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Mononuclear Cu(Ⅱ) and Trinuclear Co(Ⅱ) Complexes Based on Coumarin-Containing N2O2 Ligands: Syntheses, Structures and Fluorescence Properties

Lei GAO ,  Xiao-Yan LI ,  Chang LIU ,  Yang ZHANG ,  Wen-Kui DONG

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Citation:  GAO Lei, LI Xiao-Yan, LIU Chang, ZHANG Yang, DONG Wen-Kui. Mononuclear Cu(Ⅱ) and Trinuclear Co(Ⅱ) Complexes Based on Coumarin-Containing N2O2 Ligands: Syntheses, Structures and Fluorescence Properties[J]. Chinese Journal of Inorganic Chemistry, 2018, 34(7): 1381-1391. doi: 10.11862/CJIC.2018.151 shu

基于香豆素N2O2配体构筑的单核铜(Ⅱ)和三核钴(Ⅱ)配合物:合成、结构及荧光性质

  • .

    兰州交通大学化学与生物工程学院, 兰州 730070

    • 通讯作者: 董文魁, dongwk@126.com
  • 基金项目:

    国家自然科学基金（No.21761018）资助项目

    国家自然科学基金 21761018

摘要: 合成了2个通过不同的Salamo型香豆素类配体H2L1和H2L2构筑的配合物，[Cu（L1）（H2O）]（1）和[Co3（L2）2（μ2-OAc）2（MeOH）2]·3CH2Cl2（2），并通过元素分析、红外光谱、紫外-可见吸收光谱、荧光光谱以及X射线单晶衍射法对其进行了表征。配合物1中配位的铜（Ⅱ）离子的空间构型是扭曲的四方锥，并且配合物1通过分子间的氢键作用形成了二聚体。配合物2中所有配位的钴（Ⅱ）离子的配位数均为六，并且3个钴（Ⅱ）离子的配位空间构型均为扭曲的八面体。同时，配合物2通过分子间的氢键作用形成了一维的超分子链状结构。此外，还分别对配体H2L1和H2L2的荧光性质进行了研究，并且通过荧光滴定实验进一步验证了配合物1和2的晶体结构。

English

  • 0.   Introduction

    Salen-type ligand (R-CH=N-(CH2)2-N=CH-R) is a kind of versatile tetradentate N2O2 chelating ligand in modern coordination chemistry[1-5], and its metal complexes have been widely investigated in biological fields[6-10], electrochemical systems[11-12], luminescent[13-17] and magnetic[18-22] materials and supramolecular buildings[23-26] and so on. Specially, replacement of partial atoms of Salen or its analogues with else elements often thoroughly alters its structures and properties when an O-alkyl oxime moiety (-CH=N-O-(CH2)n-O-N=CH-) instead of the imine moiety, the bigger electronegativity of the oxygen atoms is estimated to influence strongly the electronic behaviors of the Salamo-type ligand or its derivatives, which may give rise to novel and different structures and properties of the metal(Ⅱ) complexes[27-33].

    As important raw materials and intermediates in organic chemical, coumarin has a wide range of applications in agriculture, pharmaceutical, photographic materials and other fields. Although these Salamo-type metal complexes have been in the process of development, there is still a lot of room for their supramolecular structures to be studied. The introduction of different substituted group into Salamo-type compounds may give rise to different structures, and asymmetric ligands can also greatly improve the difference of the structures[34-38]. Herein, we firstly report two new complexes [Cu(L1)(H2O)] (1) and [Co3(L2)2(μ2-OAc)2(MeOH)2]·3CH2Cl2 (2) with coumarin-containing asymmetric and symmetric Salamo-type N2O2 bisoxime ligands.

    1.   Experimental

    1.1   Materials and physical measurements

    7-Hydroxyl-4-methyl-coumarin and 3-methoxy-salicylaldehyde (98%) were purchased from Alfa Aesar and used without further purification. The other reagents and solvents were analytical grade reagents from Tianjin Chemical Reagent Factory.

