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  0   Introduction

  Crystal engineering of coordination polymers (CPs), which involves self-assembly of organic ligands with appropriate functional groups and metal ions with specific directionality and functionality, is one of the facile routes to produce materials of technological importance^[1]. The metal-ligand coordination bonds have been widely exploited in organizing molecular building blocks into diverse supramolecular architectures, making use of the strength of coordination bonds and directionality associated with metal ions^[2]. Coordina-tion polymers have attracted a great of extensive interest not only for their potential applications in adsorption, nonlinear optics, magnetism, photolumine-scence, catalysis, and electrical conductivity, but also for their intriguing variety of architectures and fascin-ating topologies^[3]. A number of topological types are applied in various CPs, because of its ability of simplifying complicated frameworks and the instru-ctive role in the rational design of some predicted functional materials^[4]. Of particular interest are inter-penetrating frameworks^[5]. These species can be reg-arded as infinite ordered polycatenanes and are characterized by the presence of two or more independent networks that cannot be separated in a topological sense without breaking of bonds. In the past decade, considerable effort has been invested in interpenetrating CPs because of their unique advantages in enhancing stability, specific surface area, gas sorption, and molecular dynamics, as well as their general structural aesthetics ^[6].

  The long-flexible ligand may be a good candidate as a unique structural motif to produce interpene-trating architectures with interesting topologies and useful functional properties^[7]. Hence we selected 3, 5-bis (pyridin-4-ylmethoxy) benzoic acid (HL) as primary ligand, because it contains a rigid spacer of phenyl ring and two freely rotating pyridyl arms, which may cause the planes of the pyridyl rings to rotate with respect to the plane of the central phenyl ring. On the other hand, d10 metal (Cd (Ⅱ), Zn (Ⅱ)) compounds have attracted extensive interest in recent years because of photoluminescent properties^[8]. With this aim of under-standing the coordination chemistry of HL^[9-10] and preparing new materials with interpenetrating networks and excellent physical properties, we have recently engaged in the research of the CPs with HL ligand^[10]. In this paper, we describe the preparations, crystal structures, and photoluminescent properties of four CPs based on HL and dicarboxylic acid ligands, namely, [Zn₂L₂ (tdc)]_n (1), {[Zn₄L₄(hbdc)₂]·H₂O}_n (2), {[Zn₂L₂(bdtc)]·H₂O}_n (3) and {[Cd₂L₂ (bdtc) H₂O]·0.5H₂O}_n (4).

  1   Experimental

  1.1   Materials and physical measurements

  The ligands and other reagents were purchased from Jinan Camolai Trading Company and used without further purification. The elemental analyses of C, H and N were performed on a Perkin-Elmer 2400 Ⅱ elemental analyzer. IR spectrum was measured in KBr pellets on a Nicolet 5DX FT-IR spectrometer. The thermogravimetric measurement was performed on preweighed samples in an oxygen stream using a Netzsch STA449C apparatus with a heating rate of 10 ℃·min^-1. The crystal data were acquired on a Bruker APEX Ⅱ diffractometer. Powder X-ray diffraction data were obtained using a Philips PW3040/60 auto-mated powder diffractometer, using Cu _Kα radiation (_λ=0.154 2 nm) with a 2_θ range of 5°~50 °. The lumi-nescence spectra were performed on a HITACHIF-2500 fluorescence spectrometer in solid state at room temperature.

  1.2   Synthesis of [Zn₂L₂(tdc)]_n (1)

  A mixture of ZnSO₄·2H₂O (0.20 mmol, 0.058 g), HL (0.10 mmol, 0.034 g), H₂tdc (0.05 mmol, 0.013 g) and NaOH (0.15 mmol, 0.006 g) in H₂O (14 mL) was sealed in a 25 mL Teon-lined stainless steel container, which was heated at 160 ℃ for 72 h and then cooled down to room temperature at a rate of 5 ℃·h^-1. Yellow crystals of 1 were collected and washed with distilled water and dried in air to give the product with 27.4% yield (based on HL). Anal. Calcd. for C₄₄H₃₂N₄O₁₂SZn₂ (%): C, 54.40; H, 3.32; N, 5.77. Found (%): C, 54.18; H, 3.39; N, 5.86. IR (KBr pellet, cm^-1): 3 444, 3 086, 2 930, 2 366, 1 631, 1 603, 1 419, 1 376, 1 235, 1 150, 1 065, 868, 797.

