Coordination-driven synthesis of Ag(I) compounds based on a double emission ligand consisting of 1,3,4-oxadiazole and cyclotriphosphazene units

Article abstract of DOI:10.1080/00958972.2012.700053

A new ligand (L) which consists of cyclotriphosphazene and 1,3,4-oxadiazole units is reported. Two new Ag(I) coordination compounds {[Ag(L)SO ₃CF₃] _n (1) and Ag₂L ₂(NO₃)₂ (2)} based on L and Ag(I) salts are obtained. Compound 1 features a 1-D chain, in which the ligand L adopts a divergent trans-conformation, whereas 2 is a discrete binuclear Ag(I) molecule in which L adopts convergent cis-conformation. Compounds 1 and 2 are fully characterized by ¹H-NMR, Infrared, elemental analysis, X-ray powder, and single-crystal diffraction. Luminescent properties of 1 and 2 are investigated.

Full text of DOI:10.1080/00958972.2012.700053

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Coordination-driven synthesis of Ag(I)
compounds based on a double emission
ligand consisting of 1,3,4-oxadiazole
and cyclotriphosphazene units
Xiang-Wen Wu a , Xiao-Yan Wang a , Qing-Long Li a , Jian-Ping Ma a
& Yu-Bin Dong a
a 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
Accepted author version posted online: 06 Jun 2012.Published
online: 06 Aug 2012.
To cite this article: Xiang-Wen Wu , Xiao-Yan Wang , Qing-Long Li , Jian-Ping Ma & Yu-Bin Dong
(2012) Coordination-driven synthesis of Ag(I) compounds based on a double emission ligand
consisting of 1,3,4-oxadiazole and cyclotriphosphazene units, Journal of Coordination Chemistry,
65:18, 3299-3307, DOI: 10.1080/00958972.2012.700053
To link to this article: http://dx.doi.org/10.1080/00958972.2012.700053
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Journal of Coordination Chemistry
Vol. 65, No. 18, 20 September 2012, 3299–3307
Coordination-driven synthesis of Ag(I) compounds based on a
double emission ligand consisting of 1,3,4-oxadiazole and
cyclotriphosphazene units
XIANG-WEN WU, XIAO-YAN WANG, QING-LONG LI,
JIAN-PING MA and YU-BIN DONG*
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
(Received 7 March 2012; in final form 19 April 2012)
A new ligand (L) which consists of cyclotriphosphazene and 1,3,4-oxadiazole units is reported.
Two new Ag(I) coordination compounds {[Ag(L)SO3CF3]n (1) and Ag2L2(NO3)2 (2)} based on
L and Ag(I) salts are obtained. Compound 1 features a 1-D chain, in which the ligand L adopts
a divergent trans-conformation, whereas 2 is a discrete binuclear Ag(I) molecule in which L
adopts convergent cis-conformation. Compounds 1 and 2 are fully characterized by 1H-NMR,
Infrared, elemental analysis, X-ray powder, and single-crystal diffraction. Luminescent
properties of 1 and 2 are investigated.
Keywords: 1,3,4-Oxadiazole; Cyclotriphosphazene; Ag(I); Coordination compounds
1. Introduction
Interest has focused on coordination compounds with potential applications in sensing,
photoluminescence, ion exchange, separations, gas storage, and catalysis [1, 2].
Recently, effort has been dedicated to functional inorganic rings and cages as scaffolds
for assembling supramolecular compounds. For example, cyclotriphosphazenes, as an
important class of inorganic nondelocalized cyclic units [3, 4], have been used to
construct organic or metal-organic supramolecular systems [5, 6]. Supramolecular
compounds based on both cyclotriphosphazenes and five-membered heterocycles are
relatively rare. We have longstanding interest in coordination chemistry of bent organic
ligands bridged by five-membered heterocycles such as oxadiazole and triazole,
especially in how different types of linkages and orientations impact the structures of
various coordination-driven supramolecular compounds [7–9]. In this contribution,
we present a new cyclotriphosphazene ligand (L) containing 1,3,4-oxadiazole,
*Corresponding author. Email: yubindong@sdnu.edu.cn
Journal of Coordination Chemistry
ISSN 0095-8972 print/ISSN 1029-0389 online ß 2012 Taylor & Francis
http://dx.doi.org/10.1080/00958972.2012.700053

