English

• Introduction

  The design and construction of the coordination polymers has attracted great attention for their potential applications, architectures, and topologies^[1-8]. Many factors such as the coordination geometry of the central atom, the structural characteristics of the ligand, the solvent system, and the counterions can play the key role in the construction of the coordination networks^[9-12]. The selection of the special ligands is very important in the construction of these coordination polymers.

  A lot of aromatic polycarboxylic acids has been extensively applied as multifunctional building blocks in the construction of metal-organic networks because of their abundant coordination modes to metal ions, allowing different type of structural topologies and because of their ability to act as H-bond acceptors and donors, depending on the number of deprotonated carboxylic groups to assemble supramolecular structures^[13-16]. Among them, semi-rigid V-shaped ligands enable the formation of uncommon frameworks or even novel topologies and interesting properties because of their flexibility and conformational diversity^[17-20].

  In order to extend our research in this field, we chose a new semi-rigid polycarboxylate ligand, 2-(2-carboxyphenoxy)terephthalic acid (H₃cpta) to construct novel coordination polymers. The H₃cpta ligand possesses the following features: (1) two rigid benzene rings of H₃cpta ligand are connected by a rotatable -O-group, which allows the ligand with subtle conformational adaptation; (2) seven potential coordination sites (six carboxylate O and one ether O) of H₃cpta ligand, which can provide more varied coordination patterns in the construction of fascinating coordination frameworks, especially with high dimensionalities. However, the metal-organic networks constructed from the H₃cpta ligand have not been reported.

  Taking into account these factors, we herein report the syntheses, crystal structures, and magnetic properties of two Co(Ⅱ) coordination polymers constructed from H₃cpta.

  1   Experimental

  1.1   Reagents and physical measurements

  All chemicals and solvents were of AR grade and used without further purification. The content of carbon, hydrogen and nitrogen were determined using an Elementar Vario EL elemental analyzer. IR spectra were recorded using KBr pellets and a Bruker EQUINOX 55 spectrometer. Thermogravimetric analysis (TGA) data were collected on a LINSEIS STA PT1600 thermal analyzer with a heating rate of 10 ℃·min^-1. Powder X-ray diffraction patterns (PXRD) were determined with a Rigaku-Dmax 2400 diffractometer using Cu Kα radiation (λ=0.154 060 nm) and 2θ ranging from 5° to 45°, in which the X-ray tube was operated at 40 kV and 40 mA. Magnetic susceptibility data were collected in the 2~300 K temperature range with a Quantum Design SQUID Magnetometer MPMS XL-7 with a field of 0.1 T. A correction was made for the diamagnetic contribution prior to data analysis.

  1.2   Synthesis of [Co(μ₂-Hcpta)(phen)(H₂O)]_n (1)

  A mixture of CoCl₂·6H₂O (0.071 g, 0.30 mmol), H₃cpta (0.060 g, 0.2 mmol), phen (0.060 g, 0.3 mmol), NaOH (0.016 g, 0.40 mmol), and H₂O (10 mL) was stirred at room temperature for 15 min, and then sealed in a 25 mL Teflon-lined stainless steel vessel, and heated at 160 ℃ for 3 days, followed by cooling to room temperature at a rate of 10 ℃·h^-1. Orange block-shaped crystals of 1 were isolated manually, and washed with distilled water. Yield: 63 % (based on H₃cpta). Anal. Calcd. for C₂₇H₁₈CoN₂O₈ (%): C 58.18, H 3.26, N 5.03; Found(%): C 58.46, H 3.24, N 5.01. IR (KBr, cm^-1): 3 438w, 3 050w, 1 702w, 1 625m, 1 594s, 1 559s, 1 528w, 1 493w, 1 452w, 1 400s, 1 355s, 1 299w, 1 243w, 1 151w, 1 100w, 1 048w, 956w, 850m, 809w, 787w, 762w, 727m, 691w, 665w, 640w, 594w, 537w.

