English

• 0.   Introduction

  In recent years, the design and hydrothermal syntheses of functional coordination polymers have attracted tremendous attention owing to their fascinating architectures and topologies, as well as potential applications in catalysis, magnetism, luminescence and gas absorption^[1-10]. Even after years of comprehensive study, it is difficult to predict the structures of coordination polymers, because a lot of factors influence the construction of complexes, such as the structural features of organic ligands, the coordination requirements of metal ions, solvent systems, temperatures, and pH values^[11-17].

  In this regard, various types of aromatic polycarboxylic acids have been proved to be versatile and efficient candidates for constructing diverse coordination polymers due to their rich coordination chemistry, tunable degree of deprotonation, and ability to act as H-bond acceptors and donors^{[3, 13, 17-20]}.

  In order to extend our research in this field, we chose a rigid linear tricarboxylic acid ligand, 2, 5-di(4-carboxylphenyl)nicotinic acid (H₃L), to construct novel coordination compounds. The ligand possesses the following features: (1) it contains a pyridyl and two phenyl rings with structural flexibility and conforma-tion, and rotation of the C-C single bond between pyridyl and phenyl rings could form numbers of coordination geometries of metal ions; (2) it has seven potential coordination sites, one N atom from pyridyl ring and six O atoms of three carboxylate groups, which is beneficial to construct coordination polymers with interesting structures by its rich coordination modes; (3) it can act as hydrogen-bond acceptor as well as donor, depending upon the degree of deprotonation.

  Taking into account these factors, we herein report the syntheses, crystal structures, and magnetic properties of two Ni(Ⅱ) coordination compounds constructed from H₃L.

  1.   Experimental

  1.1   Reagents and physical measurements

  All chemicals and solvents were of AR grade and used without further purification. 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. 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 [Ni₂(μ-HL)₂(2, 2′-bipy)₂(H₂O)₄]·6H₂O (1)

  A mixture of NiCl₂·6H₂O (0.024 g, 0.10 mmol), H₃L (0.036 g, 0.10 mmol), 2, 2′-bipy (0.016 g, 0.1 mmol), NaOH (0.012 g, 0.20 mmol), and H₂O (8 mL) was stirred at room temperature for 15 min, and then sealed in a 25 mL Teflon-lined stainless steel vessel, and heated at 120 ℃ for 3 days, followed by cooling to room temperature at a rate of 10 ℃·h^-1. Blue block-shaped crystals of 1 were isolated manually, and washed with distilled water. Yield: 60% (based on H₃L). Anal. Calcd. for C₆₀H₅₈Ni₂N₆O₂₂(%): C 54.08, H 4.39, N 6.31; Found(%): C 54.37, H 4.36, N 6.33. IR (KBr, cm^-1): 3 451m, 3 277m, 1 694m, 1 599s, 1 560s, 1 476w, 1 448m, 1 392s, 1 314w, 1 280w, 1 224w, 1 174w, 1 097w, 1 052w, 1 013w, 918w, 901w, 873w, 790w, 762m, 739w, 707w, 668w, 657w.

  1.3   Synthesis of {[Ni(μ-HL)(2, 2′-bipy)(H₂O)₂]·H₂O}_n (2)

  Synthesis of 2 was similar to 1 except using 160 ℃ instead of 120 ℃ as the temperature of hydrothermal reaction. Green block-shaped crystals of 2 were isolated manually, and washed with distilled water. Yield: 57% (based on H₃L). Anal. Calcd. for C₃₀H₂₅NiN₃O₉(%): C 57.17, H 4.00, N 6.67; Found(%): C 56.92, H 3.98, N 6.69. IR (KBr, cm^-1): 3 339w, 3 033w, 1 677m, 1 604m, 1 560s, 1 521m, 1 476w, 1 431m, 1 386s, 1 319w, 1 287m, 1 192w, 1 153w, 1 125w, 1 103w, 1 058w, 1 008w, 968w, 918w, 857w, 806w, 778m, 734w, 711w, 678w, 650w. The complexes 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 0.25 mm×0.24 mm×0.22 mm (1) and 0.26 mm×0.23 mm×0.22 mm (2) were collected at 293(2) K on a Bruker SMART APEX Ⅱ CCD diffractometer 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-2014 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 complexes 1 and 2 are listed in Table 2. Hydrogen bond parameters of complexes 1 and 2 are given in Table 3 and 4.

