English

• 0.   Introduction

  Supramolecular chemistry is an important research field including multiple-subject ranging from pharmaceutics to nanotechnology industries^[1-4]. During the last decade, great efforts have been devoted to the rational design and synthesis of supramolecular aggregates with desired structure and properties^[5-7].

  Different supramolecular interaction resulting in different solid geometry and even physicochemical properties, such as activity of pharmaceutical ingredients (APIs), magnetic behavior of molecular magnets. As is known to all, chemical reactivity and properties of organic compound are differed wildly by substitution of halogen atom^[8-10]. Furthermore, halogen atom has recently been recognized as an important factor in mediation the supramolecular network of crystalline materials^[11-12]. However, compared with the classic hydrogen-bond interactions, the contact formed by halogen atom is much weaker, so it is difficult to carry out qualitative and quantitative research, especially for the N- and O- rich ligands constructing supramolecular complex^[13-15]. Hence, related work is still at a very early stage.

  Therefore, establishing a series of halogenated ligands constructing complexes with similar structure and composition is a fundamental way for detailed recognition of the intermolecular interactions formed by halogen atom. In this aspect, tetradentate Schiff base (salen) complex is an ideal candidate, not only because the complex has diverse structures and tunable constitution^[16-18], but also because it is a well researched subject. Thus, subtle difference between analogs can be easily detected and studied^[19-20].

  Based on the aforementioned considerations, recently, we have initiated exploitation of the relationship between the composition of salen-type halogenated Schiff-base ligands and the structure of their complexes. Herein, we specifically introduced isomorphic halogenated salen as starting material, and isolated two nickel(Ⅱ) complexes [Ni(3, 5-Cl-salcy)] (1) and [Ni(3-Cl-salcy)] (2) (3, 5-Cl-salcyH₂=N, N′-(±)-bis(3, 5-dichlorosalicylidene)cyclohexane-1, 2-diamine and 3-Cl-salcyH₂=N, N′-(±)-bis(3-chlorosalicylidene)cyclo-hexane-1, 2-diamine). Theoretical analysis results reveal that halogen atoms play a key role in stabling the solid structures of title complexes.

  1.   Experimental

  1.1   Material and methods

  All chemicals were commercially available and used without further purification. Elemental analyses (C, H and N) were carried out on a Perkin-Elmer 240C instrument. Ni was analyzed on a PLASMA-SPEC(Ⅰ) ICP atomic emission spectrometer. IR spectra were recorded in a range of 400~4 000 cm^-1 on an Alpha Centaurt FT/IR Spectrophotometer using KBr pellets. ¹H NMR spectra have been recorded by using Bruker 600 MHz Digital NMR Spectrometer resonance instrument (AVANCE Ⅲ 600 MHz).

  1.2   Synthesis

  1.2.1   Synthesis of halogenated Schiff base ligand

  The halogenated tetradentate Schiff base ligand 3, 5-Cl-salcyH₂ and 3-Cl-salcyH₂ were prepared by mixing salicylaldehyde (3, 5-dichlorosalicylaldehyd and 3-chlorosalicylaldehyd for 3, 5-Cl-salcyH₂ and 3-Cl-salcyH₂, respectively) (0.2 mmol) and 1, 2-diaminocy-clohexane (0.012 mL, 0.1 mmol, mixture of cis- and trans- form) in 30mL of methanol. The obtained solution was stirred and refluxed at 80 ℃ for three hours, then the solvent was removed by rotary evaporator to give yellow powder product (Scheme 1).

  Scheme 1

  

  Scheme 1.  Schematic drawing of halogenated tetradentate Schiff base ligands 3, 5-Cl-salcyH₂ and 3-Cl-salcyH₂

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  3, 5-Cl-salcyH₂: Yield: 0.035 2 g (75%). Elemental analysis for C₂₀H₁₈Cl₄N₂O₂(%): C: 52.2; H: 3.94; N: 6.08. Found(%): C: 51.2; H: 3.93; N: 6.13. ¹H NMR (600 MHz, methanol-d₄): δ 8.38 (d, J=62.4 Hz, 1H, -N=CH-), 7.48~7.10 (m, 2H, ArH), 4.50 (s, 1H, Ar-OH), 3.85 (dt, J=6.7, 3.1 Hz, 1H, -C^*H-), 2.06~1.77 (m, 2H, -CH₂-), 1.76~1.18 (m, 2H, -CH₂-). FT-IR (cm^-1): 3 419 (O-H), 1 598 (C=N), 1 389 (-CH₂-).