  1.3   Syntheses of {[Zn₄L₄(Hhdc)₂]·H₂O}_n (2) and {[Zn₂L₂(Hhdc)]·H₂O}_n (3)

  A mixture of ZnSO₄·2H₂O (0.20 mmol, 0.058 g), HL (0.10 mmol, 0.034 g), H₃hdc (0.10 mmol, 0.018 g) and NaOH (0.30 mmol, 0.012 g) in H₂O (14 mL) was sealed in a 25 mL Teflon-lined stainless steel container, which was heated at 160 ℃ for 72 h and then cooled down to room temperature at a rate of 5 ℃·h^-1. The containing pale yellow blocklike crystals of 2 and yellow platelike crystals of 3 were obtained. The yield of 2 is about 3.0% (based on HL). Anal. Calcd. for C₉₂H₇₂N₈O₂₇Zn₄(%): C, 55.78; H, 3.56; N, 5.66. Found (%): C, 55.70; H, 3.62; N, 5.74. IR (KBr pellet, cm^-1): 3 429, 2 943, 1 640, 1 560, 1 367, 1 249, 1 161, 1 073, 1 028, 910, 792. The yield of 3 is 30.1% (based on HL). Anal. Calcd. for. C₄₆H₃₆N₄O₁₄Zn₂(%): C, 55.72; H, 3.66; N, 5.65. Found (%): C, 55.39; H, 3.62; N, 5.52. IR (KBr pellet, cm^-1): 3 458, 3 075, 2 943, 2 354, 1 617, 1 581, 1 381, 1 279, 1 175, 1 057, 1 014, 778, 719, 497.

  1.4   Synthesis of {[Cd₂L₂(bdtc)(H₂O)]·0.5H₂O}_n (4)

  A mixture of Cd (CH₃COO)₂·2H₂O (0.20 mmol, 0.053 g), HL (0.10 mmol, 0.034 g), H₂bdtc (0.05 mmol, 0.013 g) and NaOH (0.10 mmol, 0.004 g) in H₂O (14 mL) was sealed in a 25 mL Teflon-lined stainless steel container, which was heated at 160 ℃ for 72 h and then cooled down to room temperature at a rate of 5 ℃·h^-1. Yellow crystals of 4 were collected and washed with distilled water and dried in air to give the product with 11.8% yield (based on HL). Anal. Calcd. for C₄₈H₄₄Cd₂N₄O₁₅S₂(%): C, 47.81; H, 3.68; N, 4.65. Found (%): C, 47.86; H, 3.72; N, 4.61. IR (KBr pellet, cm^-1): 3 430, 2 970, 2 919, 2 368, 1 613, 1 551, 1 480, 1 377, 1 235, 1 163, 1 102, 898, 796, 673.

  1.5   X-ray crystallography study

  Data collection of 1~4 was carried out on a Bruker APEX Ⅱ diffractometer equipped with a graphite-monochromatized Mo Kα radiation (λ=0.071 073 nm) at 296(2) K. Data intensity was corrected by Lorentz-polarization factors and empirical absorption. The structure was solved by the direct methods and refined with the full-matrix least-squares refinements technique based on F². The anisotropic displacement parameters were applied to all non-hydrogen atoms. The hydrogen atoms were assigned with isotropic displacement factors and included in the final refinement cycles using geometrical restrains. All calculations were performed with SHELXS-97 and SHELXTL-97 program packages^[11]. The detailed crys-tallographic data and structure refinement parameters are summarized in Table 1. Selected bond lengths and angles are given in Table 2.

