Effect of solvent on the architectures of six Ag(I) coordination polymers based on flexible and quasi-flexible organic nitrogen donor ligands

Polyhedron 106 (2016) 178–186

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Effect of solvent on the architectures of six Ag(I) coordination polymers based on flexible and quasi-flexible organic nitrogen donor ligands Yuan Yuan a, Xiao-Nan Xue a, Wei-Wei Fan a, Qi-Ming Qiu a, Yang-Zhe Cui a, Min Liu b, Zhong-Feng Li a, Qiong-Hua Jin a,⇑, Yu-Ping Yang c, Zhen-Wei Zhang d, Wen-Xiao Geng a, Wen-Jie Zheng a a

Department of Chemistry, Capital Normal University, Beijing 100048, China The College of Materials Science and Engineering, Beijing University of Technology, Beijing 100022, China School of Science, Minzu University of China, Beijing 100081, China d 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 b c

a r t i c l e

i n f o

Article history: Received 12 October 2015 Accepted 20 December 2015 Available online 7 January 2016 Keywords: Silver(I) complexes Triphenylphosphine 1,2-Bis(4-pyridyl)ethylene 1,3-Bis(4-pyridyl)propane Terahertz spectra

a b s t r a c t The present work describes the synthesis, full characterization and architectural diversity of six new bioactive silver–organic networks, namely the coordination polymers [Ag(bpa)2(CF3SO3)(H2O)]n (1), {[Ag2(PPh3)2(bpa)2](CF3SO3)}n (2), [Ag(bpe)(CF3SO3)]n (3), [Ag(bpe)(CF3SO3)(CH3CN)]n (4), {[Ag(PPh3) (l-bpe)]1.5(BF4)}n (5) and [Ag(bpp)(CF3SO3)(CH3CN)2]n (6), which are generated via a mixed-ligand strategy using 1,2-bis(4-pyridyl)ethane (bpa), 1,2-bis(4-pyridyl)ethene (bpe) or 1,3-bis(4-pyridyl)propane (bpp) as the main building block and triphenylphosphine (PPh3) as an ancillary ligand source. Complexes 1–6 were well characterized by IR, 1H and 31P NMR spectroscopy, elemental analysis, fluorescence, THz spectroscopy and single-crystal X-ray crystallography. The complexes 1, 2 and 4–6 have a topological network structure. The type and coordination modes of the bipyridine derivatives and the choice of solvent play a key role in defining the dimensionality as well as the structural and topological features of the resulting networks. Analysis of structures revealed that complex 1 possesses a (54, 62) topological network structure connected through the bridging ligand bpa. Complex 2 has a dinuclear structure and displays a topologically promising architecture connected through hydrogen bonds between the CAH groups of aromatic ring and anions. Complexes 3 and 4 possess different 1D infinite chains which are linked by the bridging ligand bpe, and complex 4 can be simplified as having a three-dimensional mesh topology. Complex 5 has a (93, 33) topological network structure connected through the bridging ligand bpe. Like complex 4, complex 6 possesses 1D infinite chains through the bridging ligand bpp, which are linked by hydrogen bonds to form a 3D topological network. Complexes 2 and 4 are generated from CH2Cl2/CH3OH (5:5) and CH3CN respectively, while the other complexes are obtained from CH3CN/H2O (5:5). In addition, complexes 1–6 exhibit interesting fluorescence in the solid state at room temperature. Ó 2015 Elsevier Ltd. All rights reserved.

1. Introduction Molecular arrays of basic structures have inspired chemists for the past decade due to their ability to generate additional interesting physicochemical properties [1–7]. The design and crystal engineering of supramolecular coordination polymers (SCP) continue to be a very active research field because of their potential applications as functional materials in areas such as magnetism, molecular sieves, ion exchange, gas storage, sensors, luminescence, non-linear optics, biological activity, electronics, catalysis and ⇑ Corresponding author. Tel.: +86 10 68903033; fax: +86 10 68902320. E-mail address: [email protected] (Q.-H. Jin). http://dx.doi.org/10.1016/j.poly.2015.12.053 0277-5387/Ó 2015 Elsevier Ltd. All rights reserved.

conductivity [8,9]. Specifically, the silver(I) ion, due to its pliant coordination sphere and inherent lack of a ligand field stabilization effect from a d10 electronic configuration [10], has been extensively used in inorganic crystal engineering by the self-assembly of tailored building-blocks [11]. Such metal–organic coordination polymers have amazing topological structures and potential applications in host–guest chemistry [12,13]. Silver(I) is a good candidate as a soft acid, favoring coordination with soft bases, such as ligands containing halogens, sulfur and nitrogen atoms [14]. As a complementary functional ligand, the bipyridine derivatives could be chosen to build some novel structures. Vittal and his co-workers have extensively studied the reaction of AgX (X = ClO4; CH3CO2; I and NO3) with bipy using PPh3 as an ancillary ligand [15].