  3-Cl-salcyH₂: Yield: 0.034 3 g (86%). Elemental analysis for C₂₀H₂₀Cl₂N₂O₂(%): C: 61.39; H: 5.15; N: 7.15. Found(%): C: 61.57; H: 4.60; N: 7.27. ¹H NMR (600 MHz, methanol-d₄): δ 8.38 (d, J=68.5 Hz, 1H, -N=CH-), 7.57~6.92 (m, 2H, ArH), 6.65 (dt, J=34.9, 7.8 Hz, 1H, Ar-OH), 4.09~3.68 (m, 1H, -C^*H-), 2.19~1.79 (m, 2H, -CH₂-), 1.78~1.43 (m, 2H, -CH₂-). FT-IR (cm^-1): 3 432 (O-H), 1 598 (C=N), 1 389 (-CH₂-).

  1.2.2   Synthesis of [Ni(3, 5-Cl-salcy)] (1)

  Ni(NO₃)₂·6H₂O (0.060 0 g, 0.2 mmol) was dissolved in 10 mL methanol, and the solution was added to 20 mL of a methanolic solution of 3, 5-Cl-salcyH₂ (0.031 6 g, 0.1 mmol), the resulting dark red suspension was stirred for 2 h. After cooling, the reddish filtrate was sealed in a beaker and kept undisturbed at room temperature. The red block crystals of complex 1 were afforded after one week. Yield: 35%. Anal. Calcd. for C₂₀H₁₆Cl₄N₂NiO₂(%): C, 46.47; H, 3.12; N, 5.42. Found(%): C, 47.13; H, 3.31; N, 5.14.

  1.2.3   Synthesis of [Ni(3-Cl-salcy)] (2)

  Complex 2 was prepared in a similar method as that of complex 1, except the ligand 3-Cl-salcyH₂ (0.024 5 g, 0.1 mmol) was used to replace 3, 5-Cl-salcyH₂. The red block crystals of 2 were afforded after one week. Yield: 42%. Anal. Calcd. For C₂₀H₁₈Cl₂N₂NiO₂(%): C, 53.62; H, 4.05; N, 6.25; Found: C, 53.93; H, 4.12; N, 6.14.

  1.3   X-ray crystal structure analysis

  The data set of reflections were collected at 293(2) K on an Xcalibur Eos automated diffractometer with Mo Kα radiation (λ=0.071 073 nm) and a low-temp-erature device Cryostream cooler (Oxford Cryosystem). Integration of the intensities and correction for Lorentz and polarization effects were performed using the CrysAlisPro software^[21-22]. The central nickel atom was located by direct method, and successive Fourier syntheses revealed the remaining atoms. Refinements were achieved by the full-matrix method on F² using the Olex2 software package^[23]. In the final refinement, all the non-H atoms were anisotropically refined. All H atoms were placed in calculated positions and refined using the riding model approximation. For the cyclohexane, C-H bonds were fixed at 0.097 nm, and the U_iso values of the hydrogen atoms of methyl groups were set to 1.5U_{eq, C} and the U_iso values of all other hydrogen atoms were set to 1.2U_{eq, C}, with aromatic C-H distances of 0.093 nm. The detailed crystal data and structure refinement for 1 and 2 are given in Table 1. Selective bond lengths and angles of 1 and 2 are listed in Table 2.