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X.-W. Wu et al.
Scheme 1. Synthesis of 1 and 2.
bis(2,20-dioxybiphenyl)bis(2-phenoxy-5-(4-pyridyl)-1,3,4-oxadiazole)cyclotriphosphazene
and two new Ag(I) coordination compounds (1 and 2) based on it (scheme 1).
Compounds 1 and 2 have been fully characterized by 1H-NMR, Infrared (IR),
elemental analysis, X-ray powder and single-crystal diffraction. In addition, the
photoluminescence of 1 and 2 are investigated in the solid state.
2. Experimental
2.1. Physical measurements
AgSO3CF3 and AgNO3 (Acros) were used as obtained without purification. IR samples
were prepared as KBr pellets and spectra were obtained in the 400–4000 cmꢀ1 range
using a Perkin-Elmer 1600 FTIR spectrometer. Elemental analyses were performed on a
Perkin-Elmer model 2400 analyzer. 1H-NMR data were collected using a Bruker
AM-300 spectrometer. Chemical shifts are reported in ꢀ relative to TMS. All
fluorescence measurements were carried out on a Cary Eclipse spectrofluorimeter
(Varian, Australia) equipped with a xenon lamp and quartz carrier at room
temperature. XRD patterns were obtained on a D8 ADVANCE X-ray powder
˚
diffractometer (XRD) with Cu-Ka radiation (ꢁ ¼ 1.5405 A).
2.2. X-ray structural studies
Suitable single crystals of 1 and 2 were selected and mounted in air onto thin glass
fibers. X-ray intensity data of 1 and 2 were measured at 173 K on a Bruker SMART
˚
Apex CCD-based diffractometer (Mo-Ka radiation, ꢁ ¼ 0.71073 A). The raw frame
data for 1 and 2 were integrated into SHELX-format reflection files and corrected for

Ag(I) compounds
Table 1. Crystallographic parameters of 1 and 2.
3301
Parameters
1
2
Empirical formula
Formula weight
Crystal system
Space group
C51H32AgF3N9O11P3S
1236.70
Triclinic
C100H64Ag2N20O22P6
2299.27
Triclinic
ꢀ
ꢀ
P1
P1
ꢁ
˚
Unit cell dimensions (A,
)
a
b
c
ꢂ
ꢃ
ꢄ
8.8900(11)
10.6079(19)
14.672(3)
15.413(3)
88.441(3)
80.379(3)
88.504(3)
2363.7(8), 1
1.615
14.9601(19)
18.655(2)
87.538(2)
86.282(2)
86.973(2)
2470.4(5), 2
1.663
0.633
3
˚
Volume (A ), Z
Calculated density (g cmꢀ3
)
Absorption coefficient (mmꢀ1
F(000)
)
0.604
1164
1248
0.35 ꢂ 0.30 ꢂ 0.16
Crystal size (mm3)
0.26 ꢂ 0.16 ꢂ 0.12
Reflections collected
Independent reflection
Goodness-of-fit on F2
Final R indices [I 4 2ꢅ(I)]
R indices (all data)
13,109
9046 [R(int) ¼ 0.0183]
1.025
12,482
8625 [R(int) ¼ 0.0251
1.014
R1 ¼ 0.0506, wR2 ¼ 0.1289
R1 ¼ 0.0538, wR2 ¼ 0.1303
R1 ¼ 0.0641, wR2 ¼ 0.1394
R1 ¼ 0.0759, wR2 ¼ 0.1444
Lorentz and polarization effects using SAINT. Corrections for incident and diffracted
beam absorption effects were applied using SADABS. The crystals showed no evidence
of crystal decay during data collection. The structures were solved by a combination of
direct methods and difference Fourier syntheses and refined against F2 by full-matrix
least squares. Crystal data, data collection parameters, and refinement statistics for 1
and 2 are listed in table 1.
2.3. Synthesis of bis(2,20-dioxybiphenyl)bis(2-phenoxy-5-(4-pyridyl)-1,3,4-oxadia-
zole)cyclotriphosphazene (L)
To solution of A (2-phenoxy-5-(4-pyridyl)-1,3,4-oxadiazole (0.50 g, 2.1 mmol) in 30 mL
THF) was added NaH (50.4 mg, 2.1 mmol) and the mixture was stirred for 1 h at room
temperature, then B ([N3P3(2,20-dioxybiphenyl)2Cl2] (0.574 g, 1 mmol) in 20 mL THF)
was added. The mixture was heated at reflux over 3 h, allowed to cool, the precipitate
separated by filtration, washed several times with water, and the residue was purified on
a silica gel column using CH2Cl2 : MeOH ¼ 20 : 1 as the eluent to afford L as a white
crystalline solid (yield: 0.62 g, 60.8%). IR (KBr pellet, cmꢀ1): 1608(m), 1540(w),
1477(m), 1435(m), 1410(w), 1276(m), 1233(m), 1175(s), 1090(m), 1033(m), 932(w),
890(s), 818(w), 785(m), 750(m), 716(m), 701(m), 630(w), 608(m), 532(m), 409(w).
1H-NMR (300 MHz, 25ꢁC, DMSO-d6, TMS, ppm): 8.41 (d, 2H, –C5H4N), 8.26 (d, 1H,
–C6H4O), 8.02 (d, 2H, –C5H4N), 7.76(d, 1H, –C6H4O), 7.51–7.39 (m, 3H, –C6H4O,
–C12H8O2), 7.28–7.26 (m, 5H, –C6H4O, –C12H8O2), 7.03 (d, 2H, –C12H8O2).
Anal. Calcd for C50H32N9O8P3: C, 61.29; H, 3.30; N, 12.86. Found: C, 61.33;
H, 3.24; N, 12.89.

