Dinuclear Ag(i) metallamacrocycles of bis-N-heterocyclic carbenes bridged by calixarene fragments: Synthesis, structure and chemosensing behavior

Article abstract of DOI:10.1039/c3ce40918j

Dinuclear Ag(i) metallamacrocycles containing bis-N-heterocyclic carbene units and calixarene fragments [{1,1′-R²-3,3′-CH ₂{(p-R¹-C₆H₂OMe)CH₂} _m-bisimidazol-2-ylidene}₂

Full text of DOI:10.1039/c3ce40918j

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Dinuclear Ag(I) metallamacrocycles of bis-N-heterocyclic
carbenes bridged by calixarene fragments: synthesis,
structure and chemosensing behavior3
Cite this: CrystEngComm, 2013, 15,
6948
Cai-Xia Lin,b Xiao-Fei Kong,a Qing-Shan Li,a Zheng-Zhi Zhang,*a Yao-Feng Yuan*b
and Feng-Bo Xu*a
Dinuclear Ag(I) metallamacrocycles containing bis-N-heterocyclic carbene units and calixarene fragments
[{1,19-R2-3,39-CH2{(p-R1-C6H2OMe)CH2}m-bisimidazol-2-ylidene}2-Ag2](PF6)2 (6a–f), (6a: m = 1, R1 = Me, R2 =
Me; 6b: m = 1, R1 = t-Bu, R2 = Me; 6c: m = 1, R1 = Me, R2 = naphthylmethyl; 6d: m = 1, R1 = Me, R2
=
anthrylmethyl; 6e: m = 2, R1 = Me, R2 = anthrylmethyl; 6f: m = 3, R1 = t-Bu, R2 = anthrylmethyl) were
synthesized by reacting silver oxide with the corresponding bis-imidazolium salts (5a–f). Single crystal
structural analyses reveal that metallamacrocycles of diverse sizes consisting of two NHC–Ag(I)–NHC units
and two calixarene fragments are found in the structures of these dinuclear complexes. These complexes
show different configurations with the change of the upper-rims (R1) of the calixarene fragments or
N-substituents (R2) of the NHC rings. The two bis-NHC ligands in the complexes generally adopt trans-
conformations except for the pair in 6b. Complexes 6a and 6c–d, in which R1 are methyl groups, show
rectangular cavities in their structures. Complex 6b, in which R1 are tert-butyl groups of great steric
hindrance, adopts cone conformation analogous to that of the calixarene. Interestingly, cation–p
interactions are present between Ag(I) and the p–electron rich arene ring of R2 in the structures of
…
complexes 6c–f. Intermolecular C–H F hydrogen bonds exist in the crystal packing of all these complexes.
…
Moreover, intermolecular Ag Ag interactions are found in complex 6a and intermolecular p–p
interactions are observed in complexes 6c–f. These intermolecular interactions lead to the formation of
2D supramolecular layers in complex 6c and 3D supramolecular networks in complexes 6a–b and 6d–f,
respectively. The fluorescent chemosensing behaviors of these metallamacrocycles were explored for some
neutral molecules. The results showed that 6d can behave as an efficient fluorescent chemosensor for
p-benzoquinone and 6e–f exhibit fluorescent quenching behaviors for C60 or C70 fullerenes.
Received 24th May 2013,
Accepted 1st July 2013
DOI: 10.1039/c3ce40918j
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transition metal centers.1 Due to the high stability of M–C
NHC-bonds, NHC metal complexes exhibit unusual chemical
Introduction
N-Heterocyclic carbenes (NHC) are weak p-acceptors and
strong s-donors and can form strong M–C bonds with
and physical properties and have received a great deal of
interest for many years.2 NHC metal complexes are widely used
in the field of catalysis,3 medicine,4 luminescent components,5
functional materials6 and supramolecular chemistry.7 In
recent years, lots of dinuclear bis-NHC metal complexes
bridged by alkyl,8 aryl9 or ether chains10 have been studied
and some of them displayed novel structures4b,8e,9g and
showed promising applications in catalysis,9d,10b lumines-
cence11 and medicine chemistry.9c,9e,12 What we are interested
in is to design and synthesize dinuclear macrocyclic NHC
metal complexes which can be applied as host molecules in
supramolecular chemistry to recognize neutral organic mole-
cules via multiple sites.9b As is known, calixarenes are a class
of important and versatile host molecules because of their
unique conformational and special cavity structures.13 Some
attempts have been made to prepare metal NHC–calixarene
complexes by attaching NHC–metal substituents at the upper/
aState Key Laboratory and Institute of Elemento-Organic Chemistry, Nankai
University, Tianjin 300071, P. R. China. E-mail: zzzhang@nankai.edu.cn;
xufb@nankai.edu.cn; Fax: +86-22-23503710; Tel: +86-22-23503710
bDepartment of Chemistry, Fuzhou University, Fuzhou 350108, P. R. China.
E-mail: yaofeng_yuan@fzu.edu.cn
…
Electronic supplementary information (ESI) available: C–H F hydrogen-bonds
3
and intermolecular p–p interactions of 6a–f are summarized in Tables S1 and S2.
1H NMR spectra of compounds 5a–f and 6a–f are given in Fig. S1–S14. DOSY-
NMR spectrum of complex 6d is given in Fig. S15. TGA, DSC and variation
temperature 1H NMR spectrum of complex 6c are given in Fig. S16 and S17. The
determination of the association constants of 6d and BQ are given in Fig. S18. 1H
NMR spectrum of 6d and the BQ mixture in DMSO-d6 is given in Fig. S19.
Fluorescence titration spectra of 6e and 6f to fullerenes are given in Fig. S20–S23.
Crystallographic information files in CIF format, CCDC 898036, 906066, 898037,
898043, 931824 and 930716 for complexes 6a–f, respectively. For ESI and
crystallographic data in CIF or other electronic format see DOI: 10.1039/
c3ce40918j
6948 | CrystEngComm, 2013, 15, 6948–6962
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lower rims of calixarene in the literature.14 Our strategy is to
synthesize dinuclear macrocyclic bis-NHC Ag(I) complexes
using calixarene fragments as linkers. These complexes are
assembled via M–C bonds of high stability and these kinds of
macrocyclic complexes could be defined as a type of calixarene
analogue with a rigid metal-framework and flexible aryl
chains. In addition, luminescent properties can be easily
introduced to this system by attaching fluorophores to the
N-atom of the NHC rings. Two metallamacrocycles of this kind
have been prepared in our laboratory and one of them with an
anthracene fluorophore [(BIMAn)2Ag2](PF6)2 [BIMAn = bis{3-
(N-9-anthrylmethyl-imidazol-2-ylidene)methyl-5-tert-butyl-2-
methoxyphenyl}methane] behaved as an efficient fluorescent
chemosensor for C60 fullerene.15 Here, we report the contin-
uous studies on the synthesis and characterizations of this
series of dinuclear macrocyclic bis-NHC Ag(I) complexes
[{1,19-R2-3,39-CH2-{(p-R1-C6H2OMe)CH2}m-bisimdiazol-2-ylidene}2
Ag2](PF6)2 (6a–f), (6a: m = 1, R1 = Me, R2 = Me; 6b: m = 1, R1 = t-Bu,
R2 = Me; 6c: m = 1, R1 = Me, R2 = naphthylmethyl; 6d: m = 1, R1 =
Me, R2 = anthrylmethyl; 6e: m = 2, R1 = Me, R2 = anthrylmethyl; 6f:
m = 3, R1 = t-Bu, R2 = anthrylmethyl).
applied as starting materials. After sequential methylation and
bromination from 1, the corresponding dibromides 3 were
prepared.16 Treatments of the bromides 3 with N-substituted
imidazoles 4 in refluxing 1,4-dioxane gave the corresponding
bisimidazolium bromides as white solids precipitated from
the reaction solutions. The bisimidazolium bromides were
converted to 5a–f by anionic exchange with NH4PF6 in
methanol as hexafluorophosphate counteranions are usually
favorable for the preparation of a dinuclear bi-NHC Ag(I)
complex.4b,9a,17 Dinuclear NHC–Ag(I) complexes 6a–f were
afforded in 70–82% isolated yields by the reaction of bis-
NHC precursors 5a–f with 2.0 mole eq. silver oxide in
acetonitrile at 50 uC overnight.
In the 1H NMR spectra of precursors 5a–f, the characteristic
resonances for the C2–H imidazolium acidic protons appear at
9.0–9.4 ppm and the 13C NMR signals are displayed at 134.8–
136.8 ppm, which are consistent with those of the reported
imidazolium salts.18 Meanwhile, the 1H NMR spectra of
complexes 6a–f showed the disappearance of the characteristic
resonances for the acidic protons in 5a–f, which confirmed the
formation of NHC–Ag(I) complexes.
