Structures and magnetic properties of two noncentrosymmetric coordination polymers based on carboxyphosphinate ligand

Solid State Sciences 61 (2016) 111e115

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Structures and magnetic properties of two noncentrosymmetric coordination polymers based on carboxyphosphinate ligand Jianyong Li a, Chao-Chao Xue b, Siming Liu d, Zhao-Xi Wang b, c, * a

College of Basic Medicine, Nanchang University, Nanchang 330006, China Department of Chemistry, Innovative Drug Research Center, Shanghai University, Shanghai 200444, China c State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing 210093, China d Ulink College of Shanghai, Shanghai 201617, China b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 30 August 2016 Accepted 20 September 2016 Available online 20 September 2016

Two novel coordination polymers have been hydrothermally synthesized by reactions of Cu(II), Mn(II) salt with 2-carboxyethyl(phenyl)phosphinic acid (H2L), namely, [Cu(L)(H2O)]n (1) and [Mn(HL)2]n (2). Both compounds were well characterized by single crystal X-ray diffraction, elemental analysis, IR spectroscopic, power X-ray diffraction and magnetic studies. Compound 1 crystallizes in a noncentrosymmetric monoclinic Cc space group and presents an inorganic two-dimensional (2D) network, whereas compound 2 adopts a noncentrosymmetric Pca21 space group and exhibits a 2D layer structure. Magnetic studies reveal a dominant ferromagnetic interaction in 1, and weak antiferromagnetic coupling between the Mn(II) ions in 2 mediated by phosphinico group, respectively. © 2016 Elsevier Masson SAS. All rights reserved.

Keywords: Copper(II) Manganese(II) Noncentrosymmetric Carboxyphosphinate ligand Magnetic properties

1. Introduction The rational design and synthesis of coordination compounds with previously fixed specific properties such as magnetism [1], catalysis [2], luminescence [3], nonlinear optics [4] and molecular sensing [5], as well as their intringuing structural optics [6] had been studies for decades. The previous studies showed that the structure and properties of MOFs depend on factors such as the metal ions with definite coordination geometry, the nature of organic ligands, the counteranions, the reaction conditions, and so on [7]. For example, copper(II), cobalt(II), nickel(II), and manganese(II) ions with unpaired electrons are often employed for the syntheses of compounds with magnetic properties [8], while lanthanide ions with f-f electronic transitions are often used to prepare compounds with luminescent properties [9]. And we also found that a suitable reaction pH value [10] may be a strong influence on the self-assembly synthesis process [11]. Recently, phosphonate ligands are involved to construct organiceinorganic hybrid materials with beautiful architectures as well as interesting physical properties, such as sorption, catalysis, optical properties and magnetism [12]. Although many fruitful

* Corresponding author. Department of Chemistry, Innovative Drug Research Center, Shanghai University, Shanghai 200444, China. E-mail address: [email protected] (Z.-X. Wang). http://dx.doi.org/10.1016/j.solidstatesciences.2016.09.014 1293-2558/© 2016 Elsevier Masson SAS. All rights reserved.

works have been reported on phosphonate compounds, the compounds based on phosphinic acid derived from phosphonic acid have rarely been investigated [13]. Compared with mono-organicgroup-attached carboxylate or phosphonate moieties, carboxyphosphinate ligand can allow a better modulation of the structure of the resultant metal compounds [14]. We employed a V-shaped semi-rigid carboxyphosphinate ligand of 2,2'-phosphinico-dibenzoic acid to build coordination polymers with sophisticated framework and interesting properties [15]. 2-Carboxyethyl(phenyl) phosphinic acid (H2L) is a flexible ligand, which has been utilized to prepare coordination polymers with diverse structures and physical properties by us and other groups [16]. As part of our ongoing interest in the construction of coordination polymers from the carboxyphosphinate ligands, the systems of Cu(II)/Mn(II) and H2L have been investigated. Here we harvest two novel noncentrosymmetric compounds of copper(II) and manganese(II) with H2L, namely, [Cu(L)(H2O)]n (1), [Mn(HL)2]n (2). Here, we report the syntheses, crystal structures and the magnetic properties of the two compounds in details. 2. Experimental 2.1. Materials and methods All reagents and solvents used in the present work were of