  Table 1.  Crystal data and structure parameters for compounds 1~4

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  Complex	1	2	3	4
  Empirical formula	C44H32N4O12SZn2	C92H72N8O27Zn4	C46H36N4O14Zn2	C48H44Cd2N4O15S2
  Formula weight	971.54	1 983.06	999.52	1 205.79
  Crystal system	Monoclinic	Monoclinic	Monoclinic	Triclinic
  Space group	P21/c	P2 /c	P21 /c	P1
  a / nm	1.004 50(4)	1.347 87(3)	1.358 17(5)	0.808 78(2)
  b/ nm	2.133 30(9)	1.101 06(2)	1.510 87(6)	1.186 59(3)
  c / nm	1.075 02(4)	2.011 82(3)	2.335 31(9)	1.404 32(4)
  α/(°)			71.917(2)
  β/(°)	111.749(2)	131.200(1)	104.802(2)	86.625 0(10)
  γ/(°)				82.307 0(10)
  V/nm3	2.139 68(15)	2.246 49(7)	4.633 1(3)	1.269 40(6)
  Z	2	1	4	1
  Dc/ (g·cm-3)	1.508	1.464	1.433	1.577
  μ/ mm-1	1.238	1.138	1.106	0.990
  F(000)	992	1 014	2 048	608
  θmin, θmax / (°)	1.91, 27.55	1.85, 27.54	1.55, 27.51	1.53, 27.62
  Reflections collected	34 136	18 261	71 272	19 824
  Unique reflections (Rint)	4 910 (0.055 2)	5 160 (0.049 8)	10 590 (0.09 60)	5 779 (0.034 2)
  Data with I>2σ(I)	4 910	5 160	5 411	4 292
  Parameters refined	307	299	594	334
  R, wR [I>2σ(I)]	0.041 3, 0.101 6	0.053 9, 0.149 8	0.062 8, 0.179 3	0.038 9, 0.120 1
  R, wR (all data)	0.066 7, 0.113 4	0.101 7, 0.1642	0.139 2, 0.219 6	0.046 9, 0.125 6
  Goodness-of-fit on F2	1.040	0.991	0.978	1.077
  (△ρ)max, (△ρ)min/ (e·nm-3)	404, -358	1 050, 279	892, -431	1 271, -512

  Table 1.  Crystal data and structure parameters for compounds 1~4
  Table 2.  Selected bond lengths (nm) and angles (°) for 1~4

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  Complex 1
  Zn (1)-O (5)	0.192 0(3)	Zn (1)-O (1)	0.193 52(19)	Zn (1)-N (1)#1	0.202 1(2)
  Zn (1)-N (2)#2	0.207 2(2)
  O (5)-Zn (1)-O (1)	110.76(11)	O (5)-Zn (1)-N (1)#1	117.54(12)	O (1)-Zn (1)-N (1)#1	115.97(10)
  O (5)-Zn (1)-N (2)#2	111.25(11)	O (1)-Zn (1)-N (2)#2	95.93(9)	N (1)#1-Zn (1)-N (2)#2	102.75(9)
  Complex 2
  Zn (1)-O (1)	0.192 9(3)	Zn (1)-O (6)	0.196 4(3)	Zn (1)-N (1) #1	0.205 5(3)
  Zn (1)-N (2)#2	0.206 9(3)	Zn (1)-O (7)	0.258 1(3)
  O (1)-Zn (1)-0(6)	133.61(13)	O (1)-Zn (1)-N (1)#1	98.21(13)	0(6)-Zn (1)-N (1)#1	111.56(13)
  O (1)-Zn (1)-N (2)#2	114.07(14)	O (6)-Zn (1)-N (2)#2	95.69(13)	N (1)#1-Zn (1)-N (2)#2	99.50(13)
  O (6)-Zn (1)-O (7)	54.88(11)	N (1)-Zn (1)-O (7)#1	89.17(13)	N (2)-Zn (1)-O (7)#2	150.25(12)
  Complex 3
  Zn (1)-O (1)	0.200 9(4)	Zn (1)-O (2)	0.252 1(4)	Zn (1)-O (11)	0.205 8(4)
  Zn (1)-N (1)#1	0.205 0(4)	Zn (1)-O (10)	0.240 4(5)	Zn (1)-N (2)#2	0.209 0(4)
  Zn (2)-O (13)	0.191 8(3)	Zn (2)-N (3)#1	0.202 7(4)	Zn (2)-O (6)	0.193 5(3)
  Zn (2)-N (4)#3	0.203 6(4)
  O (1)-Zn (1)-N (1)#1	96.36(17)	O (1)-Zn (1)-0(11)	134.58(16)	N (1)#1-Zn (1)-O (11)	117.26(16)
  O (1)-Zn (1)-N (2)#2	111.74(16)	N (1)#1-Zn (1)-N (2)#2	101.94(16)	O (11)-Zn (1)-N (2)#2	91.26(16)
  O (1)-Zn (1)-O (10)	94.00(15)	N (1)#1-Zn (1)-O (10)	92.46(15)	O (11)-Zn (1)-O (10)	57.30(14)
  N (2)#2-Zn (1)-O (10)	148.52(15)	O (13)-Zn (2)-O (6)	128.19(17)	O (13)-Zn (2)-N (3)#1	106.79(18)
  O (6)-Zn (2)-N (3)#1	99.00(17)	O (13)-Zn (2)-N (4)#3	97.81(16)	O (6)-Zn (2)-N (4)#3	116.47(16)
  N (3)#1-Zn (2)-N (4)#3	107.23(18)
  Complex 4
  Cd (1)-N (2)#1	0.225 4(3)	Cd (1)-O (2)	0.226 0(3)	Cd (1)-O (6)	0.229 3(3)
  Cd (1)-N (1)#2	0.232 4(3)	Cd (1)-O (1W)	0.238 5(3)	Cd (1)-O (1)	0.247 6(3)
  N (2)#1-Cd (1)-O (2)	150.06(11)	N (2)#1-Cd (1)-O (6)	99.20(12)	0(2)-Cd (1)-O (6)	86.53(11)
  N (2)#1-Cd (1)-N (1)#2	110.59(12)	O (2)-Cd (1)-N (1)#2	98.78(11)	O (6)-Cd (1)-N (1)#2	89.27(11)
  N (2)#1-Cd (1)-O (1W)	84.09(11)	O (2)-Cd (1)-O (1W)	92.60(10)	O (6)-Cd (1)-O (1W)	174.82(9)
  N (1)#2-Cd (1)-O (1W)	84.09(11)	N (2)#1-Cd (1)-O (1)	95.00(10)	O (2)-Cd (1)-O (1)	55.21(9)
  O (6)-Cd (1)-O (1)	92.92(10)	N (1)#2-Cd (1)-O (1)	153.64(11)	O (1W)-Cd (1)-O (1)	90.77(10)
  Symmetry codes: #1:-x+1, y+1/2, -z+3/2, #2 x-1, -y+1/2, z+1/2, #3-x+1, y-1/2, -z+3/2, #4 x+1, -y+1/2, z-1/2 for 1; #1 x-1, y, z, #2-x-1, y+1, -z-1/2 for 2; #1 x-1, y, z, #2 x, -y+1/2, z+1/2, #3 x, -y-3/2, z+1/2 for 3; #1 x-1, y+1, z, #2 x, y, z+1 for 4.