  Table 1

  

  Table 1.  Crystallographic data and structure refinement for complexes 1 and 2

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  Complex	1	2
  Formula	C20H16Cl4N2Ni02	C20H18Cl2N2Ni02
  Formula weight	516.84	447.95
  Crystal system	Monoclinic	Triclinic
  Crystal size / mm	0.20×0.18×0.16	0.18×0.14×0.12
  Space group	P21/c	P1
  a / nm	1.352 06(14)	1.174 51(8)
  b/ nm	1.377 74(10)	1.287 43(8)
  c / nm	1.247 79(13)	1.356 64(8)
  α/(°)		86.447(5)
  β/(°)	117.130(13)	69.997(6)
  γ/(°)		76.885(6)
  Volume / nm3	2.068 6(3)	1.877 1(2)
  Dc/ (g·cm-3)	1.66	1.585
  Z	4	1
  μ / mm-1	1.475	1.336
  Reflection collected, unique (Rint)	8 941, 3 518 (0.029 0)	13 206, 6 592 (0.066 6)
  Reflection with I > 2σ(I)	1 847	2 695
  θ range for data collection / (°)	3.27~25.00	3.34~25.00
  Data, restraint, parameter	3 518, 0, 262	6 592, 0, 487
  Goodness-of-fit on F2	1.047	0.945
  R indices [I > 2σ(I)]a, b	R1=0.034 7, wR2=0.072 1	R1=0.058 6, wR2=0.061 0
  R indices (all data)	R1=0.050 4, wR2=0.080 8	R1=0.129 0, wR2=0.077 1
  (Δρ)max, (Δρ)min/ (e·nm-3)	393, -276	409, -438
  a R1=||Fo|-|Fc||/|Fo|; b wR2=[w(Fo2-Fc2)2]/[w(Fo2)2]1/2.

  Table 2

  

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

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  1
  Ni(1)-O(2)	0.184 57(18)	Ni(1)-0(1)	0.185 32(19)	Ni(1)-N(2)	0.185 1(2)
  Ni(1)-N(1)	0.185 3(2)	Ni(1)-Ni(1)ⅰ	0.331 56(7)	Cl(1)-C(4)	0.174 0(3)
  Cl(3)-C(2)	0.173 4(3)	Cl(2)-C(17)	0.174 5(3)	Cl(4)-C(19)	0.173 3(3)
  0(2)-Ni(1)-N(2)	93.93(9)	0(2)-Ni(1)-N(1)	179.74(10)	0(2)-Ni(1)-0(1)	85.61(8)
  N(2)-Ni(1)-N(1)	85.81(10)	N(2)-Ni(1)-0(1)	178.60(9)	0(1)-Ni(1)-N(1)	94.64(9)
  C(3)-C(2)-Cl(3)	118.6(2)	C(5)-C(4)-Cl(1)	119.8(3)	C(1)-C(2)-Cl(3)	118.5(2)
  C(3)-C(4)-Cl(1)	119.5(3)
  2
  Ni(1)-0(1)	0.183 8(2)	Ni(2)-0(3)	0.183 7(2)	Ni(1)-0(2)	0.184 4(2)
  Ni(2)-0(4)	0.184 4(2)	Ni(1)-N(2)	0.184 7(3)	Ni(2)-N(4)	0.184 6(3)
  Ni(1)-N(1)	0.185 5(3)	Ni(2)-N(3)	0.185 4(3)	Ni(1)-Ni(1)ⅱ	0.352 97(2)
  Ni(2)_Ni(2)ⅲ	0.338 07(10)	Cl(1)-C(2)	0.174 0(4)	Cl(3)-C(22)	0.174 3(3)
  Cl(2)-C(19)	0.174 1(4)	Cl(4)-C(39)	0.173 4(3)
  0(1)-Ni(1)-0(2)	84.26(10)	0(3)-Ni(2)-0(4)	84.02(10)	0(1)-Ni(1)-N(2)	175.91(12)
  0(3)-Ni(2)-N(4)	178.18(12)	0(2)-Ni(1)-N(2)	94.18(11)	0(4)-Ni(2)-N(4)	94.24(11)
  0(1)-Ni(1)-N(1)	95.08(11)	0(3)-Ni(2)-N(3)	94.90(11)	0(2)-Ni(1)-N(1)	175.87(13)
  0(4)-Ni(2)-N(3)	178.35(12)	N(2)-Ni(1)-N(1)	86.75(12)	N(4)-Ni(2)-N(3)	86.86(12)
  Symmetry codes: ⅰ -x+1, -y, -z for 1; ⅱ -x, 1-y, -z; ⅲ x, -y, 1-z for 2.