In the 1H NMR spectra of 6a and 6b, the proton signals,
except those for C2–H, are similar in their chemical shifts to
those of the corresponding groups in precursors 5a and 5b.
Results and discussion
1
(Table 1 and Fig. S1–S4, ESI ). However, on comparing the H
3
Synthesis of dinuclear Ag(I) complexes 6a–f
NMR spectra of 6c–f to those of 5c–f respectively, significant
upfield shifts of the corresponding groups were observed. The
upfield shift effects can be attributed to the shielding effects of
The general synthesis of complexes 6a–f is illustrated in
Scheme 1. The bisalcohols of calixarene fragment 1 were
Scheme 1 Synthesis of complexes 6a–f.
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Table 1 Comparison of the NMR chemical shifts (ppm) between complexes 6a–f and the corresponding precursors 5a–f (d6-DMSO, 298 K)
1H NMR d (ppm)
13C NMR d (ppm)
d
Ph–Ha
Im–CH2–Phb Im–CH2–Anc –OCH3
R1–He
NCNf
Im–CH2–Ph Im–CH2–An –OCH3
R1–C
5a 7.16
6a 6.77
5.41
5.21
—
—
3.76
3.56
2.26
2.04
136.8
179.4
47.3
47.9
—
—
62.1
60.4
20.3
19.2
5b 7.47
6b 7.08
5.42
5.23
—
—
3.76
3.52
1.26
1.09
136.7
179.4
47.7
48.8
—
—
62.0
60.4
30.9
29.7
5c 7.01
6c 6.26
5.40
4.85
5.94
5.64
3.60
3.02
2.19
1.75
136.8
179.8
47.3
48.2
50.1
51.0
61.8
59.9
20.3
19.1
5d 6.83
6d 5.28
5.28
4.15
6.51
6.05
3.40
2.29
2.12
1.08
136.2
181.0
45.0
46.0
47.3
48.8
61.5
60.0
20.3
19.7
5e 6.74g
5.30
4.16
6.53
6.04
6.55
6.11
3.44
2.50
2.09
1.60
136.2
45.0
47.9
50.0
47.1
49.7
60.9
59.9
59.2i
20.4
6e 6.10, 5.88g
180.9, 179.0 46.0
134.8 43.9
3.14, 2.54i 0.98, 0.43j 180.5, 178.5 45.9
20.0
5f 7.01, 6.95, 6.92h 5.35
6f 6.59, 6.48, 5.87h 4.11
3.51, 3.44i 1.07j
29.9, 29.8j
60.3, 60.1i 31.0, 30.3j
a
b
c
Ph refers to the benzene rings in the compounds. Im refers to the imidazolium rings in 5a–f or the NHC rings in 6a–f. An refers to the
arene rings of R2 in compounds 5c–d and 6c–d. OCH3 refers to the methoxy groups substituted on the benzene rings in the compounds.
d
e
f
R1 refers to the methyl or tert-butyl groups substituted on the benzene rings in compounds 5a–f and 6a–f. Carbons at the C2-position of
g
the imidazolium in compounds 5a–f or carbene-C in compounds 6a–f. Protons of the benzene rings in 5e become magnetically
nonequivalent in complex 6e. Three groups of magnetically nonequivalent protons of the benzene rings in 5f and 6f. Methoxy groups of the
benzene rings in 5f and 6f and the methoxy group close to the anthracene rings are magnetically nonequivalent to the methoxy far to
h
i
j
anthracene rings. Tert-butyl groups of the benzene rings in 5f and 6f and the tert-butyl groups close to the anthracene rings are magnetically
nonequivalent to the tert-butyl groups far from the anthracene rings in 6f.
the naphthalene or anthracene rings in the R2 groups attached
to the NHC rings of 6c–f. For example, on comparing the H
to Stokes–Einstein equation,20 the mean diffusion coefficient
1
of the peaks corresponding to 6d is 1.019 6 10210 m2 s21
NMR spectra of complex 6d to 5d, the significant shifts are
found as follows: the signals for the benzene ring protons
shifted from 6.83 to 5.28 ppm, the signals for the methylene
groups between the NHC rings and benzene rings shifted from
5.28 to 4.15 ppm, the signals for the methoxy groups of the
benzene rings shifted from 3.40 to 2.29 ppm and the signals
for the methyl groups of the benzene rings shifted from 2.02 to
1.08 ppm, respectively. In the 1H NMR spectrum of complex 6f,
the signals for the four protons on the benzene rings close to
the anthracene rings shifted upfield from 7.02 to 5.87 ppm,
the signals for the methylene groups between the NHC rings
and benzene rings shifted from 5.35 to 4.11 ppm, the signals
for the four methoxy groups adjacent to the anthracene rings
shifted from 3.51 to 2.54 ppm and the signals for the four tert-
butyl groups of the benzene rings close to the anthracene rings
(Table S3, ESI ), giving a rough particle radii of complex 6d of
10.78 Å, which is in agreement with the Ag Ag distance of
3
…
8.859 Å, obtained from the single-crystal data for 6d (Table 2).
Since the other peaks did not give an identical diffusion
coefficient, other by-product particles, such as metal–ligand
complexes of [M1L1] or [M3L3], cannot be detected from the
DOSY-NMR experiments.
These complexes are stable in their solid form and in
solution. The thermogravimetric (TG) and differential scan-
ning calorimetry (DSC) analyses of complex 6c were represen-
tatively performed to investigate the stability of this
macrocycle in its solid form. The TG and DSC curve (Fig.
S16, ESI ) of complex 6c showed an initial loss of 0.9% of the
3
crystallized solvents before the decomposition of the complex
at about 285 uC, implying the high stability of the dinuclear
Ag(I)–NHC macrocycles as a solid.21 A significant weight loss of
ca. 55.9% between 285–600 uC is assigned to the decomposi-
tion of the complex. In addition, the 1H NMR spectra of 6c
with the temperature varying from 293 K to 353 K showed little
change, implying these macrocyclic complexes are stable in
shifted from 1.05 to 0.43 ppm (Fig. S13 and S14, ESI ),
3
respectively. The carbene carbon peaks of complexes 6a–d
appeared as a singlet at 179.4, 179.4, 179.8 and 181.1 ppm,
respectively. To be noted, in the 13C NMR spectra of complexes
6e–f, the signals of the carbene carbons appeared as two
doublets at the range of 178.2–181.0 ppm, coupled by silver
solution (Fig. S17, ESI ).
3
1
isotopes (1J(13C–107Ag) = 183.1 Hz, J(13C–109Ag) = 212.5 Hz for
Crystal structures and characterizations of complexes 6a2f
1
1
complex 6e and J(13C–107Ag) = 184.0 Hz, J(13C–109Ag) = 212.4
Hz for complex 6f).17,19
To confirm the molecular structures of the prepared dinuclear
macrocyclic complexes, single crystals of 6a–f were grown and
the structures were determined by X-ray diffraction analysis.
The structural descriptions of complexes 6a–f are summarized
in Fig. 1 and Table 2. As can be seen in Fig. 2a–7a, large
cavities consisting of two NHC–Ag(I)–NHC units and two
calixarene fragments can be observed in the structures of 6a–f,
Additionally, the reaction solution of 5d with Ag2O was
subject to a DOSY-NMR experiment (Fig. S15, ESI ) to detect
3
the other formed products in the reaction. The 1H NMR of the
solution clearly showed the characteristic peaks of complex 6d
in above 90% peak strength and the other peaks, correspond-
ing to the by-products, appeared at less than 10%. According
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Table 2 Structural descriptions of complexes 6a–f according to their X-ray structure analysis
Intramolecular
…
dAg(C4)a/Å
Qb/u
bc/u
d2d/Å
h1e/u
h2 /u
f
Space group
Ag Ag/Å
6a
6b
Ibam
P2(1)/n
6.792
6.841
0.0004
42.34
39.97, 28.64
0
0
—
33.65
40.99, 49.82
33.65
5.52, 4.84
Ag1, 0.058,
Ag2, 0.046
0.032
68.570
¯
6c
6d
6e
P1
9.235
8.859
12.546
77.24
82.44
66.99, 63.38;
22.15, 7.93
63.43, 41.62, 73.19
0
0
4.927
5.071
—
74.02
86.72
68.44, 82.07
74.02
86.72
83.59, 67.18
C2/c
0.021
P1
Ag1, 0.096,
Ag2, 0.118
0.013
8.255 (A, A9)g,
14.197 (B, B9)
0, (A, A9)h, 0,
(B, B9), 0 (C, C9)
¯
6f
16.986
8.184h,
8.900, 3.758
80.21
80.21
¯
P1
a
b
dAg(C4) are the deviations of the relevant silver atoms from the plane of the four carbene carbons. Q are the dihedral angles from the
c
d
plane of the benzene rings to the (carbene-C)4 plane. b are the dihedral angles between two intramolecular benzene rings. d2 are the face-
to-face distances of two intramolecular benzene rings. h1 are the dihedral angles between the pair of NHC rings within a ligand. h2 are the
dihedral angles between the pair of NHC rings in the same NHC–Ag–NHC unit. b and d2 of complex 6e are relative to two pairs of benzene
rings (A, A9) and (B, B9) in an anti-conformation (see Fig. 1, 6e). b and d2 of complex 6f are relative to three pairs of benzene rings (A, A9) (B,
e
f
g
h
B9) and (C, C9) in an anti-conformation (see Fig. 1, 6f).