    C, H and N analyses were obtained using a GmbH VarioEL V3.00 automatic elemental analysis instrument. Elemental analyses for Cu(Ⅱ) and Co(Ⅱ) were detected by an IRIS ER/S-WP-1 ICP atomic emission spectrometer. Melting points were measured by the use of a microscopic melting point apparatus made by Beijing Taike Instrument Limited Company and were uncorrected. IR spectra were recorded on a Vertex70 FT-IR spectrophotometer, with samples prepared as KBr (400~4 000 cm-1) pellets. UV-Vis absorption spectra were recorded on a Shimadzu UV-3900 spectrometer. Luminescence spectra in solution were recorded on a Hitachi F-7000 spectrometer. Luminescence decay curve in the solid state and the quantum yield were recorded on a FLSP920 spectrometer. 1H NMR spectra were determined by a German Bruker AVANCE DRX-400 spectrometer.

    1.2   Syntheses of H2L1 and H2L2

    1, 2-Bis(aminooxy)ethane was prepared following the literature[11]. 8-Formyl-7-hydroxy-4-methylcoumarin was synthesized in the light of reported procedure[39]. H2L1 and H2L2 could be obtained by condensation of 1, 2-bis(aminooxy)ethane with 3-methoxysalicylaldehyde and 8-formyl-7-hydroxyl-4-methyl-coumarin via a nucleophilic addition (Scheme 1).

    Scheme 1

    图 Scheme 1  Synthetic routes to H2L1 and H2L2
    Scheme 1.  Synthetic routes to H2L1 and H2L2
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    1.2.1   Synthesis of H2L1

    An ethanol solution (50 mL) of 3-methoxysali-cylaldehyde (304.30 mg, 2 mmol) was added dropwise to 1, 2-bis(aminooxy)ethane (276.30 mg, 3 mmol) in ethanol solution (30 mL). The mixed solution was heated for 3 h in the range of 55~60 ℃. After vacuum concentration of the solution, the residue was purified, and an affordable colorless flocculent crystalline solid of 2-[O-(1-ethyloxyamide)]oxime-6-methoxyphenol was obtained. Yield: 42.3% (191.39 mg). Anal. Calcd. for C10H14N2O4(%): C 53.09; H 6.24; N 12.38. Found(%): C 53.32; H 6.12; N 12.27.

    A solution of 2-[O-(1-ethyloxyamide)]oxime-6-methoxyphenol (328.03 mg, 1.45 mmol) in ethanol (20 mL) was added to a solution of 8-formyl-7-hydroxyl-4-methyl-coumarin (296.06 mg, 1.45 mmol) in ethanol (20 mL) and the mixture was subjected to heating at 55 ℃ for 24 h. After being cooled to room temperature, the resulting yellow solid was collected. 1H NMR (400 MHz, CDCl3): δ 10.73 (s, 1H), 9.70 (s, 1H), 8.94 (s, 1H), 8.27 (s, 1H), 7.50 (d, J=8.9 Hz, 1H), 6.93 (s, 1H), 6.91 (s, 1H), 6.87 (s, 1H), 6.85 (s, 1H), 6.14 (s, 1H), 4.51 (s, 4H), 3.91 (s, 3H), 2.40 (s, 3H). Yield: 79.8% (477.18 mg). Anal. Calcd. for C21H20N2O7 (%): C, 61.16; H, 4.89; N, 6.79. Found(%): C, 61.25; H, 4.71; N, 6.53.

    1.2.2   Synthesis of H2L2

    A solution of 8-formyl-7-hydroxyl-4-methyl-coumarin (408.36 mg, 2.0 mmol) in ethanol (30 mL) was added to a solution of 1, 2-bis(aminooxy)ethane (92.10 mg, 1.0 mmol) in ethanol (30 mL) and the mixture was subjected to heating at 60 ℃ for 2 h. After being cooled to room temperature, the resulting white solid was collected. 1H NMR (400 MHz, CDCl3): δ 10.72 (s, 2H), 8.95 (s, 2H), 7.50 (d, J=8.9 Hz, 2H), 6.93 (d, J=8.9 Hz, 2H), 6.14 (s, 2H), 4.54 (s, 4H), 2.40 (s, 6H). Yield: 79.9% (371.07 mg). Anal. Calcd. for C24H20N2O8 (%): C, 62.07; H, 4.34; N, 6.03. Found(%): C, 62.46; H, 4.42; N, 5.78.