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analytical grade as obtained from commercial sources without further purification. FT-IR spectra were carried on KBr pellets in the range from 4000 to 400 cm
1 on a Nicolet Avatar A370 spectrophotometer. Elemental analyses for C, H were performed on a Vario EL-III elemental analyzer. Powder X-ray diffraction (PXRD) data for 1 and 2 were collected on a DX-2700 diffractometer with (Cu Ka) radiation (l ¼ 1.5406 Å) over the 2q range of 5e30 at room temperature. Variable temperature (2
300K) magnetic susceptibilities were measured on a Quantum Design MPMS-XL7 SQUID magnetometer at an applied field of 1000 Oe. The diamagnetic corrections were applied by using Pascal's constants. 2.2. Synthesis of [Cu(L)(H2O)]n (1) A mixture of Cu(NO3)2$3H2O (0.15 mmol) with H2L (0.1 mmol) and Na2SiO3$9H2O (0.02 mmol) in 8 mL of distilled water was stirred at room temperature for 30 min, and a solution of NaOH (1 mol L
1) was added to adjust pH ~ 6, then sealed in a 15 mL Teflon-lined stainless steel autoclave and heated at 85  C for 3 days. After cooling to room temperature at a rate of 5  C h
1, blue crystals of 1 were obtained in 75% yield based on Cu. Elemental analysis calcd (%) for C9H11O5PCu (293.70): C, 36.80; H, 3.77. Found: C, 36.74; H, 3.65%. IR/cm
1 (KBr): 3399(m), 3073(w), 2910(w), 1639(w), 1432(s), 1384(m), 1197(w), 1119(s), 1058 (s), 997(w), 925(w), 829(m), 732(s), 701(w), 659(w), 614(w), 528 (m), 507(w). 2.3. Synthesis of [Mn(HL)2]n (2) A mixture of MnCl2$4H2O (0.2 mmol) with H2L (0.1 mmol), and 4,4-bipy (0.05 mmol) in 8 mL of distilled water was stirred at room temperature for half an hour. The pH value of the solution was adjusted to 7.00 by addition of 13 mL triethylamine. The solution was sealed in a 15 mL Teflon-lined stainless steel autoclave and heated at 85  C for 3 days. After cooling to room temperature at a rate of 5  C h
1, colorless crystals were isolated by filtration and washed by water in 87% yield based on Mn. Elemental analysis calcd (%) for C18H20O8P2Mn (481.22): C, 44.93; H, 4.19. Found: C, 45.01; H, 4.22%. IR/cm
1 (KBr): 3416(m), 3075(w), 2948 (w), 2500(m), 1857(m), 1667(s), 1458(m), 1410(m), 1353(s), 1276(s), 1211(w), 1143(s), 1041(s), 957(m), 795(m), 691(m), 534(s), 493(w), 438(w).

Table 1 Crystal data and structure refinement information for 1 and 2. Compounds

1

2

Formula C9H11O5PCu Formula weight 293.70 Crystal system Monoclinic Space group Cc a (Å) 4.9470(9) b (Å) 27.508(5) c (Å) 8.0697(14) a ( ) 90.00 b ( ) 104.504(2) g ( ) 90.00 V (Å3) 1063.1(3) Z 4
3 1.829 Dc (g cm )
1 m (mm ) 2.206 F (000) 592 GOF on F2 1.008 R1a,wR2b[I > 2s(I)] 0.0309, 0.0604 R1a,wR2b (all data) 0.0342, 0.0622 P P a R1 ¼ jjFoj
jFcjj/ jFoj. P P b wR2 ¼ [ w(jF2oj
jF2c j)2/ w(jF2oj)2]1/2.