Y. Yuan et al. / Polyhedron 106 (2016) 178–186

In our previous work, [Ag(PPh3)4][CF3SO3] [16], [Ag(C12H8N2) (PPh3)](CF3SO3) [17] and [Ag2(l-dppb)2(CF3SO3)2] [18] have been synthesized. To expand the system and to further explore the formation of supramolecular architectures, bipyridine derivatives, such as bpa, bpe and bpp, which store readable information including symmetry, length, binding-sites and especially rigidity [19], are adopted. Following the systematic studies on the reaction of Ag(I) with bipy using PPh3 as an ancillary ligand, we further synthesized complexes 1–6. In this paper, we report the synthesis and characterization of di- and polynuclear silver(I) complexes containing bipyridine derivatives and PPh3, where the versatility of the coordination number of the Ag(I) ion allows for a variety of coordination modes with the bipyridine derivatives. Complex 1 displays a 2D network with a novel (54, 62) topology and complex 5 has a highly symmetrical structure with a novel (93, 33) topology. The luminescence of complexes 1–6 has been researched in this article and complexes 1 and 3–6 show two emission spectral peaks. In addition, in this work complexes 1–6 were characterized by Terahertz time-domain spectroscopy (THz-TDS). 2. Experimental 2.1. Materials and measurements All the chemical reagents, silver trifluoromethanesulfonate (AgCF3SO3), silver tetrafluoroborate (AgBF4), 1,2-bis(4-pyridyl) ethane (bpa), 1,2-bis(4-pyridyl)ethene (bpe), 1,3-bis(4-pyridyl) propane (bpp) and triphenylphosphine (PPh3), are commercially available and were used without further purification. Elemental analyses (C, H, N) were determined on a Elementar Vario MICRO CUBE (Germany) elemental analyzer. Infrared spectra were recorded on a Brucker EQUINOX 55 FT-IR spectrometer using KBr pellets in the range 400–4000 cm 1. Excitation and emission spectra of the solid samples were recorded on an F-4500 fluorescence spectrophotometer at room temperature. 1H and 31P NMR spectra were recorded at room temperature with Varian VNMRS 600 MHz and 243 MHz spectrometers, respectively. The THz absorption spectra were recorded on a THz time domain device of Capital Normal University of China, based on photoconductive switches for generation and electro-optical crystal detection of the far-infrared light, effective frequency in the range 0.2–4.0 THz [20,21]. 2.2. Preparation of the complexes 2.2.1. Synthesis of [Ag(dpa)2]n
nCF3SO3
nH2O (1) Bpa (0.2 mmol, 0.0368 g) and PPh3 (0.2 mmol, 0.0525 g) were added into a stirring solution of AgCF3SO3 (0.2 mmol, 0.0514 g) in a mixture of CH3CN (5 ml) and H2O (5 ml). Five hours later, a colorless liquid was filtered. Subsequent slow evaporation of the filtrate resulted in the formation of colorless and transparent crystals of the title complex. Yield: 42%. Anal. Calc. for C25H26AgF3N4O4S, elemental analysis: C, 46.67; H, 4.07; N, 8.71. Measured: C, 47.01; H, 4.19; N, 8.40%. IR (cm 1, KBr pellets): 3647m, 3369s, 3050s, 2319w, 1953w, 1816w, 1667m, 1594vs, 1558vs, 1479s, 1434vs, 1416s, 1380vs, 1229m, 1183s, 1159m, 1097s, 1058m, 1028m, 998m, 943w, 871w, 834s, 782vs, 752vs, 695vs, 562m, 521s, 506s, 493s, 478s. 1H NMR (600 MHz, CDCl3, 298 K), d (ppm): 2.0 (t, 8H, dpaCH2), 7.2–7.4 (m, overlap with the solvent peak signal, dpa-aromatic ring), 8.6 (d, 8H, dpa-aromatic ring). 2.2.2. Synthesis of {[Ag2(PPh3)2(bpa)2](CF3SO3)}n (2) Following a similar procedure as for 1, bpa (0.2 mmol, 0.0368 g) and PPh3 (0.2 mmol, 0.0525 g) were added into CH3OH (5 ml) and CH2Cl2 (5 ml) containing AgCF3SO3 (0.2 mmol, 0.0514 g). After slow evaporation of the filtrate at ambient temperature for three

179

days, colorless and transparent shaped crystals of the complex were obtained. Yield: 67%. Anal. Calc. for C62H54Ag2F6N4O6P2S2, elemental analysis: C, 52.93; H, 3.87; N, 3.98. Measured: C, 53.48; H, 3.95; N, 3.95%. IR (cm 1, KBr pellets): 3422s, 3053w, 1660w, 1607s, 1561w, 1478s, 1434vs, 1307w, 1275vs, 1224m, 1140s, 1089s, 1069s, 1033s, 998s, 837m, 743vs, 695vs, 635s, 570m, 511s, 499vs, 435m. 1H NMR (600 MHz, CDCl3, 298 K), d (ppm): 2.9 (m, 8H, bpa-CH2), 7.2–7.3 (m, overlap with the solvent peak signal, dpa-aromatic ring and PPh3-aromatic ring), 7.4 (t, J = 7.2 Hz, 18H, PPh3-aromatic ring), 8.4–8.5 (m, 8H, dpa-aromatic ring). 31P NMR (243 MHz, CDCl3), d (ppm): 11.3 (br, JAgAP = 243 Hz). 2.2.3. Synthesis of [Ag(dpe)]n
nCF3SO3 (3) Following a similar procedure as for 1, bpe (0.2 mmol, 0.0364 g) and PPh3 (0.2 mmol, 0.0525 g) were added into a mixture of CH3CN (5 ml) and H2O (5 ml) containing AgCF3SO3 (0.2 mmol, 0.0514 g). NH3
H2O was added to make the solution clear. Five hours later, the colorless liquid was filtered. After slow evaporation of the filtrate at ambient temperature for eleven days, colorless and rectangle shaped crystals of the complex were obtained. Yield: 36%. Anal. Calc. for C13H10AgF3N2O3S, elemental analysis: C, 35.55; H, 2.30; N, 6.38. Measured: C, 35.41; H, 2.15; N, 6.22%. IR (cm 1, KBr pellets): 3446m, 3040m, 1930w, 1602vs, 1557m, 1499w, 1424s, 1265vs, 1170s, 1091w, 1073w, 1035vs, 1010m, 973m, 838m, 827s, 767w, 695w, 653vs, 578m, 549s, 519m. 1H NMR (600 MHz, CDCl3, 298 K), d (ppm): 7.2–7.5 (m, overlap with the solvent peak signal, dpe-aromatic ring and ACH@CHA), 8.6 (d, dpe-aromatic ring). 2.2.4. Synthesis of [Ag(dpe)(CH3CN)]n
nCF3SO3 (4) Following a similar procedure as for 3, bpe (0.2 mmol, 0.0364 g) and PPh3 (0.2 mmol, 0.0525 g) were added into CH3CN (5 ml) and H2O (5 ml) containing AgCF3SO3 (0.2 mmol, 0.0514 g). NH3
H2O was also added to make the solution clear. After slow evaporation of the filtrate at ambient temperature for four days, colorless and needle shaped crystals of the complex were obtained. Yield: 32%. Anal. Calc. for C15H13AgF3N3O3S, elemental analysis: C, 37.52; H, 2.73; N, 8.75. Measured: C, 37.29; H, 2.59; N, 8.52%. IR (cm 1, KBr pellets): 3434m, 2378w, 1608s, 1504w, 1433m, 1266vs, 1224m, 1156s, 1029s, 980w, 835m, 636s, 573w, 553m, 517w. 1H NMR (600 MHz, CDCl3, 298 K), d (ppm): 7.2–7.5 (m, overlap with the solvent peak signal, dpe-aromatic ring and ACH@CHA), 8.6 (d, dpe-aromatic ring). 2.2.5. Synthesis of {[Ag(PPh3)(l-dpe)]1.5(BF4)}n (5) The reaction of AgBF4 (0.2 mmol, 0.0514 g) with dpe (0.2 mmol, 0.0384 g) and PPh3 (0.2 mmol, 0.0525 g) in a mixture of CH3CN (5 ml) and H2O (5 ml) generated the title complex. The solution showed white turbidity. After ammonia water was added, it turned clear. Six hours later, the colorless liquid was filtered. Subsequent slow evaporation of the filtrate resulted in the formation of colorless and transparent crystals of the title complex. Yield: 41%. Anal. Calc. for C36H30AgBF4N3P, elemental analysis: C, 59.21; H, 4.14; N, 5.75. Measured: C, 58.35; H, 4.26; N, 5.65%. IR (cm 1, KBr pellets): 3448s, 3053w, 1660w, 1607s, 1561w, 1474s, 1421vs, 1307w, 1262vs, 1224m, 1140s, 1070s, 1035s, 1005s, 998s, 837m, 758vs, 695vs, 643s, 570m, 515s, 499vs, 435m. 2.2.6. Synthesis of [Ag(bpp)(CH3CN)]n
nCH3CN
nCF3SO3 (6) Following a similar procedure as for 1, bpp (0.2 mmol, 0.0396 g) and PPh3 (0.2 mmol, 0.0525 g) were added into a mixture of CH3CN (5 ml) and H2O (5 ml) containing AgCF3SO3 (0.2 mmol, 0.0514 g). NH3
H2O was added to make the solution clear. Five hours later, the colorless liquid was filtered. After slow evaporation of the filtrate at ambient temperature for four days, colorless and block shaped crystals of the complex were obtained. Yield: 56%. Anal. Calc. for C18H20AgF3N4O3S, elemental analysis: C, 40.24; H, 3.75;