  Table 1

  

  Table 1.  Crystal data for complexes 1 and 2

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  Complex	1	2
  Empirical formula	C60H58Ni2N6O22	C30H25NiN3O9
  Formula weight	1 332.54	630.24
  Crystal system	Triclinic	Triclinic
  Space group	p1	P1
  a / nm	0.897 79(6)	0.697 47(5)
  b / nm	1.223 20(8)	0.923 50(6)
  c / nm	1.399 50(10)	2.118 55(15)
  α/(°)	99.107(6)	91.484(5)
  β/(°)	103.230(6)	90.892(6)
  γ/(°)	94.417(5)	105.347(6)
  V/ nm3	1.466 96(18)	1.315 13(16)
  Dc/ (g·cm-3)	1.508	1.592
  Z	1	2
  F(000)	692	652
  θ range for data collection / (°)	3.397~25.049	3.415~25.048
  Limiting indices	-10≤h≤10, -14≤k≤14, -16≤l≤16	-8≤h≤7, -10≤k≤10, -24≤l≤25
  Reflection collected, unique (Rint)	5 195, 4 254 (0.035 6)	4 644, 3 829 (0.032 7)
  μ / mm-1	0.729	0.803
  Data, restraint, parameter	4 254, 0, 407	3 829, 0, 389
  Goodness-of-fit on F2	1.054	1.069
  Final R indices [I≥2σ(I)]R1, wR2	0.046 3, 0.109 7	0.042 0, 0.086 8
  R indices (all data) R1, wR2	0.058 8, 0.121 2	0.054 4, 0.095 7
  Largest diff. peak and hole /(e·nm-3)	417 and -413	315 and -351

  Table 2

  

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

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  1
  Ni(1)-O(1)	0.206 6(2)	Ni(1)-O(4)A	0.207 8(2)	Ni(1)-O(7)	0.210 9(2)
  Ni(1)-O(8)	0.208 6(2)	Ni(1)-N(2)	0.207 5(2)	Ni(1)-N(3)	0.205 9(2)
  N(3)-Ni(1)-O(1)	177.71(9)	N(3)-Ni(1)-N(2)	79.30(10)	O(1)-Ni(1)-N(2)	100.39(9)
  N(3)-Ni(1)-O(4)A	93.51(9)	O(1)-Ni(1)-O(4)A	86.78(8)	N(2)-Ni(1)-O(4)A	172.81(9)
  N(3)-Ni(1)-O(8)	86.78(9)	O(1)-Ni(1)-O(8)	90.94(8)	N(2)-Ni(1)-O(8)	86.09(9)
  O(4)A-Cu(1)-O(8)	93.46(8)	N(3)-Ni(1)-O(7)	91.25(9)	O(1)-Ni(1)-O(7)	91.02(8)
  N(2)-Ni(1)-O(7)	90.72(9)	O(4)A-Ni(1)-O(7)	89.52(8)	O(8)-Ni(1)-O(7)	176.52(7)
  2
  Ni(l)-O(2)	0.202 2(2)	Ni(1)-O(3)A	0.204 4(2)	Ni(1)-O(7)	0.214 1(2)
  Ni(1)-O(8)	0.205 2(2)	Ni(1)-N(2)	0.206 1(2)	Ni(1)-N(3)	0.208 7(2)
  O(2)-Ni(1)-O(3)A	92.61(8)	O(2)-Ni(1)-O(8)	87.09(8)	O(3)A-Ni(1)-O(8)	86.68(8)
  O(2)-Ni(1)-N(2)	169.33(8)	O(3)A-Ni(1)-N(2)	97.63(8)	O(8)-Ni(1)-N(2)	90.50(9)
  N(3)-Ni(1)-O(2)	91.08(8)	N(3)-Ni(1)-O(3)A	174.54(8)	N(3)-Ni(1)-O(8)	89.49(9)
  N(3)-Ni(1)-N(2)	78.50(8)	O(2)-Ni(1)-O(7)	91.40(8)	O(3)A-Ni(1)-O(7)	89.42(8)
  O(7)-Ni(1)-O(8)	175.75(7)	N(2)-Ni(1)-O(7)	91.69(9)	N(3)-Ni(1)-O(7)	94.52(8)
  Symmetry codes: A: -x+2, -y+1, -z+2 for 1; A: x, y+1, z for 2.

