English

• 0   Introduction

  Schiff base compounds have been playing an important part in the development of coordination chemistry because of their potential application in catalysis^[1-2], bioscience^[3-4], new materials^[5], magnetic properties^[6-9] and constructing supramolecular structu-res^[10-11]. Also, the Schiff base ligands are strong donors and therefore the oxime-containing ligands were found to efficiently stabilize high oxidation states of metal ions like Cu (Ⅱ) and Ni (Ⅱ). The presence of additional donor groups together with the oxime group in the ligand molecule may result in significant increase of chelating efficiency and ability to form polynuclear complexes. Herein, two new Cu (Ⅱ) complexes with the Schiff base ligand, [Cu (L¹)₂] (1) (HL¹=1-(3-((2-hydroxybenzylidene) amino) phenyl) ethanone O-benzyl oxime) and [Cu (L²)₂] (2) (HL²=1-(3-((2-Hydroxy-naphthalen-1-ylmethylene)-amino)-phenyl)-ethanone oxime) have been synthesized and characterized by elemental analyses, IR spectra, UV-Vis spectra, fluorescence measurement and X-ray single crystal diffraction. X-ray crystallographic analyses reveal that the structures of the complexes 1 and 2 are very similar. They are both mononuclear structures and all the Cu (Ⅱ) ions are four-coordinated.

  1   Experimental

  1.1   Materials

  3-Aminoacetophenone, O-benzylhydroxylamine, salicylaldehyde and 2-hydroxy naphthaldehyde were purchased from Alfa Aesar and used without further purification. The other reagents and solvent were analytical grade from Tianjin Chemical Reagent Factory.

  1.2   Methods

  C, H and N analyses were carried out with a GmbH VariuoEL V3.00 automatic elemental analyzer. Elemental analysis for Cu was detected by an IRIS ER/S·WP-1 ICP atomic emission spectrometer. FTIR spectra were recorded on a VERTEX70 FTIR spectrophotometer, with samples prepared as KBr pellet (400~4000 cm^-1). UV-Vis absorption spectra were recorded on a Shimadzu UV-2550 spectrometer. X-Ray single crystal structure was determined on a Bruker Smart 1000 CCD area detector. Melting points were measured by the use of a microscopic melting point apparatus made in Beijing Taike Instrument Limited Company and the thermometer was uncorrected.

  1.3   Syntheses of HL¹ and HL²

  HL¹ (1-(3-((2-hydroxybenzylidene) amino) phenyl) ethanone O-benzyl oxime) and HL² (1-(3-((2-Hydroxy-naphthalen-1-ylmethylene)-amino)-phenyl)-ethanone oxime) were synthesized according to the reported method (Scheme 1)^[12-13].

  Scheme 1.  Synthetic routes of HL¹ and HL²

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  1.4   Synthesis of [Cu (L¹)₂] (1)

  A solution of copper (Ⅱ) acetate monohydrate (1.3 mg, 0.007 mmol) in methanol (4 mL) was added dropwise to a solution of HL¹ (1.7 mg, 0.005 mmol) in dichloromethane (5 mL) at room temperature. The mixing solution turned to yellow immediately. Then it was filtered and the filtrate was allowed to stand at room temperature for about one week. Brown red block single crystals which is suitable for X-ray structural determination were obtained. Anal. Calcd. for C₄₄H₃₈CuN₄O₄ (%): C, 70.43; H, 5.10; N, 7.47; Cu, 8.47. Found (%): C, 70.38; H, 5.17; N, 7.45; Cu, 8.50.

  1.5   Synthesis of [Cu (L²)₂] (2)

  A solution of copper (Ⅱ) acetate monohydrate (2.3 mg, 0.01 mmol) in methanol (3 mL) was added dropwise to a solution of HL² (1.5 mg, 0.005 mmol) in dichloromethane (5 mL) at room temperature. The color of the mixing solution turned yellow immediately, and it was allowed to stand at room temperature for three weeks. Then the solvent partially evaporated and red-brown prismatic single crystals suitable for X-ray crystallographic analysis were obtained. Anal. Calcd. for C₃₈H₃₀CuN₄O₄(%): C, 68.10; H, 4.51; N, 8.36; Cu, 9.48. Found (%): C, 67.98; H, 4.57; N, 8.29; Cu, 9.52.