  Table 2.  Selected bond lengths (nm) and angles (°) for 1~4

  CCDC: 852424, 1; 872035, 2; 887738, 3; 872037, 4.

  2   Results and discussion

  Four new 3D metal (Ⅱ) CPs have been synthesized by hydrothermal reactions of d¹⁰ metal (Ⅱ) salts, 3, 5-bis (pyridin-4-ylmethoxy) benzoic acid (HL) and dicarbo-xylic acid ligands. In the process of synthesis of 3, a by-product 2 was co-precipitated unexpectedly, and there are some differences of the crystal shape and color between 2 and 3. However, the amount of 2 difficultly resynthesized was not enough to study its other properties.

  2.1   Structure of [Zn₂L₂(tdc)]_n (1)

  Single-crystal X-ray diffraction analysis shows that 1 crystallizes in monoclinic with P2₁/c space group. The asymmetric unit of 1 consists of one Zn (Ⅱ) ion, one L^- ligand and half tdc^2- ligand. As shown in Fig. 1a, each Zn (Ⅱ) ion is four-coordinated with a distorted tetrahedral geometry supplied by two carboxylate oxygen atoms from one L^- ligand and one tdc^2- ligand, two nitrogen atoms from two L^- ligands. As shown in Fig. 1b, the L^- ligand connects three Zn (Ⅱ) ions together by two pyridyl-N atoms and one carboxylate oxygen atom to generate a 2D bilayer structure, and then the tdc^2- ligands locate up and down the layer in exo-bidentate mode to form the final 3D network.

  Figure 1.  (a) Coordination environment of Zn (Ⅱ) in 1; (b) 3D coordination framework; (c) Schematic representation of the (3, 4)-connected framework; (d) Schematic representation of the 4-fold interpenetrating net

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  Figure Scheme1.  Reaction scheme for the preparations of 1~4

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  Topologically, each Zn (Ⅱ) ion is attached to three L^- ligands and one tdc^2- ligand, which can be considered as a 4-connected node; each L^- ligand connects three Zn (Ⅱ) ions and can be considered as a 3-connected node; while each tdc^2- ligand can be seen as a linear linker between two Zn (Ⅱ) ions. Therefore, the overall network can be described as a (3, 4)-connected dmc network with point symbol of (4.8²)(4.8⁵) (Fig. 1c). Because of the spacious nature of the single network, the potential voids are filled via mutual interpenetration of identical 3D frameworks, generating a 4-fold interpenetrating architecture (Fig. 1d).