C18H20O8P2Mn 481.22 Orthorhombic Pca21 15.531(4) 5.4879(13) 22.947(5) 90.00 90.00 90.00 1955.9(8) 4 1.634 0.883 988 1.037 0.0234, 0.0584 0.0253, 0.0595

Table 2 Selected bond distances (Å) for compounds 1 and 2. 1 Cu1eO1A Cu1eO3 Cu1eO5 P1eO4 2 Mn1eO5C Mn1eO7 Mn1eO1A P1eO3 P2eO7

1.938(3) 2.003(3) 1.992(3) 1.505(3)

Cu1eO2 Cu1eO4B P1eO3

2.244(3) 1.928(3) 1.517(3)

2.289(3) 2.204(3) 2.242(3) 1.492(3) 1.511(3)

Mn1eO3B Mn1eO4 Mn1eO8D P1eO4 P2eO8

2.076(3) 2.241(3) 2.078(3) 1.522(3) 1.502(3)

Symmetry codes for 1: A: x
1/2,
yþ1/2, z
1/2; B: x
1, y, z. Symmetry codes for 2: A: xþ1/2,
yþ2, z; B: x, y
1, z; C: x
1/2,
yþ1, z; D: x, yþ1, z.

2.4. X-ray crystallography Single-crystal X-ray diffraction data for complexes 1 and 2 were collected on a Bruker SMART APEX CCD diffractometer using graphite monochromatized Mo Ka radiation (l ¼ 0.71073 Å) at room temperature using the phi and omega scan technique. Data reduction was conducted with the Bruker SAINT package. Absorption correction was performed using the SADABS program. The structures were solved by direct methods and refined on F2 by fullmatrix least-squares using SHELXL-2000 with anisotropic displacement parameters for all non-hydrogen atoms. H atoms were introduced in calculations using the riding model. Crystallographic data and structural refinement results are summarized in Table 1. Important bond distances for 1 and 2 are listed in Table 2. 3. Results and discussion 3.1. Structure description for 1 The single crystal X-ray analysis reveals that compound 1 crystallizes in the noncentrosymmetric space group Cc and is extended a 2D network, in which the ligand H2L is deprotonated completely. As shown in Fig. 1a, the asymmetric unit contains one

Fig. 1. (a) Molecular structure of 1 with 50% probability displacement ellipsoids. (b) coordination mode of L2
ligand. Hydrogen atoms are omitted for clarity. Symmetry codes: A: x
1/2,
y þ 1/2, z
1/2; B: x
1, y, z.

Cu2þ ion, one L
anion and one coordinated water molecule. The coordination geometry around Cu1 ion has a distorted square pyramidal geometry which is surrounded by two phosphinico oxygen, two carboxylate oxygen atoms from two L
ligands as well as one

J. Li et al. / Solid State Sciences 61 (2016) 111e115

Fig. 2. (a) A view of 1D inorganic chain array along the a-axis. (b) 2D network. the phenyl groups and eCH2CH2COOH of L2
ligand are omitted for clarity.

water oxygen atom (Fig. 1b). The CueO distances are in the range of 1.928(3) - 2.244(3) Å (Table 2), which are fall into those reported in the literature [17]. Each L
ligand bridges three Cu2þ ions via its two oxygen atoms of phosphinico group and one of carboxylate group. If weak coordination bonding considered, the Cu(II) ions are interconnected by one carboxylate oxygen atoms to form 1D inorganic chain along the c-axis (Fig. 2a). Furthermore, the neighboring 1D inorganic chain is connected through the phosphinico groups to form a 2D hybrid noncentrosymmetric network in the ac-plane (Fig. 2b). The 2D layers are shielded from the phenyl groups of L
ligands. 3.2. Structure description for 2 Compound 2 belongs to the orthorhombic space group Pca21

113

Fig. 4. (a) A view of the 1D inorganic chain array along the c-axis. (b) their assembly into 2D network through eCH2CH2COOH groups, the phenyl groups of the HL
ligands are omitted for clarity.