and the two bis-NHC ligands in the complexes generally adopt
trans-conformations, except for the pair in 6b. The Ag–C bond
distances are different, in the range of 2.074 Å to 2.095 Å, and
all the silver(I) atoms in the complexes have nearly a linear
coordination geometry, with the C–Ag–C bond angles ranging
from 173.5u to 179.2u, which are similar to the values reported
for Ag(I)–NHC complexes.4b,17 Moreover, in complexes 6a–f,
two NHC–Ag(I)–NHC axes are in mutually parallel positions
and the Ag to Ag separations vary from 6.792 Å to 16.986 Å.
With the change of the upper-rims of the calixarene fragments
(R1) or N-substituents of the NHC rings (R2), the configura-
tions of the complexes are different.
Ag distance is 6.792 Å. Two benzene rings are coplanar and
outwards from the mean plane of the four carbene carbon
donors (dAg(C4) = 0.0004)22 in opposite directions and the
dihedral angle (Q) between the plane of the benzene ring and
the (carbene-C)4 plane is 42.34u. Two NHC rings within a
ligand form dihedral angles of 33.65u and point to the same
side of the (carbene-C)4 plane. Two NHC rings coordinated to
the same silver(I) ion are arranged in opposite dispositions
according to the (carbene-C)4 plane. In contrast, owing to the
disordered properties of the tert-butyl groups and hexafluor-
ophosphate, complex 6b crystallizes in the P2(1)/n space group
of low symmetry. Compared with 6a, two bis-NHC ligands in
6b adopt a trans-conformation and the two intramolecular
benzene rings are no longer coplanar but form a dihedral
angle (b) of 68.570u because of the steric hindrance of the tert-
Complex 6a crystallizes in a highly symmetric Ibam space
group. As shown in Fig. 2a, two bis-NHC ligands in the
complex adopt a trans-conformation. The intramolecular Ag to
Fig. 1 Illustration of the molecular structures of the complexes.
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butyl groups. Additionally, the two benzene rings are outwards
in the same disposition from the (carbene-C)4 plane (dAg1(C4)
= 0.058, dAg2(C4) = 0.046) with dihedral angles of 39.97u and
28.64u, respectively, which makes the cavity of 6b look like a
cone (Fig. 3a). The intramolecular Ag to Ag separation is
6.841 Å, which is similar to that of 6a. The pairs of NHC rings
in each bis-NHC ligand incline towards each other with
dihedral angles of 40.99u and 49.82u, respectively, pointing to
the same side of the (carbene-C)4 plane. The pairs of NHC
rings in each NHC–Ag–NHC unit are nearly coplanar, with
dihedral angles of 5.52u and 4.84u, respectively.
As can be seen in Fig. 4a and 5a, due to the steric effects of
the R2 groups (naphylmethylene or anthrylmethylene)
attached to the NHC rings, the cations of complexes 6c and
6d show rectangular configurations as a solid, which are very
different from those of 6a and 6b. Complexes 6c and 6d
¯
crystallize in the P1 and C2/c space group, respectively. The
cations of complexes 6c and 6d are both centrosymmetric. The
intramolecular Ag to Ag separations in 6c and 6d are 9.235 Å
and 8.859 Å, respectively. Two benzene rings in 6c and 6d are
both parallel, with face-to-face distances of 4.927 Å and
5.071 Å, respectively, and the dihedral angles between the
benzene rings and the corresponding (carbene-C)4 planes of 6c
(dAg(C4) = 0.032) and 6d (dAg(C4) = 0.021) are 77.24u and
82.44u, respectively. The dihedral angles between the pair of
NHC rings within a ligand or in an NHC–Ag–NHC unit in 6c
and 6d are larger than those in complexes 6a and 6b, with
dihedral angles of 74.02u and 86.72u, respectively (Table 2).
¯
Complexes 6e and 6f both crystallize in the P1 space group.
As depicted in Fig. 6a and 7a, 28-membered and 36-membered
metallamacrocycles, formed by two linear NHC–Ag(I)–NHC
axes and two flexible calixarene fragment linkers, can be
observed in the structures of complexes 6e and 6f, respectively.
The intramolecular Ag to Ag distances of complexes 6e and 6f
are 12.546 Å and 16.986 Å, respectively, which are much longer
than those of 6a–d. In complex 6f, the cation metallamacro-
cycle is centrosymmetric, whereas a symmetric center cannot
be found in the cation of 6e and there is a short contact
between the silver cation and one oxygen atom of the methoxy
…
group with a Ag2 O2 separation of 2.967(3) Å (smaller than
the sum of the van der Waals radius 3.24 Å) (Fig. 6a). Owing to
the low symmetry of the dinuclear cation of complex 6e, the
two pairs of benzene rings in anti-dispositions in two ligands
(benzene rings A–A9 and B–B9 in Fig. 1, 6e) are not parallel but
form dihedral angles of 8.225u and 14.197u, respectively. The
dihedral angles of the planes of the four benzene rings to the
(carbene-C)4 plane (dAg1(C4) = 0.096, dAg2(C4) = 0.118) of
complex 6e are disparate, with values of 66.99u, 63.38u, 7.93u
and 22.15u. Comparably, in the cation of 6f, the three pairs of
benzene rings in anti-conformations in two ligands (A–A9, B–B9
and C, C9 in Fig. 1, 6f) are parallel, with face-to-face distances
of 3.758 Å, 8.900 Å and 8.184 Å, respectively. The dihedral
angles between the planes of the benzene rings and the
(carbene-C)4 plane (dAg(C4) = 0.013) for (A, A9), (B, B9) and (C,
C9) are 63.43u, 41.62u and 73.19u, respectively. In addition, the
pairs of NHC rings in each ligand of complexes 6e and 6f all
point to the same side of the corresponding (carbene-C)4 plane
and the pairs of NHC rings in each NHC–Ag–NHC unit of
Fig. 2 (a) Molecular structure of complex 6a (50% probability ellipsoids), hydrogen
atoms and anions have been omitted for clarity. Selected bond lengths (Å) and angles
(u): Ag1–C4 = 2.088(3); C4–Ag1–C4A = 175.98(13); N1–C4–N2 = 104.5(2). (b) The 2D
…
supramolecular layer of complex 6a via intermolecular Ag Ag interactions and C–
…
H
F hydrogen bonds. The irrelevant hydrogen atoms have been omitted for clarity.
…
(c) The 3D supramolecular architecture of complex 6a via intermolecular Ag Ag
…
interactions and C–H F hydrogen bonds. The irrelevant hydrogen atoms have been
…
omitted for clarity. In Fig. 2b and 2c, intermolecular Ag Ag contacts are drawn with
…
green dashed lines and H F contacts are drawn with yellow dashed lines.
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Fig. 3 (a) Molecular structure of complex 6b (50% probability ellipsoids),
hydrogen atoms and anions have been omitted for clarity. Selected bond
lengths (Å) and angles (u): Ag1–C4 = 2.082(13) Å, Ag1–C25 = 2.085(12), Ag2–
C41 = 2.084(14), Ag2–C20 = 2.102(14); C4–Ag1–C25 = 176.4(6), C41–Ag2–C20
= 177.3(6), N1–C4–N2 = 102.6(11), N4–C20–N3 = 104.7(12), N5–C25–N6 =
103.6(11), N7–C41–N8 = 103.9(11). (b) The 2D supramolecular layer of complex
…
6b via intermolecular C–H F hydrogen bonds. The irrelevant hydrogen atoms
have been omitted for clarity. (c) The 3D supramolecular architecture of
…
complex 6b via intermolecular C–H F hydrogen bonds. The irrelevant
…
hydrogen atoms have been omitted for clarity. In (b and c), H F contacts are
drawn with yellow dashed lines.
complexes 6e and 6f are all arranged in opposite dispositions
from the (carbene-C)4 plane.
