2H, –C6H4CN),
7.85 (t, J ¼ 7.7 Hz, 4H, –C6H4CN), 7.78 (d, 4H, –C6H4CN,
–C6H4), 7.67 (t, J ¼ 7.7 Hz, 2H, –C6H4), 7.57 (t, J ¼ 8.2 Hz, 2H,
–C6H4), 7.34 (d, J ¼ 7.4 Hz, 2H, –C6H4), 5.31 (s, 4H, –CH2).
Anal. calcd for C30H16AgF6N4O3Sb (9): C 43.90, H 1.95, N 6.82.
Found: C 43.78, H 1.82, N 6.95.
1
636 (vs), 517 (s). H NMR (300 MHz, DMSO, 25 ꢁC, TMS,
ppm): 7.99 (s, 2H, –C6H4CN), 7.86 (t, 2H, –C6H4CN, 2H,
–C6H4), 7.78 (d, J ¼ 7.6 Hz, 2H, –C6H4CN), 7.62 (t, J ¼ 7.4 Hz,
2H, –C6H4), 7.54 (t, J ¼ 7.7 Hz, 2H, –C6H4CN), 7.38 (d, J ¼ 8.3
Hz, 2H, –C6H4), 7.15 (t, J ¼ 7.5 Hz, 2H, –C6H4), 5.31 (s, 4H,
–CH2). Anal. calcd for C16H11AgF3N2O5S (5): C 38.00, H 2.17,
N 5.54. Found: C 38.12, H 2.08, N 5.43.
Preparation of 6
Preparation of 10
A solution of AgSbF6 (14.1 mg, 0.04 mmol) in benzene (8 mL)
was layered onto a solution of L3 (10.0 mg, 0.02 mmol) in THF
(8 mL). The solutions were left for about two weeks at room
temperature, and colourless crystals were obtained. Yield, 55%
(based on L3). IR (KBr, cmꢀ1): 2229 (s), 1613 (s), 1589 (s), 1476
(s), 1453 (s), 1303 (s), 1245 (s), 1220 (s), 1052 (s), 870 (s), 817 ꢁ(s),
A solution of AgPF6 (10.4 mg, 0.04 mmol) in THF (8 mL) was
layered onto a solution of L4 (10.0 mg, 0.02 mmol) in CH2Cl2 (8
mL). The solutions were left for about two weeks at room
temperature, and colourless crystals were obtained. Yield, 40%
(based on L4). IR (KBr, cmꢀ1): 3072 (m), 2975 (m), 2871 (m),
2231 (s), 1591 (s), 1558 (s), 1493 (s), 1438 (m), 1380 (m), 1302 (s),
1
735 (s), 664 (vs), 546 (s). H NMR (300 MHz, DMSO, 25 C,
1
TMS, ppm): 7.90 (d, J ¼ 7.9 Hz, 4H, –C6H4CN), 7.76 (s, 4H,
–C6H4), 7.71 (d, J ¼ 7.9 Hz, 4H, –C6H4CN), 7.56 (t, J ¼ 8.3 Hz,
2H, –C6H4), 7.36 (s, 3H, C6H6), 7.33 (d, J ¼ 7.8 Hz, 2H, –C6H4),
5.35 (s, 4H, –CH2), 3.58 (s, 4H, THF), 1.74 (s, 4H, THF). Anal.
calcd for C37H31AgF6N4O4Sb (6): C 47.27, H 3.30, N 5.96.
Found: C 47.18, H 3.48, N 5.83.
