The synthesis, structure, and luminescence of two silver(I)-dppm complexes based on sulfate anion and nitrogen heterocyclic ligands

Article abstract of DOI:10.1016/j.ica.2010.03.075

At ambient temperature, two silver(I) complexes [Ag₄(SO ₄)₂(dppm)₄]·5CH₃CH ₂OH·1/2H₂O (1) and [Ag₂(SO ₄)(dppm)₂(2-ampz)]·CH₃OH·H ₂O (2) (dppm = bis(diphenylphosphino)methane, 2-ampz = 2-aminopyrazine) were obtained by the reaction of Ag₂SO₄ with dppm in the presence of pyrazine or 2-aminopyrazine. They are characterized by IR, X-ray crystallography, luminescence and ¹H, ³¹P NMR spectroscopy. Complex 1 is a tetranuclear cluster. In complex 2, the units [Ag₂(SO₄)(dppm)₂] are connected by 2-aminopyrazine to form a 1D linear polymer. Due to the subtle interactions of different nitrogen heterocyclic ligands with silver ions, two SO ₄^2- anions in 1 adopt μ₃-O, O′, O′ and unique μ₄-O, O, O′, O′ bonding modes respectively, while SO₄^2- anion in 2 adopts μ-O, O′ bonding mode.

Full text of DOI:10.1016/j.ica.2010.03.075

Inorganica Chimica Acta 363 (2010) 2425–2429
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
The synthesis, structure, and luminescence of two silver(I)-dppm complexes
based on sulfate anion and nitrogen heterocyclic ligands
a
b
Li-Li Song a, Qiong-Hua Jin a, , Li-Na Cui , Cun-Lin Zhang
*
a Department of Chemistry, Capital Normal University, Beijing 100048, China
b Beijing Key Laboratory for Terahertz Spectroscopy and Imaging, Key Laboratory of Terahertz Optoelectronics, Ministry of Education, Department of Physics,
Capital Normal University, Beijing 100048, China
a r t i c l e i n f o
a b s t r a c t
Article history:
At ambient temperature, two silver(I) complexes [Ag4(SO4)2(dppm)4]ꢀ5CH3CH2OHꢀ1/2H2O (1) and
[Ag2(SO4)(dppm)2(2-ampz)]ꢀCH3OHꢀH2O (2) (dppm = bis(diphenylphosphino)methane, 2-ampz = 2-ami-
nopyrazine) were obtained by the reaction of Ag2SO4 with dppm in the presence of pyrazine or 2-amino-
pyrazine. They are characterized by IR, X-ray crystallography, luminescence and 1H, 31P NMR
spectroscopy. Complex 1 is a tetranuclear cluster. In complex 2, the units [Ag2(SO4)(dppm)2] are con-
nected by 2-aminopyrazine to form a 1D linear polymer. Due to the subtle interactions of different nitro-
Received 27 January 2010
Received in revised form 28 March 2010
Accepted 30 March 2010
Available online 9 April 2010
Keywords:
Silver(I)
Sulfate
Bis(diphenylphosphino)methane
2-Aminopyrazine
Fluorescence
gen heterocyclic ligands with silver ions, two SO42ꢁ anions in 1 adopt
l
3-O, O0, O0 and unique
l
4-O, O, O0,
2ꢁ
O0 bonding modes respectively, while SO4 anion in 2 adopts
l
-O, O0 bonding mode.
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
[Ag4(
l
-dppm)2(
l
-SO4)2(
l
-4,40-bpy)2]ꢀ2CH3OH (4) are obtained by
using nitrogen heterocyclic ligands 2-aminopyrimidine (2-amp)
and 4,40-bipyridine (4,40-bpy), respectively [16]. In this paper,
selecting pyrazine and 2-aminopyrazine as nitrogen heterocyclic
The metal coordination polymers have attracted great interests
not only for their potential applications as functional materials, but
also for their fascinating architectures [1–3]. The design and syn-
thesis of metal coordination polymers can be influenced by many
factors, especially influenced by the nature of metal ions, ligands,
and anions [4–6]. The coordinated anions have been found to be
efficient in influencing the structure of the d10 metal-dppm com-
ligands, two new silver(I) complexes [Ag4(
-dppm)4]ꢀ5CH3CH2OHꢀ1/2H2O (1) and [Ag2(
(2-ampz)]ꢀCH3OHꢀH2O (2) were obtained. Complex 1 is a tetranu-
clear cluster, where the SO42ꢁ anions adopt the 3-O, O0, O0 bonding
mode (IV) and
4-O, O, O0, O0 bonding mode (V), the latter mode
l3-SO4)(
l4-SO4)-
(l
l-SO4)(
l-dppm)2
l
l
plexes, such as tetranuclear complexes [Ag4(
dppm)3], [Ag4( 3-S2O3)( -S2O3)( -dppm)4] [7], [Ag2(
-SCN)2(
l
3-Cl)(
l
-S2O3)(
l
l
-
-
had not been reported (Scheme 1). In complex 2, the units [Ag2-
(SO4)(dppm)2] are connected by 2-aminopyrazine to form a 1D lin-
ear polymer. They are characterized by X-ray crystallography, IR,
luminescence, 1H, 31P NMR spectroscopy.