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N, 10.43. Measured: C, 39.99; H, 3.71; N, 10.29%. IR (cm 1, KBr pellets): 3525w, 3077w, 2937w, 2869w, 1617s, 1561w, 1507w, 1469w, 1435s, 1252vs, 1161s, 1070m, 1051s, 1028s, 841m, 815w, 756w, 660m, 637s, 573w, 517s. 1H NMR (600 MHz, CDCl3, 298 K), d (ppm): 2.0 (m, 2H, bpp-CH2CH2CH2), 2.7 (t, 4H, bppCH2CH2CH2), 7.2–7.5 (m, overlap with the solvent peak signal, bpp-aromatic ring), 8.5 (d, 4H, bpp-aromatic ring). 2.3. Crystal structure determination and refinement Single-crystal X-ray diffraction studies of complexes 1–6 were performed on a Bruker SMART diffractometer equipped with a CCD area detector with a graphite monochromator situated in the incident beam for data collection. The determination of unit cell parameters and data collections were performed with Mo Ka radiation (k = 0.71073 Å). All data were corrected by the semiempirical method using the SADABS profiles. The program SAINT [22] was used for integration of the diffraction profiles. All the structures were solved by direct methods using the SHELXS program of the SHELXTL-97 package and refined with SHELXL [23]. 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 H atoms were located in the 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 (Uiso(H) = 1.2 Ueq). C—H hydrogen atoms (aromatic) were included with the distance set to 0.93 Å. Crystallographic data and experimental details for the structural analyses are summarized in Table 1, and selected bond lengths and angles of complexes 1–6 are summarized in Table 2. 3. Results and discussion 3.1. Synthesis and characterization of complexes 1–6 Six Ag(I) complexes, {[Ag2(PPh3)2(bpa)2](CF3SO3)}n

[Ag(bpa)2(CF3SO3)(H2O)]n (2), [Ag(bpe)(CF3SO3)]n

Scheme 1. The synthesis of complexes 1–6.

(1), (3),

[Ag(bpe)(CF3SO3)(CH3CN)]n (4), {[Ag(PPh3)(l-bpe)]1.5(BF4)}n (5) and [Ag(bpp)(CF3SO3)(CH3CN)2]n (6), in the form of colorless crystalline solids, were obtained at room temperature (Scheme 1). Complexes 1–6 were obtained by the one-pot reaction of AgCF3SO3/AgBF4 with L (L = bpa, bpe, bpp) and PPh3 in CH3CN/H2O, CH2Cl2/CH3OH or CH3CN with a molar ratio 1:1:1 for Ag:L:PPh3. All the complexes are air-stable, however they are oxidized quickly at high temperature. They are soluble in common polar solvents, such as methanol, ethanol, dichloromethane, acetonitrile and dimethylsulfoxide. The different architectures of these Ag(I) coordination polymers may be explained by the effect of the solvent, N-ligand and counter anion. Complexes 1 and 2 are obtained from the same reactants in different solvents. The different polarity and coordination ability of the solvent lead to the different coordination configurations of 1 and 2. Complexes 4 and 6 are obtained under similar conditions, only with different nitrogen ligands; the good flexibility of bpp helps to form the curved 1D chain of 6. Complexes 3 and 5 are synthesized from the same reactants, except for different silver salts (AgCF3SO3 for 3, AgBF4 for 5). The different coordination ability of CF3SO3 and the tetrafluoroborate anion leads to different structures. In complex 3, the strong ability makes CF3SO3 coordinate to the Ag atom instead of PPh3; while in complex 5, the tetrafluoroborate anion cannot replace PPh3 to coordinate to the Ag atom.

3.2. Single crystal X-ray studies 3.2.1. Crystal structure of the complexes [Ag(bpa)2(CF3SO3)(H2O)]n (1) and {[Ag2(PPh3)2(bpa)2](CF3SO3)}n (2) The coordination geometry of the Ag atom of 1 is best described as a distorted tetrahedron with each Ag atom coordinated to four bpa ligands (Fig. 1). In complex 1, the water molecules fill in the cell as coordinated ligands, and the trifluoromethanesulfonate anion is uncoordinated and disordered (occupancy in a 0.5:0.5 ratio). For complex 1, the AgAN bond lengths are almost the same. The NAAgAN angle is in the range [103.9(2)–115.4(1)°], which is smaller than that of the complex [Ag3(bpe)3(btc)
12H2O]n [(N2AAg2AN2i = 180.0(4)° and N6AAg4AN6ii = 180.0(3)°)] [24]. The torsion angle between the two pyridine rings is 9.2(1)°. In complex 1, the distance between two central metals is 13.910 (2) Å, which is bigger than that of the complex {[Ag(dpa)] (CF3SO3)}n [25]. From the packing diagram of complex 1, we can see that there exist holes filled with H2O and the trifluoromethanesulfonate anion (Fig. 1a). Complex 1 displays a 2D network with a novel (54, 62) topology (Fig. 1b), which was first found in similar Mbpa complexes [26–29], while the similar complex {[Ag(dpa)] (CF3SO3)}n [25] is of a one-dimensional infinite chain structure. An HAO


H hydrogen bond is formed by the OAH group of H2O molecules with the H atom of a CAH group of the aromatic ring, and a F