1221 (s), 1051 (s), 840 (vs), 790 (s), 736 (s), 681 (s), 559 (s). H
NMR (300 MHz, DMSO, 25 ꢁC, TMS, ppm): 7.97 (s, 2H,
–C6H4CN), 7.83 (t, J ¼ 7.7 Hz, 4H, –C6H4CN), 7.76 (d, 4H,
–C6H4CN, –C6H4), 7.65 (t, J ¼ 7.7 Hz, 2H, –C6H4), 7.56 (t, J ¼
8.3 Hz, 2H, –C6H4), 7.33 (d, J ¼ 7.4 Hz, 2H, –C6H4), 5.29 (s, 4H,
–CH2), 3.58 (s, 4H, THF), 1.74 (s, 4H, THF). Anal. calcd for
6860 | CrystEngComm, 2011, 13, 6850–6863
This journal is ª The Royal Society of Chemistry 2011

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Table 2 Crystallographic data for 1–4a
C
1
39H29AgF6N4O3P
C30H20AgF6N4O3Sb
2
C68H46Ag2F6N8O12S2
3
C30H20Ag2F12N4O3Sb2
4
Empirical formula
FW
Crystal system
854.50
Orthorhombic
16.936(3)
13.756(2)
15.609(2)
90
828.12
1560.99
1171.74
Monoclinic
8.9896(12)
31.618(4)
12.7659(17)
90
105.991(2)
90
3488.1(8)
P21/c
Triclinic
10.518(2)
13.249(2)
13.926(3)
83.357(3)
82.318(3)
70.574(3)
1808.4(6)
Triclinic
7.8309(13)
13.545(2)
17.271(3)
73.472(2)
89.038(2)
80.625(3)
1731.9(5)
ꢀ
a/A
ꢀ
b/A
ꢀ
c/A
a/ꢁ
b/ꢁ
g/ꢁ
90
90
3
ꢀ
V/A
Space group
3636.4(10)
Pban
ꢁ
ꢁ
P1
P1
Z value
r calc./g cmꢀ3
4
1.561
0.673
298(2)
2260
0.0671; 0.1617
4
1.577
1.402
173(2)
5288
0.0451; 0.1166
1
1.433
0.677
298(2)
4975
0.0450; 0.0876
2
2.247
2.761
298(2)
4770
0.0473; 0.1212
m(Mo-Ka)/mmꢀ1
T/K
No. of observations (I > 3s)
Final R indices [I > 2s(I)]: R; Rw
a
2
2
R1 ¼ S||Fo| ꢀ |Fc||/S|Fo|. wR2 ¼ {S[w(Fo ꢀ Fc )2]/S[w(Fo2)2]}1/2
.
Table 3 Crystallographic data for 5–8a
C
5
16H11AgF3N2O5S
C37H31AgF6N4O4Sb
6
C33H23AgF6N4O3P
7
C33H23AgClN4O7
8
empirical formula
FW
Crystal system
508.20
939.28
Monoclinic
23.985(3)
19.144(3)
8.5795(13)
90
90.577(3)
90
3939.3(11)
C2/m
776.39
Monoclinic
24.406(4)
18.749(3)
8.3657(12)
90
90.991(2)
90
3827.3(10)
C2/m
730.87
Orthorhombic
24.970(19)
18.714(14)
8.194(6)
90
90
90
3829(5)
C2/m
Monoclinic
7.8557(10)
18.207(2)
13.4719(17)
90
103.544(2)
90
1873.3(4)
P21/m
ꢀ
a/A
ꢀ
b/A
ꢀ
c/A
a/ꢁ
b/ꢁ
g/ꢁ
3
ꢀ
V/A
Space group
Z value
r calc./g cmꢀ3
4
1.802
1.247
173(2)
3212
0.0499; 0.1528
4
1.584
1.253
173(2)
3069
0.0648; 0.1691
4
1.347
0.632
173(2)
2737
0.0586; 0.1538
4
1.268
0.641
298(2)
2157
0.0569; 0.1484
m(Mo-Ka)/mmꢀ1
T/K
No. of observations (I > 3s)
Final R indices [I > 2s(I)]:R; Rw
a
2
2
R1 ¼ S||Fo| ꢀ |Fc||/S|Fo|. wR2 ¼ {S[w(Fo ꢀ Fc )2]/S[w(Fo2)2]}1/2
.
Table 4 Crystallographic data for 9–11a
C
9
30H16AgF6N4O3Sb
C34H28AgF6N4O4P
10
C30.5H22AgCl2N4O7.5
11
empirical formula
FW
Crystal system
820.06
Monoclinic
14.038(3)
18.203(3)
13.527(2)
90
97.894(3)
90
3423.9(10)
C2/m
809.44
743.29
Monoclinic
24.744(4)
13.627(2)
19.476(3)
90
102.663(3)
90
6407(2)
C2/c
Monoclinic
13.9206(17)
18.112(2)
26.968(3)
90
100.037(2)
90
6695.6(14)
Cc
ꢀ
a/A
ꢀ
b/A
ꢀ
c/A
a/ꢁ
b/ꢁ
g/ꢁ
3
ꢀ
V/A
Space group
Z value
r calc./g cmꢀ3
4
1.591
1.427
298(2)
2437
0.0945; 0.2542
8
1.606
0.728
173(2)
10 139
0.0515; 0.1262
8
1.541
0.849
298(2)
5940
0.0567; 0.1649
m(Mo-Ka)/mmꢀ1
T/K
No. of observations (I > 3s)
Final R indices [I > 2s(I)]: R; Rw
a
2
2
R1 ¼ S||Fo| ꢀ |Fc||/S|Fo|. wR2 ¼ {S[w(Fo ꢀ Fc )2]/S[w(Fo2)2]}1/2
.