  1.6   Crystal structure determination

  The single crystals of complexes with approximate dimensions of 0.21×0.11×0.05 mm (1) and 0.18×0.14×0.09 mm (2) were placed on a Bruker Smart 1000 CCD area detector. The diffraction data were collected using a graphite monochromated Mo Kα radiation (λ=0.071 073 nm) at 298(2) K. Empirical absorption correction was applied to the data using SADABS program^[14]. The structure was solved by direct methods and refined by full-matrix leastsquares method on F² using the SHELXTL program^[15]. All nonhydrogen atoms were refined anisotropically. All the hydrogen atoms were generated geometrically and refined isotropically using the riding model. Details of the crystal parameters, data collection and refinements for complexes 1 and 2 are summarized in Table 1.

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

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  Complex	1	2
  Empirical formula	C44H38CuN4O4	C38H30CuN4O4
  Formula weight	750.32	670.21
  Crystal system	Triclinic	Monoclinic
  Space group	P1	C2/c
  a/nm	0.781 30(6)	2.940 0(4)
  b/nm	0.939 05(8)	0.584 20(7)
  c/nm	1.237 2(1)	1.870 0(2)
  α/(°)	94.549(2)	90
  β/(°)	93.738(1)	102.660(2)
  γ/(°)	91.377(1)	90
  V/nm3	0.902 6(1)	3.159 3(4)
  Z	1	4
  Dc/(g.cm3)	1.38	1.409
  μ/(mm-1)	0.656	0.74
  F(000)	391	1 388
  θ range for data collection/(°)	2.61~25.02	1.41~25.10
  Limiting indices	-7≤h≤9;-9≤k≤11;-14≤l≤13	-35≤h≤33;-6≤k≤6;-22≤l≤22
  Reflections collected, unique	4 607, 3 119(Rint=0.073 4)	7 968, 2 805(Rint=0.086 0)
  Completeness to θ/%	97.8(θ=25.02°)	100%(θ=25.10°)
  Data, restraints, parameters	3 119, 0, 242	2 085, 0, 216
  GOF on F2	1.027	0.965
  Final R indices [I > 2σ(I)]	R1=0.080 0, wR2=0.175 8	R1=0.057 0, wR2=0.130 1
  R indices (all data)	R1=0.128 9, WR2=0.196 5	R1=0.107 3, wR2=0.157 4
  (△ρ)max, (△ρ)min/(e • nm-3)	521, -526	941, -876

  2   Results and discussion

  2.1   IR spectra analyses

  The FTIR spectra of HL¹, HL² and their corresponding Cu (Ⅱ) complexes 1 and 2 exhibit various bands in the 400~4 000 cm^-1 region. The most important FTIR bands for HL¹, HL² and complex 1~2 are given in Table 2. The free ligand HL¹ and HL² exhibit characteristic C=N stretching bands at 1 617 and 1 620 cm^-1, while that of complex 1 and complex 2 were observed in the 1 600 cm^-1 and 1 602 cm^-1, respectively. The C=N stretching frequencies are all shifted to lower frequencies by ca. 17 and 18 cm^-1 upon complexation respectively, indicating a decrease in the C=N bond order due to the coordinated bond of the Cu (Ⅱ) atom with the imino nitrogen lone pair^[16]. In the 1 445~1 564 cm^-1 region, the observed bands were attributed to aromatic C=C vibrations. Upon coordination these bands shift to lower frequencies for the Cu (Ⅱ) complexes^[17]. The Ar-O stretching frequency appears as a strong band within the 1 178~1 144 cm^-1 as reported for similar ligands^[18]. This band occurs at 1 178 cm^-1 for the ligand HL¹, and at 1 144 cm^-1 for complex 1, the band occurs at 1 182 cm^-1 for the ligand HL², and at 1 137 cm^-1 for complex 2. The Ar-O stretching frequency is shifted to a lower frequency, indicating that the Cu-O bond was formed between the Cu (Ⅱ) ion and phenolic oxygen atom of phenolic hydroxyl group^[13]. The far-infrared spectra of complexes 1 and 2 was also obtained in the region 500~100 cm^-1 in order to identify frequencies due to the Cu-O and Cu-N bonds. The FTIR spectrum of complex 1 showed ν(Cu-N) and ν(Cu-O) vibration absorption frequencies at 540 cm^-1 and 503 cm^-1 (or 519 and 463 cm^-1 for complex 2), respectively. These assignments are consistent with the literature frequency values^[19].