    1.3   Synthesis of complex 1

    A dropwise addition of an methanolic solution (2 mL) of copper(Ⅱ) acetate monohydrate (1.99 mg, 0.01 mmol) to a solution of H2L1 (4.12 mg, 0.01 mmol) in acetone (3 mL) was carried out at room temperature, and immediately the mixed solution color changed to dark brown. The mixed solution was filtered and the filtrate was kept undisturbed in the dark to avoid decomposition of the coumarin-containing building blocks. Single-crystals suitable for X-ray crystallography were grown up via partial solvent evaporation after ca. two weeks, and collected carefully by filtration, washed gradually with n-hexane, and dried at room temperature. Yield: 45.3%(2.23 mg). Anal. Calcd. for C21H20CuN2O8 (%): C, 51.27; H, 4.10; N, 5.69; Cu, 19.29. Found (%): C, 51.53; H, 4.28; N, 5.37; Cu, 18.93.

    1.4   Synthesis of complex 2

    A dropwise addition of an methanolic solution (2 mL) of cobalt(Ⅱ) acetate tetrahydrate (2.49 mg, 0.01 mmol) to a solution of H2L2 (4.64 mg, 0.01 mmol) in dichloromethane (5 mL) was carried out at room temperature, and immediately the mixed solution color changed to brown. The mixed solution was filtered and the filtrate was kept undisturbed in the dark to avoid decomposition of the coumarin-containing building blocks. Single-crystals suitable for X-ray crystallography were grown up via partial solvent evaporation after ca. two weeks, and collected carefully by filtration, washed gradually with n-hexane, and dried at room temperature. Yield: 70.1% (3.65 mg). Anal. Calcd. for C57H56Cl6Co3N4O22(%): C, 44.50; H, 3.67; N, 3.64; Co, 11.49. Found(%): C, 44.76; H, 3.86; N, 3.43; Co, 11.23.

    1.5   Crystal structure determinations of complexes 1 and 2

    X-ray single crystal diffraction data of complexes 1 and 2 were recorded using a SuperNova Dual (Cu at zero) and Bruker APEX-Ⅱ CCD diffractometers with a monochromated Mo Kα radiation (λ=0.071 073 nm) source at 290.80(10) and 296.15(10) K, respectively. The Lp corrections were applied to the SAINT program[40] and semi-empirical correction were applied to the SADABS program[41]. The crystal structures were solved by the direct methods (SHELXS-2014)[42]. All of the non-hydrogen atoms were refined anisotropically. The organic hydrogen atoms were generated geometrically. The aqua hydrogen atoms were located from difference maps and refined with isotropic temperature factors. Crystal data and experimental parameters involved in the structure determinations are presented in Table 1.

    表 1

    表 1  Crystal data and structure refinement parameters for complexes 1 and 2
    Table 1.  Crystal data and structure refinement parameters for complexes 1 and 2
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    Complex 1 2
    Empirical formula C2lH20CuN2O8 C57H56Cl6Co3N4O22
    Formula weight 491.93 1 538.54
    Crystal system Triclinic Triclinic
    Space group P1 P1
    a / nm 0.769 19(9) 1.036 3(4)
    b / nm 1.109 66(10) 1.140 7(4)
    c / nm 1.203 52(14) 1.436 9(5)
    β /(°) 79.991(10) 97.421(5)
    V /nm3 1.006 90(19) 1.589 6(10)
    Z 2 1
    Dc / (g·cm-3) 1.623 1.607
    μ/ mm-1 1.139 1.106
    F(000) 506 785
    Crystal size / mm 0.24×0.21×0.17 0.27×0.22×0.19
    θ range / (°) 3.692~26.885 1.892~28.320
    Limiting indices -8≤h≤9, -13≤k≤13, -14≤l≤14 -13≤h≤13, -15≤k≤13, -19≤l≤19
    Independent reflection 3 968 7 712
    Completeness to θ / % 99.8 98.2
    Data, restraint, parameter 3 968, 0, 292 7 712, 67, 453
    G0F on F2 1.039 1.065
    Final R indices [I > 2σ(I)] R=0.043 4, wR=0.092 5 R=0.068 1, wR=0.202 9
    Largest diff. peak and hole / (e·nm-3) 342 and -319 138 and -189.8

    CCDC: 1561039, 1; 1561040, 2.

    2.   Results and discussion

    2.1   Crystal structure of complex 1

    As presented in Fig. 1 and Table 2, the complex 1 crystallizes in the triclinic systrm, space group P1, which comprises one Cu(Ⅱ) ion, one deprotonated (L1)2- unit and one coordinated water molecule.