In particular, cation–p interactions between the silver
cations and naphthalene rings or anthracene rings of R2
adjacent to the same NHC unit are found in the structures of
complex 6c–f (Fig. 4a–7a). Although Ag(I)–arene interactions
have been studied in many silver complexes,23 reports of the
interactions which exist in Ag(I)–NHC complexes are relatively
limited.24 As summarized in Table 3, the separations between
the silver atoms and coordinating arene ring carbons of
complexes 6a–f are in the range of 2.993 Å to 3.4185 Å (smaller
than the sum of the van der Waals radius, 3.42 Å).25 The
coordination modes between the silver atoms and arene p–
electron systems generally follow g2 or g3-hapticity.26 The
distances of the silver atoms to the centers of the nearest six-
membered interacting arene rings (d1) are in the range of
3.252 Å to 3.860 Å and the relative perpendicular distances (d2)
are in the range of 2.802 Å to 3.114 Å. In complex 6c, the silver
atom coordinates with the C29 and C30 atoms of the
naphthalene ring, with separations of 3.364(4) Å and 3.060(4)
Å, indicating a g2 coordination mode between the silver atom
and the arene p–electron system. The distance of the silver
atom to the centers of the nearest six-membered interacted
arene ring is 3.776 Å, and the relative perpendicular distance is
2.8026 Å (Table 3). In contrast, the coordination mode of the
silver cation with the anthracene p–electron system in complex
6d follows a g3-hapticity, coordinating with the C12, C13 and
C14 atoms of the anthracene ring with separations of 3.229(7),
2.994(7) and 3.159(7) Å, respectively. The distance of the silver
atoms to the centers of the nearest six-membered interacting
arene rings is 3.410 Å and the relative perpendicular distance
is 2.931 Å. In complexes 6e and 6f, the multi-arene linkers
between two NHC–Ag(I)–NHC units in one molecule are more
flexible. There are three groups of Ag(I)–arene p interactions
between the two silver cations and three anthracene rings in 6e
and there are four groups in 6f (Fig. 6a and 7a). The Ag(I)–
arene p interactions exist more generally compared to those in
6c and 6d.
The crystal packing of complexes 6a–f
According to the analyses of the crystal packing of these
complexes, it can be found that weak intermolecular interac-
…
…
tions involve C–H F hydrogen bonds (in 6a–f), Ag Ag
interactions (in 6a) and p–p interactions (in 6c–f) and C–
H
27
…
F hydrogen bonds
(Table S1, ESI ) play the most
3
important role in the crystal packing of these complexes.
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Fig. 4 (a) Molecular structure of complex 6c (50% probability ellipsoids),
hydrogen atoms and anions have been omitted for clarity. Selected bond
lengths (Å) and angles (u): Ag1–C14 = 2.076(3), Ag1–C27A = 2.074(3); C14–
Ag1–C27A = 175.25(10), N1–C14–N2 = 104.0(2), N3–C27–N4 = 104.1(2). (b) The
2D supramolecular layer of complex 6c via intermolecular p–p interaction and
…
C–H F hydrogen bonds viewed along the a axis. The irrelevant hydrogen atoms
have been omitted for clarity. (c) The 2D supramolecular layers of complex 6c
viewed along b axis. The irrelevant hydrogen atoms have been omitted for
clarity. In (b and c), intermolecular p–p interactions are drawn with black dashed
…
lines and H F contacts are drawn with yellow dashed lines.
Fig. 5 (a) Molecular structure of complex 6d (50% probability ellipsoids),
hydrogen atoms and anions have been omitted for clarity. Selected bond
lengths (Å) and angles (u): Ag1–C31 = 2.095(6), Ag1–C18A = 2.095(6), C18A–
Ag1–C31 = 178.3(3), N2–C18–N1 = 105.2(5), N4–C31–N3 = 104.5(5). (b) The 2D
In the crystal packing of complex 6a, weak intermolecular
28
…
Ag Ag interactions are found with separations of 3.413 Å
and a 3D architecture is assembled by these argentophilic
supramolecular layer of complex 6d via intermolecular p–p interaction and C–
…
H
F hydrogen bonds viewed along the b axis. The irrelevant hydrogen atoms
…
contacts and intermolecular weak C–H F interactions among
have been omitted for clarity. (c) The 3D supramolecular network of complex
6d, viewed along the a axis. The irrelevant hydrogen atoms have been omitted
for clarity. In (b and c), intermolecular p–p interactions are drawn with black
the hydrogen atoms of the methyl groups attached to the NHC
…
dashed lines and H F contacts are drawn with yellow dashed lines.
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Fig. 7 (a) Molecular structure of complex 6f (30% probability ellipsoids),
Fig. 6 (a) Molecular structure of complex 6e (30% probability ellipsoids),
hydrogen atoms and anions have been omitted for clarity. Selected bond
lengths (Å) and angles (u): Ag1–C95 = 2.087(4), Ag1–C18 = 2.093(4), Ag2–C73 =
2.106(4), Ag2–C40 = 2.117(4), C95–Ag1–C18 = 174.17(2), C73–Ag2–C40 =
173.5(2), N2–C18–N1 = 104.1(3), N4–C40–N3 = 104.4(3), N5–C73–N6 =
103.8(3), N7–C95–N8 = 103.3(3). (b) The 2D supramolecular layer of complex 6e
hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and
angles (u): Ag1–C18 = 2.093(3), Ag1–C59 = 2.090(3); C18–Ag1–C59A =
179.22(10), N2–C18–N1 = 104.3(2), N3–C59–N4 = 103.7(2). (b) The 2D
supramolecular layer of complex 6f via intermolecular p–p interaction and C–
…
H
F hydrogen bonds. The irrelevant hydrogen atoms have been omitted for
clarity. (c) The 3D supramolecular network of complex 6f via intermolecular p–p
…
…
via intermolecular p–p interaction and C–H F hydrogen bonds viewed along
interactions and C–H F hydrogen bonds. The irrelevant hydrogen atoms have
the b axis. The irrelevant hydrogen atoms have been omitted for clarity. (c) The
3D supramolecular network of complex 6e via intermolecular p–p interactions
been omitted for clarity. In (b and c), intermolecular p–p interactions are drawn
…
with black dashed lines and H F contacts are drawn with yellow dashed lines.
…
and C–H F hydrogen bonds. The irrelevant hydrogen atoms have been omitted
for clarity. In (b and c), intermolecular p–p interactions are drawn with black
…
dashed lines and H F contacts are drawn with yellow dashed lines.
However, in the lattice of complex 6b, due to the steric
hindrance of the tert-butyl groups, there is no intermolecular
…
Ag Ag interaction and the 3D network of 6b is assembled
rings and the fluorine atoms of hexafluorophosphate (C(1)–
…
…
directly by intermolecular C–H
dimensions (Fig. 3b and 3c).
F interactions in three
H(1B) F(4) = 3.315(3) Å (0.5 + x, 20.5 + y, 0.5 2 z) and C(1)–
…
H(1C) F(2) = 3.237(3) Å (1 2 x, 2y, z)) (Fig. 2b and 2c).
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Table 3 Structural features of 6d–f with Ag(I)–arene p interactions
d1a/Å
d2b/Å
Typec
d3d/Å
6c
3.776
3.410
3.853
3.253
3.860
3.691
3.251
2.802
2.931
3.098
3.085
3.114
2.987
3.011
g2
g3
g3
g2
g3
g3
g2
Ag1–C29 = 3.364(4), Ag1–C30 = 3.060(4)
6d
Ag1–C12 = 3.229(7), Ag1–C13 = 2.994(7), Ag1–C14 = 3.159(7)
Ag1–C1 = 3.308(5), Ag1–C2 = 3.354(5), Ag1–C14 = 3.382(5)
Ag1–C97 = 3.110(5), Ag1–C98 = 3.262(7)
Ag2–C67 = 3.418(5), Ag2–C68 = 3.347(4), Ag2–C69 = 3.370(4)
Ag1–C1 = 3.201(3), Ag1–C2 = 3.234(4), Ag1–C14 = 3.325(3)
Ag1–C61 = 3.056(3), Ag1–C62 = 3.159(3)
6ee
6ff
a
b
d1 are the distances of the silver atoms to the centers of the nearest six-membered interacting arene rings. d2 are the perpendicular
c
distances of the silver atoms to the nearest six-membered interacting arene rings. The coordination modes between the silver atoms and
arene p–electron systems. d3 are the distances of the silver atoms to the weak interacting C atoms of the arene interaction. Three groups of
intermolecular cation–p interactions between two Ag and three anthracenyl groups. Four groups of cation–p interactions in two pairs
d
e
f
between two Ag and four anthracenyl groups.
