English

• 0.   Introduction

  As is generally known, salen-type ligands (R¹-CH=N-(CH₂)₂-N=CH-R²) and their derivatives are a class of important N₂O₂ chelating ligands^[1-3], their metal complexes have been extensively investigated in modern coordination chemistry for the past several decades^[4-7], because they not only show a variety of properties in catalytic and optical properties^[8-13], but also have some advantages in the fields of antibacterial activities^[14-21], electrochemical conducts^[22-24], supramole-cular buildings^[25-32], ions recognitions^[33-38] and so on. Recently, new researches have been expanded in the use of salamo-type ligands (R¹-CH=N-O-(CH₂)_n-O-N=CH-R²)^[39-43], and their complexes have been applied in a very wide and diversified subjects such as supra-molecular architectures^[44-45] and luminescence properties^[46-49]. As derivatives of salen-type compounds, salamo -type compounds are more significant, because the electronic and steric effects of the ligands on salamo-metal-assisted catalysis may be controlled by the introduction of proper substituents into the benzene rings. Furthermore, it is important to introduce suitable functional groups into the organic moieties of the ligands in order to improve the properties of these metal complexes^[50-51]. Now, the synthesis of structurally-specific, superior properties of salamo-type metal complexes, and study of their applications have become an important chemical field and potential areas.

  Based on previous works, we have designed and synthesized two multihalogen-substituted salamo-type manganese(Ⅱ) complexes by the coordination reactions of salamo-type bisoxime ligands H₂L¹, H₂L² with manganese(Ⅱ) acetate tetrahydrate, respectively. To the best of our knowledge, the aforementioned manganese(Ⅱ) salamo-type complexes haven′t been reported^[52-54]. Here, elemental analyses, FT-IR, UV-visible absorption spectra, single-crystal X-ray diffractions, fluorescence spectra and Hirshfeld surfaces of the two manganese(Ⅱ) complexes were investigated in detail to study their structural features and spectral characteristics.

  1.   Experimental

  1.1   Materials and physical measurements

  2-Hydroxy-3, 5-dichlorobenzaldehyde and 2-hydroxy-5-nitrobenzaldehyde (99%) were purchased from Alfa Aesar and used directly without purification. All other solvents and chemicals were analytical grade and obtained from Tianjin Chemical Reagent Factory. Elemental analysis data of C, H and N were performed on a GmbH VarioEL V3.00 automatic elemental analysis instrument. Elemental analysis for manganese(Ⅱ) was detected with an IRIS ER/S-WP-1 ICP atomic emission spectrometer. Melting points were measured with a microscopic melting point apparatus made by Beijing Taike Instrument Limited Company and were uncorrected. Fourier transform IR spectra were recorded with a VERTEX70 FT-IR spectro-photometer, with samples prepared as KBr (500~4 000 cm^-1) and CsI (100~500 cm^-1) pellets. UV-visible absorption spectra were collected on a Shimadzu UV-3900 spectrophotometer. Fluorescent spectra were recorded on F-7000 spectrophotometer. Single crystal X-ray structure determinations were made by a SuperNova and Bruker D8 Venture diffractometers, respectively. Hirshfeld surfaces analyses and two-dimensional fingerprint plots of complexes 1 and 2 were calculated using Crystal Explorer program.

  1.2   Synthesis of the ligands H₂L¹ and H₂L²

  The major reaction steps, containing the synthesis of 4, 4′, 6, 6′-tetrachloro-2, 2′ -(ethylenediyldioxybis(nitrilomethylidyne))diphenol (H₂L¹) and 5-nitro-4′, 6′-dichloro-2, 2′-(ethylenedioxybis(azomethine))diphenol (H₂L²) are given in Scheme 1.

  Scheme 1

  

  Scheme 1.  Syntheses routes to H₂L¹ and H₂L²

  下载: 全尺寸图片 幻灯片

  1, 2-Bis(aminooxy)ethane was prepared in accor-dance with the previously literatures^[55-56]. Yield: 56.8%. Anal. Calcd. for C₂H₈N₂O₂(%): C, 26.08; H, 8.76; N, 30.42. Found(%): C, 25.97; H, 8.70; N, 30.49.

  1.2.1   Synthesis of H₂L¹

  The salamo-type bisoxime ligand (H₂L¹) was synthesized according to our previous work^{[54, 57]}. Fig. 1 shows the high resolution mass spectrum of ligand H₂L¹. In the high resolution mass spectrum, a strong peak appeared at m/z=437.030 9, which is consistent with the relative molecular mass determined by the elemental analysis. ¹H NMR (500 MHz, DMSO-d₆): δ 4.48 (s, 4H, -CH₂), 7.53 (t, J=2.6 Hz, 2H, -ArH), 7.61 (t, J=2.6 Hz, 2H, -ArH), 8.47 (d, J=2.0 Hz, 2H, -N=CH), 10.38 (s, 2H, -OH). Yield: 72.8%. m.p. 204~205 ℃. Anal. Calcd. for C₁₆H₁₂Cl₄N₂O₄(%): C, 43.87; H, 2.76; N, 6.39. Found(%): C, 43.95; H, 2.68; N, 6.28.

  Figure 1

  

  Figure 1.  High resolution mass spectrum of H₂L¹

  下载: 全尺寸图片 幻灯片

  1.2.2   Synthesis of H₂L²

  A solution of 2-hydroxy-3, 5-dichlorobenzaldehyde (382.02 mg, 2.0 mmol) in ethanol (100 mL) was added dropwise to a solution of 1, 2-bis(aminooxy)ethane (368.4 mg, 4.0 mmol) in ethanol (40 mL), then the mixture was subjected to heating at 55 ℃ for 6 h. The solution was concentrated in vacuum and the residue was purified by column chromatography (SiO₂, chloro-form/ethyl acetate, 25:1, V/V) to afford 2-(O-(1-ethylo-xyamide))oxime-4, 6-dichlorophenol. Yield: 65.6%, m.p. 92~93 ℃. Anal. Calcd. for C₉H₁₀Cl₂N₂O₃(%): C, 40.78; H, 3.80; N, 10.57. Found(%): C, 40.92; H, 3.69; N, 10.63.