  Table 3

  

  Table 3.  Hydrogen bond parameters for complex 1

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  D-H···A	d(D-H) / nm	d(H·A) /nm	d(D ···A) / nm	∠DHA/(°)
  O(6)-H(6)···O(9)A	0.082	0.175	0.256 0	169.6
  O(7)-H(1W)···O(10)	0.082	0.205	0.281 2	154.3
  O(7)-H(2W)···O(3)B	0.084	0.183	0.264 1	160.8
  O(8)-H(3W)···O(2)	0.082	0.195	0.267 9	148.3
  O(8)-H(4W)···N(1)C	0.085	0.196	0.278 3	164.8
  O(9)-H(5W)···O(2)D	0.085	0.192	0.276 8	179.7
  O(9)-H(6P)···O(3)E	0.084	0.187	0.270 6	173.4
  O(10)-H(7W)···O(5)F	0.086	0.201	0.282 6	160.1
  O(10)-H(8W)···O(11)D	0.085	0.197	0.280 2	165.3
  O(11)-H(9W)···O(10)	0.085	0.203	0.281 4	152.8
  O(11)-H(10P)···O(1)	0.093	0.209	0.288 6	155.6
  Symmetry codes: A: x, y-1, z+1; B: -x+2, -y+1, -z+2; C: x, y+1, z; D: -x+1, -y+1, -z+1; E: x, y, z-1; F: x, y+1, z-1.

  Table 4

  

  Table 4.  Hydrogen bond parameters for complex 2

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  D-H···A	d(D-H) / nm	d(H·A) /nm	d(D ···A) / nm	∠DHA/(°)
  O(6)-H(6)···O(9)A	0.082	0.181	0.263 1	176.5
  O(7)-H(1W)···O(4)B	0.080	0.191	0.267 8	161.4
  O(7)—H(2W)···O(1)	0.082	0.201	0.271 1	142.6
  O(8)-H(3W)···O(4)C	0.076	0.210	0.285 2	176.6
  O(8)-H(4W)···O(5)D	0.082	0.194	0.274 2	163.8
  O(9)-H(5W)···O(1)E	0.079	0.206	0.285 0	177.0
  O(9)-H(6W)···O(2)F	0.090	0.203	0.292 7	174.2
  Symmetry codes: A: x, y+1, z+1; B: x, y+1, z; C: x+1, y+1, z; D: -x+1, -y+2, -z+2; E: -x, -y+1, -z+1; F: -x+1, -y+1, -z+1.

  CCDC: 1909474, 1; 1909475, 2.

  2.   Results and discussion

  2.1   Description of the structure

  2.1.1   [Ni₂(μ-HL)₂(2, 2′-bipy)₂(H₂O)₄]·6H₂O (1)

  Single-crystal X-ray diffraction analysis reveals that complex 1 crystallizes in the triclinic space group P1. Its asymmetric unit contains one crystallogra-phically unique Ni(Ⅱ) ion, one μ-HL^2- block, one chelating 2, 2′-bipy moiety, two H₂O ligands, and three lattice water molecules. As depicted in Fig. 1, the six-coordinated Ni1 center is bound by two O atoms from two μ-HL^2- blocks, two O atoms from two H₂O ligands, and two N atoms from 2, 2′-bipy moiety, thus resulting in an octahedral {NiN₂O₄} environment. The lengths of the Ni-O bonds range from 0.206 6(2) to 0.210 9(2) nm, whereas the Ni-N distances vary from 0.205 9(2) to 0.207 5(2) nm; these bonding parameters are comp-arable to those found in other reported Ni(Ⅱ) comp-lexes^{[10, 15]}. In 1, the HL^2- block behaves as a μ-spacer (mode Ⅰ, Scheme 1). Its nicotinate N donor remains uncoordinated while two COO^- groups are mono-dentate. The dihedral angles between pyridyl and phenyl rings in the HL^2- are 49.84° and 54.79°. The μ-HL^2- blocks connect two Ni1 ions to give a Ni₂ molecular unit having a Ni…Ni distance of 1.337 1(2) nm (Fig. 2). These discrete Ni₂ units are assembled to a 3D supra-molecular framework through O-H…O/N hydrogen bond (Fig. 3 and Table 3).