  Table 2.  Main bands in IR spectra of the ligand HL¹, HL² and their Cu (Ⅱ) complexes

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  cm-1
  	ν(C=N)	ν(Ar-0)	ν(Cu-N)	ν(Cu-0)	ν(C=C) benzene ring skeleton
  HL1	1 617	1 178	-	-	1 564	1 490	1 452
  Complex 1	1 600	1 144	540	503	1 531	1 500	1 445
  HL2	1 620	1 182	-	-	1 589	1 543	1 483
  Complex 2	1 602	1 137	519	463	1 548	1 526	1 456

  2.2   UV-Vis absorption spectra analyses

  The absorption spectra of ligand HL¹ and its corresponding Cu (Ⅱ) complex 1 were determined in diluted CH₂Cl₂ solution, and ligand HL² and its corresponding Cu (Ⅱ) complex 2 were determined in diluted DMF solution as shown in Fig. 1 and Fig. 2.

  Figure 1.  UV-Vis absorption spectra of HL¹ and the complex 1 in diluted CH₂Cl₂ solution at room temperature (c=5×10^-5 mol·L^-1)

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  Figure 2.  UV-Vis absorption spectra of HL² and the complex 2 in diluted DMF solution at room temperature (c=5×10^-5 mol·L^-1)

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  UV-Vis spectrum of the free ligand HL¹ exhibits three absorption peaks at ca. 224, 262 and 347 nm (Fig. 1). The absorption peak of HL¹ at 224 nm assigned to the π-π^* transition of the benzene rings shifts to low energy region by ca. 7 nm in complex 1, indicating Cu (Ⅱ) ion coordinated with the O and N atoms of ligand units. The absorption peak of HL¹ at 262 nm attributed to the intra-ligand π-π^* transition of the C=N bonds is shifted to 269 nm in complex 1 upon complexation. The absorption peak of HL¹ at 347 nm is absent in complex 1, however, a new absorption peak is observed at 388 nm assigned to an L→M charge-transfer transition which is characteristic of a transition metal complex with N₂O₂ coordination sphere^[20]. It can be seen that the absorption peaks of complex 2 are obviously different from those of the HL¹ upon complexation (Fig. 2). Compared with complex 2, an important feature of the absorption spectrum of HL² is shown that three absorption peaks are observed at 243, 382 and 437 nm, which are absent in the spectrum of complex 2. The other feature is that the absorption peak at 267 and 320 nm in HL² is shifted to 269 and 311 nm in complex 2, respectively, indicating that the coordination of Cu (Ⅱ) atom with HL².

  2.3   Fluorescence spectra

  The emission spectrum of the complex 1 in diluted CH₂Cl₂ solution at room temperature is shown in Fig. 3. An intense excitation peak is observed at 311 nm. The bluish violet emission for complex 1 can be observed, where the maximum emission wavelength was at 430 nm. The Stokes shift between the maximum wavelength of the fluorescence emission and the fluorescence excitation is 119 nm. This red-shift might be related to the coordination of the Cu (Ⅱ) atom to the ligand and increase of the rigidity of the ligands, which can diminish the loss of energy via vibrational motions and increase the emission efficiency.

  Figure 3.  Emission spectrum of the complex 1 in diluted CH₂Cl₂ at room temperature

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  2.4   Structural Description of the complexes 1 and 2

  The single crystal structures of complexes 1 and 2 were confirmed by X-ray crystallography (Fig. 4 and 5). The selected bond lengths and angles of complexes 1 and 2 are listed in Table 3. The complex 1 crystallizes in the triclinic system and P1 space group, whereas the complex 2 crystallizes in the monoclinic system and C2/c space group. Both of the complexes can be described as centrosymmetric mononuclear Cu (Ⅱ) complexes. The Cu (Ⅱ) ion lying on the inversion centre, is four-coordinated in a trans-CuN₂O₂ square-planar geometry, with two phenolic O and two imino N atoms from two N, O-bidentate oxime-type ligands (HL¹ and HL²).