This journal is ª The Royal Society of Chemistry 2011
CrystEngComm, 2011, 13, 6850–6863 | 6861

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Soc. Rev., 2009, 38, 1418; (j) P. Mal, B. Breiner, K. Rissanen and
J. R. Nitschke, Science, 2009, 324, 1697.
C34H28AgF6N4O4P (10): C 50.45, H 3.48, N 6.92. Found: C
50.65, H 3.42, N 6.84.
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2009, 38, 1400; (b) K. Takaoka, M. Kawano, M. Tominaga and
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Chem., Int. Ed., 2005, 44, 4896; (e) M. Ruben, J. Rojo,
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Preparation of 11
A solution of AgClO4 (8.5 mg, 0.04 mmol) in THF (8 mL) was
layered onto a solution of L4 (10.0 mg, 0.02 mmol) in CH2Cl2 (8
mL). The solutions were left for about two weeks at room
temperature, and colourless crystals were obtained. Yield, 50%
(based on L4). IR (KBr, cmꢀ1): 3078 (m), 2926 (m), 2861 (m),
2251 (s), 2230 (s), 1590 (s), 1558 (s), 1493 (s), 1455 (m), 1437 (m),
1387 (m), 1371 (m), 1294 (s), 1220 (s), 1145 (s), 1086 (vs), 997 (s),
ꢂ
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1
863 (s), 792 (s), 736 (s), 681 (s), 622 (s). H NMR (300 MHz,
DMSO, 25 ꢁC, TMS, ppm): 7.98 (s, 2H, –C6H4CN), 7.86 (t, J ¼
7.4 Hz, 4H, –C6H4CN), 7.77 (d, 4H, –C6H4CN, –C6H4), 7.65 (t, J
¼ 7.7 Hz, 2H, –C6H4), 7.56 (t, J ¼ 8.2 Hz, 2H, –C6H4), 7.33 (d, J
¼ 7.9 Hz, 2H, –C6H4), 5.74 (s, 0.5H, CH2Cl2), 5.30 (s, 4H,
–CH2). Anal. calcd for C30.5H22AgCl2N4O7.5 (11): C 49.28, H
2.98, N 7.53. Found: C 49.34, H 2.92, N 7.56.
Single-crystal structure determination
Suitable single crystals of 1–11 were selected and mounted in air
onto thin glass fibres. The X-ray intensity data of 1, 3, 4, 8, 9 and
11 were measured at 298 K and the data of 2, 5–7 and 10 at 173 K
on a Bruker SMART APEX CCD-based diffractometer (Mo-Ka
€
U. Mullerb, Chem. Soc. Rev., 2009, 38, 1284.
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ꢀ
radiation, l ¼ 0.71073 A). The raw frame data for 1–11 were
integrated into SHELX-format reflection files and corrected for
Lorentz and polarization effects using SAINT.15 Corrections for
incident and diffracted beam absorption effects were applied
using SADABS.15 None of the crystals showed evidence of
crystal decay during data collection. All structures were solved
by a combination of direct methods and difference Fourier
syntheses and refined against F2 by the full-matrix least squares
technique. SQUEEZE/PLATON19 was used to account for some
disordered solvent of 2, 3, 5, 7 and 8 and the contribution of
those species were removed from the structure factor calcula-
tions. Crystal data, data collection parameters, and refinement
statistics for 1–11 are listed in Tables 2–4. Relevant interatomic
bond distances and bond angles for 1–11 are given in Tables S1–
S11.†
ꢂ
J. Lewinski, W. Bury, I. Justyniak and J. Lipkowski, Angew. Chem.,
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S.-R. Zheng, Z.-Q. Yu, M. Pan and C.-Y. Su, Inorg. Chem., 2007,
46, 5814; (g) B. A. Blight, J. A. Wisner and M. C. Jennings, Angew.
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Acknowledgements
This work was supported by the National Natural Science
Foundation of China (grant no. 91027003, 21072118 and
20871076) and Shangdong Natural Science Foundation (grant
no. JQ200803).
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