l
l
l
l-OAc)2(
dppm)]2 [8] and [Ag(
l
l-dppm)Ag]2 [9].
To our knowledge, Ag(I) complexes containing SO42ꢁ anions are
2ꢁ
rare, and in these reported complexes the bonding mode of SO4
anion can also influence the structure of the complex. The reported
2ꢁ
-O, O0 (III)
l
4-O, O0, O00, O00
2. Experimental
bonding modes of SO4 are (I) O– (II)
l
(IV) l
3-O, O0, O0 [10–13] (Scheme 1). However, due to the presence
2.1. Materials and physical measurements
of many subtle interactions, the rational design and construction of
specific architecture are still a challenge to chemists. In our
previous work, we find that introducing nitrogen heterocyclic li-
gand into the reaction system is important for generating some
intriguing architectures [14,15], for example Ag(I)-dppm
All reagents were supplied by J&K Chemical Ltd. and were used
as received without further purification. All experiments were per-
formed at ambient temperature. Elemental analyses (C, H, N) were
performed on a Flash EA 1112 analyzer. IR spectra were recorded
from KBr pellets on a Bruker EQUINOX 55 FT-spectrometer. NMR
experiments were carried out on a JNM ECA-600 (JEOL) spectrom-
eter. Emission spectrum was recorded on a Hitachi F-4500 Lumi-
nescence Spectrophotometer.
complexes [Ag2(l-dppm)2(
l-SO4)(2-amp)2]ꢀCH3OH (3) and
* Corresponding author.
E-mail address: jinqh@mail.cnu.edu.cn (Q.-H. Jin).
0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.03.075

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L.-L. Song et al. / Inorganica Chimica Acta 363 (2010) 2425–2429
Table 1
Crystallographic data and structure refinement summary complexes 1–2.
1
2
Formula
Molecular weight
T (K)
C
110H119P8S2O13.5Ag4
C54H55N3P4SO6Ag2
1217.44
93(2)
2400.41
298(2)
Wavelength (Å)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
0.71073
Triclinic
P1
15.2615(14)
15.2652(14)
25.633(2)
91.0540(10)
94.0980(10)
111.8312(10)
5522.8(9)
0.71073
Monoclinic
P21/c
21.6443(3)
21.1753(3)
13.4627(16)
90.00
90.00
90.00
6170.2(13)
4
1.327
ꢀ
a
(°)
b (°)
c
(°)
V (Å3)
Z
2
Dcalc (mg mꢁ3
)
1.443
Crystal size (mm)
Goodness-of-fit F2
Refinement method
0.49 ꢂ 0.48 ꢂ 0.45
0.53 ꢂ 0.47 ꢂ 0.40
1.037
1.003
Full-matrix least-
squares on F2
R1 = 0.0840
wR2 = 0.2081
Full-matrix least-
squares on F2
R1 = 0.0562
wR2 = 0.1636
R1 = 0.0633,
wR2 = 0.1707
1.487 and ꢁ0.676
2ꢁ
Scheme 1. Five bonding modes of the SO4 anion in the Ag(I) complexes.