  2-Hydroxy-5-nitrobenzaldehyde (334.24 mg, 2.0 mmol) was dissolved in the ethanol solution (15 mL) and added to a stirred colorless ethanol solution (20 mL) of the above-obtained 2-(O-(1-ethyloxyamide))oxime-4, 6-dichlorophenol (530.18 mg, 2 mmol). The mixture was heated and stirred at 55 ℃ about 6 h before being allowed to cool to room temperature. Then the suspension solution was filtered and washed with ethanol/hexane (1:4, V/V). After dried under vacuum, the resulting white solid of H₂L² was collected. The high resolution mass spectrum and nuclear magnetic resonance spectrum of the ligand H₂L² are shown in Fig. 2 and 3, respectively. A strong peak appeared at m/z=412.096 0 in the high resolution mass spectrum, which is consistent with the relative molecular mass determined by the elemental analysis. ¹H NMR (500 MHz, DMSO-d₆): δ 4.48 (s, 4H, -CH₂), 7.07 (dd, J=9.0, 3.0 Hz, 1H, -ArH), 7.53 (d, J=2.5 Hz, 1H, -ArH), 7.59 (d, J=2.5 Hz, 1H, -ArH), 8.15 (dd, J=9.0, 3.0 Hz, 1H, -ArH), 8.42 (s, 2H, -N=CH), 8.48 (s, 1H, -ArH), 10.40 (s, 1H, -OH), 11.59 (s, 1H, -OH). Yield: 68%. m.p. 174 ~175 ℃. Anal. Calcd. for C₁₆H₁₃Cl₂N₃O₆(%): C 46.40; H 3.16; N 10.14. Found(%): C 46.59; H 3.05; N 10.03.

  Figure 2

  

  Figure 2.  High resolution mass spectrum of H₂L²

  下载: 全尺寸图片 幻灯片

  Figure 3

  

  Figure 3.  ¹H NMR spectrum of H₂L²

  下载: 全尺寸图片 幻灯片

  1.3   Syntheses of complexes 1 and 2

  1.3.1   Synthesis of complex 1

  A solution of manganese(Ⅱ) acetate tetrahydrate (2.45 mg, 0.014 mmol) in mixed solvent of methanol (2.0 mL) and ethanol (3.0 mL) was added dropwise to a chloroform solution (3.0 mL) of H₂L¹ (2.19 mg, 0.005 mmol) at room temperature. The color of the mixing solution turned brown immediately. After the mixture was stirred for 1 h, the mixture was filtered. The resulting filtrate was left undisturbed for about several days to form clear light brown block-like crystals suitable for X-ray crystallographic analysis. Yield: 45.7%. Anal. Calcd. for C₁₆H₁₄Cl₄MnN₂O₆(%): C, 36.46; H, 2.68; N, 5.32; Mn, 10.42. Found(%): C, 36.74; H, 2.52; N, 5.19; Mn, 10.59.

  1.3.2   Synthesis of complex 2

  A mixed solution of methanol (2.0 mL) and ethanol (4.0 mL) of manganese(Ⅱ) acetate tetrahydrate (3.72 mg, 0.015 mmol) was added to a chloroform solution (3.0 mL) of H₂L² (2.07 mg, 0.005 mmol) at room temperature. After the mixture was stirred for 2 h, the mixture was fltered off. The resulting fltrate was left undisturbed for about one week to form block-like crystals suitable for X-ray crystallographic analysis. Yield: 40.5%. Anal. Calcd. for C₁₆H_15.73Cl₂MnN₃O_8.37(%): C, 37.70; H, 3.11; N, 8.24; Mn, 10.78. Found(%): C, 37.75; H, 3.22; N, 8.06; Mn, 10.64.

  1.4   Crystal structure determinations of complexes 1 and 2

  The single crystal of complex 1 with approxi-mated dimensions of 0.21 mm×0.15 mm×0.12 mm was placed on a SuperNova diffractometer. The diffraction data were collected using a graphite monochromated Mo Kα radiation source (λ=0.071 073 nm) at 293(2) K. While the X-ray diffraction data of complex 2 with approximated dimensions of 0.26 mm×0.22 mm×0.20 mm was placed on a Bruker D8 Venture diffractometer. The diffraction data were collected using a graphite monochromated Mo Kα radiation source (λ=0.071 073 nm) at 291(2) K. In addition, multi-scan absorption corrections were applied. The crystal structures were solved using direct methods and refined anisotropically by the full-matrix least-squares techniques based on c with SHELXL-2014/7^[58] and SHELXL-2018 prog-rams^[58], respectively. The positions for hydrogen atoms were fixed on geometrically idealized positions and refined via a riding model. The non-hydrogen atoms were refined anisotropically with displacement para-meters. Selected data of collection parameters and structure refinement of complexes 1 and 2 are summ-arized in Table 1.

  Table 1

  

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

  下载: 导出CSV

  Complex	1	2
  Formula	C16H14Cl4MnN2O6	C16H15.73Cl2MnN3O8.37
  Formula weight	527.03	509.81
  Crystal system	Monoclinic	Triclinic
  Space group	C2/c	P1
  a/nm	1.728 35(17)	0.764 9(2)
  b/nm	1.515 65(17)	1.159 4(2)
  c/nm	0.776 92(6)	1.427 0(2)
  α/(°)		110.121(6)
  β/(°)	97.161(9)	100.257(9)
  γ/(°)		102.123 4(19)
  V/nm3	2.019 3(3)	1.117 7(4)
  Z	4	2
  Dc/(g·cm-3)	1.734	1.515
  μ/mm-1	1.220	0.877
  F(000)	1 060	517
  θ range/(°)	3.314~26.993	3.329~25.996
  Index ranges	-21 ≤ h ≤ 21, -19 ≤ k ≤ 18, -9 ≤ l ≤ 5	-7 ≤ h ≤ 9, -14 ≤ k ≤ 14, -17 ≤ l ≤ 17
  Reflection collected	4 100	8 032
  Independent reflection	2 172	4 234
  Rint	0.016 2	0.028 6
  Data, restraint, parameter	2 172, 1, 127	4 234, 3, 291
  GOF	1.099	0.995
  Final R1, wR2 indices [I>2σ(I)]	0.043 8, 0.125 4	0.054 9, 0.134 1
  R1, wR2 indices (all data)	0.057 6, 0.136 8	0.075 4, 0.140 5
  Largest differences peak and hole/(e·nm-3)	990, -488	425, -330

  CCDC: 1813346, 1; 1816807, 2.