  Figure 4.  Molecular structure of complex 1 showing 30% probability displacement ellipsoids

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  Figure 5.  Molecular structure of complex 2 showing 30% probability displacement ellipsoids

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  Table 3.  Selected bond lengths (nm) and bond angles (°) for complexes 1 and 2

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  1
  Cul-02a	0.l88 8(4)	Cul-02	0.l88 8(4)	Cul-N2a	0.200 0(4)
  Cul-N2	0.200 0(4)
  02a-Cul-02	l80.00(l)	02-Cul-N2a	88.35(2)	N2a-Cul-N2	l80.00(2)
  C5-N2-Cul	l2l.8(4)	02a-Cul-N2a	9l.65(2)	02a-Cul-N2	88.35(2)
  C9-N2-Cul	l2l.5(3)	Cll-02-Cul	l27.0(4)
  2
  Cul-0lb	0.l88 5(3)	Cul-0l	0.l88 5(3)	Cul-Nlb	0.20l 4(3)
  Cul-Nl	0.20l 4(3)
  0l-Cul-0lb	l80.00(9)	0l-Cul-Nlb	89.6l (l)	Nlb-Cul-Nl	l79.99(2)
  Cl2-N2-Cul	l20.7(3)	0lb-Cul-Nlb	90.39(l)	0lb-Cul-Nl	89.6l (l)
  Cll-N2-Cul	l23.l (3)	C7-0l-Cul	l30.5(3)
  Symmetry codes: a: 1-x, 1-y, 1-z for 1；b:-x, -y+1, -z+2 for 2

  As shown in Fig. 6, complex 1 is stabilized by the π_{centroid (C10-C15)}-π_{centroid (C10-C15)} stacking interactions of benzene rings linking the neighboring molecules into a 1D infinite chain parallel to the a axis (Table 4). In addition, this adjacent chains along a axis are further held together by the other intermolecular π_{centroid (C17-C22)}-π_{centroid (C17-C22)} stacking interactions (Fig. 7) to form 2D supramolecular structure parallel to the ac planes (Fig. 8). Whereas in complex 2, as illustrated in Fig. 9, each oxime nitrogen atom N2 of the two ligand molecules is hydrogen-bonded to the-O2H2A group of the oxime group from the other neighboring molecule, which resulted in the formation of a classical six-member ring and a 1D infinite chain synchronously. Furthermore, this linkage is further stabilized by four C17-H17…π(Cg3) interactions to form the 2D infinite supramolecular planar (Fig. 10 and Table 5).

  Figure 6.  View of the 1D single chain motif within complex 1 along the a axis

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  Table 4.  Putative π-π stacking interactions for complex 1

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  Ring (I)	Ring (J)	d (Cg-Cg)/nm	d (Cg (I)-perp)/nm	d (Cg (J)-perp)/nm	Slippage/nm
  Cgl*	Cg1	0.406 6(4)	0.353 8(3)	0.353 7(3)	0.200 5
  Cg2*	Cg2	0.387 2(4)	0.357 3(3)	0.357 3(3)	0.l49 2
  *Cgl and Cg2 are the centroids of benzene ring Cl0-Cl5 and Cl7-C22 of complex 1, respectively

  Figure 7.  View of the 1D single chain motif within complex 1 along the c axis

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  Figure 8.  Part of 2D supramolecular structure of the complex 1 showing the formation the two π…π stacking interaction

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  Figure 9.  View of a 1D single chain motif containing hydrogen bonds for complex 2

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  Figure 10.  Part of 2D supramolecular structure of the complex 2 showing the formation of C17-H17…Cg3 and O2-H2A…N2 hydrogen bond

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  Table 5.  Hydrogen-bonding for complex 2

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  D-H…A	d (D-H)/nm	d (H…A)/nm	d (D…A)/nm	∠DHA/(°)	Symmetry code
  02-H2A…N2	0.082 0	0.208	0.278 9 (6)	l45	l/2-x, 3/2-y, 2-z
  Cl7-Hl7…Cg3*	0.093 0	0.295	0.379 8(4)	l53	x, l+y, z
  *Cg3 is the centroid of benzene ring Cl-C5-Cl0 of complex 2