Final R1 and wR2 indices
R1 and wR2 indices (all data) R1 = 0.1862,
wR2 = 0.2817
2.2. Synthesis of the complex 1
Maximum and minimum
1.428 and ꢁ1.323
peaks (e Åꢁ3
)
Complex 1 was obtained by reaction of Ag2SO4 (0.2 mmol,
0.0623 g), bis(diphenylphosphino)methane(dppm) (0.4 mmol,
0.1532 g), pyrazine (pz) (0.4 mmol, 0.0361 g) in a mixture of 5 ml
dichloromethane, 5 ml methanol and 5 ml ethanol. They were stir-
red for 3 h and filtered. Colorless crystal was obtained from the fil-
trate after standing in the room temperature for several days. Anal.
Calc. for C110H119P8S2O13.5Ag4: C, 55.03; H, 4.96. Found: C, 55.23;
H.5.14%. IR data (cmꢁ1, KBr pellets): 3423m, 3050w, 1637w,
1482w, 1435s, 1400w, 1385w, 1308w, 1123s, 1099s,1025w,
1000w, 780w, 739s, 717w, 692s, 618m, 514w, 480w, 439w.
Table 2
Selected bond lengths (Å) and angles (°) for complexes 1–2.
Complex 1
Ag(1)–P(1)
Ag(1)–O(1)
Ag(2)–P(2)
Ag(2)–O(1)
Ag(3)–P(4)
Ag(3)–O(2)
Ag(4)–P(6)
Ag(4)–O(2)
P(1)–Ag(1)–P(8)
P(4)–Ag(3)–P(5)
2.441(3)
2.331(9)
2.447(3)
2.329(9)
2.465(4)
2.714(10)
2.482(4)
2.526(10)
121.66(12)
119.61(13)
Ag(1)–P(8)
Ag(1)–O(5)
Ag(2)–P(3)
Ag(2)–O(6)
Ag(3)–P(5)
Ag(3)–O(6)
Ag(4)–P(7)
Ag(1)–O(7)
2.448(3)
2.414(9)
2.446(4)
2.437(10)
2.490(4)
2.348(8)
2.485(4)
2.361(8)
2.3. Synthesis of the complex 2
P(3)–Ag(2)–P(2)
P(6)–Ag(4)–P(7)
118.22(12)
116.13(12)
Complex 2 was obtained by reaction of Ag2SO4 (0.2 mmol,
0.0623 g), bis(diphenylphosphino)methane(dppm) (0.4 mmol,
0.1536 g), 2-aminopyrazine (2-ampz) (0.4 mmol, 0.0381 g) in a
mixture of 5 ml dichloromethane and 5 ml methanol. They were
stirred for 3 h and filtered. Colorless crystal was obtained from
the filtrate after standing in the room temperature for several days.
Anal. Calc. for C54H55N3P4SO6Ag2: C, 53.27; H, 4.52; N, 3.45. Found:
C, 53.46; H, 4.69; N, 3.62%. IR data (cmꢁ1, KBr pellets): 3442m,
1632w, 1534m, 1482w, 1435s, 1385w, 1096s, 778w, 741s, 718w,
692s, 618m, 515w, 479w, 423w.
Complex 2
Ag(1)–P(1)
Ag(1)–O(1)
Ag(2)–P(2)
2.4244
2.4287
2.4556
2.386(6)
3.1301
145.82(6)
116.21(13)
107.73(16)
Ag(1)–P(3)
Ag(1)–N(1)
Ag(2)–P(4)
Ag(2)–N(2)
2.4413
2.507(6)
2.4502
Ag(2)–O(2)
2.491(5)
Ag(1)–Ag(2)
P(1)–Ag(1)–P(3)
P(1)–Ag(1)–O(1)
O(2)–Ag(2)–P(4)
P(4)–Ag(2)–P(2)
O(1)–Ag(1)–P(3)
O(2)–Ag(2)–P(2)
141.42(7)
97.66(13)
109.16(18)
calculated sites and included in the final refinement in the riding
model approximation with displacement parameters derived from
the parent atoms to which they were bonded. Further crystallo-
graphic data and experimental details for structural analyses of
both complexes are summarized in Table 1, and selected bond
lengths and angles for complexes 1–2 in Table 2.
2.4. X-ray crystallography
Single-crystal X-ray diffraction studies of complexes 1–2 were
performed on a Bruker SMART diffractometer equipped with CCD
area detector with a graphite monochromator situated in the inci-
dent beam for data collection. The determination of unit cell
parameters and data collections were performed with Mo Ka radi-
ation (k = 0.71073 Å) by x scan mode. All data were corrected by
semi-empirical method using SADABS program. The program SAINT
was used for integration of the diffraction profiles.