  2.   Results and discussion

  2.1   FT-IR spectra

  Infrared spectroscopy of complexes 1 and 2 are measured at various bands within the region of 4 000~100 cm^-1 and major infrared bands are delineated in Table 2.

  Table 2

  

  Table 2.  Main infrared data of H₂L¹, H₂L² and their complexes 1 and 2

  下载: 导出CSV

  cm-1
  Compound	Ar-O	C=N	M-N	M-O	C=C
  H2L1	1 217	1 609	—	—	1 462, 1 575, 1 595
  1	1 209	1 607	463	511	1 486, 1 579, 1 597
  H2L2	1 315	1 614			1 475, 1 572, 1 594
  2	1 285	1 602	507	474	1 492, 1 578, 1 598

  It can be seen from the IR spectra that the C=N stretching vibration band of H₂L¹ exhibited a characteristic absorption at 1 609 cm^-1, and that of complex 1 appeared at 1 607 cm^-1. A typical Ar=O vibration band in H₂L¹ emerged at 1 217 cm^-1, and that of complex 1 was at approximately 1 209 cm^-1. The changes in the spectrum of complex 1 show that M-N/O interactions were formed in the IR spectrum upon complexation. In addition, the appearance of new medium intensity bands for complex 1 at approximately 463 and 511 cm^-1 were attributed to M-N and M-O stretching vibration bands. The infrared spectrum of complex 1 showed the expected absorption bands at ca. 3 395, 1 637 and 557 cm^-1 which could be assigned to the coordinated water molecules, indicating the presence of coordinated water molecules^[59]. The facts mentioned above are in accordance with the results of crystal X-ray diffractions.

  A typical C=N stretching band of the free ligand H₂L² appeared at 1 614 cm^-1, and that of complex 2 appeared at 1 602 cm^-1. The Ar-O vibration band in H₂L² emerged at 1 315 cm^-1, and that of complex 2 was at approximately 1 285 cm^-1. The shift of Ar-O stretching frequencies could be evidence of the Mn-O bond formation between the Mn(Ⅱ) ion and oxygen atoms of phenolic groups. In the far-IR spectrum of complex 2, the M-O and M-N stretching frequencies were also obtained^[60]. The bands at ca. 507 and 474 cm^-1 could be attributed to M-N and M-O vibration bands. The changes in the spectra of complex 2 show that H₂L² coordinates with Mn(Ⅱ) ions^[61].

  2.2   UV-Vis absorption spectra

  UV-Vis spectra of the free ligands in 25 μmol·L^-1 ethanol solution and their corresponding complexes 1 and 2 in 1.0 mmol·L^-1 ethanol solution at 298 K were measured within a range of 220~550 nm (Fig. 4 and 5).

  Figure 4

  

  Figure 4.  UV-Vis absorption spectra of H₂L¹ and complex 1 in ethanol solution

  下载: 全尺寸图片 幻灯片

  Figure 5

  

  Figure 5.  UV-Vis absorption spectra of H₂L² and complex 2 in ethanol solution

  下载: 全尺寸图片 幻灯片

  Obviously, the absorption peaks of ligand H₂L¹ are different from those of complex 1. The UV-Vis spectrum of H₂L¹ had two relatively intense absorption peaks at ca. 276 and 324 nm. The absorption band at 276 nm could be assigned to the π-π* transition for the benzene rings; and the second peak at 324 nm could be assigned to the n-π* transition for the C=N group. In contrast to H₂L¹, the absorption peaks were bathochromically shifted^[62] (Fig. 4). These phenomena are owing to the reaction of H₂L¹ with the Mn(Ⅱ) ions.

  The absorption spectrum of ligand H₂L² shown in Fig. 5 included two relatively intense peaks centered at ca. 276 and 324 nm, which could be assigned to the π-π* transition for the benzene rings and the n-π* transition for the C=N group. But in complex 2, the absorption peak at 276 nm showed a hypsochromic shift to 270 nm, and the disappearance of the absorption peak of the ligand at 324 nm might be caused by coordination of the two N atoms of C=N groups with the Mn(Ⅱ) ion. For complex 2, a new absorption peak appeared at 368 nm due to the transfer of electrons from the ligand to the Mn(Ⅱ) ion.

  2.3   Crystal structures of complexes 1 and 2

  2.3.1   Crystal structure of complex 1

  X-ray diffraction analysis demonstrated that complex 1 possesses a symmetric mononuclear structure and crystallizes in the monoclinic system with C2/c space group. Complex 1 is built up by one C₁₆H₁₄Cl₄MnN₂O₆ molecule, which contains one Mn(Ⅱ) ion, one completely deprotonated ligand (L¹)^2- and two coordinated water molecules. The molecular structure with atomic labeling of complex 1 is depicted in Fig. 6. Selected bond lengths and angles of complex 1 are listed in Table 3.

  Figure 6

  

  Figure 6.  (a) Molecular structure of complex 1; (b) Coordination polyhedron for Mn(Ⅱ) ion

  Symmetry codes: #1: 2-x, y, 1/2-z; Hydrogen atoms are omitted for clarity

  下载: 全尺寸图片 幻灯片

  Table 3

  

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

  下载: 导出CSV

  1
  Mn1-O2	0.211 97(19)	Mn1-O1W	0.216 3(2)	Mn1-N1	0.229 3(3)
  Mn1-O2#1	0.211 98(19)
  O2-Mn1-O2	93.69(11)	O2-Mn1-O1W	94.44(8)	O1W-Mn1-O1W	167.23(12)
  O2-Mn1-N1	80.00(9)	O2-Mn1-O1W#1	94.28(8)	O1W-Mn1-N1	84.88(9)
  O2-Mn1-N1#1	173.57(9)	N1-Mn1-N1	106.33(13)	O1W-Mn1-N1#1	87.47(9)
  2
  Mn1-O4	0.205 6(3)	Mn1-O1	0.207 7(2)	Mn1-O1W	0.219 9(2)
  Mn1-N1	0.221 9(3)	Mn1-N2	0.229 7(3)	Mn1-O2W	0.220 1(2)
  O4-Mn1-O1	91.83(10)	O4-Mn1-O1W	83.72(11)	O1-Mn1-O1W	98.09(9)
  O4-Mn1-O2W	101.12(11)	O1-Mn1-O2W	85.57(9)	O1W-Mn1-O2W	173.88(9)
  O4-Mn1-N1	171.40(11)	O1-Mn1-N1	82.98(9)	O1W-Mn1-N1	90.20(9)
  O2W-Mn1-N1	85.37(10)	O4-Mn1-N2	82.46(10)	O1-Mn1-N2	173.75(9)
  O1W-Mn1-N2	83.85(9)	O2W-Mn1-N2	93.02(10)	N1-Mn1-N2	102.99(9)
  Symmetry codes: #1: 2-x, y, 1/2-z for 1.