  1.3   Synthesis of [Co₃(μ₅-cpta)₂(2, 2′-bipy)₂]_n (2)

  The preparation of 2 was similar to that of 1 except 2, 2′-bipy (0.047 g, 0.30 mmol) was used instead of phen and different amount of NaOH (0.024 g, 0.60 mmol) was used. Pink block-shaped crystals of 2 were isolated manually, washed with distilled water. Yield: 55% (based on H₃cpta). Anal. Calcd. for C₅₀H₃₀Co₃N₄O₁₄: C 55.22, H 2.78, N 5.15; Found(%): C 55.02, H 2.81, N 5.11. IR (KBr, cm^-1): 1 590s, 1 554m, 1 529w, 1 477w, 1 452m, 1 396s, 1 345s, 1 237m, 1 156w, 1 094w, 1 059w, 1 018w, 956w, 879w, 870w, 834w, 798m, 767s, 737w, 706w, 661w, 589w, 537m. The compounds are insoluble in water and common organic solvents, such as methanol, ethanol, acetone and DMF.

  1.4   Structure determinations

  The data of two single crystals with dimensions of 0.26 mm×0.24 mm×0.21 mm for 1 and 0.27 mm×0.22 mm×0.21 mm for 2, respectively, were collected at 293(2) K on a Bruker SMART APEX Ⅱ CCD diffrac-tometer with Mo Kα radiation (λ=0.071 073 nm). The structures were solved by direct methods and refined by full matrix least-square on F² using the SHELXTL-97 program^[21]. All non-hydrogen atoms were refined anisotropically. All the hydrogen atoms were positioned geometrically and refined using a riding model. A summary of the crystallography data and structure refinements for 1 and 2 is given in Table 1. The selected bond lengths and angles for compounds 1 and 2 are listed in Table 2. Hydrogen bond parameters of compound 1 are given in Table 3.

  Table 1.  Crystal data for compounds 1 and 2

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  Compound	1	2
  Chemical formula	C27H18Co3N208	C50H30Co3N4O14
  Molecular weight	557.36	1 087.57
  Crystal system	Monoclinic	Monoclinic
  Space group	P21/c	P21/c
  a / nm	1.043 61(5)	1.199 75(6)
  b / nm	0.792 95(4)	1.494 46(4)
  c / nm	2.789 04(14)	1.306 61(7)
  β/(°)	94.042(5)	115.402(6)
  V/ nm3	2.302 3(2)	2.116 2 (2)
  Z	4	2
  F(000)	1140	1 102
  θ range for data collection / (°)	3.28~25.05	3.34-25.04
  Limiting indices	-11≤h≤12, -9≤k≤9, -19≤1≤33	-12≤h≤14, -17≤k≤17, -15≤l≤10
  Reflections collected, unique (Rint)	8 222, 4 088 (0.056 3)	7 382, 3 733 (0.041 3)
  Dc(g·cm3)	1.608	1.707
  μ/ mm-1	0.805	1.243
  Data, restraints, parameters	4 088, 0, 345	3 733, 0, 322
  Goodness-of-fit on F2	1.080	1.038
  Final R indices[I≥2σ(I)] R1, wR2	0.050 1, 0.070 9	0.043 7, 0.073 9
  R indices (all data) R1, wR2	0.088 1, 0.086 2	0.064 4, 0.083 0
  Largest diff. peak and hole / (e·nm-3)	460 and -435	327 and -319