3. Results and discussion
3.1. Synthesis of the complexes
All structures were solved by direct methods using SHELXS-97 pro-
gram of the SHELXL-97 [17] package and refined with SHELXL-97 package
[18]. Metal atom centers were located from the E-maps and other
non-hydrogen atoms were located in successive difference Fourier
syntheses. The final refinements were performed by full-matrix
least-squares methods with anisotropic thermal parameters for
non-hydrogen atoms on F2. All the hydrogen atoms were first
found in difference electron density maps, and then placed in the
Recently, we have synthesized four complexes by the reactions
of Ag2SO4 and dppm with nitrogen heterocyclic ligands. The syn-
thetic routes are summarized in Scheme 2. The molar ratio of
Ag2SO4:dppm:nitrogen heterocyclic ligand (1:2:2) and the choice
of the solvent have great influence on the experimental products.
The nitrogen heterocyclic ligands (2-aminopyrimidine, 4,40-bipyri-
dine and 2-aminopyrazine), which have strong coordination ability

L.-L. Song et al. / Inorganica Chimica Acta 363 (2010) 2425–2429
2427
Scheme 2. Four reactions of AgSO4 with dppm and different nitrogen heterocyclic ligands.
with Ag atoms, act as bridging ligands. Furthermore, coordination
2ꢁ
modes of SO4 and dppm are the same in complexes 2–4, where
2ꢁ
SO4 and dppm behave as bridging ligands. Different nitrogen
heterocyclic ligands result in various crystal structures. In complex
2, 2-aminopyrazine coordinate to Ag atoms by its heterocyclic
nitrogen atoms and form hydrogen bonds with the sulfate anions
by its amino groups. In complex 1 the pyrazine does not act as a
ligand, but it facilitates the generation of the unique coordination
2ꢁ
mode of SO4 anion, which may be due to the subtle interaction
of pyrazine with metal silver ions in the system.
3.2. Description of the crystal structures of complexes 1–2
3.2.1. Crystal structure of complex 1
The crystal structural analysis shows that in complex 1 four Ag
atoms form a square, whose edges are bridged by four dppm li-
gands. Two types of coordination geometries are observed for the
four independent Ag atoms. Ag(3) is coordinated by two phospho-
rus atoms from two dppm ligands and one oxygen atom from one
SO42ꢁ to form a distorted trigonal pyramid. While Ag(1), Ag(2), and
Ag(4) are coordinated by two phosphorus atoms from two dppm
ligands and two oxygen atoms from two SO42ꢁ to form a distorted
2ꢁ
tetrahedron (Fig. 1a). Furthermore, two SO4 anions adopt differ-
Fig. 1a. Perspective view of complex 1. Hydrogen atoms are omitted for clarity.
2ꢁ
ent bonding modes. One SO4 anion adopts
l
3-O, O0, O0 bonding
mode (IV) to bridge three Ag atoms, which is only observed in
[Ag4(L)2(SO4)2(H2O)4] (L = 2-amino-4,6-dimethylpyrimidine) [13].
two silver atoms (3.1301 Å) is 0.21 Å shorter than the sum of the
covalent radii (3.44 Å), which indicates that there exists Ag–Ag
2ꢁ
The other SO4 anion adopts a unique
l
4-O, O, O0, O0 bonding
mode (V) to bridge four Ag atoms (Fig. 1b). Since two SO42ꢁ anions
are coordinated to Ag atoms in different modes, the edges of the
distorted square are not equivalent. Compared with similar com-
2ꢁ
bond in complex 2. Due to the presence of the bridging SO4 an-
ion, the two Ag atoms in Ag2(
coordination environments, hence all bond lengths and angles in
Ag2(
-P, P0-dppm)2 unit are different. The crystal packing along c
l
-P, P0-dppm)2 core have different
pound Ag4(l3-S2O3)(l-S2O3)(l-dppm)4 [7], the average bond
length of Ag–P (2.463) is 0.01 Å shorter, and P–Ag–P angle
(118.9°) is 3.4° larger.
l
-axis shows the interactions among one-dimensional chains
(Fig. 2c).