  The coordination sphere of the hexa-coordinated Mn(Ⅱ) ion is completed by two phenolic oxygen atoms (Mn1-O2 0.211 97(19) nm and Mn1-O2#1 0.211 98(19) nm) and two nitrogen atoms (Mn1-N1 0.229 3(3) nm and Mn1-N1#1 0.229 3(3) nm) coming from the completely deprotonated unit (L¹)^2- and two oxygen atoms (Mn1-O1W, 0.216 3(2) nm and Mn1-O1W#1, 0.216 3(2) nm) of the coordinated water molecules. Therefore, the Mn(Ⅱ) ion forms a slightly distorted octahedral geometry. The distances of the Mn(Ⅱ) ion and the phenolic oxygen atoms (O2 and O2#1) of the fully deprotonated (L¹)^2- unit are clearly shorter than those of the nitrogen atoms (N1 and N1#1) from the (L¹)^2- unit (Fig. 6). There are one intramolecular hydrogen bond (C8#1-H8B…O1W#1), three intermolecular hydrogen bonds (O1W#2-H1A…O2#2, O1W#2-H1A…Cl1#2, O1W#3-H1B…O2#3) in complex 1, finally forming a 1D supramolecular structure (Fig. 7 and 8).

  Figure 7

  

  Figure 7.  View of intramolecular hydrogen bonding interactions of complex 1

  Symmetry codes: #1: 2-x, y, 1/2-z

  下载: 全尺寸图片 幻灯片

  Figure 8

  

  Figure 8.  View of 1D supramolecular architecture of complex 1 formed by hydrogen bonding interactions

  Symmetry codes: #2: 2-x, 1-y, -z; #3: x, 1-y, -1/2+z

  下载: 全尺寸图片 幻灯片

  2.3.2   Crystal structure of complex 2

  X-ray crystallographic analysis reveals that complex 2 belongs to triclinic crystal system with space group P1, and has a symmetric mononuclear structure. Fig. 9(a) and (b) showed the molecular structure and the octahedral unit of complex 2. Selected bond lengths and angles are provided in Table 4.

  Figure 9

  

  Figure 9.  (a) Molecular structure of complex 2; (b) Coordination polyhedron for Mn(Ⅱ) ion

  Hydrogen atoms are omitted for clarity

  下载: 全尺寸图片 幻灯片

  Table 4

  

  Table 4.  Hydrogen bonding parameters of complexes 1 and 2

  下载: 导出CSV

  D-H…A	d(D-H)/nm	d(H…A)/nm	d(D…A)/nm	∠DHA/(°)
  C8#1-H8B…O1W#1	0.097	0.252	0.337 9(4)	148
  O1W#2-H1A…O2#2	0.089	0.210	0.290 9(3)	151.7
  O1W#2-H1A…Cl1#2	0.089	0.278	0.338 4(2)	127
  O1W#3-H1B…O2#3	0.088	0.192	0.272 1(3)	149.5
  O1W-H1WA…N2	0.089	0.251	0.300 5(4)	116
  O1W-H1WB…O4	0.089	0.240	0.284 1(4)	111
  O2W-H2WA…N1	0.089	0.251	0.299 6(4)	115
  O2W-H2WB…O1	0.089	0.246	0.290 7(4)	111
  C8-H8A…N2	0.097	0.249	0.287 9(5)	104
  C9-H9A…N1	0.097	0.245	0.286 7(5)	106
  O1W#1-H1WB…O1#1	0.089	0.213	0.283 1(3)	136
  O2W#1-H2WB…O4#1	0.089	0.220	0.286 4(4)	131
  C3-H3#2…O3#2	0.093	0.258	0.346 0(5)	158
  C14#3-H14…O6#3	0.093	0.252	0.321 1(5)	131
  Symmetry codes: #1: 2-x, y, 1/2-z; #2: 2-x, 1-y, -z; #3: x, 1-y, -1/2+z for 1; #1: 1-x, 2-y, 1-z; #2: x, 1+y, z; #3: 1-x, 2-y, 2-z for 2.

  Single crystal X-ray diffraction analysis showed that the crystal structure of complex 2 was similar to that of complex 1, forming a 1:1 ((L²)^2- and Mn(Ⅱ)) mononuclear structure. Complex 2 contained one Mn(Ⅱ) ion, one full deprotonated (L²)^2- unit and two coor-dinated water molecules. The hexa-coordinated Mn(Ⅱ) ion (Mn1) is located in the cis-N₂O₂ coordination cavity (Mn1-O1, 0.207 7(2) nm, Mn1-O4, 0.205 6(3) nm, Mn1-N1 0.221 9(3) nm and Mn1-N2 0.229 7(3) nm) of the completely deprotonated (L²)^2- unit, and two oxygen atoms (Mn1-O1W, 0.219 9(2) nm and Mn1-O2W 0.220 1(2) nm) of the coordinated H₂O molecules occupied together the axial positions. All of the six oxygen atoms coordinate to the Mn(Ⅱ) ion (Mn1) constituting an octahedral geometry, as shown in Fig. 9(b). Six intramolecular hydrogen bonds (O1W-H1WA…N2, O1W-H1WB…O4, O2W-H2WA…N1, O2W-H2WB…O1, C8-H8A…N2 and C9-H9A…N1) and four intermolecular hydrogen bonding interactions(O1W#1-H1WB…O1#1, O2W#1-H2WB…O4#1, C3-H3#2…O3#2 and C14#3-H14…O6#3) are observed and shown in Fig. 10. With the help of hydrogen bond interactions in complex 2, the adjacent complex 2 molecule units are linked together forming an infinite 2D supramolecular network, which is shown in Fig. 11.