  Table 2.  Selected bond distances (nm) and bond angles (°) for compounds 1 and 2

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  1
  Co(1)-O(1)	0.212 7(3)	Co(1)-O(2) A	0.210 1(2)	Co(1)-O(6) A	0.209 3(2)
  Co(1)-O(8)	0.203 8(2)	Co(1)-N(1)	0.218 7(3)	Co(1)-N(2)	0.214 8(3)
  O(8)-Co(1)-O(6) A	89.09(10)	O(8)-Co(1)-O(2) A	175.40(10)	O(6) A-Co(1)-O(2) A	87.40(10)
  O(8)-Co(1)-O(1)	93.85(10)	O(6) A-Co(1)-O(1)	95.90(9)	O(2) A-Co(1)-O(1)	83.56(10)
  O(8)-Co(1)-N(2)	93.05(11)	O(6) A1-Co(1)-N(2)	169.13(11)	O(2) A-Co(1)-N(2)	90.95(10)
  O(1)-Co(1)-N(2)	94.59(11)	O(8)-Co(1)-N(1)	84.85(11)	O(6) A-Co(1)-N(1)	92.39(11)
  O(2) A-Co(1)-N(1)	98.26(11)	O(1)-Co(1)-N(1)	171.59(10)	N(2)-Co(1)-N(1)	77.21(12)
  2
  Co(1)-O(1)	0.223 9(2)	Co(1)-O(2)	0.210 9(2)	Co(1)-O(4) B	0.210 6(2)
  Co(1)-O(7) A	0.201 7(2)	Co(1)-N(1)	0.214 5(3)	Co(1)-N(2)	0.210 6(3)
  Co(2)-O(1)	0.215 0(2)	Co(2)-O(1) B	0.215 0(2)	Co(2)-O(4)	0.213 0(2)
  Co(2)-O(4) B	0.213 0(2)	Co(2)-O(6) A	0.209 4(2)	Co(2)-O(6) C	0.209 4(2)
  O(7) A-Co(1)-N(2)	91.74(10)	O(7) A-Co(1)-O(4) B	88.19(9)	N(2)-Co(1)-O(4) B	113.48(10)
  O(7) A-Co(1)-O(2)	154.32(11)	N(2)-Co(1)-O(2)	109.33(10)	O(4) B-Co(1)-O(2)	96.27(9)
  O(7) A-Co(1)-N(1)	80.95(10)	N(2)-Co(1)-N(1)	76.87(11)	O(4) B-Co(1)-N(1)	165.36(10)
  O(2)-Co(1)-N(1)	89.49(10)	O(7) A-Co(1)-O(1)	96.02(9)	N(2)-Co(1)-O(1)	166.52(10)
  O(4) B-Co(1)-O(1)	77.86(8)	O(2)-Co(1)-O(1)	60.61(9)	N(1)-Co(1)-O(1)	93.45(10)
  O(6) A-Co(2)-O(4)	92.21(8)	O(6) C-Co(2)-O(4)	87.79(8)	O(6) A-Co(2)-O(1)	91.99(8)
  O(6) C-Co(2)-O(1)	88.01(8)	O(4)-Co(2)-O(1)	100.67(8)	O(4) B-Co(2)-O(1)	79.33(8)
  Co(2)-O(1)-Co(1)	94.45(9)	Co(1) B-O(4)-Co(2)	99.06(9)
  Symmetry transformations used to generate equivalent atoms: A: -x+1, y-1/2, -z+1/2 for 1; A: x, -y+1/2, z-1/2; B: -x+1, -y+1, -z+1; C: -x+1, y+1/2, -z+3/2 for 2

  Table 3.  Hydrogen bond lengths (nm) and angles (°) of compound 1

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  D-H…A	d(D-H) / nm	d(H…A) / nm	d(D…A) / nm	∠DHA/(°)
  O(4)-H(4)…O(7) A	0.082	0.184	0.264 3	164.2
  O(8)-H(1W)…O(1) B	0.082	0.204	0.277 2	148.3
  O(8)-H(2W)…O(7) C	0.086	0.198	0.275 9	151.9
  Symmetry code: A: -x+1, -y+1, -z; B: -x+1, y+1/2, -z+1/2; C: -x+1, y-1/2, -z+1/2

  CCDC: 1507502, 1; 1507503, 2.