    图 1

    图 1  (a) X-ray crystal structure and atom numbering of complex 1 with 30% probability displacement ellipsoids; (b) Coordination polyhedron for Cu(Ⅱ) ion of complex 1
    Figure 1.  (a) X-ray crystal structure and atom numbering of complex 1 with 30% probability displacement ellipsoids; (b) Coordination polyhedron for Cu(Ⅱ) ion of complex 1
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    表 2

    表 2  Selected bond lengths (nm) and angles (°) for complex 1
    Table 2.  Selected bond lengths (nm) and angles (°) for complex 1
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    Cu1-O1 0.191 5(2) Cu1-O8 0.228 9(2) Cu1-N2 0.197 3(2)
    Cu1-O5 0.195 3(2) Cu1-N1 0.201 3(2)
    O1-Cu1-O5 84.18(8) O5-Cu1-O8 94.76(9) N2-Cu1-O8 90.83(9)
    O1-Cu1-O8 93.66(9) O5-Cu1-N1 167.45(10) N2-Cu1-N1 98.21(10)
    O1-Cu1-N1 88.98(9) O5-Cu1-N2 87.77(9)
    O1-Cu1-N2 171.08(9) N1-Cu1-O8 96.17(9)

    The Cu(Ⅱ) ion is penta-coordinated by two oxime nitrogen (N1 and N2) atoms and two deprotonated phenoxo oxygen (O1 and O5) atoms, the four atoms are all from one deprotonated (L1)2- unit, and one oxygen (O8) atom from the coordinated water molecule (Fig. 1a). The coordination sphere around the Cu(Ⅱ)ion is best described as a distorted tetragonal pyramid since the τ value was estimated to be τ=0.060 5 (Fig. 1b)[43-44]. Note worthily, this 1:1 type of Cu(Ⅱ) complex is different from the earlier reported structures of 1:2[35, 37, 45], 2:2[28, 46-48], 2:3[49] and 2:4[49] type in the Salamo-type Cu(Ⅱ) complexes. The bond length of typical Cu-O distance in square pyramidal is 0.236 9(2) nm, which was found in similar complex [Cu(MeO-Salen)(H2O)][47]. In addition, the mean plane (N2O2) and Sal(1) (3-methoxysalicylaldehyde) have a dihedral angle of 13.75(3)°, and the dihedral angle of Sal(2) (8-formyl-7-hydroxyl-4-methyl-coumarin) with the mean plane is 13.05(3)°. The reasons for these differences can be attributed to their asymmetric structure[50-52].

    As presented in Table 3 and Fig. 2, the supramolecular structure of the complex 1 is linked by intermolecular hydrogen bonding interactions O8-H8A…O1#1, O8-H8B…O5#1 and O8-H8A…O2#1, which perform a dimer supramolecular structure[53-56]. Each of the complex 1 molecule is linked to the hydrogen bonds with another complex 1 molecule, leading to a very stable spatial structure[57-59].

    表 3

    表 3  Hydrogen bonding parameters for complexes 1 and 2
    Table 3.  Hydrogen bonding parameters for complexes 1 and 2
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    D-H…A d(D-H) / nm d(H…A) / nm d(D…A) / nm ∠D-H…A/(°)
    1
    O8-H8A…O1#1 0.088 0.255 0.303 6(3) 116
    O8-H8A…O2#1 0.088 0.204 0.291 9(3) 175
    O8-H8B…O5#1 0.088 0.193 0.278 7(3) 166
    2
    O11-H11A…O1#1 0.089 0.182 0.270 8(5) 179
    Symmetry codes: #1: 2-x, 2-y, 1-z for 1; -x, 1-y, 1-z for 2.

    图 2

    图 2  View of a dimer formed by complex 1 molecules via the O-H…O hydrogen bonding interactions
    Figure 2.  View of a dimer formed by complex 1 molecules via the O-H…O hydrogen bonding interactions
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    2.2   Crystal structure of complex 2

    X-ray crystallographic analysis reveals complex 2 possesses a symmetric trinuclear structure. It crystallizes in the triclinic system, space group P1, comprises three Co(Ⅱ) ions, two deprotonated (L2)2- units, two μ2-acetate ions, two coordinated methanol molecules and three lattice dichloromethane molecules. Selected bond lengths and angles are listed in Table 4.