  Figure 1

  

  Figure 1.  Asymmetric unit of complex 1 with 30% probability thermal ellipsoids

  H atoms and lattice water molecules are omitted for clarity except H of COOH group; Symmetry code: A:-x+2, -y+1, -z+2

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  Scheme1

  

  Scheme1.  Coordination modes of HL^2- ligands in complexes 1 and 2

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  Figure 2

  

  Figure 2.  Dinuclear Ni(Ⅱ) unit of complex 1

  H atoms are omitted for clarity except the H of the COOH group; Symmetry code: A:-x+2, -y+1, -z+2

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  Figure 3

  

  Figure 3.  Perspective of 3D supramolecular framework parallel to ac plane in 1

  2, 2′-bipy ligands and water molecules are omitted for clarity; Symmetry codes: A: x, y-1, z; B:-x+1, -y+2, -z+1; C: -x+1, -y+1, -z+1

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  2.1.2   {[Ni(μ-HL)(2, 2′-bipy)(H₂O)₂]·H₂O}_n (2)

  The asymmetric unit of 2 consists of one Ni(Ⅱ) ion, one μ-HL^2- block, one 2, 2′-bipy ligand, two coordinated and one lattice water molecules. As shown in Fig. 4, six-coordinates Ni1 ion reveals a distorted octahedral {NiN₂O₄} environment, filled by two carboxylate O atoms from two individual μ-HL^2- blocks, two O atoms from two H₂O ligands, and a pair of N atoms from 2, 2′-bipy ligand. The Ni-O distances range from 0.202 2(2) to 0.214 1(2) nm, whereas the Ni-N distances vary from 0.206 1(2) to 0.208 7(2) nm; these bonding parameters are comparable to those observed in other Ni(Ⅱ) complexes^{[15, 17-18]}. In 2, the HL^2- block acts as a μ-linker via monodentate COO^- groups (mode Ⅱ, Scheme 1), and the nicotinate N atom remains uncoordinated. In HL^2-, two dihedral angles between pyridyl and benzene rings are 19.52° and 42.02°. The HL^2- linkers connect the adjacent Nil centers to form a zigzag 1D chain with the Ni1…Ni1 separation of 0.923 5(2) nm (Fig. 5).

  Figure 4

  

  Figure 4.  Asymmetric unit of complex 2 with 30% probability thermal ellipsoids

  H atoms and lattice water molecules were omitted for clarity except H of COOH group; Symmetry code: A: x, y+1, z

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  Figure 5

  

  Figure 5.  One dimensional chain viewed along a axis in 2

  probability thermal ellipsoids Symmetry codes: A: x, y+1, z; B: x, y-1, z

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  The nickel(Ⅱ) compounds 1 and 2 were prepared hydrothermally under similar reaction conditions, except using different reaction temperatures (120 ℃ for 1 and 160 ℃ for 2). The HL^2- ligands adopt different coordination modes at 120 and 160 ℃ (Scheme 1), which results in distinct structures^[22-25].

  2.2   TGA analysis

  To determine the thermal stability of complexes 1 and 2, their thermal behaviors were investigated under nitrogen atmosphere by thermogravimetric analysis (TGA). As shown in Fig. 6, complex 1 lost its six lattice and four coordinated water molecules in the range of 36~178 ℃ (Obsd. 13.2%; Calcd. 13.5%), followed by the decomposition at 278 ℃. The TGA curve of 2 revealed that one lattice and two coordinated water molecules were released between 142 and 218 ℃ (Obsd. 8.9%; Calcd. 8.6%), and the dehydrated solid began to decompose at 271 ℃.

  Figure 6

  

  Figure 6.  TGA curves of complexes 1 and 2

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  2.3   Magnetic properties

  Variable-temperature magnetic susceptibility studies were carried out on powder sample of 2 in the 2~300 K temperature range. The χ_MT value at 300 K was 1.05 cm³·mol^-1·K, which is close to the expected one (1.00 cm³·mol^-1·K) for one magnetically isolated Ni(Ⅱ) ion (S=1, g=2.0). Upon cooling, the χ_MT value decreased very slowly from 1.05 cm³·mol^-1·K at 300 K to 0.981 cm³·mol^-1·K at 17 K, and then decreased steeply to 0.663 cm³·mol^-1·K at 2 K. In the 2~300 K interval, the χ_M^-1 vs T plot for 2 obeys the Curie-Weiss law with a Weiss contant θ of -5.23 K and a Curie constant C of 1.05 cm³·mol^-1·K. An empirical (Weng′s) formula can be applied to analyze the 1D systems with S=1, using numerical procedures^[26-27]:

  $ {{\chi _{\rm{M}}} = \frac{{N{\beta ^2}{g^2}}}{{kT}}\frac{A}{B}} $

  $ {A = 2.0 + 0.0194x + 0.7777{x^2}} $

  $ {B = 3.0 + 4.346x + 3.232{x^2} + 5.834{x^2}} $

  with ${x = |\mathit{J}|kT}$

  Using this method, the best-fit parameters for 2 were obtained: g=2.08, J=-0.94 cm^-1, and R=7.7×10^-5, where $R = \sum {{{\left({{T_{{\rm{obs}}}} - {T_{{\rm{calc}}}}} \right)}^2}} /\sum {{{\left({{T_{{\rm{obs}}}}} \right)}^2}} $. The J value of -0.94 cm^-1 indicates that the coupling between the Ni(Ⅱ) centers is antiferromagnetic.