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X.-W. Wu et al.
2.4. Synthesis of [Ag(L)SO3CF3]n (1)
The solution of AgSO3CF3 (5.20 mg, 0.02 mmol) in THF (7 mL) was layered onto a
solution of L (19.6 mg, 0.02 mmol) in MeOH (7 mL). The system was left for one day at
room temperature and colorless crystals of 1 were obtained (yield: 15.6 mg, 63.1%). IR
(KBr pellet, cmꢀ1): 1608(w), 1539(w), 1475(w), 1437(w), 1414(w), 1275(m), 1232(m),
1176(s), 1094(m), 1038(w), 976(w), 934(m), 890(s), 830(w), 786(m), 758(m), 712(w),
1
610(m), 531(m). H-NMR (300 MHz, 25ꢁC, DMSO-d6, TMS, ppm): 8.52 (d, 4H,
p-C5H4N), 8.25 (d, 2H, p-C6H4O), 7.78 (d, 4H, o-C5H4N), 7.74 (d, 4H, –C6H4O), 7.62
(d, 4H, –C12H8O2), 7.48 (t, 2H, m-C6H4O), 7.43–7.04 (m, 8H, –C12H8O2), 7.07 (d, 4H,
–C12H8O2). Anal. Calcd for C51H32AgF3N9O11P3S: C, 49.53; H, 2.61; N, 10.19. Found:
C, 45.46; H, 2.56; N, 10.25.
2.5. Synthesis of Ag2L2(NO3)2 (2)
The solution of AgNO3 (3.40 mg, 0.02 mmol) in THF (7 mL) was layered onto a
solution of L (19.6 mg, 0.02 mmol) in MeOH (7 mL). The system was left for three days
at room temperature and colorless crystals of 2 were obtained (yield: 16.32 mg, 71%).
IR (KBr pellet, cmꢀ1): 1658(s), 1613(w), 1542(w), 1476(w), 1439(w), 1414(w), 1268(m),
1259(s), 1230(m), 1172(s), 1096(m), 1035(w), 979(w), 930(m), 892(s), 782(m), 758(m),
1
712(w), 610(m), 531(m). H-NMR (300 MHz, 25ꢁC, DMSO-d6, TMS, ppm): 8.49 (d,
4H, p-C5H4N), 8.25 (d, 2H, p-C6H4O), 7.77 (d, 4H, o-C5H4N), 7.74 (d, 4H, –C6H4O),
7.62 (d, 4H, –C12H8O2), 7.49 (t, 2H, m-C6H4O), 7.43-7.04 (m, 8H, –C12H8O2), 7.07 (d,
4H, –C12H8O2). Anal. Calcd for C100H64Ag2N20O22P6: C, 52.24; H, 2.81; N, 12.18.
Found: C, 52.29; H, 2.73; N 12.09.
3. Results and discussion
3.1. Description of the crystal structure of 1
L was prepared from 2-phenoxy-5-(4-pyridyl)-1,3,4-oxadiazole (A) and N3P3(2,20-
dioxybiphenyl)2Cl2 (B). Compounds 1 and 2 were obtained by combination of L with
AgX [X ¼ SO3CFꢀ3 (1) and NO3ꢀ (2)] in mixed solutions (THF : CH3OH ¼ 1 : 1) under
ambient conditions.
ꢀ
Compound 1 crystallizes in the triclinic space group P1. As shown in figure 1 two
arms, which are located at the same phosphorus (P3) in each ligand, adopt divergent
trans-conformation to coordinate to two Ag(I) centers. Each Ag(I) is two-coordinate
with a long non-bonding Agꢃ ꢃ ꢃO contact (O from one SO3CFꢀ3 ); the coordination sites
are occupied by two pyridyl N-donors from two ligands. The Ag–N distances range
˚
˚
from 2.175(3) to 2.187(3) A, while the Agꢃ ꢃ ꢃO distance is 2.597(4) A. The Ag–N and
Agꢃ ꢃ ꢃO distances are comparable to reported values [10, 11].
The Ag(I) centers in 1 are connected to each other by L to form a 1-D chain, and
these chains are further linked by Agꢃ ꢃ ꢃAg interactions to form infinite 1-D double
˚
chains (figure 2). The corresponding Agꢃ ꢃ ꢃAg distance is 3.076(4) A (figure 3a) which is
consistent with reported values [12]. These parallel double chains are joined to generate