  2.2   Structure of {[Zn₄L₄(Hhdc)₂]·H₂O}_n (2)

  Crystallographic analysis reveals that 2 crystall-izes in the monoclinic with space group P2/c. The asymmetric unit of 2 consists of one Zn (Ⅱ) ion, one L^- ligand, half Hhdc^2- ligand and a quarter of lattice H₂O molecule. As shown in Fig. 2a, each Zn (Ⅱ) ion is four-coordinated with a distorted tetrahedral geometry supplied by two pyridyl-N atoms from two L^- ligands, two carboxylic oxygen atoms from one L^- ligand and one Hhdc^2- ligand. It is worthy to note that the distance of Zn (1)…O (7) is 0.258 1(3) nm, which is a nonnegligible week interaction, and the Zn (Ⅱ) ion can be considered as a five coordinated, disorted square pyramidal geometry. As shown in Fig. 2b, the L^- ligand connects three Zn (Ⅱ) ions together by two pyridyl-N atoms and one carboxylate oxygen atom to generate a 2D layer structure, and then the Hhdc^2- ligands locate up and down the layer in exo-bidentate mode to form the final 3D network.

  Figure 2.  (a) Coordination environment of Zn (Ⅱ) in 2; (b) 3D coordination framework; (c) Schematic representation of the (3, 4)-connected framework; (d) Schematic representation of the 4-fold interpenetrating net

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  Each Zn (Ⅱ) ion is attached to three L^- ligands and one Hhdc^2- ligand to represent a 4-connected node; each L^- ligand presents a 3-connected node; and each Hhdc^2- ligand can be seen as a linear linker between two Zn (Ⅱ) ions. 2 possesses a 3D (3, 4)-connected fsc net with point symbol of (6³)(6⁵.8) topo-logy (Fig. 2c). The identical 3D frameworks interlock each other, generating a 4-fold interpenetrating archi-tecture (Fig. 2d).

  2.3   Structure of {[Zn₂L₂(Hhdc)]·H₂O}_n (3)

  Crystallographic analysis reveals that 3 crystall-izes in the monoclinic with space group P2₁/c. The asymmetric unit of 3 consists of two Zn (Ⅱ) ions, two L^- ligands, one Hhdc^2- ligand and one lattice H₂O molecule. As shown in Fig. 3a, Zn (1) is connected by four carboxylic oxygen atoms from one L^- ligand and one Hhdc^2- ligand, two pyridyl-N atoms from two L^- ligands in a disorted octahedral geometry, and Zn (2) is connected by two carboxylic oxygen atoms from one L^- ligand and one Hhdc^2- ligand, two pyridyl-N atoms from two L^- ligands in a distorted tetrahedral coordina-tion geometry. As shown in Fig. 3b, the L^- ligands connect three Zn (Ⅱ) ions together to generate a 2D layer structure, and then the Hhdc^2- ligands locate up and down the layers in exo-bidentate mode to form the final 3D network.

  Figure 3.  (a) Coordination environment of Zn (Ⅱ) in 3; (b) 3D coordination framework; (c) Schematic representation of the (3, 4)-connected framework; (d) Schematic representation of the 4-fold interpenetrating net

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  Each Zn (Ⅱ) ion is attached to three L^- ligands and one Hhdc^2- ligand to represent a 4-connected node; each L^- ligand presents a 3-connected node; and each Hhdc^2- ligand can be seen as a linear linker between two Zn (Ⅱ) ions. 3 possesses a 3D (3, 4)-connected fsc net with the (6³)(6⁵.8) topology and a 4-fold interpenetrating architecture.

  2.4   Structure of {[Cd₂L₂(bdtc)(H₂O)]·0.5H₂O}_n (4)

  Crystallographic analysis reveals that 4 crysta-llizes in the triclinic space group P1. The asymmetric unit of 4 consists of one Cd (Ⅱ) ion, one L^- ligand, half bdtc^2- ligand, half coordinated water molecule and quarter lattice water molecule. As shown in Fig. 4a, each Cd (Ⅱ) ion is six-coordinated with a distorted octahedral geometry supplied by two pyridyl-N atoms from two L^- ligands, three carboxylic oxygen atoms from one L^- ligand and one bdtc^2- ligand, and one water molecule. As shown in Fig. 4b, the L^- ligand connects three Cd (Ⅱ) ions together by two pyridyl-N atoms and two carboxylate oxygen atoms, the bdtc^2- ligand connect two Cd (Ⅱ) ions together by two carboxylate oxygen atoms to generate a 2D (3, 4)-conn-ected layer structure.