  2   Results and discussion

  2.1   Description of the structure

  2.1.1   [Co(μ₂-Hcpta)(phen)(H₂O)]_n (1)

  The X-ray crystallography analyses reveal that compound 1 has a 1D chain structure. Its asymmetric unit contains one crystallographically unique Co(Ⅱ) atom, one μ₂-Hcpta^2- block, one phen moiety, and one coordination water molecule. As depicted in Fig. 1, the six-coordinated Co1 atom displays a distorted octahedral {CoN₂O₄} geometry filled by four O atoms from two different μ₂-Hcpta^2- blocks and one coor-dinated water molecule and two N atoms from one phen ligand. The lengths of the Co-O bonds range from 0.203 8(2) to 0.212 7(3) nm, whereas the Co-N distances vary from 0.214 8(3) to 0.218 7(3) nm; these bonding parameters are comparable to those found in other reported Co(Ⅱ) compounds^{[10, 22-24]}. In 1, the Hcpta^2- ligand acts as a μ₂-linker (Scheme 1, modeⅠ), in which two deprotonated carboxylate groups show the η¹:η⁰ monodentate and η¹:η¹ bidentate modes, respectively. The dihedral angle between two phenyl rings in the Hcpta^2- is 81.03°. The angle of C-O_etheric-C is 119.16°. The carboxylate groups of Hcpta^2- ligands bridge alternately neighboring Co(Ⅱ) atoms in a syn-anti coordination fashion to form a 1D chain with the Co…Co separation of 0.505 5(3) nm (Fig. 2). The present structure shows 1D zigzag metal organic chain wherein the 2-connected Co1 nodes are interconnected by the μ₂-Hcpta^2- linkers (Fig. 3). These chains can be topologically classified as a uninodal 2-connected net with the 2C1 topology. The adjacent chains are connected together by O-H…O hydrogen bonds (Table 3), forming a 2D supramolecular sheet (Fig. 4).

  图Scheme1 Coordination modes of Hcpta^2-/cpta^3- ligands in compounds 1 and 2 Scheme1. Coordination modes of Hcpta^2-/cpta^3- ligands in compounds 1 and 2

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  图1 Drawing of the asymmetric unit of compound 1 with 30% probability thermal ellipsoids Figure1. Drawing of the asymmetric unit of compound 1 with 30% probability thermal ellipsoids

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  图2 View of a 1D metal-organic chain parallel to the bc plane Figure2. View of a 1D metal-organic chain parallel to the bc plane

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  图3 Topological representation of a 1D metal-organic zigzag chain in 1 displaying a uninodal 2-connected underlying net with the 2C1 topology Figure3. Topological representation of a 1D metal-organic zigzag chain in 1 displaying a uninodal 2-connected underlying net with the 2C1 topology

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  图4 Perspective of a 2D supramolecular network along the bc plane in 1 Figure4. Perspective of a 2D supramolecular network along the bc plane in 1

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  2.1.2   [Co₃(μ₅-cpta)₂(2, 2′-bipy)₂]_n (2)

  The asymmetric unit of 2 consists of two crystallographically distinct Co(Ⅱ) atoms (Co1 with full occupancy; Co2 is located on a 2-fold rotation axis), one μ₅-cpta^3- block, and one 2, 2′-bipy ligand. As shown in Fig. 5, the Co1 atom is six-coordinated and adopts a distorted octahedral {CoN₂O₄} geometry completed by four carboxylate O from three distinct μ₅-cpta^3- blocks and two N atoms from one 2, 2′-bipy ligand. The six-coordinated Co2 center is located on a 2-fold rotation axis and is surrounded by six O atoms from six different cpta^3- blocks, thus adopting a distorted octahedral {CoO₆} geometry. The Co-O distances range from 0.201 7(2) to 0.223 9(2) nm, whereas the Co-N distances vary from 0.210 6(3) to 0.214 5(3) nm; these bonding parameters are compa-rable to those observed in other Co(Ⅱ) compounds^{[10, 22-24]}. In 2, the cpta^3- block acts as a μ₅-spacer (Scheme 1, modeⅡ), in which the carboxylate groups exhibit the μ₂-η¹:η¹ and μ₂-η⁰:η² bidentate and μ₂-η¹:η² tridentate modes. In the cpta^3-, the dihedral angle between the two phenyl rings is 87.37°. The angle C-O_etheric-C is 119.73°. Three adjacent Co(Ⅱ) ions are bridged by means of six carboxylate groups from the four different cpta^3- blocks, giving rise to a centrosymmetric tricobalt(Ⅱ) subunit (Fig. 6). In this Co₃ unit, the Co…Co distance of 0.322 3(3) nm is close to those reported for other carboxylate-bridged trinuclear Co(Ⅱ) comp-ounds^[25-27]. The adjacent Co₃ subunits are further interlinked by the cpta^3- blocks into a 2D metal-organic network (Fig. 7). It has the shortest distance of 1.107 0(3) nm between the neighboring tricobalt(Ⅱ) subunits. This structure features an intricate 2D metal-organic layer, which from the topological point of view, is assembled from the 3-connected Co1 and 4-connected Co2 nodes, as well as the 5-connected μ₅-cpta^3- nodes (Fig. 8). Its topological analysis discloses a trinodal 3, 4, 5-connected underlying net with a very rare 3, 4, 5L45 topology and point symbol of (4³)₂(4⁴.8⁶)₂(4⁵.6). The (4³), (4⁴.8⁶), and (4⁵.6) notations correspond to the Co1, μ₅-cpta^3-, and Co2 nodes, respectively.