HAC hydrogen bond is formed by the fluorine atom from the trifluoromethanesulfonate anion with the CAH group of the aromatic ring, which stabilize the basic skeleton of complex 1. The complex 2 has a distorted tetrahedral configuration with each Ag atom coordinated by two N atoms from two bpa ligands, one P atom from one PPh3 ligand and one O atom from a trifluoromethanesulfonate anion (Fig. 2). Complex 2 consists of dinuclear cells, which are linked by hydrogen bonds between the aromatic rings and O atoms from trifluoromethanesulfonate anion to generate the 2D network (Fig. 2a). The average AgAN and AgAP bond lengths are 2.318 (6) and 2.371(9) Å, respectively, which are shorter than those of the complex [Ag2(PPh3)4(AMP)2(SO4)] (AgAN: 2.491(6) Å, AgAP: 2.465(2) Å) [30]. The P(1)AAg(1)AN(1) and P(1)AAg(1)AN(2) angles are 131.3(7)° and 128.9(7)°, respectively, which are bigger than those of [Ag2(PPh3)4(AMP)2(SO4)] (P(1)AAg(1)AN(1): 102.2(2)°, P (2)AAg(1)AN(1): 104.7(2)°) [30]. The N(1)AAg(1)AN(2) angle is

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Y. Yuan et al. / Polyhedron 106 (2016) 178–186 Table 1 Crystallographic data for complexes 1–6.

a b

Complex

1

2

3

4

5

6

Formula Formula weight T (K) Crystal system Space group a (Å) b (Å) c (Å) a (°) b (°) c (°) V (Å3) Z Dcalc (Mg/m3) Theta range (°) F(0 0 0) Data/restraint/parameters Reflections collected/unique Goodness-of-fit (GOF) on F2 Rint R1a[I > 2r(I)] wR2b[I > 2r(I)] R1(all data) wR2(all data) Residuals (e Å 3)

C25H26AgF3N4O4S 643.43 298(2) orthorhombic Fddd 30.5765(15) 28.363(2) 12.2756(7) 90.00 90.00 90.00 10645.9(11) 16 1.606 25.02 5216 2360/0/209 6129 1.098 0.0182 0.0473 0.1257 0.0575 0.1396 0.794, 0.706

C62H54Ag2F6N4O6P2S2 1406.890 298(2) triclinic  P1

C13H10AgF3N2O3S 439.16 298(2) triclinic  P1

9.1201(7) 9.7030(8) 17.5709(14) 84.892(1) 77.047(1) 89.522(2) 1509.2(2) 1 1.548 25.02 712 5221/0/534 7658 1.062 0.0253 0.0721 0.1830 0.1073 0.2151 1.214, 0.932

6.7190(5) 11.0729(11) 11.1121(12) 76.000(2) 72.7740(10) 76.2890(10) 753.89(12) 2 1.935 25.02 432 2617/0/208 3799 1.056 0.0220 0.0446 0.1105 0.0538 0.1158 0.841, 0.615

C15H13AgF3N3O3S 480.22 298(2) orthorhombic Pnma 13.7074(5) 6.7722(3) 19.0313(13) 90.00 90.00 90.00 1766.66(16) 4 1.805 25.02 952 1663/0/259 3615 1.075 0.0201 0.0743 0.1997 0.0880 0.2140 1.671, 0.649

C36H30AgBF4N3P 730.28 298(2) cubic I-43d 23.580(2) 23.580(2) 23.580(2) 90.00 90.00 90.00 13111(2) 16 1.480 25.03 5920 1938/0/169 30 414 1.083 0.0738 0.0453 0.1015 0.0696 0.1099 0.549, 0.306

C18H20AgF3N4O3S 537.31 298(2) monoclinic P21/n 10.9122(10) 9.2098(6) 22.2653(14) 90.00 91.104(9) 90.00 2237.2(3) 4 1.595 25.01 1080 3929/0/337 7990 1.036 0.0184 0.0466 0.1091 0.0754 0.1276 0.490, 0.408

P P R = (||Fo| |Fc||)/ |Fo|. P P wR = [ w(|Fo|2 |Fc|2)2/ w(F20)]1/2.

Table 2 Selected bond lengths (Å) and angles (°) for complexes 1–6. Bond length (Å) Complex 1 Ag(1)AN(1) Ag(1)AN(2)

Bond angle (°) 2.3433(3) 2.3490(3)

N(1)AAg(1)AN(2) N(2)AAg(1)AN(1)

115.393(1) 107.428(1)

2.3040(6) 2.3322(6) 2.3712(9)

N(1)AAg(1)AN(2) P(1)AAg(1)AN(1) P(1)AAg(1)AN(2)

89.863(3) 131.276(7) 128.980(7)

2.1410(9) 2.1420(9) 2.7730(5)

N(1)AAg(1)AO(2) N(1)AAg(1)AN(2) N(2)AAg(1)AO(2)

90.791(5) 176.957(6) 91.396(5)

Complex 4 Ag(1)AN(1) Ag(1)AN(2) Ag(1)AN(3)

2.1537(9) 2.1625(9) 2.7654(9)

N(1)AAg(1)AN(2) N(1)AAg(1)AN(3) N(2)AAg(1)AN(3)

176.585(6) 91.572(6) 91.843(6)

Complex 5 Ag(1)AN(1) Ag(1)AN(1) Ag(1)AP(1)

2.3965(7) 2.3965(5) 2.3936(3)

N(1)AAg(1)AN(1) N(1)AAg(1)AP(1)

90.517(5) 124.898(9)

Complex 6 Ag(1)AN(1) Ag(1)AN(2) Ag(1)AN(3)

2.1496(8) 2.1494(7) 2.7759(6)

N(1)AAg(1)AN(2) N(1)AAg(1)AN(3) N(2)AAg(1)AN(3)

174.364(4) 92.752(6) 92.859(6)

Complex 2 Ag(1)AN(1) Ag(1)AN(2) Ag(1)AP(1) Complex 3 Ag(1)AN(1) Ag(1)AN(2) Ag(1)AO(2)

89.9(3)°, which is similar to the OAAgAN angle of [Ag2(PPh3)4(AMP)2(SO4)] (86.9(2)°) [30]. 3.2.2. Crystal structures of the complexes [Ag(bpe)]n
nCF3SO3 (3) and [Ag(bpe)(CH3CN)]n
nCF3SO3 (4) As for complex 3, the Ag(1) atom is coordinated by two nitrogen atoms of two bpe molecules and one O atom of a trifluoromethanesulfonate anion, forming a three-coordinated T-shaped configuration (Fig. S1). Complex 3 is of a similar structure as the complex {[Ag(bpe)](OTf)}n [25], and single-crystal X-ray diffraction analysis reveals that 3 crystallizes in the triclinic system with the space  Silver atoms and bpe ligands connect alternately to form group P1.