In complexes 6c–f, p–p stackings29 (Table S2, ESI ) between
Fluorescent chemosensing behaviors
3
the intermolecular arene rings attached to the NHC rings are
involved in the weak interactions. In complex 6c, as can be
seen in Fig. 4b and 4c, 2D supramolecular layers are formed
Fluorescent sensing behavior of complex 6d for p-benzoqui-
none. As mentioned above, since complex 6d possesses a
rectangular cavity, with an intramolecular Ag to Ag distance of
8.859 Å and two parallel benzene rings with a separation of
5.072 Å, it can enclose some small organic functional
molecules. p-Benzoquinone (BQ) is a planar molecule with
…
via intermolecular C–H F interactions and p–p stackings
among the intermolecular naphthalene rings, with a face-to-
face separation of 3.2915(13) Å (center-to-center separation of
3.820(2) Å). However, in complex 6d a 3D network was
assembled by the p–p contacts of the intermolecular anthra-
cene rings, with a face-to-face separation of 3.367(3) Å (center-
30
…
an O O distance of 5.292 Å and a complementary relation-
ship of size and shape between 6d and BQ is present. A
fluorescence titration experiment of complex 6d by BQ was
carried out in acetonitrile at room temperature. As can be seen
in Fig. 8a, after the gradual addition of BQ, the fluorescent
emission intensity of 6d sequentially decreased. When the BQ/
6d molar ratio reached 5, the fluorescence of 6d was
completely quenched. The quenching was found to follow a
conventional Stern–Volmer relationship9b and the association
…
to-center separation = 3.955(4) Å) and C–H F interactions
(Fig. 5b and 5c). In the crystal packing of complexes 6e and 6f,
similar p–p stacking interactions among the intermolecular
anthracene rings are found, with a face-to-face distance of
3.4124(16) Å (center-to-center separation of 3.953(3) Å) for 6e
(Fig. 6b and 6c) and a face-to-face distance of 3.3705(11) Å
(center-to-center separation of 3.6135(18) Å) for 6f (Fig. 7b and
7c), respectively. 3D architectures of complexes 6e and 6f were
formed via these p–p stacking interactions together with the
constant is estimated to be 2.45 6 104 M21 (Fig. S18, ESI ).
3
The Job plot analysis31(Fig. 8b) indicates the formation of a
1 : 1 inclusion complex between 6d and BQ (Scheme 2).
However, when complexes 6e and 6f with larger cavities were
…
intermolecular C–H F interactions.
Fig. 8 (a) Fluorescence titration experiments of 6d (1.0 6 1025 mol L21) with increasing BQ concentration in acetonitrile (lex = 370 nm) at room temperature. The
concentrations of BQ for the curves from top to bottom are 0.0, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 1.5, 2.5, 5.0, 8.0 6 1025 mol L21. Ka = 2.45 6 104
M
21. (b) Job plot of the
fluorescence titration curves at 416 nm.
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Scheme 2 Fluorescence titration of complex 6d with p-benzoquinone (BQ).
fragments or the N-substituents (R2) of the NHC rings. Cation–
p interactions are formed between the silver cations and arene
rings in complexes 6c–f. In the crystal packing of the
complexes, 2D supramolecular layers of 6c and 3D supramo-
applied as host molecules, no obvious quenching behaviors
were observed at the same molar ratio of BQ/host, which
indicates that complexes 6e and 6f cannot form the close 1 : 1
host–guest inclusion complexes with BQ. The fluorescent
quenching may be attributed to a photo-induced electron
transfer (PET) process between the functional NHC metalla-
macrocycle and BQ. Attempts to determine the solid-state
structures of the inclusion complex were carried out but
suitable single crystals for X-ray single crystal diffraction
analysis were not obtained.
Sensing behaviors of complexes 6e and 6f for fullerenes. On
the basis of our previous work in the recognition of C60 with
[(BIMAn)2Ag2](PF6)2 (Ka = 3.48 6 105 M21),15 the correspond-
ing inclusion complexations when applying 6e and 6f as host
molecules were studied through fluorescence titrations.
Similar inclusion behaviors for C60 and C70 were observed
and the fluorescence quenching behaviors were all found to
lecular architectures of 6a, 6b and 6d–f are formed via
…
intermolecular C–H
…
F
hydrogen bonds, intermolecular
Ag Ag interactions and p–p stackings. Additionally, complex
6d showed excellent fluorescent chemosensing behavior for
p-benzoquinone and complexes 6e and 6f exhibited recogni-
tion properties for C60 and C70 fullerenes. It can be anticipated
that these kinds of metallamacrocycles can be further
designed and synthesized and will exhibit more particular
recognition behavior.
Experimental section
follow a Stern–Volmer equation (Fig. S20–S23, ESI ). For
3
General procedure
complex 6e, the association constants to C60 and C70 were
6.97 6 104 M21 and 1.06 6 105
M
21, respectively, and for
All the reactions were carried out under a dry nitrogen
atmosphere using standard Schlenk techniques unless stated
otherwise. The solvents were purified by standard methods.
The ESI-MS spectra were obtained on a Finnigan LCQ
spectrometer. 1H, 13C and DOSY-NMR spectra were recorded
on a Bruker AV400 spectrometer. Chemical shifts, d, are
reported in ppm relative to the internal standard TMS. J values
are given in Hz. Elemental analyses were measured using a
YanacoMT-3 elemental analyzer. The fluorescence spectra
were measured with a Cary Eclipse fluorescence spectro-
photometer. Compounds 3a–d were prepared according to the
literature.16 Thermogravimetric analysis (TGA) and differential
scanning calorimetry (DSC) analyses were performed using a
NETZSCH STA 409 PC/PG instrument at a heating rate of 10 uC
complex 6f, the association constants to C60 and C70 were 9.17
6 104 M21 and 1.64 6 105 M21, respectively. As mentioned
above, the association constant of [(BIMAn)2Ag2](PF6)2 for C60
is larger than that of complex 6e, which suggests that receptors
substituted with tert-butyl groups as the upper-rim may be
more helpful for this kind of inclusive process. The association
constants of the host molecule to C60 and C70 showed not
much difference on comparing the approximate molecular
sizes of C60 and C70 (with diameter of 7.1 and 8.0 Å,
respectively). However, when complex 6d was applied as a
host molecule, the florescence intensity remained almost
constant with the addition of fullerene. From these results, it
can be induced that the size effect may play an important role
in the sensing behavior for fullerenes. The quenching
behaviors of 6e and 6f to C60 or C70 can be also attributed to
min21 under high purity N2 with a flow rate of 40 mL min21
.
General procedure for the synthesis of precursors 5a–f
a
photo-induced electron transfer process between the
metallamacrocycle system and the fullerenes.
A 1,4-dioxane (30 mL) solution of bromide 3 (1.0 eq.) and
N-substituted imidazole 4 (2.2 eq.) was refluxed for 2 days to
give bisimidazolium bromide as a white solid. The bromide
was dissolved in methanol (35 mL), NH4PF6 (1.96 g, 12 mmol)
was added and the mixture was stirred for 3 h to precipitate a
white solid. The solid was collected, washed with Et2O and
dried in a vacuum to give precursors 5a–f.
[1-Methyl-3,5-bis(N-methylimidazol-2-yl)methyl-4-methoxy-
benzene] hexafluorophosphate 5a: 80%. 1H NMR (400 MHz,
DMSO-d6): d 9.12 (s, 2H, Im–H) (Im = imidazole), 7.70 (s, 4H,
Conclusions
A series of macrocyclic dinuclear bis-NHC Ag(I) complexes, 6a–
f, consisting of two NHC–Ag(I)–NHC units bridged with two
calixarene fragments, have been designed and synthesized.
The configurations of these complexes can be easily modified
with the change of the upper-rims (R1) of the calixarene
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123.52, 123.29, 122.82, 122.80, 60.94 (OCH3), 47.86 (Im–CH2–
Im–H), 7.16 (s, 2H, Ph–H) (Ph = benzene), 5.41 (s, 4H, Im–CH2–
Ph), 3.86 (s, 6H, Im–CH3), 3.76 (s, 3H, –OCH3), 2.26 (s, 3H, Im–
CH3); 13C NMR (100 MHz, DMSO-d6): d 154.04 (C–OCH3 of Ph),
136.81 (NCHN of Im), 134.63 (C–CH3 of Ph), 131.37, 128.13,
123.84, 122.53 (Im), 62.09 (OCH3), 47.26 (Im–CH2–Ph), 35.81
(Im–CH3), 20.23 (CH3–Ph). ESI-MS [M 2 PF62]+: at m/z 457.2.