  2.5   Substituent effects

  The overall structures of the two complexes are found to be identical except that the oxime portion and aromatic ring differs in the ligands. The bond lengths of complex 1 are different from those of complex 2 due to the different substituent group in the bidentate ligands. In both bases, two imino nitrogen and two phenolic oxygen atoms form the square base with the Cu-N bonds being slightly longer than the corresponding Cu-O bonds. The elongation of the Cu-N bonds probably due to the weaker coordina-tion ability of the nitrogen atom than that of phenolic oxygen atom. Similar elongation has been observed in Cu (Ⅱ) complexes with Schiff base ligands^[21-22]. However, the coordination bond Cu-N (0.200 0 nm) of complex 1 is shorter than the Cu-N (0.201 4 nm) of complex 2, but Cu-O (0.188 8 nm) of complex 1 is almost equal to the Cu-O (0.188 5 nm) of complex 2. Meanwhile, the angle of N2-Cu1-O2 (88.35°) in complex 1 is smaller with the angle of N1-Cu1-O1 (89.61°) in complex 2. In addition, the supramolecular structures of the two complexes 1 and 2 are also similar two-dimensional supramolecular structure linking by different intermolecular interaction, in which complex 1 is stabilized by two π…π interaction, while that of complex 2 by intermolecular O-H…N and C-H…π hydrogen bond interactions. The substituent effects also give rise to the variations in IR and UV-Vis spectra in complexes 1 and 2.

  3   Conclusions

  According to the data and discussion above, two Schiff base mononuclear Cu (Ⅱ) complexes 1 and 2 have been synthesized and characterized structurally. The Cu (Ⅱ) complexes are tetra-coordinated by two nitrogen atoms and two oxygen atoms of two deprotonated L-units defining the N₂O₂ basal plane. The coordination environment around Cu (Ⅱ) atom is best regarded as the square-planar geometry. Complexes 1 and 2 also formed a 2D-layer supramolecular structure by different intermolecular interaction, π…π interaction and O-H…N, C-H…π hydrogen bond interactions, respectively. Consequently, the intermolecular non-classical hydrogen-bonding plays a very important role in the construction of supramolecular networks structure. Furthermore, the substituted groups on the ligands could play a small impact on the coordination geometries and supramolecular structure of complexes 1 and 2.

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• 

  Scheme 1  Synthetic routes of HL¹ and HL²

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  Figure 1  UV-Vis absorption spectra of HL¹ and the complex 1 in diluted CH₂Cl₂ solution at room temperature (c=5×10^-5 mol·L^-1)

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  Figure 2  UV-Vis absorption spectra of HL² and the complex 2 in diluted DMF solution at room temperature (c=5×10^-5 mol·L^-1)

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  Figure 3  Emission spectrum of the complex 1 in diluted CH₂Cl₂ at room temperature

  c=5.00×10^-5 mol·L^-1, λ_ex=311 nm, λ_em=430 nm

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  Figure 4  Molecular structure of complex 1 showing 30% probability displacement ellipsoids

  Symmetry code: a: 1-x, 1-y, 1-z

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  Figure 5  Molecular structure of complex 2 showing 30% probability displacement ellipsoids

  Symmetry code: a:-x, 1-y, 2-z

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  Figure 6  View of the 1D single chain motif within complex 1 along the a axis

  Hydrogen atoms are omitted for clarity; Symmetry code: a: 2-x, 1-y, 1-z

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  Figure 7  View of the 1D single chain motif within complex 1 along the c axis

  Symmetry code: a: 3-x, 1-y, 2-z

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  Figure 8  Part of 2D supramolecular structure of the complex 1 showing the formation the two π…π stacking interaction

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  Figure 9  View of a 1D single chain motif containing hydrogen bonds for complex 2

  Hydrogen atoms, except those forming hydrogen bonds, are omitted for clarity; Symmetry code: a: 1/2-x, 3/2-y, 2-z

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  Figure 10  Part of 2D supramolecular structure of the complex 2 showing the formation of C17-H17…Cg3 and O2-H2A…N2 hydrogen bond