Fig. 1. The molecular entities of complex 1. Thermal ellipsoids are drawn at the 30% probability level.

an infinite 1D chain with trifluoromethanesulfonate anions serving as the counter ion (Fig. 3). The AgAN distance in 3 (2.141(4) Å) is much shorter than those of the complexes {[Ag(bpe)](OTf)}n (2.149(5)–2.168(5) Å) [25] and {Ag[C(CN)3](bpe)} (2.158(3) Å) [31]. The AgANAAg angle (176.9(2)°) in 3 is longer than those of the complex in Ref. [25] (170.0(2)° and 161.8(2)°). The results show that the formation of 3 is close to a linear structure. The Ag


Ag distance is 3.801(1) Å, which is longer than the sum of the van der Waals radii of two silver atoms (3.44 Å), indicating that the silver atoms in adjacent layers are not involved in a metal– metal bonding interaction. The center atom of complex 4 is coordinated by two nitrogen atoms of two bpe molecules with an AgAN distance of 2.158(9) Å and one N atom of CH3CN with an AgAN distance of 2.765(9) Å, forming a three-coordinated T-shaped configuration (Fig. S2). The silver atoms and the bpe ligands connect alternately to form an infinite 1D chain with the trifluoromethanesulfonate anions acting

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Fig. 1a. The packing diagram of complex 1 along the c axis. The anion and solvent molecules are simplified as balls.

Fig. 2a. The 2-D structure with bridging by hydrogen bonds of 2.

Fig. 3. The 1-D infinite chains with bridging by bpe ligands of complex 3. 4

2

Fig. 1b. The 2-D structure with (5 , 6 ) topology with bridging by hydrogen bonds of complex 1.

as the counter ion (Fig. 4). The AgAN bond length (2.158(9) Å) is shorter than that of the complex Ag(tcm)(bpe) [32] (tcm = cyanoform) (2.201(3) Å) and is longer than that of the complex {[Ag (tbpe)](4-hb)0.5
3H2O} [33] (4-hb = 4-hydroxybenzoic acid) (2.151 (2) Å). The Ag1AN3 distance of 2.765(9) Å, which is shorter than that of the complex [Ag(l-bpe)(H2O)](CF3CO2)
CH3CN [34] (3.316 (3) Å), just agrees with the sum of the van der Waals radii. The

NAAgAN angle (176.6(3)°) of complex 4 is similar to that of complex 3 (176.9(2)°). However, the Ag


Ag distance is 4.956(1) Å, which is longer than that of complex 3. In complex 3, the torsion angle between the two pyridine rings is 8.1(2)°, while the two pyridine rings in complex 4 are parallel. In complex 4, the silver atoms are linked through bpe to form an 1D infinite chain (Fig. 4), which are further bridged through hydrogen bonds between the aromatic rings and trifluoromethanesulfonate anions to form a 3D supramolecular framework (Figs. 4a, S3 and S4).

Fig. 2. The molecular entities of complex 2. Thermal ellipsoids are drawn at the 30% probability level.

Y. Yuan et al. / Polyhedron 106 (2016) 178–186

183

Fig. 4. The 1-D infinite chains with bridging by bpe ligands of complex 4.

3.2.3. Crystal structure of the complex {[Ag(PPh3)(l-bpe)]1.5(BF4)}n (5) Complex 5 is cubic, in the I-43d space group. The silver atom is coordinated by three nitrogen atoms of the dpe ligands and the phosphorus atom of the PPh3 ligand (Fig. 5). The AgAN(1), AgAN (1)#1 and AgAN(1)#2 bond distances in complex 5 are equal [2.394(5) Å], and are shorter than those in the complexes of {[Ag2(bpe)2(H2O)2]
(4-sb)
3H2O}n (4-sb = 4-sulfobenzoate) [35] and [Ag(bpe)(ClO4)]n [36]. In 5, the AgAP bond and AgAN bond are of the same length (2.394(3) Å), which agrees with those in {Ag2(O2CCF3)2{Ph2P(CH2)nPPh2}(bpe) [37]. The N(1)AAg(1)AN(1) #2(90.6(2)) and N(1)#1AAg(1)AP(1) (124.9(2)°) angles show that the coordination geometry of the Ag(I) ion is distorted tetrahedral. Compared with previously reported Ag–bpe complexes [38], complex 5 has higher symmetry. So far, no other Ag–bpe complexes crystallized in the cubic crystal system have been reported, according to data retrieved from the CSD [39]. Unlike the networks of the complexes {[Ag(bpe)0.5(4-hb)
3H2O]} (4-hb = 4-hydroxybenzoic acid) [40] and {[Ag2(bpe)2(H2O)2]
(4-sb)
3H2O}n (4-sb = 4-sulfobenzoate) [35], the silver atoms are linked by bpe to form a 1D infinite chain and the 1D infinite chains are further linked into a 3D structure through hydrogen bonds and p


p stacking in complex 5. The crystal structure of complex 5 consists of 2D layers with a novel (93, 33) topology and shows 2-fold parallel interpenetration (via the coordination bonds) (Figs. S5 and 5a). 3.2.4. Crystal structure of the complex [Ag(bpp) (CH3CN)]n
nCH3CN
nCF3SO3 (6) Compared with bpa and bpe, the bipyridine derivative ligand bpp with free rotation of the pyridyl rings, is more flexible. The molecular structure of 6 is shown in Fig. S6. Single-crystal X-ray diffraction analysis reveals that complex 6 is a 1D sinusoidal chain,

Fig. 5. The molecular entities of complex 5. Thermal ellipsoids are drawn at the 30% probability level.

Fig. 5a. The 2D layers with (93, 33) topology, showing 2-fold parallel interpenetration, of complex 5.

which is comprised of [Ag(CH3CN)] units bridged by bpp ligands (Fig. 6). The silver atoms are linearly coordinated by two N atoms from two different bpp ligands with an N1AAgAN2 angle of 174.4 (2)°. The N atom from the CH3CN molecule is coordinated with the Ag(I) ion, forming the [Ag(CH3CN)] unit with an Ag1AN3 distance of 2.776(6) Å. The N2AAg1AN3 angle is 92.8(2)°, indicating that the acetonitrile molecules and cationic chain [–Ag1–bpp–Ag1– bpp–Ag1] are vertical. The center metal atoms of complex 6 are

Fig. 4a. The 3-D structure with bridging by hydrogen bonds of 4 along the b axis.

Fig. 6. The 1-D infinite chains with bridging by bpe ligands of complex 6.