Anal. calcd for C18H24F12N4OP2: C, 47.27; H, 5.29; N, 12.25.
Found: C, 47.24; H, 5.18; N, 12.45.
[1-(Tert-butyl)-3,5-bis(N-methylimidazol-2-yl)methyl-4-meth-
oxybenzene] hexafluorophosphate 5b: 79%. 1H NMR (400
MHz, DMSO-d6): d 9.11 (s, 2H, Im–H), 7.70 (s, 4H, Im–H), 7.47
(s, 2H, Ph–H), 5.42 (s, 4H, Im–CH2–Ph), 3.86 (s, 6H, Im–CH3),
3.76 (s, 3H, Ph–OCH3), 1.26 (s, 9H, t-Bu); 13C NMR (100 MHz,
DMSO-d6): d 154.43 (C–OCH3 of Ph), 147.91 (C–t-Bu of Ph),
136.66 (NCHN of Im), 128.74, 127.68, 123.80, 122.44 (Im),
62.08 (OCH3), 47.71 (Im–CH2–Ph), 35.82 (Im–CH3), 34.31
(t-Bu), 30.93 (CH3 of t-Bu). ESI-MS: [M 2 PF62]+: at m/z
499.2. Anal. calcd for C21H30F12N4OP2: C, 39.14; H, 4.69; N,
8.69. Found: C, 39.04; H, 4.88; N 8.69.
[1-Methyl-3,5-bis(N-naphthylmethylimidazol-2-yl)methyl-4-
methoxybenzene] hexafluorophosphate 5c: 89%. 1H NMR (400
MHz, DMSO-d6): d 9.32 (s, 2H, Im–H), 8.10 (m, 2H, Naph–H)
(Naph = Naphthalene), 8.04 (d, 4H, J = 8.0 Hz, Naph–H), 7.82
(s, 2H, Im–H), 7.69 (s, 2H, Im–H), 7.63–7.51 (m, 8H, Im–H and
Naph–H), 7.01 (s, 2H, Ph–H), 5.94 (s, 4H, Naph–CH2–Im), 5.40
(s, 4H, Im–CH2–Ph), 3.60 (s, 3H, –OCH3), 2.19 (s, 3H, –CH3);
13C NMR (100 MHz, DMSO-d6): d 153.92 (C–OCH3 of Ph),
136.76 (NCHN of Im), 134.55 (C–CH3 of Ph), 133.44, 131.01,
130.33, 129.89, 129.74, 127.17, 126.45, 125.64, 123.08, 122.93,
122.72, 61.81 (OCH3), 50.08 (Im–CH2–Naph), 47.52 (Im–CH2–
Ph), 20.25 (CH3–Ph). ESI-MS [M 2 PF62]+: at m/z 709.3. Anal.
calcd for C38H36F12N4OP2: C, 53.40; H, 4.25; N, 6.56. Found: C,
53.19; H, 4.29; N, 5.75.
[1-Methyl-3,5-bis(N-anthrylmethylimidazol-2-yl)methyl-4-
methoxybenzene] hexafluorophosphate 5d: 75%. 1H NMR (400
MHz, DMSO-d6): d 9.04 (s, 2H, Im–H), 8.86 (s, 4H, An–H), (An
= anthracene), 8.45 (d, 4H, J = 11.2 Hz, An–H), 8.23 (d, 4H, J =
10.8 Hz, An–H), 7.70–7.59 (m, 12H, Im–H and An–H), 6.83 (s,
2H, Ph–H), 6.51 (s, 4H, An–CH2–Im), 5.28 (s, 4H, Im–CH2–
Ph), 3.40 (s, 3H, –OCH3), 2.12 (s, 3H, –CH3); 13C NMR (100
MHz, DMSO-d6): d 153.54 (C–OCH3 of Ph), 136.12 (NCHN of
Im), 134.36 (C–CH3 of Ph), 131.06, 130.57, 130.33, 130.16,
129.42, 128.27, 122.75, 126.59, 123.43, 123.26, 122.91,
122.77, 125.59, 123.43, 123.26, 122.91, 122.77, 61.51
(OCH3), 47.25 (Im–CH2–An), 45.02 (Im–CH2–Ph), 20.27
(CH3–Ph). ESI-MS [M 2 PF62]+: at m/z 809.3. Anal. calcd
for C46H40F12N4OP2: C, 57.87; H, 4.22; N, 5.87. Found: C,
57.84; H, 4.12; N, 5.57.
An), 44.99 (Im–CH2–Ph), 28.33 (Ph–CH2–Ph), 20.38 (CH3–Ph).
2 +
ESI-MS [M
2
PF6
]
at m/z 943.4. Anal. calcd for
C
55H50F12N4O2P2: C, 60.66; H, 4.63; N, 5.15. Found: C, 60.39;
H, 4.63; N, 5.07.
5f: 68%. 1H NMR (400 MHz, DMSO-d6): d 9.09 (s, 2H,
NCHN), 8.86 (s, 2H, An–H), 8.48 (d, 4H, J = 8.8 Hz, An–H), 8.23
(d, 4H, J = 8.8 Hz, An–H), 7.69–7.60 (ddd, 12H, J = 17.5, 14.8,
6.2 Hz, An–H, Im–H), 7.02 (d, 2H, J = 2.1 Hz, Ph–H), 6.95 (d,
2H, J = 2.1 Hz, Ph–H), 6.92 (s, 2H, Ph–H), 6.55 (s, 4H, An–CH2),
5.35 (s, 4H, Im–CH2–Ph), 3.96 (s, 4H, Ph–CH2–Ph), 3.51 (s, 6H,
Ph–OCH3 with Im), 3.44 (s, 3H, middle Ph–OCH3), 1.07 (d,
27H, J = 16.1 Hz, t-Bu). 13C NMR (100 MHz, DMSO-d6): d 152.91
(C–OCH3 of Ph), 152.70 (C–OCH3 of Ph), 145.35 (C–t-Bu of Ph),
144.60 (C–t-Bu of Ph), 134.84 (NCHN of Im), 132.43, 130.94,
129.99, 129.49, 129.05, 128.30, 127.21, 126.66, 125.99, 124.81,
124.46, 123.19, 122.39, 122.13, 121.71, 121.67, 59.71 (OCH3),
59.21 (OCH3), 47.08 (Im–CH2–An), 43.85 (Im–CH2–Ph), 32.80
(t-Bu), 32.71 (t-Bu), 29.88 (CH3 of t-Bu), 29.75 (CH3 of t-Bu),
27.95 (Ph–CH2–Ph). ESI-MS [M 2 PF62]+ at m/z 1203.3. Anal.
calcd for C73H78F12N4O3P2: C, 64.98; H, 5.83; N, 4.15. Found: C,
64.85; H, 5.69; N, 4.24.
General procedure for the synthesis of complexes 6a–f
A sample of precursor 5 (0.50 mmol) was dissolved in 50 mL of
acetonitrile and silver oxide (1.0 mmol) was added to the
solution. The mixture was stirred at 50 uC for 8 h with the
exclusion of light. After cooling to room temperature, the
suspension was filtered through Celite to collect the filtrate.
The volatiles were evaporated in vacuo at room temperature.
Pure complex
6 was afforded by recrystallization from
acetonitrile–ethyl ether.
6a: 82%. 1H NMR (400 MHz, DMSO-d6): d 7.47 (s, 8H, Im–H),
6.77 (s, 4H, Ph–H), 5.21 (s, 8H, Ph–CH2–Ph), 3.82 (s, 12H, Im–
CH3), 3.56 (s, 6H, Ph–OCH3), 2.04 (s, 6H, Ph–CH3); 13C NMR
(100 MHz, DMSO-d6): d 179.35 (carbene), 152.04 (C–OCH3 of
Ph), 132.80, 129.22, 128.23, 121.99, 121.43, 117.03 (Im), 60.42
(OCH3), 47.85 (Im–CH2–Ph), 37.16 (Im–CH3), 19.18 (CH3–Ph);
ESI-MS: [M 2 2PF62]2+/2: at m/z 417.3 (for 107Ag), 419.2 (for
109Ag). Anal. calcd for C36H44Ag2F12N8O2P2: C, 38.38; H, 3.94;
N, 9.95. Found: C, 38.13; H, 4.19; N, 9.59.