  Figure 10

  

  Figure 10.  View of intramolecular hydrogen bonding interactions of complex 2

  下载: 全尺寸图片 幻灯片

  Figure 11

  

  Figure 11.  View of 2D supramolecular architecture of complex 2 formed by hydrogen bonding interactions

  Symmetry codes: #1: 1-x, 2-y, 1-z; #2: x, 1+y, z; #3: 1-x, 2-y, 2-z

  下载: 全尺寸图片 幻灯片

  2.4   Hirshfeld surfaces analyses

  The Hirshfeld surfaces of the free ligands and their complexes 1 and 2 were analyzed using Crystal Explorer program. The surface analyses of H₂L¹, H₂L² and complexes 1 and 2 have been mapped with d_norm (standard high resolution), curvedness and shape index(Fig. 12)^[63]. When mapped with the function of d_norm, the surface of H₂L produces several spherical red depressions, indicating the main presence of type C-H…O interactions, and other visible depressions correspond to H…H and C…H interactions. For complexes 1 and 2, more intense red depressions can be seen on the Hirshfeld surfaces which marks the O…H/H…O interactions persisting. The 2D fingerprint plots are used to explain the atom pair contacts of the crystal, which can quantify the intermolecular interactions. Meantime, it could be decomposed to highlight contributions from different interactions. The 2D fingerprint plot of H…H, C…H/H…C and O…H/H…O interactions in the complexes are depicted in Fig. 13.

  Figure 12

  

  Figure 12.  Hirshfeld surfaces of complexes 1 and 2 mapped with dnorm, shape index and curvedness

  下载: 全尺寸图片 幻灯片

  Figure 13

  

  Figure 13.  Two dimensional fingerprint plots of complexes 1 and 2 with major decomposition plots

  下载: 全尺寸图片 幻灯片

  In complex 1, the proportions of C…H/H…C, O…H/H…O, H…H and Cl…H interactions cover 4.1%, 16.5%, 17.8% and 39.7% of the Hirshfield surfaces, respectively, while the proportions of C…H/H…C, O…H/H…O, H…H and Cl…H interactions in complex 2 cover 1.7%, 19.1%, 24.4% and 6.6%, respectively. Because of the existence of hydrogen bonds, complexes 1 and 2 can be more stable^[64].

  2.5   Fluorescence properties

  The fluorescence behaviors of H₂L¹, H₂L² and their corresponding complexes 1 and 2 were measured in ethanol solution (25 μmol·L^-1) at room temperature within wavelength range of 350~600 nm and displayed in Fig. 14~15.

  Figure 14

  

  Figure 14.  Emission spectra of H₂L¹ and complex 1 in ethanol solution

  下载: 全尺寸图片 幻灯片

  Figure 15

  

  Figure 15.  Emission spectra of H₂L² and complex 2 in ethanol solution

  下载: 全尺寸图片 幻灯片

  The spectrum of H₂L¹ is non-fluorescent upon excitation at 370 nm in ethanol solution. However, complex 1 exhibited an intense fluorescence intensity (Fig. 14) at 418 nm upon excitation at 370 nm, because of the photoinduced electron transfer mechanism. In complex 1, the Mn(Ⅱ) ion is coordinated with the lone pair electrons of C=N and phenol oxygen atoms of benzene rings, which enhances the planar steel of the molecules, resulting in enhancement of fluorescence^[65].

  The spectrum of H₂L² is also non-fluorescent upon excitation at 375 nm. But complex 2 exhibited an intense emission peak at ca. 434 nm upon excitation at 375 nm (Fig. 15), which can be attributed to the photoinduced electron transfer mechanism. As same as complex 1, the Mn(Ⅱ) ion in complex 2 is coordinated with the N atoms of the C=N group and phenol oxygen atoms of benzene rings, leading to the increased coplanarity of molecule and enhanced fluorescence.

  3.   Conclusions

  In conclusion, we have designed and synthesized two Mn(Ⅱ) complexes with two salamo-type ligands H₂L¹ and H₂L², and characterized them by physico-chemical methods and single-crystal X-ray diffractions. X-ray crystal structures revealed that the structural features of complexes 1 and 2 are very similar, and the water molecules participate in the coordination. In the IR spectra of complexes 1 and 2, the M-O and M-N vibrational absorption bands were observed. The UV-Vis spectra clearly indicate that the ligand (L¹)^2- or (L²)^2- units of complexes 1 or 2 are coordinated with the Mn(Ⅱ) ions. The fluorescent results of complexes 1 and 2 showed relatively strong emission peaks compared to the corresponding free ligands. The Hirshfeld surfaces and 2D fingerprint plots could explain the atom pair contacts of the crystal, which could quantify the intermolecular interactions.

  
  Acknowledgements: This work was supported by the National Natural Science Foundation of China (Grant No.21761018) and the Program for Excellent Team of Scientific Research in Lanzhou Jiaotong University (Grant No.201706), which are gratefully acknowledged.
• 1. [1]

     Liu P P, Wang C Y, Zhang M, et al. Polyhedron, 2017, 129:133-140 doi: 10.1016/j.poly.2017.03.019

  2. [2]

     Song X Q, Liu P P, Liu Y A, et al. Dalton Trans., 2016, 45:8154-8163 doi: 10.1039/C6DT00212A

  3. [3]

     Subramaniam P, Anbarasan S, Devi S S, et al. Polyhedron, 2016, 119:14-22

  4. [4]

     Akine S, Miyashita M, Piaob S, et al. Inorg. Chem. Front., 2014, 1:53-57 doi: 10.1039/C3QI00067B

  5. [5]

     Dong X Y, Zhao Q, Kang Q P, et al. Crystals, 2018, 8:230 doi: 10.3390/cryst8050230

  6. [6]

     Zhang L W, Li X Y, Kang Q P, et al. Crystals, 2018, 8:173 doi: 10.3390/cryst8040173

  7. [7]

     Li X Y, Kang Q P, Liu L Z. Crystals, 2018, 8:43 doi: 10.3390/cryst8010043

  8. [8]

     Peng Y D, Li X Y, Kang Q P, et al. Crystals, 2018, 8:1079

  9. [9]