and exhibits a 2D layered structure. The asymmetric unit of 2 consists of one Mn2þ ion and two HL
anions (Fig. 3a). The Mn(II) center is octahedrally coordinated by four phosphinico oxygen atoms and two carboxylate oxygen atoms from six HL
ligands. The Mn is at a center of noncentrosymmetric, The MneO distances are in the range of 2.0795(16) - 2.2921 (17) Å (Table 2), which are in the range of those reported in the literature [18]. Each HL
ligand bridges three Mn2þ ions via its two oxygen atoms of phosphinico group and one of carbonyl group (Fig. 3b), which is similar to one of its Cd compound. In compound 2, the HL
ligand exhibits very different coordination mode from its compounds in document [19]. The Mn(II) ions are interconnected by double phosphinico groups of two HL
anions into a two-fold symmetrical chiral inorganic chain along the c-axis (Fig. 4a). Furthermore, the neighboring 1D inorganic chain is connected through the organic part (-CH2CH2COOH) of HL
anion to form a 2D hybrid noncentrosymmetric layer paralleled to the ab plane (Fig. 4b). 3.3. IR spectra and thermogravimetric analysis Infrared spectra of 1 and 2 show strong characteristic bands of P]O in the region from 1535 to 1041 cm
1 and middle peaks of PeO around 1021e691 cm
1. Nevertheless in the IR spectra of 1,

Fig. 3. (a) Molecular structure of 2 with 50% probability displacement ellipsoids. (b) Environment of the four groups around the phosphorus atom in HL
ligand. Hydrogen atoms are omitted for clarity. Symmetry codes: A: x þ 1/2,
y þ 2, z; B: x, y
1, z; C: x
1/2,
y þ 1, z; D: x, y þ 1, z.

Fig. 5. TGA curves for 1 (red) and 2 (black). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

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J. Li et al. / Solid State Sciences 61 (2016) 111e115

no peaks are observed near 1700 cm
1 for eCOOH group, but strong peaks are around 1432e1639 cm
1. In the spectra of 2, there is a strong peak of 1667 cm
1, which indicates the existence of eCOOH group [20]. And no absorption peaks occurring in the range of 1600e1500 cm
1 further prove that the carboxyl group is not deprotonated, which are in agreement with the crystal structure of 2. To examine the thermal stabilities of compounds 1 and 2, thermogravimetric (TG) analyses were carried out in a nitrogen atmosphere from 30 to 800  C. The TGA curves show that compounds 1 and 2 both are stable up to 200  C and then decompose completely until 450 and 550  C, with total weight loss of 60.0 and 54.1%, respectively (see Fig. 5). 3.4. Magnetic properties The temperature-dependent susceptibilities of crystalline sample of 1 and 2 were measured from 300 to 2 K under a direct current

of 1000 Oe. The plot of cmT and c
1 m versus T for compounds 1 and 2 are depicted in Fig. 6. At room temperature, the cmT value of 1 is 0.44 emu K mol
1, slightly larger than the spin-only value of 0.375 emu K mol
1 based on uncoupled one copper(II) ions 2þ (S2þ Cu ¼ 1/2 and assuming gCu ¼ 2.0). When the temperature is lowered, the cMT value keeps almost a constant in 300e50 K range and then increases to a maximum value of 0.77 emu K mol
1 at 2 K. This magnetic behavior indicates the presence of weak ferromagnetic interactions exist in 1. In the whole temperature range, the magnetic susceptibility obeys the CurieeWeiss law with a Curie constant C ¼ 0.442 emu K mol
1 and a positive Weiss constant q ¼ 1.17 K, corresponding a g value of 2.17 for 1. The positive q value suggests that there is weak ferromagnetic coupling in 1. According to the structure of 1, there is a 1D chain formed by single oxygen atom bridging with the CueCu distance of 4.4808(8) Å and Cu(1)eO(2)eCu(1) bond angle of 128.988(122) . Furthermore, the 1D chains are connected by OePeO units formed a 2D network with the shortest CueCu distance of 4.947(1) Å

Fig. 6. Plots of cMT and c
1 M vs T for 1 (a) and 2 (b).