1
6b: 85%. H NMR (400 MHz, DMSO): d 7.49 (s, 4H, Im–H),
7.08 (s, 4H, Ph–H), 5.23 (s, 8H, –CH2–), 3.78 (s, 12H, Im–CH3),
3.52 (s, 6H, Ph–OCH3), 1.09 (s, 18H, t-Bu); 13C NMR (100 MHz,
DMSO-d6): d 179.40 (carbene), 152.22 (C–OCH3 of Ph), 146.95
(C–t-Bu of Ph), 128.68, 125.07, 121.94, 121.34, 117.97 (Im),
60.41 (OCH3), 48.07 (Im–CH2–Ph), 37.14 (Im–CH3), 32.94
(t-Bu), 29.73 (CH3 of t-Bu); ESI-MS: at m/z [M 2 2PF62]2+/2: at
m/z 459.3 (for 107Ag), 461.2 (for 109Ag). Anal. calcd for
{Bis[3-(N-9-anthrylmethylimidazol-2-yl)methyl-5-methyl-2-
methoxyphenyl]methane} hexafluorophosphate 5e: 73%. 1H
NMR (400 MHz, DMSO-d6): d 9.09 (s, 2H, NCHN), 8.86 (s, 2H,
An–H), 8.47 (d, 4H, J = 8.7 Hz, An–H), 8.23 (d, 4H, J = 8.7 Hz,
An–H), 7.69–7.60 (ddd, 12H, J = 14.7, 12.4, 7.1 Hz, An–H, Im–
H), 6.74 (d, 4H, J = 9.0 Hz, Ph–H), 6.53 (s, 4H, An–CH2), 5.30 (s,
4H, Im–CH2), 3.84 (s, 2H, Ph–CH2–Ph), 3.44 (s, 6H, 2-OCH3),
2.09 (s, 6H, Ph–CH3). 13C NMR (100 MHz, DMSO-d6): d 153.83
(C–OCH3 of Ph), 136.15 (NCHN of Im), 133.50, 133.41, 131.77,
131.08, 130.59, 130.15, 129.42, 128.04, 127.73, 127.67, 125.58,
C
42H56Ag2F12N8O2P2: C, 41.67; H, 4.66; N, 9.26, Found: C,
41.35; H, 4.96; N, 9.24.
6c: 70%. 1H NMR (400 MHz, DMSO-d6): d 7.92 (t, 8H, J = 8.2
Hz, Naph–H), 7.83 (d, 4H, J = 8.0 Hz, Naph–H), 7.62 (d, 4H, J =
1.2 Hz, Im–H), 7.49 (t, 4H, J = 7.5 Hz, Naph–H), 7.40 (m, 8H, J =
1.2 Hz, J = 6.8 Hz, Im–H, Naph–H), 7.28 (t, 4H, J = 7.6 Hz,
Naph–H), 7.22 (d, 4H, J = 6.8 Hz, Naph–H), 6.26 (s, 4H, Ph–H),
5.64 (s, 8H, Naph–CH2–Im), 4.89 (s, 8H, Im–CH2–Ph), 3.02 (s,
6H, –OCH3), 1.75 (s, 6H, –CH3); 13C NMR (100 MHz, DMSO-d6):
d 179.78 (carbene), 151.58 (C–OCH3 of Ph), 132.51, 132.37,
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131.34, 129.38, 128.94, 127.82, 127.67, 127.40, 125.91, 125.57,
125.10, 124.26, 122.04, 121.93, 121.17, 117.00 (Im), 59.92
(OCH3), 51.03 (Im–CH2–Naph), 48.23 (Im–CH2–Ph), 19.13
(CH3–Ph); ESI-MS [M 2 2PF62]2+/2: at m/z 669.4 (for 107Ag),
671.3 (for 109Ag). Anal. calcd for C76H68Ag2F12N8O2P2: C, 55.96;
H, 4.20; N, 6.87. Found: C, 55.98; H, 4.39; N, 6.66.
6d: 73%. 1H NMR (400 MHz, DMSO-d6): d 8.66 (s, 4H, An–H),
8.329 (d, 8H, J = 8.9 Hz, An–H), 8.05 (d, 8H, J = 8.4 HZ, An–H),
7.60 (d, 4H, J = 1.2 HZ, Im–H), 7.52 (m, 8H, An–H), 7.41 (m, 8H,
An–H), 7.15 (d, 4H, J = 1.2 HZ, Im–H), 6.05 (s, 8H, An–CH2–Im),
5.28 (s, 8H, Ph–H), 4.15 (s, 8H, Im–CH2–Ph), 2.29 (s, 6H,
–OCH3), 1.08 (s, 6H, –CH3); 13C NMR (100 MHz, DMSO-d6): d
181.01 (carbene), 151.22 (C–OCH3 of Ph), 132.65, 131.03,
130.07, 129.06, 128.85, 127.06, 126.81, 126.38, 125.20, 123.71,
123.22, 121.20, 60.02 (OCH3), 48.82 (Im–CH2–An), 45.99 (Im–
CH2–Ph), 19.70 (CH3–Ph). ESI-MS [M 2 2PF62]2+/2: at m/z
769.2 (for 107Ag), 771.2 (for 109Ag). Anal. calcd. for
C92H76Ag2F12N8O2P2: C, 60.34; H, 4.18; N, 6.12. Found: C,
60.40; H, 4.13; N, 6.16.
ometer using Mo–Ka radiation (0.71073 Å). Absorption
corrections were performed using CrystalClear. All the
structures were solved using direct methods, which yielded
the positions of all non-hydrogen atoms. These were refined
first isotropically and then anisotropically. For the structure
of 6a, each asymmetric unit contains 0.5 Et2O solvent
molecules. The diethyl ether molecule is disordered and
the atoms (C12–C15, O3) are assigned to a partial site-
occupancy of 0.25, respectively. For the structure of 6b, the
tert-butyl group and two PF6 anions are disordered and the
atoms (C14–C16, F1–F6 and F7–F12) are assigned to partial
site-occupancies of 0.548, 0.803 and 0.559, respectively. The
final
R indices (0.1235 and 0.2169 for R1 and wR2,
respectively) are a little high because of many uses of
restrains (470 restraints for 760 parameters) to resolve the
disordered groups in the molecule. The single crystal of 6b
has been grown in other mixed solvents but could not be
obtained in better quality. For the structure of 6c, each
asymmetric unit contains 2 CH3CN crystallized solvent
molecules. The naphthylmethyl group and PF6 anion are
disordered and the atoms (C28–C38) and (F1–F4) are
assigned to partial site-occupancies of 0.744 and 0.676,
respectively. For the structure of 6d, each asymmetric unit
contains 4.5 CH3CN, 0.5 Et2O and 1.0 H2O crystallized
solvents. The atoms (C55, C56, N7), (C57, C58, N8), (C59,
C60, N9), (C51–C54, O2), O3, O4 and O49 are assigned to
partial site-occupancies of 0.25, 0.3, 0.2 and 0.25, 0.25, 0.125
and 0.125, respectively. The hydrogens attached to the
disordered solvents were not added. For the structure of 6e,
each asymmetric unit contains 1.5 CH3CN solvent molecules.
For the structure of 6f, each asymmetric unit contains 2
CH3CN solvent molecules. One of the CH3CN molecules is
disordered and the atoms (C75, C76 and N5) are assigned to
a partial site-occupancy of 0.6. Furthermore, two methoxy
groups and the PF6 anion of 6f are disordered and the atoms
C42, C54 and F1–F6 are assigned to partial site-occupancies
of 0.6, 0.5 and 0.852, respectively. All of the disordered parts
were restrained using DFIX, ISOR and SIMU instructions to
make the displacement parameters more reasonable. It
should be noted that the ADPs for some atoms in 6e are a
bit large because these long chain atoms or groups in the
macrocyclic frame are slightly disordered. Attempts to solve
these atoms into two positions with suitable variable site-
occupations were not satisfied. All the hydrogen atoms of the
ligand were placed in calculated positions with fixed
isotropic thermal parameters and were included in the
structure factor calculations in the final stage of the full-
matrix least-squares refinement.