  CCDC: 1892682, 1; 1855958, 2.

  2.   Results and discussion

  2.1   Structure description

  The identity of 1 and 2 were elucidated by single-crystal X-ray diffraction, elemental analysis results of were fully consistent with the crystallographic formulation. Single-crystal X-ray diffraction reveals that complex 1 crystallizes in the monoclinic P2₁/c (No.14) space group, which unit cell contains one crystallography independent Ni(Ⅱ) forming two racemic neutral monomers [Ni((+)-3, 5-Cl-salcy)] and [Ni((-)-3, 5-Cl-salcy)]. As shown in Fig. 1, the central Ni(Ⅱ) exhibits tetra-coordinated environment which is defined by [N₂O₂] in the equatorial plane from Schiff-base ligand. The bond lengths of Ni-O(N) are in a range of 0.183 7(3)~0.185 5(4) nm, and bond angles of O(N)-Ni-O vary from 84.23(15)° to 178.38(16)°, which are favorably comparable with the corresponding values observed in salen-type Ni(Ⅱ) analogous^[24-25].

  Figure 1

  

  Figure 1.  (a) Asymmetric unit of 1 with displacement ellipsoids drawn at 30% probability level; (b) π…π non-bonding contact of self-assembled supramolecular dimer built up by symmetry operation: 1-x, -y, -z

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  The dihedral angle calculated between the planes of two benzene rings for 1 is 8.23(10)°, thus, the whole molecule exhibit coplanar configuration. Owing to the π-π interactions (the distances of Cg1^ⅰ…Cg1 and Cg2^ⅰ…Cg2 are equal to each other with centroid-to-centroid distance of 0.387 4(32) nm, Cg1: centroid of C1~C6 ring, Cg3:C15~C20 ring, Symmetry code: ^ⅰ 1-x, -y, -z), two neighboring molecules are further linked to each other to form a self-assembled supramolecular dimer (Fig. 1(b)), in which the Ni…Ni distance of ca. 0.331(26) nm (Fig. 2) is smaller than the sum of two nickel atoms′ van der Waals radius^[26].

  Figure 2

  

  Figure 2.  Ni…Ni no bond interactions in 1, built up by symmetry operation: 1-x, -y, -z

  van der Waals radius for Ni atom: 200 pm

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  It is noteworthy that according to the analysis result of PLATON software^[27], except π-π interactions, there is not any classical or unclassical hydrogen bond in the crystal structure. By comparison, Hirshfeld surface gives us qualitative and quantitative contributions of the interactions in the crystal packing. Detailed discussion is addressed in Hirshfeld surface analysis section.

  Complex 2 crystallizes in the triclinic P1 (No.2) space group, and its asymmetric unit contains two identical, but crystallogaphically independent mononu-clear Ni(Ⅱ) unit. The Ni(Ⅱ) centers present same coor-dination environment with 1 by chelating with chloride salen-type ligand via [N₂O₂] in the equatorial plane. The bond lengths of Ni-O and Ni-N in the two Ni(Ⅱ) moieties are in a range of 0.183 7(2)~0.184 4(2) nm and 0.184 6(3)~0.185 5(3) nm, respectively. The bond angles around Ni(Ⅱ) centers have been found to be 84.02(10)° to 94.90(11)°, respectively (Fig. 3).