J. Li et al. / Solid State Sciences 61 (2016) 111e115

between the chains. In general, all the oxygen-bridged compounds with large bond angle present antiferromagnetic coupling [21]. Thus, weak ferromagnetic interaction is anticipated between the Cu(II) ions through OePeO bridges, which is consist with the cases previously reported [22]. For compound 2, the cmT value is 3.98 emu K mol
1 at room temperature, which is slightly lower than the spin-only value (4.375 emu K mol
1) of one isolated MnII (S ¼ 5/2) ions assuming g ¼ 2.0. Upon cooling, cMT smoothly decreases and reaches 3.82 emu K mol
1 at 2 K, indicating antiferromagnetic interactions occurred. The magnetic susceptibility data follows the CurieeWeiss law with C ¼ 4.00 emu K mol
1 and q ¼
1.81 K. The C value corresponds to the value expected for Mn(II) ion with g ¼ 1.92. The negative q suggests antiferromagnetic interaction between Mn(II) ions. In 2, there is a 1D chain constructed from Mn(II) ions interconnected by double phosphinico groups with the shortest distance between MneMn being 5.4879(14) Å. Moreover, the 1D chains are connected by eCH2CH2COOH groups, and the shortest MneMn distance between these 1D chains is 8.0029(20) Å, which is too long to mediate an efficient magnetic exchange coupling. Thus, the antiferromagnetic interaction between the Mn(II) ions originates from the double phosphinico groups. 4. Conclusions In summary, we have been successfully synthesized and characterized two novel coordination polymers exhibiting noncentrosymmetric 2D architectures constructed from a flexible carboxylphosphinate ligand. Compound 1 has an inorganic 2D network, whereas compound 2 exhibits a 2D layer structure. Variable-temperature magnetic analyses reveal weak ferromagnetic or antiferromagnetic couplings between the metal ions through phosphinico group.

[4]

[5] [6]

[7]

[8] [9]

[10]

[11]

[12]

Acknowledgements [13]

This work was financially supported by Natural Science Foundation of Shanghai (16ZR1411400) and National Natural Science Foundation of China (21171115).

[14]

Supplementary material [15]

CCDC-1499158 (1) and 1499159 (2) contain the supplementary crystallographic 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.

[16]

References [1] (a) L. Zhang, L. Liu, C. Huang, X. Han, L. Guo, H. Xu, H. Hou, Y. Fan.Cryst, Growth Des. 15 (2015) 3426; (b) J. Ferrando-Soria, A. Fernandez, E. Moreno Pineda, S.A. Varey, R.W. Adams, I.J. Vitorica-Yrezabal, F. Tuna, G.A. Timco, C.A. Muryn, R.E.P. Winpenny, J. Am. Chem. Soc. 137 (2015) 7644; (c) S. Langley, M. Helliwell, R. Sessoli, S.J. Teat, R.E.P. Winpenny, Inorg. Chem. 47 (2008) 497; (d) Y.-Z. Zheng, M. Evangelistib, R.E.P. Winpenny, Chem. Sci. 2 (2011) 99. [2] (a) Alejo M. Lifschitz, Mari S. Rosen, C. Michael McGuirk, Chad A. Mirkin, J. Am. Chem. Soc. 137 (2015) 7252; (b) L.-Q. Ma, C. Abney, W.-B. Lin, Chem. Soc. Rev. 38 (2009) 1248; (c) S. Chessa, N.J. Clayden, M. Bochmann, J.A. Wright, Chem. Commun. (2009) 797; (d) W.J. Youngblood, S.H.A. Lee, Y. Kobayashi, E.A. Hernandez-Pagan, P.G. Hoertz, T.A. Moore, A.L. Moore, D. Gust, T.E. Mallouk, J. Am, Chem. Soc. 131 (2009) 926; (e) D.Y. Shopov, B. Rudshteyn, J. Campos, V.S. Batista, R.H. Crabtree, G.W. Brudvig, J. Am. Chem. Soc. 137 (2015) 7243. [3] (a) X.-G. Liu, K. Zhou, J. Dong, C.-J. Zhu, S.-S. Bao, L.-M. Zheng, Inorg. Chem. 48