     Peng Y D, Wang F, Gao L, et al. J. Chin. Chem. Soc., 2018, 65:893-899 doi: 10.1002/jccs.201800038

  10. [10]

      Li X Y, Chen L, Gao L, et al. RSC Adv., 2017, 7:35905-35916 doi: 10.1039/C7RA06796H

  11. [11]

      Xu L, Li N, Zhao L. Z. Kristallogr.:New Cryst. Struct., 2016, 231:967-968

  12. [12]

      Li L H, Dong W K, Zhang Y, et al. Appl. Organomet. Chem., 2017, e3818

  13. [13]

      Chin T K, Endud S, Jamil S, et al. Catal. Lett., 2013, 143:282-288 doi: 10.1007/s10562-012-0959-1

  14. [14]

      Gao L, Liu C, Wang F, et al. Crystals, 2018, 8:77 doi: 10.3390/cryst8020077

  15. [15]

      Wu H L, Bai Y H, Zhang Y H, et al. Z. Anorg. Allg. Chem., 2014, 640:2062-2071 doi: 10.1002/zaac.201400109

  16. [16]

      Wu H L, Pan G L, Wang H, et al. J. Photochem. Photobiol. B, 2014, 135:33-43 doi: 10.1016/j.jphotobiol.2014.04.005

  17. [17]

      Wu H L, Pan G L, Bai Y C, et al. J. Chem. Res., 2014, 38:211-217 doi: 10.3184/174751914X13933417974082

  18. [18]

      Wu H L, Bai Y C, Zhang Y H, et al. J. Coord. Chem., 2014, 67:3054-3066 doi: 10.1080/00958972.2014.959507

  19. [19]

      Wang F, Xu Y L, Aderinto S O, et al. J. Photochem. Photobiol. A, 2017, 332:273-282 doi: 10.1016/j.jphotochem.2016.09.004

  20. [20]

      Wu H L, Wang H, Wang X L, et al. New J. Chem., 2014, 38:1052-1061 doi: 10.1039/c3nj01145c

  21. [21]

      Wu H L, Pan G L, Bai Y C, et al. Res. Chem. Intermed., 2015, 41:3375-3388 doi: 10.1007/s11164-013-1440-5

  22. [22]

      Hao J, Li X Y, Wang L, et al. Spectrochim. Acta Part A, 2018, 204:388-402 doi: 10.1016/j.saa.2018.06.074

  23. [23]

      Wang L, Hao J, Zhai L X, et al. Crystals, 2017, 7:277 doi: 10.3390/cryst7090277

  24. [24]

      Ömer S, Ümmühan Ö Ö, Nurgul S, et al. Tetrahedron, 2016, 72:5843-5852 doi: 10.1016/j.tet.2016.08.004

  25. [25]

      Li J, Zhang H J, Chang J, et al. Crystals, 2018, 8:176 doi: 10.3390/cryst8040176

  26. [26]

      Chai L Q, Zhang K Y, Tang L J, et al. Polyhedron, 2017, 130:100-107 doi: 10.1016/j.poly.2017.04.010

  27. [27]

      Dong X Y, Li X Y, Liu L Z, et al. RSC Adv., 2017, 7:48394-48403 doi: 10.1039/C7RA07826A

  28. [28]

      Jia H R, Chang J, Zhang H J, et al. Crystals, 2018, 8:272 doi: 10.3390/cryst8070272

  29. [29]

      Chen L, Dong W K, Zhang H, et al. Cryst. Growth Des., 2017, 17:3636-3648 doi: 10.1021/acs.cgd.6b01860

  30. [30]

      Zhang L W, Liu L Z, Wang F, et al. Molecules, 2018, 23:1141 doi: 10.3390/molecules23051141

  31. [31]

      Dong X Y, Zhao Q, Wei Z L, et al. Molecules, 2018, 23:1006 doi: 10.3390/molecules23051006

  32. [32]

      Chai L Q, Tang L J, Chen L C, et al. Polyhedron, 2017, 122:228-240 doi: 10.1016/j.poly.2016.11.032

  33. [33]

      Dong W K, Li X L, Wang L, et al. Sens. Actuators B, 2016, 229:370-378 doi: 10.1016/j.snb.2016.01.139

  34. [34]

      Wang B J, Dong W K, Zhang Y, et al. Sens. Actuators B, 2017, 247:254-264 doi: 10.1016/j.snb.2017.02.154

  35. [35]

      Wang F, Gao L, Zhao Q, et al. Spectrochim. Acta Part A, 2018, 190:111-115 doi: 10.1016/j.saa.2017.09.027

  36. [36]

      Dong Y J, Li X L, Zhang Y, et al. Supramol. Chem., 2017, 29:518-527 doi: 10.1080/10610278.2017.1285031

  37. [37]

      Hao J, Li X Y, Zhang Y, et al. Materials, 2018, 11:523 doi: 10.3390/ma11040523

  38. [38]

      Dong W K, Akogun S F, Zhang Y, et al. Sens. Actuators B, 2017, 238:723-734 doi: 10.1016/j.snb.2016.07.047

  39. [39]

      Dong W K, Ma J C, Zhu L C, et al. Cryst. Growth Des., 2016, 16:6903-6914 doi: 10.1021/acs.cgd.6b01067

  40. [40]

      Wang L, Li X Y, Zhao Q, et al. RSC Adv., 2017, 7:48730-48737 doi: 10.1039/C7RA08789F

  41. [41]

      Dong W K, Li G, Wang Z K, et al. Spectrochim. Acta Part A, 2014, 133:340-347 doi: 10.1016/j.saa.2014.04.190

  42. [42]

      Hao J, Li L H, Zhang J T, et al. Polyhedron, 2017, 134:1-10 doi: 10.1016/j.poly.2017.05.060

  43. [43]

      Zhang H, Dong W K, Zhang Y, et al. Polyhedron, 2017, 133:279-293 doi: 10.1016/j.poly.2017.05.051

  44. [44]

      Ma J C, Dong X Y, Dong W K, et al. J. Coord. Chem., 2016, 69:149-159 doi: 10.1080/00958972.2015.1108410

  45. [45]

      Hao J, Liu L Z, Dong W K, et al. J. Coord. Chem., 2017, 70:1936-1952 doi: 10.1080/00958972.2017.1324152