  Figure 3

  

  Figure 3.  Molecular structure of 2 showing the atom-labeling scheme

  Displacement ellipsoids are drawn at the 40% probability level; H atoms are omitted for clarity

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  Intermolecular interaction analysis shows that the distance between Cg1^ⅱ…Cg1 is equal to Cg2^ⅱ…Cg2 (Symmetry code: ^ⅱ -x, 1-y, -z) and Cg3^ⅲ…Cg3 is equal to Cg4^ⅲ…Cg4 (Symmetry code: ^ⅲ x, -y, 1-z), with centroid-to-centroid distance being 0.419 6(2) and 0.382 2(2) nm, respectively, where Cg1, Cg2, Cg3 and Cg4 are the centroids of the C1~C6, C5~C20, C21~C26 and C35~C40, respectively. Beside these offset π-π stacking created by neighboring monomers, hydrogen bonds formed by phenolic oxygen atoms also play an important part in linking the neighboring racemic monomers to form self-assembled supramole-cular dimers (C8-H8…O1^ⅲ: D…A 0.339 3(5) nm, D-H…A 145°). According to the analysis result of PLATON software^[27], although there is no classic H-bond interactions in 2, C-H…Cl hydrogen bonds play a key role in stabilizing the crystal structure. As illustrated in Fig. 4, the adjacent monomers are connected by multiple C-H…Cl hydrogen bonds interactions to generate a two-dimensional layered structure. Detailed hydrogen-bond geometry information is summarized in Table 3.

  Figure 4

  

  Figure 4.  Two-dimensional layer structure of complex 2 formed by intramolecular hydrogen bonding

  Symmetry codes: ^ⅳ-1+x, 1+y, z; ^ⅴ-x, 1-y, -z; Intramolecular hydrogen bonds are shown as a dashed line

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  Table 3

  

  Table 3.  PLATON analysis result of 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/(°)
  C(8)-H(8)…O(1)	0.098	0.254	0.339 3(5)	145
  C(17)-H(17)…Cl(3)	0.093	0.276	0.342 9(4)	130
  C(29)-H(29B)…Cl(2)	0.097	0.278	0.372 4(4)	163
  C(32)-H(32B)…Cl(1)	0.097	0.283	0.358 7(4)	136

  2.2   IR absorbance spectrum

  The IR spectra of the complexes are very similar in the given region, and therefore, the spectrum of complex 1 is described here representatively. The IR spectrum (Fig. 5) showed a broad band centered in a range of 2 950~2 850 cm^-1 and a strong peak at 1 447 cm^-1 are assigned to ν(-CH₂-) vibrations indicating the presence of -CH₂- group of the cyclohexane unit. The strong peak at 1 632 cm^-1 corresponds to the vibration of the C=N bonds. The characteristic peaks at 1 132 and 575 cm^-1 are attributed to the vibrations of ν(Ni-O) and ν(Ni-O), respectively, and the peak at 729 cm^-1 is attributed to the ν(C-Cl). These results are consistent with the structural analysis.

  Figure 5

  

  Figure 5.  IR spectrum of 1

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  2.3   Hirshfeld surface analysis

  The bundle of inter-related weak molecular interactions is difficult to be unraveled by traditional methods^[28]. Hirshfeld surface analysis provides us a new perspective on the issue. This analysis method can provide detailed explanation about the nearby environment of the molecules in a crystal, and the comparison between similar structures can give a more specific description of the difference^[29]. Although hydrogen bond interaction formed by halogen is weak and cannot be easily find out by traditional methods, Hirshfeld surface in the 2D fingerprint plots show that, for complex 1, the Cl…H-C interaction (Fig. 6a) covers the highest proportion (42.5%) of the total plots, whereas the C…H-C (Fig. 6b) contacts only cover less than a third proportion of Cl…H-C interaction (14.0%). These results indicate that the halogen atoms in 1 play the most important part in stabilizing the solid stature.

  Figure 6

  

  Figure 6.  Two-dimensional fingerprint plots of complex 1 resolved into Cl…H/H…Cl (a) and C…H/H…C (b)

  Surfaces in the right hand columns highlight the relevant surface patches associated with the specific contacts in the total Hirshfeld surface area of the complex

  下载: 全尺寸图片 幻灯片

  As shown in Fig. 7, Cl…H/H…Cl bonding still appears to be a major contributor in the crystal packing of 2, and the proportion is significantly lower than that in 1, merely comprising 26.1% of the total Hirshfeld surfaces, whereas C…H/H…C close contacts contribution appear higher in the 2D fingerprint plot(19.8%). These results indicate that although the structure and composition of 2 is similar with 1, different substitution number of chlorine atoms may result in an entirely different intermolecular interactions in solid structures.