  3.   Conclusions

  In summary, we have synthesized two Ni(Ⅱ)coordination compounds whose structures depend on the hydrothermal reaction temperature. This work demonstrates that the hydrothermal reaction temperature has a significant effect on the structures of the coordination compounds.

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• 

  Figure 1  Asymmetric unit of complex 1 with 30% probability thermal ellipsoids

  H atoms and lattice water molecules are omitted for clarity except H of COOH group; Symmetry code: A:-x+2, -y+1, -z+2

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  Scheme1  Coordination modes of HL^2- ligands in complexes 1 and 2

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  Figure 2  Dinuclear Ni(Ⅱ) unit of complex 1

  H atoms are omitted for clarity except the H of the COOH group; Symmetry code: A:-x+2, -y+1, -z+2

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  Figure 3  Perspective of 3D supramolecular framework parallel to ac plane in 1

  2, 2′-bipy ligands and water molecules are omitted for clarity; Symmetry codes: A: x, y-1, z; B:-x+1, -y+2, -z+1; C: -x+1, -y+1, -z+1

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  Figure 4  Asymmetric unit of complex 2 with 30% probability thermal ellipsoids

  H atoms and lattice water molecules were omitted for clarity except H of COOH group; Symmetry code: A: x, y+1, z

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  Figure 5  One dimensional chain viewed along a axis in 2

  probability thermal ellipsoids Symmetry codes: A: x, y+1, z; B: x, y-1, z

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  Figure 6  TGA curves of complexes 1 and 2

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  Table 1.  Crystal data for complexes 1 and 2

  Complex	1	2
  Empirical formula	C60H58Ni2N6O22	C30H25NiN3O9
  Formula weight	1 332.54	630.24
  Crystal system	Triclinic	Triclinic
  Space group	p1	P1
  a / nm	0.897 79(6)	0.697 47(5)
  b / nm	1.223 20(8)	0.923 50(6)
  c / nm	1.399 50(10)	2.118 55(15)
  α/(°)	99.107(6)	91.484(5)
  β/(°)	103.230(6)	90.892(6)
  γ/(°)	94.417(5)	105.347(6)
  V/ nm3	1.466 96(18)	1.315 13(16)
  Dc/ (g·cm-3)	1.508	1.592
  Z	1	2
  F(000)	692	652
  θ range for data collection / (°)	3.397~25.049	3.415~25.048
  Limiting indices	-10≤h≤10, -14≤k≤14, -16≤l≤16	-8≤h≤7, -10≤k≤10, -24≤l≤25
  Reflection collected, unique (Rint)	5 195, 4 254 (0.035 6)	4 644, 3 829 (0.032 7)
  μ / mm-1	0.729	0.803
  Data, restraint, parameter	4 254, 0, 407	3 829, 0, 389
  Goodness-of-fit on F2	1.054	1.069
  Final R indices [I≥2σ(I)]R1, wR2	0.046 3, 0.109 7	0.042 0, 0.086 8
  R indices (all data) R1, wR2	0.058 8, 0.121 2	0.054 4, 0.095 7
  Largest diff. peak and hole /(e·nm-3)	417 and -413	315 and -351