  46. [46]

      杨玉华, 郝静, 董银娟, 等.无机化学学报, 2017, 33:1280-1292 doi: 10.11862/CJIC.2017.150YANG Yu-Hua, HAO Jing, DONG Yin-Juan, et al. Chinese. J. Inorg. Chem., 2017, 33:1280-1292 doi: 10.11862/CJIC.2017.150

  47. [47]

      Akine S, Taniguchi T, Saiki T, et al. J. Am. Chem. Soc., 2005, 127:540-541 doi: 10.1021/ja046790k

  48. [48]

      Zhao Q, Wei Z L, Kang Q P, et al. Spectrochim. Acta Part A, 2018, 203:472 doi: 10.1016/j.saa.2018.06.007

  49. [49]

      Dong W K, Zheng S S, Zhang J T, et al. Spectrochim. Acta Part A, 2017, 184:141-150 doi: 10.1016/j.saa.2017.04.061

  50. [50]

      张宏佳, 常健, 贾浩然, 等.无机化学学报, 2018, 34:2261-2270 doi: 10.11862/CJIC.2018.261ZHANG Hong-Jia, CHANG Jian, JIA Hao-Ran, et al. Chinese J. Inorg. Chem., 2018, 34:2261-2270 doi: 10.11862/CJIC.2018.261

  51. [51]

      常健, 张宏佳, 贾浩然, 等.无机化学学报, 2018, 34:2097-2107 doi: 10.11862/CJIC.2018.256CHANG Jian, ZHANG Hong-Jia, JIA Hao-Ran, et al. Chinese J. Inorg. Chem., 2018, 34:2097-2107 doi: 10.11862/CJIC.2018.256

  52. [52]

      Dong W K, Sun Y X, Zhao C Y, et al. Polyhedron, 2010, 29:2087-2097 doi: 10.1016/j.poly.2010.04.006

  53. [53]

      Dong X Y, Wang L, Yang Y H, et al. Asian J. Chem., 2013, 8:4289-4292

  54. [54]

      Dong W K, Zhao C Y, Sun Y X, et al. Inorg. Chem. Commu., 2009, 12:234-236 doi: 10.1016/j.inoche.2008.12.019

  55. [55]

      Zheng S S, Dong W K, Zhang Y, et al. New J. Chem., 2017, 41:4966-4973 doi: 10.1039/C6NJ04090J

  56. [56]

      Dong W K, Lan P F, Zhou W M, et al. J. Coord. Chem., 2016, 69:1272-1283 doi: 10.1080/00958972.2016.1168520

  57. [57]

      Wang L, Dong X Y, Zhao L, et al. Asian J. Chem., 2013, 6:3440-3442

  58. [58]

      Sheldrick G M. Acta Crystallogr. Sect. A:Found. Crystallogr., 2008, A64:112-122

  59. [59]

      王莉, 康全鹏, 郝静, 等.无机化学学报, 2018, 34:525-533 doi: 10.11862/CJIC.2018.035WANG Li, KANG Quan-Peng, HAO Jing, et al. Chinese J. Inorg. Chem., 2018, 34:525-533 doi: 10.11862/CJIC.2018.035

  60. [60]

      Dong X Y, Gao L, Wang F, et al. Crystals, 2017, 7:267 doi: 10.3390/cryst7090267

  61. [61]

      Dong W K, Ma J C, Dong Y J, et al. Polyhedron, 2016, 115:228-235 doi: 10.1016/j.poly.2016.05.017

  62. [62]

      Gao L, Wang F, Zhao Q, et al. Polyhedron, 2018, 139:7-16 doi: 10.1016/j.poly.2017.10.004

  63. [63]

      Ghosh K, Harms K, Chattopadhyay S. Polyhedron, 2017, 123:162-175 doi: 10.1016/j.poly.2016.10.027

  64. [64]

      Wang F, Liu L Z, Gao L, et al. Spectrochim. Acta Part A, 2018, 203:56-64 doi: 10.1016/j.saa.2018.05.088

  65. [65]

      Kang Q P, Li X Y, Zhao Q, et al. Appl. Organomet. Chem., 2018, 32:e4379 doi: 10.1002/aoc.4379

• 

  Scheme 1  Syntheses routes to H₂L¹ and H₂L²

  下载: 全尺寸图片 幻灯片
  

  Figure 1  High resolution mass spectrum of H₂L¹

  下载: 全尺寸图片 幻灯片
  

  Figure 2  High resolution mass spectrum of H₂L²

  下载: 全尺寸图片 幻灯片
  

  Figure 3  ¹H NMR spectrum of H₂L²

  下载: 全尺寸图片 幻灯片
  

  Figure 4  UV-Vis absorption spectra of H₂L¹ and complex 1 in ethanol solution

  下载: 全尺寸图片 幻灯片
  

  Figure 5  UV-Vis absorption spectra of H₂L² and complex 2 in ethanol solution

  下载: 全尺寸图片 幻灯片
  

  Figure 6  (a) Molecular structure of complex 1; (b) Coordination polyhedron for Mn(Ⅱ) ion

  Symmetry codes: #1: 2-x, y, 1/2-z; Hydrogen atoms are omitted for clarity

  下载: 全尺寸图片 幻灯片
  

  Figure 7  View of intramolecular hydrogen bonding interactions of complex 1

  Symmetry codes: #1: 2-x, y, 1/2-z

  下载: 全尺寸图片 幻灯片
  

  Figure 8  View of 1D supramolecular architecture of complex 1 formed by hydrogen bonding interactions

  Symmetry codes: #2: 2-x, 1-y, -z; #3: x, 1-y, -1/2+z

  下载: 全尺寸图片 幻灯片
  

  Figure 9  (a) Molecular structure of complex 2; (b) Coordination polyhedron for Mn(Ⅱ) ion

  Hydrogen atoms are omitted for clarity

  下载: 全尺寸图片 幻灯片
  

  Figure 10  View of intramolecular hydrogen bonding interactions of complex 2

  下载: 全尺寸图片 幻灯片
  

  Figure 11  View of 2D supramolecular architecture of complex 2 formed by hydrogen bonding interactions