3.2.2. Crystal structure of complex 2
The crystal structural analysis shows that in complex 2 two
four-coordinated Ag atoms are triply bridged by the two dppm li-
3.3. Emission spectra of complexes
gands and one SO42ꢁ anion, forming an eight-member ring Ag2P4C2
The solid-state fluorescence emission spectra of complex 1 and
2 were measured at room temperature, and the fluorescence emis-
sion spectra are displayed in Figs. 3a and 3b. When excited at
350 nm, complex 1 displays a fluorescence emission peak at
2ꢁ
(Fig. 2a), where the SO4 anion adopts the
l
-O, O0 bonding mod-
e(II). The units [Ag2(l-SO4)(l-dppm)2] are connected by 2-amino-
pyrazine to form a 1D linear polymer (Fig. 2b). The distance of the

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L.-L. Song et al. / Inorganica Chimica Acta 363 (2010) 2425–2429
2ꢁ
Fig. 1b. Perspective view of coordination geometries of two SO4 anions.
Fig. 2c. Crystal packing of complex 2 along c-axis.
Fig. 2a. Perspective view of [Ag2(l-SO4)(l-dppm)2] unit. Hydrogen atoms are
omitted for clarity.
380 nm. The emission of complex 1 can be assigned to the metal-
to-ligand charge transfer (MLCT) or ligand-to-metal charge
transfer (LMCT) between the silver(I) atom and the ligand dppm,
Fig. 3a. Emission spectra measured in the solid state at room temperature for
complex 1.
because the free ligand dppm possesses similar emission (kex
=
heterocyclic ligand leads to strong fluorescence character in com-
plex 2. It may be the MLCT or LMCT among the silver(I) atom
and the ligands dppm and 2-ampz.
322 nm, kem = 430 nm), although a sizable blue-shift (50 nm) is ob-
served in 1. Complex 2 displays a strong fluorescence emission
peak at 504 nm (kex = 350 nm). The introduction of nitrogen
Fig. 2b. Perspective view of a 1D linear polymer of complex 2.

L.-L. Song et al. / Inorganica Chimica Acta 363 (2010) 2425–2429
2429
2ꢁ
illustrate that SO4 anion has an important role in the formation
of structure, but also give important information for designing
new luminescent metal complexes.
Acknowledgements
This work has been supported by the National Science Founda-
tion of China (Grant no. 20871085), the Committee of Education of
Beijing Foundation of China (Grant no. KM200610028006), the Pro-
ject-sponsored by SRF for ROCS and SEM, the subsidy of Beijing
Personnel Bureau, National Keystone Basic Research Program
(973 Program) under grant no. 2007CB310408, 2006CB302901,
State Key Laboratory of Functional Materials for Informatics,
Shanghai Institute of Microsystem and Information Technology,
Chinese Academy of Sciences.
Appendix A. Supplementary material
CCDC 759139 and 759140 contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif. Supplementary data associ-
ated with this article can be found, in the online version, at
doi:10.1016/j.ica.2010.03.075.
Fig. 3b. Emission spectra measured in the solid state at room temperature for
complex 2.
The luminescence of some mixed-ligand Cu(I) and Ag(I) has
been reported [20,21]. Recently, we attend to use various auxiliary
ligands to synthesize Cu(I)/Ag(I)-dppm complexes and investigate
their luminescent properties [16,19,22]. It is well known that these
emission spectra are very similar. Such similarities may be attrib-
uted to the existence of conjugate unsaturated ligands. This result
may give important information for designing new luminescent
metal complexes.
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The 1H NMR and 31P NMR spectra of complexes 1 and 2 have
been measured at room temperature in DMSO. The 1H NMR spectra
of complex 1 and 2 show the broad multiplet in the range 7.06–
7.69 ppm and 7.07–7.63 ppm, respectively, which is assigned as
the signals of aromatic protons. There are the singlet at 6.41 ppm
and the doublet at 7.82 and 7.85 ppm in complex 2, which is attrib-
uted to the signals of 2-ampz protons. Compared with the free 2-
ampz ligand (7.72, 7.90, 7.94 ppm), the signals of 2-ampz in 2
are shifted to the lower field.
31P NMR spectra of compound 1 and 2 are well resolved, includ-
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coupling constants of compound 1 and 2 are 1137 and 1199 Hz,
respectively. Compared with the free dppm ligand (ꢁ22.7 ppm),
the corresponding phosphorus resonances in the complex 1 and
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4. Conclusions
In summary, two new silver(I)-dppm complexes were synthe-
sized and characterized. The results of this research not only