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

  1
  Ni(1)-O(1)	0.206 6(2)	Ni(1)-O(4)A	0.207 8(2)	Ni(1)-O(7)	0.210 9(2)
  Ni(1)-O(8)	0.208 6(2)	Ni(1)-N(2)	0.207 5(2)	Ni(1)-N(3)	0.205 9(2)
  N(3)-Ni(1)-O(1)	177.71(9)	N(3)-Ni(1)-N(2)	79.30(10)	O(1)-Ni(1)-N(2)	100.39(9)
  N(3)-Ni(1)-O(4)A	93.51(9)	O(1)-Ni(1)-O(4)A	86.78(8)	N(2)-Ni(1)-O(4)A	172.81(9)
  N(3)-Ni(1)-O(8)	86.78(9)	O(1)-Ni(1)-O(8)	90.94(8)	N(2)-Ni(1)-O(8)	86.09(9)
  O(4)A-Cu(1)-O(8)	93.46(8)	N(3)-Ni(1)-O(7)	91.25(9)	O(1)-Ni(1)-O(7)	91.02(8)
  N(2)-Ni(1)-O(7)	90.72(9)	O(4)A-Ni(1)-O(7)	89.52(8)	O(8)-Ni(1)-O(7)	176.52(7)
  2
  Ni(l)-O(2)	0.202 2(2)	Ni(1)-O(3)A	0.204 4(2)	Ni(1)-O(7)	0.214 1(2)
  Ni(1)-O(8)	0.205 2(2)	Ni(1)-N(2)	0.206 1(2)	Ni(1)-N(3)	0.208 7(2)
  O(2)-Ni(1)-O(3)A	92.61(8)	O(2)-Ni(1)-O(8)	87.09(8)	O(3)A-Ni(1)-O(8)	86.68(8)
  O(2)-Ni(1)-N(2)	169.33(8)	O(3)A-Ni(1)-N(2)	97.63(8)	O(8)-Ni(1)-N(2)	90.50(9)
  N(3)-Ni(1)-O(2)	91.08(8)	N(3)-Ni(1)-O(3)A	174.54(8)	N(3)-Ni(1)-O(8)	89.49(9)
  N(3)-Ni(1)-N(2)	78.50(8)	O(2)-Ni(1)-O(7)	91.40(8)	O(3)A-Ni(1)-O(7)	89.42(8)
  O(7)-Ni(1)-O(8)	175.75(7)	N(2)-Ni(1)-O(7)	91.69(9)	N(3)-Ni(1)-O(7)	94.52(8)
  Symmetry codes: A: -x+2, -y+1, -z+2 for 1; A: x, y+1, z for 2.

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  Table 3.  Hydrogen bond parameters for complex 1

  D-H···A	d(D-H) / nm	d(H·A) /nm	d(D ···A) / nm	∠DHA/(°)
  O(6)-H(6)···O(9)A	0.082	0.175	0.256 0	169.6
  O(7)-H(1W)···O(10)	0.082	0.205	0.281 2	154.3
  O(7)-H(2W)···O(3)B	0.084	0.183	0.264 1	160.8
  O(8)-H(3W)···O(2)	0.082	0.195	0.267 9	148.3
  O(8)-H(4W)···N(1)C	0.085	0.196	0.278 3	164.8
  O(9)-H(5W)···O(2)D	0.085	0.192	0.276 8	179.7
  O(9)-H(6P)···O(3)E	0.084	0.187	0.270 6	173.4
  O(10)-H(7W)···O(5)F	0.086	0.201	0.282 6	160.1
  O(10)-H(8W)···O(11)D	0.085	0.197	0.280 2	165.3
  O(11)-H(9W)···O(10)	0.085	0.203	0.281 4	152.8
  O(11)-H(10P)···O(1)	0.093	0.209	0.288 6	155.6
  Symmetry codes: A: x, y-1, z+1; B: -x+2, -y+1, -z+2; C: x, y+1, z; D: -x+1, -y+1, -z+1; E: x, y, z-1; F: x, y+1, z-1.

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  Table 4.  Hydrogen bond parameters for complex 2

  D-H···A	d(D-H) / nm	d(H·A) /nm	d(D ···A) / nm	∠DHA/(°)
  O(6)-H(6)···O(9)A	0.082	0.181	0.263 1	176.5
  O(7)-H(1W)···O(4)B	0.080	0.191	0.267 8	161.4
  O(7)—H(2W)···O(1)	0.082	0.201	0.271 1	142.6
  O(8)-H(3W)···O(4)C	0.076	0.210	0.285 2	176.6
  O(8)-H(4W)···O(5)D	0.082	0.194	0.274 2	163.8
  O(9)-H(5W)···O(1)E	0.079	0.206	0.285 0	177.0
  O(9)-H(6W)···O(2)F	0.090	0.203	0.292 7	174.2
  Symmetry codes: A: x, y+1, z+1; B: x, y+1, z; C: x+1, y+1, z; D: -x+1, -y+2, -z+2; E: -x, -y+1, -z+1; F: -x+1, -y+1, -z+1.

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