  图5 Drawing of the asymmetric unit of compound 2 with 30% probability thermal ellipsoids Figure5. Drawing of the asymmetric unit of compound 2 with 30% probability thermal ellipsoids

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  图6 Tricobalt(Ⅱ) subunit in compound 2 Figure6. Tricobalt(Ⅱ) subunit in compound 2

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  图7 2D metal-organic framework along the a axis in compound 2 Figure7. 2D metal-organic framework along the a axis in compound 2

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  图8 Topological representation of a 2D metal-organic network in 2 displaying a trinodal 3, 4, 5-connected underlying layer with the 3, 4, 5L45 topology and point symbol of (4³)₂(4⁴.8⁶) 2(4⁵.6) Figure8. Topological representation of a 2D metal-organic network in 2 displaying a trinodal 3, 4, 5-connected underlying layer with the 3, 4, 5L45 topology and point symbol of (4³)₂(4⁴.8⁶) 2(4⁵.6)

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  2.2   TGA analysis and PXRD results

  To determine the thermal stability of compounds 1 and 2, their thermal behaviors were investigated under nitrogen atmosphere by thermogravimetric analysis (TGA). As shown in Fig. 9, the TGA curve of 1 reveals that one coordinated aqua ligand is released between 148~210 ℃ (Obsd. 3.5%; Calcd. 3.2%), and the dehydrated solid begins to decompose at 308 ℃. The TGA curve of 2 indicates that the compound is stable up to 367 ℃, and then decompose upon further heating. The patterns for the as-synthesized bulk material closely match the simulated ones from the single-crystal structure analysis, which is indicative of the pure solid-state phase (Fig. 10 and 11).

  图9 TGA curves of compounds 1 and 2 Figure9. TGA curves of compounds 1 and 2

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  图10 PXRD patterns of compound 1 at room temperature Figure10. PXRD patterns of compound 1 at room temperature

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  图11 PXRD patterns of compound 2 at room temperature Figure11. PXRD patterns of compound 2 at room temperature

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  2.3   Magnetic properties

  Variable-temperature magnetic susceptibility studies were carried out on powder samples of compounds 1 and 2 in the 2~300 K temperature range. For 1, as shown in Fig. 12, the room temperature values of χ_MT(3.21 cm³·mol^-1·K) is larger than the value (1.83 cm³·mol^-1·K) expected for one magnetically isolated high-spin Co(Ⅱ) ions (S=3/2, g=2.0). This is a common phenomenon for Co(Ⅱ) ions due to their strong spin-orbital coupling interactions^{[10, 22-24]}. When the temperature is lowered, the χ_MT values decrease slowly until about 116 K, then decrease quickly to 1.23 cm³·mol^-1·K at 2.0 K. Between 88 and 300 K, the magnetic susceptibilities can be fitted to the Curie-Weiss law with C=3.55 cm³·mol^-1·K and θ=-28.4 K. These results indicate an antiferromagnetic interaction between the adjacent Co(Ⅱ) centers in compound 1. We tried to fit the magnetic data of 1 using the following expression for a 1D Co(Ⅱ) chain^[28]:

  图12 Temperature dependence of χ_MT (О) and 1/χM(□) vs T for compound 1 Figure12. Temperature dependence of χ_MT (О) and 1/χM(□) vs T for compound 1

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  Using this rough model, the susceptibilities above 65 K were simulated, leading to J=-9.87 cm^-1, g=2.43. The negative J parameters indicate that an weak antiferromagnetic exchange coupling exists between the adjacent Co(Ⅱ) centers in 1, which is agreement with negative θ value. According to the structure of 1, there is one magnetic exchange pathway within the chain through one syn-anti carboxylate bridges, which could be responsible for the observed antiferromagnetic exchange.

  For the cobalt(Ⅱ) network 2, as shown in Fig. 13, the χ_MT value at room temperature of 8.85 cm³·mol^-1·K, is much larger than the value (5.61 cm³·mol^-1·K) expected for three magnetically isolated high-spin Co(Ⅱ) ions with S=3/2. Upon lowering the temperature, the χ_MT value rapidly decreases to a minimum value of 7.96 cm³·mol^-1·K at 21 K, then abruptly increases to a sharp maximum (9.59 cm³·mol^-1·K) at 2.9 K. Finally, it decreases to 9.27 cm³·mol^-1·K at 2 K. In the 50~300 K range, the magnetic susceptibilities can be fitted to the Curie-Weiss law with C=9.06 cm³· mol^-1·K and θ=-8.9 K. It should be noted that magnetic research for high spin Co system is fairly complicated and difficult because many factors, especially the strong spin-orbital coupling, can influence the magnetic behavior. The first decrease for χ_MT value (300~21 K) and the small negative θ value may be mainly due to the strong spin-orbital coupling of the single-ion behavior at high temperature. The χ_MT value abruptly increases (21~2.9 K) can be interpreted by ferromagnetic coupling interactions within the Co₃ unit, which is strong enough to compensate for the single-ion behavior resulting from spin-orbital coupling. The magnetic data can be fit by an expression for the S=3/2 system with dominant zero field splitting effects, D, and the magnetic coupling (zJ) between the neighboring Co(Ⅱ) centers, neglecting the magnetic coupling between the two terminal Co(Ⅱ) centers within the Co₃ unit^[25-27]:

  图13 Temperature dependence of χ_MT (О) and 1/χM(□) vs T for compound 2 Figure13. Temperature dependence of χ_MT (О) and 1/χM(□) vs T for compound 2

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  Where N is Avogadro′s number, μ_B is Bohr magneton, k is Boltzmann′s constant, and g is Lande factor. The best fit in the range of 50~300 K was obtained with values of g=2.37, D=96.3 cm^-1, and zJ=0.78 cm^-1 with the agreement factor R(R=∑[(χ_MT)_obs-(χ_MT)_calc]²/∑(χ_MT)²) of 5.76×10^-5. The main magnetic exchange pathway is the exchange between adjacent Co(Ⅱ) ions within the Co₃ cluster to the μ₂-O_carboxyl bridge with the superexchange angle Co-O_carboxyl-Co of 99.05(3) °.

  3   Conclusions

  In summary, two new coordination polymers, namely [Co(μ₂-Hcpta)(phen)(H₂O)]_n (1) and [Co₃(μ₅-cpta)₂(2, 2′-bipy)₂]_n(2) have been synthesized under hydrothermal conditions. The compounds feature the 1D chain and 2D sheet structures, respectively. Magnetic studies for two compounds show an antiferromagnetic coupling between the adjacent Co(Ⅱ) centers.