    表 4

    表 4  Selected bond lengths (nm) and angles (°) for complex 2
    Table 4.  Selected bond lengths (nm) and angles (°) for complex 2
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    Co1-O3 0.217 4(2) Co2-O11 0.218 4(3) Co2-N2 0.207 2(4)
    Co1-O6 0.215 8(3) Co2-O9 0.206 2(3) Co2-O3 0.203 0(3)
    Co1-O10 0.202 8(3) Co2-N1 0.209 8(3) Co2-O6 0.205 9(3)
    O3#1-Co1-O3 180.0 O10-Co1-O10#1 180.0 O3-Co2-N2 165.36(12)
    O6-Co1-O3#1 102.10(10) O6-Co2-O11 90.08(10) O3-Co2-O6 83.52(10)
    O6-Co1-O3 77.90(10) O9-Co2-N1 92.25(12) O3-Co2-O9 94.31(11)
    O6#1-Co1-O6 180.0 O9-Co2-N2 98.05(13) O3-Co2-O11 86.12(11)
    O10-Co1-O3#1 93.05(10) N1-Co2-O11 87.77(12) O6-Co2-N1 172.03(12)
    O10-Co1-O3 86.95(10) N2-Co2-N1 98.62(13) O6-Co2-N2 88.65(12)
    O10#1-Co1-O6#1 89.58(10) N2-Co2-O11 81.53(13) O6-Co2-O9 89.96(11)
    O10-Co1-O6#1 90.42(10) O3-Co2-N1 88.67(12) O9-Co2-O11 179.57(12)
    Symmetry codes : #1: -x+1, -y+2, -z+1

    As presented in Fig. 3, complex 2 is formed with the Co1 ion occupying the center of symmetry and the other two Co(Ⅱ) ions (Co2 or Co2#1) to be related by this center of symmetry[60-62]. The two deprotonated (L2)2- units, two μ2-acetate ions and the two coordinated methanol molecules are also centrosymmetric related (Fig. 3a). All of the six oxygen atoms coordinate to Co1 constituting an octahedral geometry: one μ2-acetate ion serves as bridging group for Co1 and Co2 and another coordinates to Co1 and Co2#1, in both cases via Co-O-C-O-Co bridges. The Co…Co distances between central Co(Ⅱ) ion (Co1) and the terminal Co(Ⅱ) ions (Co2) is 0.313 0(2) nm[24, 46]. Then, all of the hexacoordinated Co(Ⅱ) ions of complex 2 have distorted octahedral geometries (Fig. 3b)[63-65].

    图 3

    图 3  (a) X-ray crystal structure and atom numberings of complex 2 with 30% probability displacement ellipsoids; (b) Coordination polyhedrons for Co1(Ⅱ) and Co2(Ⅱ) ions of complex 2
    Figure 3.  (a) X-ray crystal structure and atom numberings of complex 2 with 30% probability displacement ellipsoids; (b) Coordination polyhedrons for Co1(Ⅱ) and Co2(Ⅱ) ions of complex 2
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    As shown in Fig. 4 and Table 3, the 1D supramolecular chain of complex 2 is composed by intermolecular O11-H11A…O1#1 hydrogen bonding interactions. The oxygen (O11) atoms of the coordinated methanol molecules as donors form hydrogen bonds with carbonyl oxygen (O1#1) atoms of adjacent complex 2 molecules[66].

    图 4

    图 4  View of the 1D supramolecular structure of complex 2 showing the O-H…O hydrogen bondings
    Figure 4.  View of the 1D supramolecular structure of complex 2 showing the O-H…O hydrogen bondings
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    2.3   FT-IR spectra

    The FT-IR spectra of H2L1 and H2L2 with their corresponding complexes 1 and 2 demonstrate different bands in the 400~4 000 cm-1 region (Table 5). The characteristic C=N stretching bands of the ligands H2L1 and H2L2 appear at 1 612 and 1 613 cm-1, and those of complexes 1 and 2 appear at 1 597 and 1 581 cm-1, respectively[67]. The C=N stretching frequencies are shifted to lower frequencies, indicating that the Cu(Ⅱ) and Co(Ⅱ) ions are coordinated by azomethine nitrogen atoms of (L1)2- and (L2)2- moieties. In addition, characteristic C=O stretching bands at 1 733 and 1 731 cm-1 are exhibited by the ligands H2L1 and H2L2, and the complexes 1 and 2 at 1 718 and 1 710 cm-1 show the characteristic C=O stretching bands, respectively[39]. The ligands H2L1 and H2L2 exhibit characteristic Ar-O stretching frequencies at 1 261 and 1 282 cm-1, while those of the complexes 1 and 2 appear at 1 221 and 1 220 cm-1, respectively[68]. The Ar-O stretching frequencies are shifted to lower frequencies, which could be evidence of the Cu-O or Co-O bond formation between Cu(Ⅱ) or Co(Ⅱ) ions and oxygen atoms of phenolic groups[65].