Ag(I) compounds
3303
Figure 1. The structure of 1 with hydrogen atoms removed for clarity.
Figure 2. The 1-D double chain of 1.
Figure 3. (a) The metal-metal bond between two Ag(I)’s from two adjacent chains. (b) The 2-D
supramolecular network arranged by 1. (c) ꢆ–ꢆ interactions between two adjacent 2,20-biphenol molecules.
˚
2-D sheets (figure 3b) via interchain ꢆ–ꢆ interactions (dꢆ–ꢆ ¼ ꢄ3.8 A). The interchain
ꢆ–ꢆ interactions are the result of the two adjacent 2,20-biphenol molecules (figure 3c).
3.2. Description of the crystal structure of 2
In order to study the impact of various counterions on self-assembly based on L, NO3ꢀ
was used instead of ellipsoidal SO3CFꢀ3 . Compound 2 was crystallized with L and
AgNO3 in the same solvent system at room temperature. Similar to 1, 2 crystallizes in
ꢀ
the triclinic space group P1. The two arms adopt convergent cis-conformations,
different from those in 1. Like in 1, Ag(I) is two-coordinate with a long non-bonding
Agꢃ ꢃ ꢃO contact (O comes from one NOꢀ3 ); the coordination positions are occupied by

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X.-W. Wu et al.
Figure 4. The structure of 2 with hydrogen atoms removed for clarity.
Figure 5. (a) ꢆ-ꢆ interactions between two 1,3,4-oxadiazole rings from two Ag2L2(NO3)2 molecules. (b) The
2-D supramolecular network arranged by 2. (c) ꢆ-ꢆ interactions between two adjacent 2,20-biphenol
molecules.
two pyridyl N-donors from two ligands (figure 4). The pyridyl rings of two arms in each
L are partly parallel, the dihedral angle between two pyridyls is 32.064(8)ꢁ and the
˚
distance of pyridyl N(1)–N(6) is 3.765(8) A. The Ag–N distances (ranging from 2.184(6)
˚
˚
to 2.201(5) A) are slightly longer than those of 1, while the Agꢃ ꢃ ꢃO distance (2.593(1) A)
is slightly shorter than that of 1.
Compared to 1, two Ag(I) centers in 2 are connected by L to form a discrete binuclear
Ag2L2(NO3)2; these discrete molecules are linked through ꢆ–ꢆ interactions
˚
(dꢆ–ꢆ ¼ ꢄ3.7 A) between two 1,3,4-oxadiazole rings from two different molecules
(figure 5a) into an infinite 1-D chain. Parallel chains stack to form a 2-D network
0
˚
(figure 5b) through ꢆ–ꢆ interactions (dꢆ–ꢆ ¼ ꢄ3.8 A) from two adjacent 2,2 -biphenol
molecules (figure 5c).
3.3. XRPD patterns of 1 and 2
Compounds 1 and 2 are obtained as pure phases, confirmed by X-ray powder
diffraction. As shown in figure 6, XRPD patterns of 1 and 2 obtained from the bulk
crystalline solids are identical to those of simulated ones based on single crystals.