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  Scheme1  Coordination modes of Hcpta^2-/cpta^3- ligands in compounds 1 and 2

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  Figure 1  Drawing of the asymmetric unit of compound 1 with 30% probability thermal ellipsoids

  Hydrogen atoms were omitted for clarity except those of COOH groups; Symmetry codes: A: -x+1, y-1/2, -z+1/2

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  Figure 2  View of a 1D metal-organic chain parallel to the bc plane

  Phen ligands are omitted for clarity; Symmetry codes: A: -x+1, y+1/2, -z+1/2; B: x, y+1, z; C: -x+1, -1/2+y, -z+1/2; D: x, y-1, z

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  Figure 3  Topological representation of a 1D metal-organic zigzag chain in 1 displaying a uninodal 2-connected underlying net with the 2C1 topology

  Viewed along the a axis; Color codes: 2-connected Co1 nodes (greenish yellow balls), centroids of 2-connected μ₂-Hcpta^2- linkers (gray)

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  Figure 4  Perspective of a 2D supramolecular network along the bc plane in 1

  Blue lines present the H-bonds; Symmetry codes: A: -x+1, -y+1, -z

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  Figure 5  Drawing of the asymmetric unit of compound 2 with 30% probability thermal ellipsoids

  Hydrogen atoms were omitted for clarity, Symmetry codes: A: x, -y+1/2, z-1/2; B: -x+1, -y+1, -z+1; C: -x+1, y+1/2, -z+3/2

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  Figure 6  Tricobalt(Ⅱ) subunit in compound 2

  Symmetry code: A: -x+1, -y+1, -z+2

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  Figure 7  2D metal-organic framework along the a axis in compound 2

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  Figure 8  Topological representation of a 2D metal-organic network in 2 displaying a trinodal 3, 4, 5-connected underlying layer with the 3, 4, 5L45 topology and point symbol of (4³)₂(4⁴.8⁶) 2(4⁵.6)

  Viewed along the a axis; Color codes: 3-connected Co1 and 4-connected Co2 nodes (greenish yellow balls), centroids of 5-connected μ₅-cpta^3- nodes (gray)

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  Figure 9  TGA curves of compounds 1 and 2

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  Figure 10  PXRD patterns of compound 1 at room temperature

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  Figure 11  PXRD patterns of compound 2 at room temperature

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  Figure 12  Temperature dependence of χ_MT (О) and 1/χM(□) vs T for compound 1

  The blue curve represents the best fit to the equations in the text; The red line shows the Curie-Weiss fitting

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  Figure 13  Temperature dependence of χ_MT (О) and 1/χM(□) vs T for compound 2

  The blue curve represents the best fit to the equations in the text; The red line shows the Curie-Weiss fitting

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  Table 1.  Crystal data for compounds 1 and 2

  Compound	1	2
  Chemical formula	C27H18Co3N208	C50H30Co3N4O14
  Molecular weight	557.36	1 087.57
  Crystal system	Monoclinic	Monoclinic
  Space group	P21/c	P21/c
  a / nm	1.043 61(5)	1.199 75(6)
  b / nm	0.792 95(4)	1.494 46(4)
  c / nm	2.789 04(14)	1.306 61(7)
  β/(°)	94.042(5)	115.402(6)
  V/ nm3	2.302 3(2)	2.116 2 (2)
  Z	4	2
  F(000)	1140	1 102
  θ range for data collection / (°)	3.28~25.05	3.34-25.04
  Limiting indices	-11≤h≤12, -9≤k≤9, -19≤1≤33	-12≤h≤14, -17≤k≤17, -15≤l≤10
  Reflections collected, unique (Rint)	8 222, 4 088 (0.056 3)	7 382, 3 733 (0.041 3)
  Dc(g·cm3)	1.608	1.707
  μ/ mm-1	0.805	1.243
  Data, restraints, parameters	4 088, 0, 345	3 733, 0, 322
  Goodness-of-fit on F2	1.080	1.038
  Final R indices[I≥2σ(I)] R1, wR2	0.050 1, 0.070 9	0.043 7, 0.073 9
  R indices (all data) R1, wR2	0.088 1, 0.086 2	0.064 4, 0.083 0
  Largest diff. peak and hole / (e·nm-3)	460 and -435	327 and -319

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  Table 2.  Selected bond distances (nm) and bond angles (°) for compounds 1 and 2