  Figure 7

  

  Figure 7.  Two dimensional fingerprint plots of complex 2 resolved into Cl…H/H…Cl (a) and C…H/H…C (b) contacts

  Surfaces in the right hand columns highlight the relevant surface patches associated with the specific contacts in the total Hirshfeld surface area of the complex

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  3.   Conclusions

  In summary, two new salen-type halogenated Schiff-base Ni(Ⅱ) complexes have been synthesized by conventional method. The structures of the complexes were determined by single-crystal X-ray diffractions. A detailed comparison of Hirshfeld surface analysis result indicate that although the interaction formed by halogen atom is weak, halogen atoms can play an important role in supramolecular interaction. As different supramolecular interaction can lead a totally different physicochemical properties, further work will continue focus on the synthesis of halogenate ligands constructed complexes to systematically explore the regulating effect of halogen atoms.

  Acknowledgement: This work was supported by Fund for Less Developed Regions of the National Natural Science Foundation of China (Grant No.31760257); Joint Research Projects of Yunnan province of Local of institutions (partial) of higher education (Grant No.2017FH001-002); Agricultural plastic film and products research and development of Plateau area (Grant No.2016DH006); The Kunming University Chemistry & Chemical engineering students′ science and technology innovation project (Grant No.HXHG1808).

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  Scheme 1  Schematic drawing of halogenated tetradentate Schiff base ligands 3, 5-Cl-salcyH₂ and 3-Cl-salcyH₂

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  Figure 1  (a) Asymmetric unit of 1 with displacement ellipsoids drawn at 30% probability level; (b) π…π non-bonding contact of self-assembled supramolecular dimer built up by symmetry operation: 1-x, -y, -z

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  Figure 2  Ni…Ni no bond interactions in 1, built up by symmetry operation: 1-x, -y, -z

  van der Waals radius for Ni atom: 200 pm

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  Figure 3  Molecular structure of 2 showing the atom-labeling scheme

  Displacement ellipsoids are drawn at the 40% probability level; H atoms are omitted for clarity

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  Figure 4  Two-dimensional layer structure of complex 2 formed by intramolecular hydrogen bonding

  Symmetry codes: ^ⅳ-1+x, 1+y, z; ^ⅴ-x, 1-y, -z; Intramolecular hydrogen bonds are shown as a dashed line

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  Figure 5  IR spectrum of 1

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  Figure 6  Two-dimensional fingerprint plots of complex 1 resolved into Cl…H/H…Cl (a) and C…H/H…C (b)

  Surfaces in the right hand columns highlight the relevant surface patches associated with the specific contacts in the total Hirshfeld surface area of the complex

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  Figure 7  Two dimensional fingerprint plots of complex 2 resolved into Cl…H/H…Cl (a) and C…H/H…C (b) contacts

  Surfaces in the right hand columns highlight the relevant surface patches associated with the specific contacts in the total Hirshfeld surface area of the complex

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  Table 1.  Crystallographic data and structure refinement for complexes 1 and 2

  Complex	1	2
  Formula	C20H16Cl4N2Ni02	C20H18Cl2N2Ni02
  Formula weight	516.84	447.95
  Crystal system	Monoclinic	Triclinic
  Crystal size / mm	0.20×0.18×0.16	0.18×0.14×0.12
  Space group	P21/c	P1
  a / nm	1.352 06(14)	1.174 51(8)
  b/ nm	1.377 74(10)	1.287 43(8)
  c / nm	1.247 79(13)	1.356 64(8)
  α/(°)		86.447(5)
  β/(°)	117.130(13)	69.997(6)
  γ/(°)		76.885(6)
  Volume / nm3	2.068 6(3)	1.877 1(2)
  Dc/ (g·cm-3)	1.66	1.585
  Z	4	1
  μ / mm-1	1.475	1.336
  Reflection collected, unique (Rint)	8 941, 3 518 (0.029 0)	13 206, 6 592 (0.066 6)
  Reflection with I > 2σ(I)	1 847	2 695
  θ range for data collection / (°)	3.27~25.00	3.34~25.00
  Data, restraint, parameter	3 518, 0, 262	6 592, 0, 487
  Goodness-of-fit on F2	1.047	0.945
  R indices [I > 2σ(I)]a, b	R1=0.034 7, wR2=0.072 1	R1=0.058 6, wR2=0.061 0
  R indices (all data)	R1=0.050 4, wR2=0.080 8	R1=0.129 0, wR2=0.077 1
  (Δρ)max, (Δρ)min/ (e·nm-3)	393, -276	409, -438
  a R1=||Fo|-|Fc||/|Fo|; b wR2=[w(Fo2-Fc2)2]/[w(Fo2)2]1/2.