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be disordered with an occupancy ratio of 0.711(9):0.289(9). Complex 6 shows a 1D sinusoidal chain, and the CH3CN molecule participates in the coordination environment. Two adjacent Ag atoms are additionally pillared by the bpp ligands, giving rise to a double 1D chain composed of repeating –Ag1–bpp–Ag1–bpp–Ag1–suc– rings. Such double chains are further extended into an intricate 3D supramolecular network via intermolecular H-bonding interactions (OAH


N) between the trifluoromethanesulfonate anions (O) and aromatic rings (H


N) from the bpp ligands (Figs. 6a, b and S7). The structure of complex 6 is different from the complex [Ag (bpp)](CF3SO3) [41], which displays double helices of cationic chains that are bridged by Ag


Ag interactions. The presence of anions in polymers 6 gives rise to the extension of the metal–organic structure into a 3D H-bonded network, which discloses a rather rare topology. 4. Spectroscopy properties analysis 4.1. Luminescent properties

Fig. 6a and b. The 3-D structure with bridging by hydrogen bonds of 6 along the a and b axes.

At ambient temperature, the luminescent excitation and emission spectra of complexes 1–6 were measured in the solid state (Fig. 7). The bipyridine derivatives bpa, bpe and bpp exhibit luminescent signals centered at 350 and 364 nm with kex = 329 nm for bpa, at 375 and 393 nm with kex = 320 nm for bpe and at 448 and 469 nm with kex = 350 nm for bpp. PPh3 exhibit an emission peak at 450 nm with excitation at 435 nm. In the emission spectra of complexes 1–6, the emission peaks are found at 487 and 518 nm with kex = 329 nm for 1, at 412 nm with kex = 344 nm for 2, at 390 and 466 nm with kex = 363 nm for 3, at 399 and 467 nm with kex = 363 nm for 4, at 388 and 400 nm with kex = 245 nm for 5 and at 485 and 516 nm with kex = 329 nm for 6. It is notable that all the complexes except 2 have two emission spectral peaks. Compared with the free bipyridine derivatives, the emission maxima of complexes 1–6 are slightly red-shifted, which may be attributed to metal-to-ligand charge transfer (MLCT). The emission peak at 518 nm of complex 1 and the peak at 516 nm of complex 6 may be attributed to MLCT/LMCT [42–44], which is caused by AgAN containing chromophores or a center metal Ag(I) transition from 4d10–4d95s1 and 4d10–4d95p1 [33,43,45–47]. Compared with the emission maxima of the complex [Ag(dpa)(BF4)]n [43], the emission maxima of complexes 1 and 6 are obviously red-shifted, which may be attributed to the metal-to-ligand charge transfer (MLCT). The high emission of the d10–Ag(I) complexes may be attributed to the coordination of the ligand to the silver(I) ion, which enhances the rigidity of the ligand and thus reduces the loss of energy through a non-radioactive relaxation process [48–50]. The emission peak at 412 nm of complex 2 and the peak at 400 nm of complex 5 are assigned to PPh3 ligand-based emissions, which are derived from a ligand-centered [p–p⁄] transition. The emission peak at 466 nm of complex 3 and the peak at 467 nm of complex 4 are assigned to bpe ligand-based emissions, which are derived from a ligand-centered [p–p⁄] transition. 4.2. 1H and

Fig. 7. The luminescent emission spectra of 1–6 in the solid state at room temperature.

bridged by the bpp ligands, to form one-dimensional sinusoidal chains (Fig. 6). Both the AgAN bond distances and NAAgAN angle are found to be in good agreement with those in [Ag(bpp)](CF3SO3) [41]. The Ag


Ag distance is 4.697(1) Å, which indicates that the silver atoms in 6 are not involved in a metal–metal bonding interaction. The free trifluoromethanesulfonate anion is found to

31

P NMR spectra

At room temperature, the 1H NMR spectra of complexes 1–6 and the 31P NMR spectrum of complex 2 have been measured in CDCl3 solution. The 1H NMR spectra of complexes 1–6 exhibit signals for the protons of the CAH groups adjacent to the N atom from the bipyridine derivatives at 8.5 ppm (doublet peaks). The multiple signals in the range 7.2–7.5 ppm are assigned to protons from the benzene rings of PPh3 and the other protons from the bipyridine ring of the bipyridine derivatives. In complexes 1, 3, 4 and 6 the signals of the protons from the bipyridine ring of bpa are at 8.5

Y. Yuan et al. / Polyhedron 106 (2016) 178–186

(doublet peaks) and 7.2–7.5 ppm (multiplet peak), which indicates that the environment of bpa is similar in each complex. The multiplet signals in the range 1.9–2.1 ppm for complex 1 and the triplet signals at 2.9 ppm in complex 2 are assigned to the protons of the two methylene groups of bpa. In complex 2, triplet signals at 7.4 ppm are assigned to the protons of the benzene rings of PPh3 and the multiplet signals at 8.4–8.5 ppm are ascribed to the protons of the bipyridine ring connected to the N atoms in bpa. Complexes 3 and 4 have similar signals, indicating a similar chemical environment of the bpa ligands in both complexes. In complex 6, the multiplet signals centered at 2.0 ppm are assigned to the protons of the middle methylene groups of bpp and the triplet signals at 2.7 ppm are ascribed to the protons of the two other methylene groups of bpp. In the 31P NMR spectrum of complex 2, all the phosphorus atoms in each molecule are chemically equivalent because only a single resonance signal (11.3 ppm, JAgAP = 243 Hz) is found, with 108Ag–31P coupling.

4.3. Study of THz spectroscopy properties The room temperature terahertz (THz) absorption spectra of the metal salts (AgBF4, AgCF3SO3), bipyridine derivatives (bpa, bpe, bpp), triphenylphosphine (PPh3) and complexes 1–6 were measured in the range 0.2–4.0 THz. All the above compounds, except PPh3, have characteristic resonance peaks, which may be explained by the fact that in polar molecules the dipoles rotate and vibrate, resulting in strong absorption and chromatic dispersion. The peaks found for each compound are as follows (in THz): bpa 1.15, 1.27; bpe 0.92, 1.00; bpp 0.92, 1.00; AgBF4 0.38, 0.46, 0.51; AgCF3SO3 0.69, 0.84, 1.00, 1.16, 1.30; complex 1 0.45, 0.54, 0.64, 0.77, 1.01, 1.17, 1.30; complex 2 0.95, 1.57, 2.17, 2.33, 2.59, 2.82; complex 3 0.40, 0.49, 0.62, 0.74; complex 4 0.46, 0.70, 0.93; complex 5 0.40, 0.60, 0.78, 1.13; complex 6 0.39, 0.49, 0.65, 0.77, 0.93 (Fig. 8). By comparing the THz absorption spectra of the products with those of the reactants, we can see that most peaks of the ligands and

Fig. 8. The terahertz spectra of 1–6 in the range 0.2–4.0 THz.