[17]

[18]

[19] [20] [21] [22]

115

(2009) 1901;
nez, J.C. Rodrı guez-Ubis, (b) E. Brunet, H.M.H. Alhendawi, O. Juanes, L. Jime J. Mat. Chem. 19 (2009) 2494; (c) T.-H. Zhou, F.-Y. Yi, P.-X. Li, J.-G. Mao, Inorg. Chem. 49 (2010) 905. (a) Z.-L. Wu, J. Dong, W.-Y. Ni, B.-W. Zhang, J.-Z. Cui, B. Zhao, Inorg. Chem. 54 (2015) 5266; (b) G. Di Carlo, A.O. Biroli, F. Tessore, S. Rizzato, A. Forni, G. Magnano, M. Pizzotti, J. Org. Chem. 80 (2015) 4973. G. Dura, M.C. Carrion, F.A. Jalo, B.R. Manzano, A.M. Rodríguez, K. Mereiter, Cryst. Growth Des. 15 (2015) 3321. (a) M.T. Wharmby, J.P.S. Mowat, S.P. Thompson, P.A. Wright, J. Am, Chem. Soc. 133 (2011) 1266; (b) V. Chandrasekhar, T. Senapati, A. Dey, S. Hossain, Dalton Trans. 40 (2011) 5394; (c) G.K.H. Shimizu, R. Vaidhyanathan, J.M. Taylor, Chem. Soc. Rev. 38 (2009) 1430; (d) A. Clearfield, Dalton Trans. (2008) 6089; (e) J.-G. Mao, Coord. Chem. Rev. 251 (2007) 1493. (a) S.R. Batten, R. Robson, Angew. Chem. Int. Ed. 37 (1998) 1460; (b) P.J. Hagrman, D. Hagrman, J. Zubieta, Angew. Chem. Int. Ed. 38 (1999) 2639; (c) A.J. Blake, N.R. Champness, P. Hubberstey, W.S. Li, M.A. Withersby, € der, Coord.Chem. Rev. 183 (1999) 117; M. Schro (d) O.M. Yaghi, M. O'Keeffe, N.W. Ockwig, H.K. Chae, M. Eddaoudi, J. Kim, Nature 423 (2003) 705. (a) M. Andruh, Chem. Commun. (2007) 2565; (b) M. Andruh, Chem. Commun. 47 (2011) 3025. (a) R.W. Gable, B.F. Hoskins, R. Robson, J. Chem, Soc. Chem. Commun. (1990) 1677; (b) B.F. Hoskins, R. Robson, J. Am, Chem. Soc. 112 (1990) 1546. (a) T.F. Liu, D. Fu, S. Gao, Y.Z. Zhang, H.L. Sun, G. Su, Y.J. Liu, J. Am, Chem. Soc. 125 (2003) 13976; (b) Y.Y. Niu, H.G. Zheng, H.W. Hou, X.Q. Xin, Coord. Chem. Rev. 248 (2004) 169; (c) X.C. Huang, Y.Y. Lin, J.P. Zhang, X.M. Chen, Angew. Chem. Int. Ed. 45 (2006) 1557; (d) M.J. Zaworotko, Nature 451 (2008) 410. (a) H. Yang, S. Gao, J. Lü, B. Xu, J. Lin, R. Cao, Inorg. Chem. 49 (2010) 736; ~ udo, M. Du, C.-S. Liu, Inorg. Chem. 49 (b) S.-M. Fang, Q. Zhang, M. Hu, E.C. San (2010) 9617. (a) Y.-Z. Zheng, M. Evangelisti, R.E.P. Winpenny, Angew. Chem. Int. Ed. 50 (2011) 3692; b) Y.