  Symmetry codes: #1: 1-x, 2-y, 1-z; #2: x, 1+y, z; #3: 1-x, 2-y, 2-z

  下载: 全尺寸图片 幻灯片
  

  Figure 12  Hirshfeld surfaces of complexes 1 and 2 mapped with dnorm, shape index and curvedness

  下载: 全尺寸图片 幻灯片
  

  Figure 13  Two dimensional fingerprint plots of complexes 1 and 2 with major decomposition plots

  下载: 全尺寸图片 幻灯片
  

  Figure 14  Emission spectra of H₂L¹ and complex 1 in ethanol solution

  下载: 全尺寸图片 幻灯片
  

  Figure 15  Emission spectra of H₂L² and complex 2 in ethanol solution

  下载: 全尺寸图片 幻灯片

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

  Complex	1	2
  Formula	C16H14Cl4MnN2O6	C16H15.73Cl2MnN3O8.37
  Formula weight	527.03	509.81
  Crystal system	Monoclinic	Triclinic
  Space group	C2/c	P1
  a/nm	1.728 35(17)	0.764 9(2)
  b/nm	1.515 65(17)	1.159 4(2)
  c/nm	0.776 92(6)	1.427 0(2)
  α/(°)		110.121(6)
  β/(°)	97.161(9)	100.257(9)
  γ/(°)		102.123 4(19)
  V/nm3	2.019 3(3)	1.117 7(4)
  Z	4	2
  Dc/(g·cm-3)	1.734	1.515
  μ/mm-1	1.220	0.877
  F(000)	1 060	517
  θ range/(°)	3.314~26.993	3.329~25.996
  Index ranges	-21 ≤ h ≤ 21, -19 ≤ k ≤ 18, -9 ≤ l ≤ 5	-7 ≤ h ≤ 9, -14 ≤ k ≤ 14, -17 ≤ l ≤ 17
  Reflection collected	4 100	8 032
  Independent reflection	2 172	4 234
  Rint	0.016 2	0.028 6
  Data, restraint, parameter	2 172, 1, 127	4 234, 3, 291
  GOF	1.099	0.995
  Final R1, wR2 indices [I>2σ(I)]	0.043 8, 0.125 4	0.054 9, 0.134 1
  R1, wR2 indices (all data)	0.057 6, 0.136 8	0.075 4, 0.140 5
  Largest differences peak and hole/(e·nm-3)	990, -488	425, -330

  下载: 导出CSV

  Table 2.  Main infrared data of H₂L¹, H₂L² and their complexes 1 and 2

  cm-1
  Compound	Ar-O	C=N	M-N	M-O	C=C
  H2L1	1 217	1 609	—	—	1 462, 1 575, 1 595
  1	1 209	1 607	463	511	1 486, 1 579, 1 597
  H2L2	1 315	1 614			1 475, 1 572, 1 594
  2	1 285	1 602	507	474	1 492, 1 578, 1 598

  下载: 导出CSV

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

  1
  Mn1-O2	0.211 97(19)	Mn1-O1W	0.216 3(2)	Mn1-N1	0.229 3(3)
  Mn1-O2#1	0.211 98(19)
  O2-Mn1-O2	93.69(11)	O2-Mn1-O1W	94.44(8)	O1W-Mn1-O1W	167.23(12)
  O2-Mn1-N1	80.00(9)	O2-Mn1-O1W#1	94.28(8)	O1W-Mn1-N1	84.88(9)
  O2-Mn1-N1#1	173.57(9)	N1-Mn1-N1	106.33(13)	O1W-Mn1-N1#1	87.47(9)
  2
  Mn1-O4	0.205 6(3)	Mn1-O1	0.207 7(2)	Mn1-O1W	0.219 9(2)
  Mn1-N1	0.221 9(3)	Mn1-N2	0.229 7(3)	Mn1-O2W	0.220 1(2)
  O4-Mn1-O1	91.83(10)	O4-Mn1-O1W	83.72(11)	O1-Mn1-O1W	98.09(9)
  O4-Mn1-O2W	101.12(11)	O1-Mn1-O2W	85.57(9)	O1W-Mn1-O2W	173.88(9)
  O4-Mn1-N1	171.40(11)	O1-Mn1-N1	82.98(9)	O1W-Mn1-N1	90.20(9)
  O2W-Mn1-N1	85.37(10)	O4-Mn1-N2	82.46(10)	O1-Mn1-N2	173.75(9)
  O1W-Mn1-N2	83.85(9)	O2W-Mn1-N2	93.02(10)	N1-Mn1-N2	102.99(9)
  Symmetry codes: #1: 2-x, y, 1/2-z for 1.

  下载: 导出CSV

  Table 4.  Hydrogen bonding parameters of complexes 1 and 2

  D-H…A	d(D-H)/nm	d(H…A)/nm	d(D…A)/nm	∠DHA/(°)
  C8#1-H8B…O1W#1	0.097	0.252	0.337 9(4)	148
  O1W#2-H1A…O2#2	0.089	0.210	0.290 9(3)	151.7
  O1W#2-H1A…Cl1#2	0.089	0.278	0.338 4(2)	127
  O1W#3-H1B…O2#3	0.088	0.192	0.272 1(3)	149.5
  O1W-H1WA…N2	0.089	0.251	0.300 5(4)	116
  O1W-H1WB…O4	0.089	0.240	0.284 1(4)	111
  O2W-H2WA…N1	0.089	0.251	0.299 6(4)	115
  O2W-H2WB…O1	0.089	0.246	0.290 7(4)	111
  C8-H8A…N2	0.097	0.249	0.287 9(5)	104
  C9-H9A…N1	0.097	0.245	0.286 7(5)	106
  O1W#1-H1WB…O1#1	0.089	0.213	0.283 1(3)	136
  O2W#1-H2WB…O4#1	0.089	0.220	0.286 4(4)	131
  C3-H3#2…O3#2	0.093	0.258	0.346 0(5)	158
  C14#3-H14…O6#3	0.093	0.252	0.321 1(5)	131
  Symmetry codes: #1: 2-x, y, 1/2-z; #2: 2-x, 1-y, -z; #3: x, 1-y, -1/2+z for 1; #1: 1-x, 2-y, 1-z; #2: x, 1+y, z; #3: 1-x, 2-y, 2-z for 2.

  下载: 导出CSV
•