185

AgX disappeared or moved in the complexes. New peaks in the range 0.39–0.65 THz appear in the obtained complexes, indicating that the THz absorption spectra are associated with the coordination of silver(I) ions and the ligands. Although the correspondence between the crystal structures and observed spectra does not allow a definitive characterization, it is possible to make tentative assignments of many of the observed features in the terahertz region for the samples [51]. The absorption spectra of complexes 3 and 6 exhibit more new absorption peaks than that of complex 4, owing to the higher symmetry of the crystal structure of complex 4 (space  for 3, P2(1)/n for 6, Pnma for 4). group P1 In previous work, we have studied the THz absorption spectra of complexes which are obtained by the reactions of dppm and pyridine derivative with Ag salts [52]. In the THz spectra of these complexes in Ref. [52], two or three absorption peaks exist in the range of above 0.83 THz in each case, while in 1–6 the absorption peaks appear in the range 0.39–2.82 THz. This is mainly because of the differences in constitution and symmetry. The results in this paper are a supplement to the THz spectroscopic properties of Ag complexes containing nitrogen and phosphorous ligands. 4.4. Thermogravimetric analysis In order to investigate the thermal stability of these compounds, TGA analyses were carried out for complexes 1–6. Experiments for these samples were carried out from room temperature to 800 °C. It was found that the TGA curve of complex 5 showed a one-step weight loss profile, while the TGA curves of 1– 4 and 6 showed two-step weight loss processes (Fig. 9). Complexes 2, 3 and 5 possess good thermal stability up to 250 °C due to the absence of PPh3 and bipyridine derivatives in the compounds. In the temperature range 250–650 °C, complexes 1–3 and 6 rapidly decomposed to silver oxides, while complexes 4 and 5 rapidly decomposed to elemental silver. In complexes 4 and 6, the initial weight loss of 4.7% (calcd 4.5%) for 4 and 7.9% (calcd 7.6%) for 6 in the temperature range 100– 250 °C is assigned to the removal of one acetonitrile molecule per formula unit. When the temperature was increased to 300 °C, these compounds began to rapidly decompose [53]. In complexes 1–6, the final weight loss of 81.9% (calcd 81.5%) for 1, 83.1% (calcd 83.9%) for 2, 73.6% (calcd 73.4%) for 3, 78.9% (calcd 79.2%) for 4, 85.2% (calcd 85.6%) for 5, 78.4% (calcd 78.2%) for 6 in the temperature range 250–800 °C is assigned to the removal of the ligands per formula unit.

Fig. 9. Thermogravimetric analysis (TGA) curves for the heating of complexes 1–6 to 800 °C in dry air.

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5. Conclusion Six new Ag(I) complexes containing bipyridine derivatives and PPh3 have been synthesized and characterized by IR, elemental analysis, luminescence, NMR and THz time domain spectroscopy. The crystal structures of complexes 1, 2, 4–6 are of different topological networks. The different architectures of these Ag(I) coordination polymers may be explained by the affect of solvent, N-ligand and counter anion. Complexes 1–6 exhibit interesting emissions in the solid state. Compared with the free bipyridine derivatives, the emission maxima of complexes 1–6 are slightly red-shifted. The emission spectral peaks of complexes 1 and 6 may be attributed to MLCT/LMCT transitions. Our results indicate that the ligands, anions, metal–ligand coordination and hydrogen bonds can affect the THz spectra of Ag(I) complexes. The absorption peaks of the complexes appear in the range 0.39–2.82 THz. Moreover, this series of experimental studies further enrich the THz spectroscopic properties of Ag complexes with nitrogen and phosphorous ligands and lay a certain foundation for the identification of THz time domain spectra. Acknowledgements This work has been supported by the National Natural Science Foundation of China (Grant Nos. 21171119, 11104360 and 11204191), the National High Technology Research and Development Program 863 of China (Grant No. 2012AA063201), the Committee of Education of the Beijing Foundation of China (Grant No. KM201210028020), the Scientific Research Base Development Program of the Beijing Municipal Commission of Education, the National Special Fund for the development of Major Research Equipment and Instruments (Grant No. 2012YQ14000508), the Technology Foundation for Selected Overseas Chinese, the Beijing Municipal Education Commission (KM201510028006) and the Scientific Research Base Development Program of the Beijing Municipal Commission of Education. Appendix A. Supplementary data CCDC 890646, 1414685, 890641, 913942, 1414686 and 890645 contains the supplementary crystallographic data for 1–6. These data can be obtained free of charge via http://www.ccdc.cam.ac. uk/conts/retrieving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: [email protected]. Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.poly.2015.12.053. References [1] S.K. Chandran, R. Thakuria, A. Nangia, CrystEngComm 10 (2008) 1891. [2] D.L. Reger, R.F. Semeniuc, M.D. Smith, Dalton Trans. (2008) 2253. [3] Q.X. Yang, Z.J. Chen, J.S. Hu, Y. Hao, Y.Z. Li, Q.Y. Lu, H.G. Zheng, Chem. Commun. 49 (2013) 3585. [4] T.J. Burchell, R.J. Puddephatt, Inorg. Chem. 45 (2006) 650. [5] C. Ganesamoorthy, M.S. Balakrishna, Inorg. Chem. 48 (2009) 3768. [6] Z.T. Wang, L. Zhu, F. Yin, Z.Q. Su, Z.D. Li, C.Z. Li, J. Am. Chem. Soc. 134 (2012) 4258. [7] Q.X. Yang, X.Q. Chen, J.H. Cui, J.S. Hu, M.D. Zhang, L. Qin, G.F. Wang, Q.Y. Lu, H. G. Zheng, Cryst. Growth Des. 12 (2012) 4072.