  1
  Co(1)-O(1)	0.212 7(3)	Co(1)-O(2) A	0.210 1(2)	Co(1)-O(6) A	0.209 3(2)
  Co(1)-O(8)	0.203 8(2)	Co(1)-N(1)	0.218 7(3)	Co(1)-N(2)	0.214 8(3)
  O(8)-Co(1)-O(6) A	89.09(10)	O(8)-Co(1)-O(2) A	175.40(10)	O(6) A-Co(1)-O(2) A	87.40(10)
  O(8)-Co(1)-O(1)	93.85(10)	O(6) A-Co(1)-O(1)	95.90(9)	O(2) A-Co(1)-O(1)	83.56(10)
  O(8)-Co(1)-N(2)	93.05(11)	O(6) A1-Co(1)-N(2)	169.13(11)	O(2) A-Co(1)-N(2)	90.95(10)
  O(1)-Co(1)-N(2)	94.59(11)	O(8)-Co(1)-N(1)	84.85(11)	O(6) A-Co(1)-N(1)	92.39(11)
  O(2) A-Co(1)-N(1)	98.26(11)	O(1)-Co(1)-N(1)	171.59(10)	N(2)-Co(1)-N(1)	77.21(12)
  2
  Co(1)-O(1)	0.223 9(2)	Co(1)-O(2)	0.210 9(2)	Co(1)-O(4) B	0.210 6(2)
  Co(1)-O(7) A	0.201 7(2)	Co(1)-N(1)	0.214 5(3)	Co(1)-N(2)	0.210 6(3)
  Co(2)-O(1)	0.215 0(2)	Co(2)-O(1) B	0.215 0(2)	Co(2)-O(4)	0.213 0(2)
  Co(2)-O(4) B	0.213 0(2)	Co(2)-O(6) A	0.209 4(2)	Co(2)-O(6) C	0.209 4(2)
  O(7) A-Co(1)-N(2)	91.74(10)	O(7) A-Co(1)-O(4) B	88.19(9)	N(2)-Co(1)-O(4) B	113.48(10)
  O(7) A-Co(1)-O(2)	154.32(11)	N(2)-Co(1)-O(2)	109.33(10)	O(4) B-Co(1)-O(2)	96.27(9)
  O(7) A-Co(1)-N(1)	80.95(10)	N(2)-Co(1)-N(1)	76.87(11)	O(4) B-Co(1)-N(1)	165.36(10)
  O(2)-Co(1)-N(1)	89.49(10)	O(7) A-Co(1)-O(1)	96.02(9)	N(2)-Co(1)-O(1)	166.52(10)
  O(4) B-Co(1)-O(1)	77.86(8)	O(2)-Co(1)-O(1)	60.61(9)	N(1)-Co(1)-O(1)	93.45(10)
  O(6) A-Co(2)-O(4)	92.21(8)	O(6) C-Co(2)-O(4)	87.79(8)	O(6) A-Co(2)-O(1)	91.99(8)
  O(6) C-Co(2)-O(1)	88.01(8)	O(4)-Co(2)-O(1)	100.67(8)	O(4) B-Co(2)-O(1)	79.33(8)
  Co(2)-O(1)-Co(1)	94.45(9)	Co(1) B-O(4)-Co(2)	99.06(9)
  Symmetry transformations used to generate equivalent atoms: A: -x+1, y-1/2, -z+1/2 for 1; A: x, -y+1/2, z-1/2; B: -x+1, -y+1, -z+1; C: -x+1, y+1/2, -z+3/2 for 2

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  Table 3.  Hydrogen bond lengths (nm) and angles (°) of compound 1

  D-H…A	d(D-H) / nm	d(H…A) / nm	d(D…A) / nm	∠DHA/(°)
  O(4)-H(4)…O(7) A	0.082	0.184	0.264 3	164.2
  O(8)-H(1W)…O(1) B	0.082	0.204	0.277 2	148.3
  O(8)-H(2W)…O(7) C	0.086	0.198	0.275 9	151.9
  Symmetry code: A: -x+1, -y+1, -z; B: -x+1, y+1/2, -z+1/2; C: -x+1, y-1/2, -z+1/2

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