  Figure 4.  (a) Local coordination environment of Cd (Ⅱ) in 4; (b) Wires or sticks representation of the 2D layer; (c) Schematic representation of the 3-fold interpenetrating net

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  The topology analysis suggests the (3, 4)-connected net with the (6³)(6⁶) topology, and each 2D layer is filled via mutual interpenetration to generate a 3-fold interpenetrating architecture (Fig. 4c). Simultan-eously, the adjacent layers are linked each other by hydrogen bonds (O (1W)-H (1WB)…O (5)#3 0.276 1(5) nm, O (3W)-H (1WA)…O5#4 0.276 8(13) nm; Symmetry codes: #3: x+1, y, z, 4#:-x, 1-y, 2-z) to complete the finally 3D supramolecular network.

  2.5   PXRD analysis and thermal property

  Powder X-ray diffraction (PXRD) analysis of 1, 3, 4 has been performed at room temperature. The PXRD patterns are in reasonably good agreement with the calculated ones (Fig. 5), confirming the phase purity of the as-synthesized products.

  Figure 5.  Simulated (a) and experimental (b) PXRD patterns of complexes 1, 3 and 4

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  Thermogravimetric analyses (TGA) were carried out under air atmosphere to examine the thermal stability of complexes 1, 3 and 4 and the results are shown in Fig. 6. The TGA curve of 1 shows the framework collapsed at the temperature range of 305~510 ℃. For 3, the first weight loss of 1.88 % occurred in the temperature range of 70~120 ℃, due to the release of coordinated water molecules (Calcd. 1.80%), and the decomposition of the residue occurs at the range of 320~510 ℃. The TGA curve of 4 shows the first weight loss of 2.51% occurred in the temperature range of 100~145 ℃, due to the release of water molecules (Calcd. 2.24%), and the decomposition of the residue occurs at the range of 275~330 ℃, which may be caused by the complete decomposition of bdtc in 4 (Obsd. 19.87%, Calcd. 19.24%). A rapid weight loss can be detected from 500~600 ℃, which may be attributed to the complete decomposition of the organic ligands.

  Figure 6.  TG curves of complexes 1, 3 and 4

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  2.6   Photoluminescent properties

  Taking the excellent luminescent properties of Zn (Ⅱ) and Cd (Ⅱ) into account, the solid-state lumin-escent spectra of HL, complexes 1, 3 and 4 have been studied at room temperature (Fig. 7). 1 shows broad fluorescent emission spectra from 450 to 600 nm and the emission maxima at 504 nm (λ_ex=300 nm). 3 shows broad fluorescent emission spectra from 400 to 600 nm and the emission maxima at 450 nm (λex=360 nm), while 4 presents broad fluorescent emission spectra from 400 to 550 nm and the emission maxima at 452 nm (λ_ex=362 nm). In order to understand the nature of the emission, we analyzed the photolumin-escence property of free HL ligand and found that the strongest emission peak at 474 nm (λ^ex=363 nm). In comparison with that of HL, the maximum emission wavelengths of 1 occurs slightly redshifted, 3 and 4 occur slightly blueshifted, which are probably due to L-and auxiliary ligands to metal charge transitions. The enhancement of the intensity of luminescence in the CPs may be attributed to the rigidity of them. The complex enhances the "rigidity" of the ligand and thus reduces the loss of energy through a radiationless pathway^[12].

  Figure 7.  Solid-state luminescent spectra of HL, complexes 1, 3 and 4 at room temperature

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  3   Conclusions

  In summary, complexes 1~4 display four-and three-fold interpenetrated (3, 4)-connected coordination polymers. The interpenetration effectively reduced the solvent voids, in which clathrate water molecules reside. The results show that the flexible ligand can take different modes to meet the coordination nature of the metal cations, and the ligands, the metal center, and the reaction conditions have great influence on the structure of the final assembly. The long-flexible ligand with rigid spacers is much more conducive to form interpenetrated framework. The complexes with spacious voids in their frameworks favour interpenetrated crystal forms. The luminescent spectra show that 1, 3 and 4 have different luminescent properties, both the auxiliary ligands and metal centers will influence the intensity and shift of luminescence.