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

  1
  Ni(1)-O(2)	0.184 57(18)	Ni(1)-0(1)	0.185 32(19)	Ni(1)-N(2)	0.185 1(2)
  Ni(1)-N(1)	0.185 3(2)	Ni(1)-Ni(1)ⅰ	0.331 56(7)	Cl(1)-C(4)	0.174 0(3)
  Cl(3)-C(2)	0.173 4(3)	Cl(2)-C(17)	0.174 5(3)	Cl(4)-C(19)	0.173 3(3)
  0(2)-Ni(1)-N(2)	93.93(9)	0(2)-Ni(1)-N(1)	179.74(10)	0(2)-Ni(1)-0(1)	85.61(8)
  N(2)-Ni(1)-N(1)	85.81(10)	N(2)-Ni(1)-0(1)	178.60(9)	0(1)-Ni(1)-N(1)	94.64(9)
  C(3)-C(2)-Cl(3)	118.6(2)	C(5)-C(4)-Cl(1)	119.8(3)	C(1)-C(2)-Cl(3)	118.5(2)
  C(3)-C(4)-Cl(1)	119.5(3)
  2
  Ni(1)-0(1)	0.183 8(2)	Ni(2)-0(3)	0.183 7(2)	Ni(1)-0(2)	0.184 4(2)
  Ni(2)-0(4)	0.184 4(2)	Ni(1)-N(2)	0.184 7(3)	Ni(2)-N(4)	0.184 6(3)
  Ni(1)-N(1)	0.185 5(3)	Ni(2)-N(3)	0.185 4(3)	Ni(1)-Ni(1)ⅱ	0.352 97(2)
  Ni(2)_Ni(2)ⅲ	0.338 07(10)	Cl(1)-C(2)	0.174 0(4)	Cl(3)-C(22)	0.174 3(3)
  Cl(2)-C(19)	0.174 1(4)	Cl(4)-C(39)	0.173 4(3)
  0(1)-Ni(1)-0(2)	84.26(10)	0(3)-Ni(2)-0(4)	84.02(10)	0(1)-Ni(1)-N(2)	175.91(12)
  0(3)-Ni(2)-N(4)	178.18(12)	0(2)-Ni(1)-N(2)	94.18(11)	0(4)-Ni(2)-N(4)	94.24(11)
  0(1)-Ni(1)-N(1)	95.08(11)	0(3)-Ni(2)-N(3)	94.90(11)	0(2)-Ni(1)-N(1)	175.87(13)
  0(4)-Ni(2)-N(3)	178.35(12)	N(2)-Ni(1)-N(1)	86.75(12)	N(4)-Ni(2)-N(3)	86.86(12)
  Symmetry codes: ⅰ -x+1, -y, -z for 1; ⅱ -x, 1-y, -z; ⅲ x, -y, 1-z for 2.

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  Table 3.  PLATON analysis result of hydrogen bond parameters for complex 2

  D-H …A	d(D-H) / nm	d(H …A) / nm	d(D …A) / nm	∠DHA/(°)
  C(8)-H(8)…O(1)	0.098	0.254	0.339 3(5)	145
  C(17)-H(17)…Cl(3)	0.093	0.276	0.342 9(4)	130
  C(29)-H(29B)…Cl(2)	0.097	0.278	0.372 4(4)	163
  C(32)-H(32B)…Cl(1)	0.097	0.283	0.358 7(4)	136

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