6e: 75%. 1H NMR (400 MHz, DMSO-d6) d 8.70 (s, 4H, An–H),
8.22 (d, 8H, J = 8.7 Hz, An–H), 8.08 (d, 8H, J = 8.2 Hz, An–H),
7.75 (s, 4H, Im–H), 7.53–7.42 (m, 16H, An–H), 7.34 (s, 4H, Im–
H), 6.07 (d, 10H, J = 27.1 Hz, Ph–H, An–CH2–Im), 5.88 (s, 4H,
Ph–H), 4.16 (s, 8H, Im–CH2–Ph), 2.98 (s, 4H, Ph–CH2–Ph), 2.50
(s, 12H, –OCH3), 1.60 (s, 12H, Ph–CH3). 13C NMR (100 MHz,
DMSO-d6):
d 181.01 (carbene), 180.84 (carbene), 179.02
(carbene), 178.90 (carbene), 152.86 (C–OCH3 of Ph), 132.68,
132.57, 131.04, 130.15, 129.14, 129.07, 128.87, 126.93, 126.68,
125.18, 123.79, 123.24, 121.04 (Im), 59.94 (OCH3), 50.01 (Im–
CH2–An), 46.01 (Im–CH2–Ph), 26.61 (Ph–CH2–Ph), 20.04 (CH3–
Ph). ESI-MS [M 2 2PF62]2+/2: at m/z 903.5 (for 107Ag), 905.5 (for
109Ag). Anal. calcd. for C110H96F12N8O4P2: C, 62.92; H, 4.61; N,
5.34. Found: C 62.65; H, 4.32; N, 5.61.
1
6f: 73%. H NMR (400 MHz, DMSO-d6): d 8.73 (s, 4H, An–
H), 8.34 (d, 8H, J = 8.9 Hz, An–H), 8.07 (d, 8H, J = 8.4 Hz, An–
H), 7.88 (s, 4H, Im–H), 7.60–7.58 (m, 8H, An–H), 7.40–7.36 (m,
8H, An–H), 7.32 (s, s, 4H, Im–H), 6.59 (s, 4H, Ph–H), 6.48 (s,
4H, Ph–H), 6.11 (s, 8H, An–CH2–Im), 5.87 (s, 4H, Ph–H), 4.11
(s, 8H, Im–CH2–Ph), 3.54 (s, 8H, Ph–CH2–Ph), 3.14 (s, 6H,
2-OCH3 of middle Ph), 2.54 (s, 12H, 4-OCH3), 0.98 (s, 18H,
t-Bu of middle Ph), 0.43 (s, 36H, t-Bu). 13C NMR (100 MHz,
DMSO-d6):
d 180.54 (carbene), 180.40 (carbene), 178.57
(carbene), 178.43 (carbene), 154.57 (C–OCH3 of Ph), 152.39
(C–OCH3 of Ph), 145.49 (C–t-Bu of Ph), 145.36 (C–t-Bu of Ph),
132.80, 131.70, 131.08, 130.15, 129.10, 128.93, 128.28, 127.11,
127.05, 126.56, 125.73, 125.15, 123.80, 121.06 (Im), 60.31
(OCH3), 60.05 (OCH3), 49.69 (Im–CH2–An), 45.87 (Im–CH2–
Ph), 33.70 (t-Bu), 33.19 (t-Bu), 30.97 (CH3 of t-Bu), 30.28 (CH3
of t-Bu), 28.37 (Ph–CH2–Ph). ESI-MS [M 2 2PF6
1163.5 (for 107Ag), 1165.5 (for 109Ag). Anal. calcd for
146H152Ag2F12N8O6P2: C, 66.92; H, 5.85; N, 4.28. Found: C,
]
2 2+/2: at m/z
All the calculations were performed using the SHELXTL
system of computer programs.32 The crystallographic data are
summarized in Table 4 for 6a–c and Table 5 for 6e–f.
C
66.78; H, 5.69; N, 4.07.
Crystallography
Single crystals of complexes 6a–f suitable for X-ray diffraction
analysis were obtained by the slow diffusion of diethyl ether
into their acetonitrile–ethanol solutions at room tempera-
ture, respectively. Diffraction intensity data of 6a–f were all
collected at 113(2) K on a Rigaku Saturn724 CCD diffract-
Acknowledgements
This work is supported by the National Natural Science
Foundation of China (No. 21172114, No. 21172036).
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Table 4 Summary of crystallographic data for complexes 6a–c
6a?Et2O
6b
6c?2CH3CN
CCDC
Chemical formula
Formula weight
Crystal system
Space group
a (Å)
898036
C40H54Ag2F12N8O3P2
1200.57
Orthorhombic
Ibam
12.616(4)
18.479(5)
20.409(6)
90
90
90
906066
C42H56Ag2F12N8O2P2
1210.63
Monoclinic
P2(1)/n
20.903(4)
10.785(3)
21.922(7)
90
898037
C80H74Ag2F12N10O2P2
1713.17
Triclinic
¯
P1
11.967(3)
13.539(3)
13.776(4)
116.722(12)
96.41(2)
103.815(17)
1873.2(8)
1
1.519
0.650
b (Å)
c (Å)
a (u)
b (u)
90.808(13)
90
4942(2)
c (u)
Volume (Å3)
Z
4758(2)
8
1.676
0.984
4
Dcalcd (g cm23
)
1.627
0.947
Abs coeff (mm21
)
F(000)
Crystal size (mm)
hmin, hmax/u
Reflections collected/unique
Rint
2424
2448
872
0.20 6 0.18 6 0.12
1.95, 25.03
21 462/2166
0.0321
0.18 6 0.16 6 0.12
1.34 to 24.99
29 406/8468
0.0889
0.30 6 0.22 6 0.16
2.09 to 25.03
16 051/6588
0.0501
Max. and min. transmission
Data/restraints/parameters
Goodness-of-fit on F2a
Final R indicesb [I . 2s(I)] R1, wR2
R and Rw (all data) R1, wR2
0.8910, 0.8275
42 166/72/193
1.041
0.0276, 0.0780
0.0287, 0.0790
0.836 and 20.405
0.8948, 0.8480
8468/470/760
1.032
0.1235, 0.2169
0.1667, 0.2438
1.141 and 20.916
0.9031, 0.8288
6588/540/624
0.986
0.0345, 0.0688
0.0415, 0.0713
0.507 and 20.666
Largest diff. peak and hole (e Å23
)
a
2
b
Goof = [Sw(Fo 2 Fc2)2/(n 2 p)]1/2, where n is the number of reflections and p is the number of parameters refined. R1 =S(||Fo| 2 |Fc||)/
S|Fo|; wR2 = 1/[s2(Fo2) + (0.0691P) + 1.4100P] where P = (Fo + 2Fc2)/3.
2
Table 5 Summary of crystallographic data for complexes 6d–f
6d?4.5CH3CN?0.5Et2O?H2O
6e?1.5CH3CN
6f?4CH3CN
CCDC
898043
C103H96.5Ag2F12N11O4.50P2
2066.1
Monoclinic
C2/c
16.080(6)
26.639(9)
25.248(8)
90.00
98.115(6)
90.00
10 706(6)
4
1.284
0.469
931824
C113H101 50
930716
C154H164Ag2F12N12O6P2
2784.66
Formula
Formula weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
.
Ag2F12N9.50O4P2
2162.22
Triclinic
Triclinic
¯
¯
P1
P1
15.946(3)
17.488(3)
19.160(3)
68.336(4)
85.729(9)
86.013(9)
4946.8(16)
2
12.733(2)
15.734(3)
19.262(4)
83.265(8)
80.083(8)
70.440(6)
3574.7(11)
1
1.294
a (u)
b (u)
c (u)
Volume (Å3)
Z
Dcalcd (g cm23
)
1.451
0.511
Abs coeff (mm21
)
0.371
F(000)
Crystal size (mm)
hmin, hmax/u
Reflections collected/unique
Rint
4238
2218
1452
0.20 6 0.20 6 0.10
1.49, 25.02
39 764/9393
0.0918
0.20 6 0.18 6 0.12
1.25 to 25.02
41 166/17 387
0.0366
0.20 6 0.18 6 0.12
1.38 to 25.02
30 722/12 570
0.0360
Max. and min. transmission
Data/restraints/parameters
Goodness-of-fit on F2a
Final R indicesb [I . 2s(I)], R1, wR2
R and Rw (all data), R1, wR2
0.9546 and 0.9120
9393/369/726
1.109
0.0906, 0.2328
0.1036, 0.2443
0.943 and 20.713
0.9412, 0.9047
17 387/57/1340
1.056
0.0543, 0.1345
0.0656, 0.1423
1.315 and 20.781
0.9568, 0.9295
12 570/485/997
1.047
0.0414, 0.1159
0.0465, 0.1189
0.966 and 20.529
Largest diff. peak and hole (e Å23
)
a
2
b
Goof = [Sw(Fo 2 Fc2)2/(n 2 p)]1/2, where n is the number of reflections and p is the number of parameters refined. R1 = S(||Fo| 2 |Fc||)/
S|Fo|; wR2 = 1/[s2(Fo2) + (0.0691P) + 1.4100P] where P = (Fo + 2Fc2)/3.
2
6960 | CrystEngComm, 2013, 15, 6948–6962
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