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  Figure 1  (a) Coordination environment of Zn (Ⅱ) in 1; (b) 3D coordination framework; (c) Schematic representation of the (3, 4)-connected framework; (d) Schematic representation of the 4-fold interpenetrating net

  Thermal ellipsoids are shown at the 50% probability level in (a); Symmetry codes: #1:-x+1, y+1/2, -z+3/2, #2: x-1, -y+1/2, z+1/2

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  Scheme1  Reaction scheme for the preparations of 1~4

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  Figure 2  (a) Coordination environment of Zn (Ⅱ) in 2; (b) 3D coordination framework; (c) Schematic representation of the (3, 4)-connected framework; (d) Schematic representation of the 4-fold interpenetrating net

  Thermal ellipsoids are shown at the 50% probability level in (a); Symmetry codes: #1: x-1, y, z; #2:-x+1/2, y+1, -z-1/2

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  Figure 3  (a) Coordination environment of Zn (Ⅱ) in 3; (b) 3D coordination framework; (c) Schematic representation of the (3, 4)-connected framework; (d) Schematic representation of the 4-fold interpenetrating net

  Thermal ellipsoids are shown at the 50% probability level in (a); Symmetry codes: #1: x-1, y, z; #2: x, -y+1/2, z+1/2; #3: x, -y-3/2, z+1/2

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  Figure 4  (a) Local coordination environment of Cd (Ⅱ) in 4; (b) Wires or sticks representation of the 2D layer; (c) Schematic representation of the 3-fold interpenetrating net

  Thermal ellipsoids are shown at the 50% probability level in (a); Symmetry codes: #1: x-1, y+1, z; #2: x, y, z+1

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  Figure 5  Simulated (a) and experimental (b) PXRD patterns of complexes 1, 3 and 4

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  Figure 6  TG curves of complexes 1, 3 and 4

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  Figure 7  Solid-state luminescent spectra of HL, complexes 1, 3 and 4 at room temperature

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  Table 1.  Crystal data and structure parameters for compounds 1~4

  Complex	1	2	3	4
  Empirical formula	C44H32N4O12SZn2	C92H72N8O27Zn4	C46H36N4O14Zn2	C48H44Cd2N4O15S2
  Formula weight	971.54	1 983.06	999.52	1 205.79
  Crystal system	Monoclinic	Monoclinic	Monoclinic	Triclinic
  Space group	P21/c	P2 /c	P21 /c	P1
  a / nm	1.004 50(4)	1.347 87(3)	1.358 17(5)	0.808 78(2)
  b/ nm	2.133 30(9)	1.101 06(2)	1.510 87(6)	1.186 59(3)
  c / nm	1.075 02(4)	2.011 82(3)	2.335 31(9)	1.404 32(4)
  α/(°)			71.917(2)
  β/(°)	111.749(2)	131.200(1)	104.802(2)	86.625 0(10)
  γ/(°)				82.307 0(10)
  V/nm3	2.139 68(15)	2.246 49(7)	4.633 1(3)	1.269 40(6)
  Z	2	1	4	1
  Dc/ (g·cm-3)	1.508	1.464	1.433	1.577
  μ/ mm-1	1.238	1.138	1.106	0.990
  F(000)	992	1 014	2 048	608
  θmin, θmax / (°)	1.91, 27.55	1.85, 27.54	1.55, 27.51	1.53, 27.62
  Reflections collected	34 136	18 261	71 272	19 824
  Unique reflections (Rint)	4 910 (0.055 2)	5 160 (0.049 8)	10 590 (0.09 60)	5 779 (0.034 2)
  Data with I>2σ(I)	4 910	5 160	5 411	4 292
  Parameters refined	307	299	594	334
  R, wR [I>2σ(I)]	0.041 3, 0.101 6	0.053 9, 0.149 8	0.062 8, 0.179 3	0.038 9, 0.120 1
  R, wR (all data)	0.066 7, 0.113 4	0.101 7, 0.1642	0.139 2, 0.219 6	0.046 9, 0.125 6
  Goodness-of-fit on F2	1.040	0.991	0.978	1.077
  (△ρ)max, (△ρ)min/ (e·nm-3)	404, -358	1 050, 279	892, -431	1 271, -512

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  Table 2.  Selected bond lengths (nm) and angles (°) for 1~4