-Z. Zheng, M. Evangelisti, F. Tuna, R.E.P. Winpenny, J. Am, Chem. Soc. 134 (2012) 1057; (c) S.-S. Bao, N.-Z. Li, J.M. Taylor, Y. Shen, H. Kitagawa, L.-M. Zheng, Chem. Mater. 27 (2015) 8116. (a) S. Midollini, A. Orlandini, P. Rosa, L. Sorace, Inorg. Chem. 44 (2005) 2060; (b) L.-J. Dong, C.-C. Zhao, X. Xu, Z.-Y. Du, Y.-R. Xie, J. Zhang, Cryst. Growth Des. 12 (2012) 2052. (a) F. Cecconi, S. Dominguez, N. Masciocchi, S. Midollini, A. Sironi, A. Vacca, Inorg. Chem. 42 (2003) 2350; (b) S. Midollini, A. Orlandini, P. Rosa, L. Sorace, Inorg. Chem. 44 (2005) 206; (c) F. Costantino, A. Ienco, S. Midollini, A. Orlandini, A. Rossin, L. Sorace, Eur. J. Inorg. Chem. (2010) 3179. (a) L.-F. Wu, Z.-X. Wang, C.-C. Xue, H.-P. Xiao, M.-X. Li, CrystEngComm. 16 (2014) 5627; (b) Z.-X. Wang, L.-F. Wu, H.-P. Xiao, X.-H. Luo, M.-X. Li, Cryst. Growth Des. 16 (2016), http://dx.doi.org/10.1021/acs.cgd.6b00747. (a) C.-C. Xue, M.-X. Li, M. Shao, Z.-X. Wang, Russ. J. Coord. Chem. 42 (2016) 442; (b) C.-C. Zhao, Z.-G. Zhou, X. Xu, L.-J. Dong, G.-H. Xu, Z.-Y. Du, Polyhedron 12 (2013) 18; (c) Y.-P. Zhao, J.-W. Zhang, C.-C. Zhao, Z.-Y. Du, Inorg. Chim. Acta 414 (2014) 121. (a) F. Costantino, A. Ienco, S. Midollini, A. Orlandini, A. Rossin, A. Vacca, Eur. J. Inorg. Chem. (2008) 3046; (b) F. Costantino, A. Ienco, S. Midollini, Cryst. Growth Des. 10 (2010) 7. (a) V.A. Blatov, IUCr CompComm Newsl. 7 (2006) 4; (b) V.A. Blatov, A.P. Shevchenko, V.N. Serezhkin, J. Appl. Crystallogr. 33 (2000) 1193; (c) V.A. Blatov, M. O'Keeffe, D.M. Proserpio, CrystEngComm. 12 (2009) 44. Y.-H. Sun, X. Xu, Z.-Y. Du, L.-J. Dong, C.-C. Zhao, Y.-R. Xie, Dalton Trans. 40 (2011) 9295. Z.-X. Wang, Q.-F. Wu, H.-J. Liu, M. Shao, H.-P. Xiao, M.-X. Li, CrystEngComm. 12 (2010) 1139. Z.-X. Wang, M.-X. Li, H.-P. Xiao, Inorg. Chem. Commun. 12 (2009) 201. (a) H.-C. Yao, Y.-Z. Li, S. Gao, Y. Song, L.-M. Zheng, X.-Q. Xin, J. Solid State Chem. 177 (2004) 4557; (b) Y. Wang, S.-S. Bao, W. Xu, J. Chen, S. Gao, L.-M. Zheng, J. Solid State Chem. 177 (2004) 1297; (c) H.-H. Song, L.-M. Zheng, C.-H. Lin, S.-L. Wang, X.-Q. Xin, S. Gao, Chem. Mater. 11 (1999) 2382.