  Symmetry code: a: 1/2-x, 3/2-y, 2-z; b: x, 1+y, z

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

  Complex	1	2
  Empirical formula	C44H38CuN4O4	C38H30CuN4O4
  Formula weight	750.32	670.21
  Crystal system	Triclinic	Monoclinic
  Space group	P1	C2/c
  a/nm	0.781 30(6)	2.940 0(4)
  b/nm	0.939 05(8)	0.584 20(7)
  c/nm	1.237 2(1)	1.870 0(2)
  α/(°)	94.549(2)	90
  β/(°)	93.738(1)	102.660(2)
  γ/(°)	91.377(1)	90
  V/nm3	0.902 6(1)	3.159 3(4)
  Z	1	4
  Dc/(g.cm3)	1.38	1.409
  μ/(mm-1)	0.656	0.74
  F(000)	391	1 388
  θ range for data collection/(°)	2.61~25.02	1.41~25.10
  Limiting indices	-7≤h≤9;-9≤k≤11;-14≤l≤13	-35≤h≤33;-6≤k≤6;-22≤l≤22
  Reflections collected, unique	4 607, 3 119(Rint=0.073 4)	7 968, 2 805(Rint=0.086 0)
  Completeness to θ/%	97.8(θ=25.02°)	100%(θ=25.10°)
  Data, restraints, parameters	3 119, 0, 242	2 085, 0, 216
  GOF on F2	1.027	0.965
  Final R indices [I > 2σ(I)]	R1=0.080 0, wR2=0.175 8	R1=0.057 0, wR2=0.130 1
  R indices (all data)	R1=0.128 9, WR2=0.196 5	R1=0.107 3, wR2=0.157 4
  (△ρ)max, (△ρ)min/(e • nm-3)	521, -526	941, -876

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  Table 2.  Main bands in IR spectra of the ligand HL¹, HL² and their Cu (Ⅱ) complexes

  cm-1
  	ν(C=N)	ν(Ar-0)	ν(Cu-N)	ν(Cu-0)	ν(C=C) benzene ring skeleton
  HL1	1 617	1 178	-	-	1 564	1 490	1 452
  Complex 1	1 600	1 144	540	503	1 531	1 500	1 445
  HL2	1 620	1 182	-	-	1 589	1 543	1 483
  Complex 2	1 602	1 137	519	463	1 548	1 526	1 456

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  Table 3.  Selected bond lengths (nm) and bond angles (°) for complexes 1 and 2

  1
  Cul-02a	0.l88 8(4)	Cul-02	0.l88 8(4)	Cul-N2a	0.200 0(4)
  Cul-N2	0.200 0(4)
  02a-Cul-02	l80.00(l)	02-Cul-N2a	88.35(2)	N2a-Cul-N2	l80.00(2)
  C5-N2-Cul	l2l.8(4)	02a-Cul-N2a	9l.65(2)	02a-Cul-N2	88.35(2)
  C9-N2-Cul	l2l.5(3)	Cll-02-Cul	l27.0(4)
  2
  Cul-0lb	0.l88 5(3)	Cul-0l	0.l88 5(3)	Cul-Nlb	0.20l 4(3)
  Cul-Nl	0.20l 4(3)
  0l-Cul-0lb	l80.00(9)	0l-Cul-Nlb	89.6l (l)	Nlb-Cul-Nl	l79.99(2)
  Cl2-N2-Cul	l20.7(3)	0lb-Cul-Nlb	90.39(l)	0lb-Cul-Nl	89.6l (l)
  Cll-N2-Cul	l23.l (3)	C7-0l-Cul	l30.5(3)
  Symmetry codes: a: 1-x, 1-y, 1-z for 1；b:-x, -y+1, -z+2 for 2

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  Table 4.  Putative π-π stacking interactions for complex 1

  Ring (I)	Ring (J)	d (Cg-Cg)/nm	d (Cg (I)-perp)/nm	d (Cg (J)-perp)/nm	Slippage/nm
  Cgl*	Cg1	0.406 6(4)	0.353 8(3)	0.353 7(3)	0.200 5
  Cg2*	Cg2	0.387 2(4)	0.357 3(3)	0.357 3(3)	0.l49 2
  *Cgl and Cg2 are the centroids of benzene ring Cl0-Cl5 and Cl7-C22 of complex 1, respectively

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  Table 5.  Hydrogen-bonding for complex 2

  D-H…A	d (D-H)/nm	d (H…A)/nm	d (D…A)/nm	∠DHA/(°)	Symmetry code
  02-H2A…N2	0.082 0	0.208	0.278 9 (6)	l45	l/2-x, 3/2-y, 2-z
  Cl7-Hl7…Cg3*	0.093 0	0.295	0.379 8(4)	l53	x, l+y, z
  *Cg3 is the centroid of benzene ring Cl-C5-Cl0 of complex 2

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