  Complex 1
  Zn (1)-O (5)	0.192 0(3)	Zn (1)-O (1)	0.193 52(19)	Zn (1)-N (1)#1	0.202 1(2)
  Zn (1)-N (2)#2	0.207 2(2)
  O (5)-Zn (1)-O (1)	110.76(11)	O (5)-Zn (1)-N (1)#1	117.54(12)	O (1)-Zn (1)-N (1)#1	115.97(10)
  O (5)-Zn (1)-N (2)#2	111.25(11)	O (1)-Zn (1)-N (2)#2	95.93(9)	N (1)#1-Zn (1)-N (2)#2	102.75(9)
  Complex 2
  Zn (1)-O (1)	0.192 9(3)	Zn (1)-O (6)	0.196 4(3)	Zn (1)-N (1) #1	0.205 5(3)
  Zn (1)-N (2)#2	0.206 9(3)	Zn (1)-O (7)	0.258 1(3)
  O (1)-Zn (1)-0(6)	133.61(13)	O (1)-Zn (1)-N (1)#1	98.21(13)	0(6)-Zn (1)-N (1)#1	111.56(13)
  O (1)-Zn (1)-N (2)#2	114.07(14)	O (6)-Zn (1)-N (2)#2	95.69(13)	N (1)#1-Zn (1)-N (2)#2	99.50(13)
  O (6)-Zn (1)-O (7)	54.88(11)	N (1)-Zn (1)-O (7)#1	89.17(13)	N (2)-Zn (1)-O (7)#2	150.25(12)
  Complex 3
  Zn (1)-O (1)	0.200 9(4)	Zn (1)-O (2)	0.252 1(4)	Zn (1)-O (11)	0.205 8(4)
  Zn (1)-N (1)#1	0.205 0(4)	Zn (1)-O (10)	0.240 4(5)	Zn (1)-N (2)#2	0.209 0(4)
  Zn (2)-O (13)	0.191 8(3)	Zn (2)-N (3)#1	0.202 7(4)	Zn (2)-O (6)	0.193 5(3)
  Zn (2)-N (4)#3	0.203 6(4)
  O (1)-Zn (1)-N (1)#1	96.36(17)	O (1)-Zn (1)-0(11)	134.58(16)	N (1)#1-Zn (1)-O (11)	117.26(16)
  O (1)-Zn (1)-N (2)#2	111.74(16)	N (1)#1-Zn (1)-N (2)#2	101.94(16)	O (11)-Zn (1)-N (2)#2	91.26(16)
  O (1)-Zn (1)-O (10)	94.00(15)	N (1)#1-Zn (1)-O (10)	92.46(15)	O (11)-Zn (1)-O (10)	57.30(14)
  N (2)#2-Zn (1)-O (10)	148.52(15)	O (13)-Zn (2)-O (6)	128.19(17)	O (13)-Zn (2)-N (3)#1	106.79(18)
  O (6)-Zn (2)-N (3)#1	99.00(17)	O (13)-Zn (2)-N (4)#3	97.81(16)	O (6)-Zn (2)-N (4)#3	116.47(16)
  N (3)#1-Zn (2)-N (4)#3	107.23(18)
  Complex 4
  Cd (1)-N (2)#1	0.225 4(3)	Cd (1)-O (2)	0.226 0(3)	Cd (1)-O (6)	0.229 3(3)
  Cd (1)-N (1)#2	0.232 4(3)	Cd (1)-O (1W)	0.238 5(3)	Cd (1)-O (1)	0.247 6(3)
  N (2)#1-Cd (1)-O (2)	150.06(11)	N (2)#1-Cd (1)-O (6)	99.20(12)	0(2)-Cd (1)-O (6)	86.53(11)
  N (2)#1-Cd (1)-N (1)#2	110.59(12)	O (2)-Cd (1)-N (1)#2	98.78(11)	O (6)-Cd (1)-N (1)#2	89.27(11)
  N (2)#1-Cd (1)-O (1W)	84.09(11)	O (2)-Cd (1)-O (1W)	92.60(10)	O (6)-Cd (1)-O (1W)	174.82(9)
  N (1)#2-Cd (1)-O (1W)	84.09(11)	N (2)#1-Cd (1)-O (1)	95.00(10)	O (2)-Cd (1)-O (1)	55.21(9)
  O (6)-Cd (1)-O (1)	92.92(10)	N (1)#2-Cd (1)-O (1)	153.64(11)	O (1W)-Cd (1)-O (1)	90.77(10)
  Symmetry codes: #1:-x+1, y+1/2, -z+3/2, #2 x-1, -y+1/2, z+1/2, #3-x+1, y-1/2, -z+3/2, #4 x+1, -y+1/2, z-1/2 for 1; #1 x-1, y, z, #2-x-1, y+1, -z-1/2 for 2; #1 x-1, y, z, #2 x, -y+1/2, z+1/2, #3 x, -y-3/2, z+1/2 for 3; #1 x-1, y+1, z, #2 x, y, z+1 for 4.

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