Ag(I) compounds
3305
Figure 6. The XRPD patterns (black lines) obtained from the as-synthesized solids of 1 and 2 and the
simulated XRPD patterns (blue lines) from single crystals of 1 and 2.
Figure 7. Solid-state photoinduced emission spectra of 1 and 2 at room temperature.
3.4. Fluorescence of 1 and 2
Synthesis of organic–inorganic coordination compounds by judicious choice of
conjugated organic spacers and metal centers have proven to be an efficient method
for obtaining new luminescent materials [13]. The photoluminescence properties of
these two new compounds as well as the free ligand have been examined in the solid
state at room temperature. L excitation spectra show a lambda-max at 337 nm, L
exhibits two emission maxima at 377 and 510 nm, and 1 which has the same maximum
excitation wavelength as L, exhibits a fluorescence enhancement at 377 nm and a
fluorescence quenching at 510 nm. While 2 excitation spectra show a lambda-max at
409 nm, the fluorescence of 2 is completely quenched (figure 7). To understand different
fluorescences of 1 and 2, we study the coplanarities of three rings of each arm in L. In 1,
the dihedral angle between oxadiazole ring (C6, C7, N4, N5, O11) and phenyl ring

3306
X.-W. Wu et al.
(C8, C9, C10, C11, C12, and C13) is 2.57(14)ꢁ, and the dihedral angle between
oxadiazole ring and pyridyl ring (C1, C2, C3, C4, C5, and N6) is 4.74(12)ꢁ. In 2, the
dihedral angle between oxadiazole ring (C20, C21, N4, N5, and O1) and phenyl ring
(C14, C15, C16, C17, C18, and C19) is 4.03(15)ꢁ, bigger than that of 1, and the dihedral
angle between oxadiazole ring and pyridyl ring (C22, C23, C24, C25, C26, and N6) is
13.02(15)ꢁ, also bigger than that of 1. So the coplanarity of the three rings in 1 is better
than that of 2, which may lead to their different fluorescence properties [14].
4. Conclusions
Two new coordination compounds have been synthesized on the basis of a new double
emission ligand, bis(2,20-dioxybiphenyl)bis(2-phenoxy-5-(4-pyridyl)-1,3,4-oxadiazole)-
cyclotriphosphazene (L) and AgX [X ¼ SO3CFꢀ3 (1) and NO3ꢀ (2)]. [Ag(L)SO3CF3]n (1)
shows a 1-D chain structure and L adopts divergent trans-conformation, whereas
Ag2L2(NO3)2 (2) is a discrete molecule, in which L adopts convergent cis-conformation.
Compounds 1 and 2 are formed at room temperature compared with 2-D and 3-D
.
.
silver-organic coordination polymers [AgL]n nASF6, [AgL]n nSbF6 [15] and
[Ag(NO3)(APZ)]n, {[Ag(APZ)2][CF3COO]. H2O}n [16] under ambient conditions.
Furthermore, 1 exhibits strong fluorescence at 377 nm but 2 is completely quenched.
So, we conclude that the different counterions SO3CFꢀ3 and NO3ꢀ in 1 and 2 result in
their distinct structures and fluorescence properties. We are currently expanding the
results presented here by preparing new ligands of this type with different substituted
organic functional groups. We anticipate this approach to be useful for construction of
a variety of new coordination compounds with interesting fluorescent properties.
Supplementary material
Additional crystallographic details and complete bond lengths and angles, coordinates
and displacement parameters have been deposited at the Cambridge Crystallographic
Data Center (CCDC) as supplementary publication no: CCDC 2155347 for 1 and
CCDC 800579 for 2. Copies of the data can be obtained free of charge on application to
CCDC, 12 Union Road, Cambridge CB21EZ, UK (Fax: (þ44)1223-336-033; E-mail:
deposit@ccdc.cam.ac.uk).
Acknowledgments
This work was supported by NSFC (Nos. 91027003 and 21072118), 973 Program
(No. 2012CB821705), PCSIRT, Shangdong Natural Science Foundation
(No. JQ200803), and Taishan scholars’ construction project special fund.

Ag(I) compounds
3307
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