[8] C. Janiak, Dalton Trans. 14 (2003) 2781. [9] G. Blanco-Brieva, J.M. Campos-Martin, S.M. Al-Zahrani, J.L.G. Fierro, Fuel 90 (2011) 190. [10] A.P. Cote, G.K.H. Shimizu, Coord. Chem. Rev. 245 (2003) 49. [11] A.J. Blake, N.R. Champness, P. Hubberstey, W.S. Li, M.R. Withersby, M. Schröder, Coord. Chem. Rev. 183 (1999) 117. [12] C. Janiak, Dalton Trans. (2003) 2781. [13] (a) O.R. Evans, W. Lin, Acc. Chem. Res. 35 (2002) 511; (b) S. Kitagawa, R. Kitaura, S. Noro, Angew. Chem., Int. Ed. 43 (2004) 2334. [14] S.E.H. Etaiw, D.M.A. El-Aziz, A.S.B. El-din, Polyhedron 28 (2009) 873. [15] R. Prajapati, K. Kimura, L. Mishra, Inorg. Chim. Acta 362 (2009) 3219. [16] J. Wen, Y.-H. Jiang, M.-H. Wu, Q.-H. Jin, H.-L. Gong, Z. Kristallogr, NCS 226 (2011) 269. [17] J.-Q. Wu, Q.-H. Jin, K.-Y. Hu, C.-L. Zhang, Acta Crystallogr. E65 (2009) m1096. [18] L.-N. Cui, Z.-F. Li, Q.-H. Jin, X.-L. Xin, C.-L. Zhang, Inorg. Chem. Commun. 20 (2012) 126. [19] J.-M. Lehn, Supramolecular Chemistry: Concepts and Perspectives, VCH, Weinheim, 1995. [20] S. Xu, M. Liu, Y.-P. Yang, Y.-H. Jiang, Z.-F. Li, Q.-H. Jin, X. Wang, X.-N. Xue, Polyhedron 87 (2015) 293. [21] L.-L. Zhang, H. Zhong, C. Deng, C.-L. Zhang, Y.-J. Zhao, Appl. Phys. Lett. 94 (2009) 211106. [22] G.M. Sheldrick, SHELXS-97 and SHELXL-97, Software for Crystal Structure Analysis, Siemens Analytical X-ray Instruments Inc., Wisconsin, Madison, USA, 1997. [23] G.M. Sheldrick, SHELXTL NT Version 5.1, Program for Solution and Refinement of Crystal Structures, University of Gottingen, Germany, 1997. [24] G.-G. Luo, S.-H. Wu, Z.-H. Pan, Z.-J. Xiao, J.-C. Dai, Inorg. Chem. Commun. 39 (2014) 34. [25] X.-J. Li, R. Cao, D.-F. Sun, W.-H. Bi, Y.-Q. Wang, M.-C. Hong, Acta Crystallogr. E59 (2003) m416. [26] L. Carlucci, G. Ciani, D.M. Proserpio, S. Rizzato, CrystEngComm 5 (2003) 190. [27] L. Carlucci, G. Ciani, D.M. Proserpio, S. Rizzato, Chem. Commun. (2000) 1319. [28] K.N. Lazarou, V. Psycharis, A. Terzis, C.P. Raptopoulou, Polyhedron 30 (2011) 963. [29] G.J. Halder, K.W. Chapman, S.M. Neville, B. Moubaraki, K.S. Murray, J.-F. Letard, C.J. Kepert, J. Am. Chem. Soc. 130 (2008) 17552. [30] L.-N. Cui, K.-Y. Hu, Q.-H. Jin, Z.-F. Li, J.-Q. Wu, C.-L. Zhang, Polyhedron 30 (2011) 2253. [31] Brendan F. Abrahams, Stuart R. Batten, Bernard F. Hoskins, Richard. Robson, Inorg. Chem. 42 (2003) 2654. [32] B.F. Abrahams, S.R. Batten, B.F. Hoskins, R. Robson, Inorg. Chem. 42 (2003) 2654. [33] S.E.-D.H. Etaiw, M.M. El-Bendary, J. Coord. Chem. 63 (2010) 1038. [34] M. Nagarathinam, J.J. Vittal, Angew. Chem., Int. Ed. 45 (2006) 4337. [35] X.F. Zheng, L.G. Zhu, Polyhedron 30 (2011) 666. [36] S. Kitagawa, S. Matsuyama, M. Munakata, T. Emori, J. Chem. Soc., Dalton Trans. (1991) 2869. [37] M.C. Brandys, R.J. Puddephatt, Chem. Commun. (2001) 1508. [38] Porntiva Suvanvapee, Jaursup Boonmak, Sujittra Youngme, Inorg. Chim. Acta 437 (2015) 11. [39] F.H. Allen, Acta Crystallogr. B58 (2002) 380. [40] S.E.-D.H. Etaiw, M.M.EL. Bendary, J. Coord. Chem. 63 (2010) 1038. [41] L. Carlucci, G. Ciani, D.W.v. Gudenberg, D.M. Proserpio, Inorg. Chem. 36 (1997) 3812. [42] L.-L. Song, Q.-H. Jin, L.-N. Cui, C.-L. Zhang, Inorg. Chim. Acta 363 (2010) 2425. [43] X. Huang, Z.-F. Li, Q.-H. Jin, Q.-M. Qiu, Y.-Z. Cui, Q.-R. Yang, Polyhedron 65 (2013) 129. [44] Q.-H. Jin, L.-M. Chen, P.-Z. Li, S.-F. Deng, R. Wang, Inorg. Chim. Acta 362 (2009) 5224. [45] R. Prajapati, K. Kimura, L. Mishra, Inorg. Chim. Acta 362 (2009) 3219. [46] G.-P. Yang, Y.-Y. Wang, P. Liu, A.-Y. Fu, Y.-N. Zhang, J.-C. Jin, Q.-Z. Shi, Cryst. Growth Des. 10 (2010) 1443. [47] S.E.-D.H. Etaiw, A.S.B. El-din, J. Inorg. Organomet. Polym. 20 (2010) 684. [48] K. Zhou, X.-L. Wang, C. Qin, H.-N. Wang, G.-S. Yang, Y.-Q. Jiao, P. Huang, K.-Z. Shao, Z.-M. Su, Dalton Trans. 42 (2013) 1352. [49] K. Zhou, C. Qin, X.-L. Wang, K.-Z. Shao, L.-K. Yan, Z.-M. Su, CrystEngComm 16 (2014) 7860. [50] K. Zhou, C. Qin, X.-L. Wang, K.-Z. Shao, L.-K. Yan, Z.-M. Su, Dalton Trans. 43 (2014) 10695. [51] Q.-M. Qiu, M. Liu, Z.-F. Li, Q.-H. Jin, X. Huang, Z.-W. Zhang, C.-L. Zhang, Q.-X. Meng, J. Mol. Struct. 1062 (2014) 125. [52] Q.-M. Qiu, X. Huang, Y.-H. Zhao, M. Liu, Q.-H. Jin, Z.-F. Li, Z.-W. Zhang, C.-L. Zhang, Q.-X. Meng, Polyhedron 83 (2014) 16. [53] H. Zhang, G.L. Zhuang, X.J. Kong, Cryst. Growth Des. 13 (2013) 2493.