    表 5

    表 5  FT-IR spectra of the ligands and their complexes 1 and 2
    Table 5.  FT-IR spectra of the ligands and their complexes 1 and 2
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    cm-1
    Compound νC=N νAr-O νM-N νM-O νC=O νC=C
    H2L1 1 612 1 261 — — 1 733 1 467
    H2L2 1 613 1 282 — — 1 731 1 450
    Complex 1 1 597 1 221 561 456 1 718 1 408
    Complex 2 1 581 1 220 525 461 1 710 1 400

    2.4   UV-Vis absorption spectra

    The UV-Vis absorption spectra of the ligands H2L1 and H2L2 with their corresponding complexes 1 and 2 in the dichloromethane solutions (10 μmol·L-1) at 298 K are shown in Fig. 5. For the ligand H2L1, the peak at 273 nm can be assigned to the π-π* transitions of the phenyl rings, the peak at 281 nm can be assigned to the π-π* transitions of the phenyl rings of coumarin group, the peak at 330 nm can be assigned to the n-π* transitions of the oxime group, and the peak at 345 nm can be assigned to the n-π* transitions of lactone carbonyl group[69]. Upon coordination of the ligand H2L1, the π-π* transitions of the phenyl rings and the phenyl rings of coumarin group in complex 1 are bathochromically shifted to 280 and 290 nm, respectively, indicating the coordination of Cu(Ⅱ) ion with the (L1)2- units[70]. Compared with the free ligand H2L1, the absorption peak at 330 nm disappears from the UV-Vis spectrum of complex 1, which indicates that the oxime nitrogen atoms are involved in coordination to the Cu(Ⅱ) ion. Meanwhile, the n-π* transitions of the lactone carbonyl group in complex 1 assumes a hypsochromic shift to 340 nm indicating the coordination of the (L1)2- units with Cu(Ⅱ) ion. For the ligand H2L2, the peak at 290 nm can be assigned to the π-π* transitions of the phenyl rings of coumarin group, the peak at 330 nm can be assigned to the n-π* transitions of the oxime group, and the peak at 345 nm can be assigned to the n-π* transitions of lactone carbonyl group. Compared with the free ligand H2L2, the absorption peak at 330 nm disappears from the UV-Vis spectrum of complex 2, which indicates that the oxime nitrogen atoms are involved in coordination to the Co(Ⅱ) ion[70]. Additio-nally, two weak broad absorption peaks are observed at 394 and 383 nm for complexes 1 and 2, these new absorption peaks can be assigned to L→M charge-transfer (LMCT) transitions which are characteristic of the transition metal complexes with N2O2 coordination sphere[70].

    图 5

    图 5  UV-Vis spectra of the ligands and their complexes 1 and 2
    Figure 5.  UV-Vis spectra of the ligands and their complexes 1 and 2
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    2.5   Fluorescence properties

    The fluorescent spectra of H2L1 and H2L2 (25 μmol·L-1) in DMF solution were measured at room temperature (Fig. 6). The ligands H2L1 and H2L2 exhibit broad emissions at about 432 nm upon excitation at 392 nm, which should be assigned to intraligand π*-π transition[70-72].

    图 6

    图 6  Fluorescent spectra of H2L1 and H2L2 in DMF
    Figure 6.  Fluorescent spectra of H2L1 and H2L2 in DMF
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    Luminescence decay curves of H2L1 and H2L2 in the solid state were measured at room temperature (Fig. 7 and Fig. 8). The fluorescence lifetimes of ligands H2L1 and H2L2 are obtained by fitting 3.01 and 1.47 μs, respectively, and the quantum yield results of H2L1 and H2L2 in the solid state were measured at excitation range of 375~415 nm and luminescence range of 480~635 nm. The quantum yields of H2L1 and H2L2 in the solid state are 2.56% and 0.54%, respectively.

    图 7

    图 7  Luminescence decay curves of H2L1 in the solid state
    Figure 7.  Luminescence decay curves of H2L1 in the solid state
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    图 8

    图 8  Luminescence decay curves of H2L2 in the solid state
    Figure 8.  Luminescence decay curves of H2L2 in the solid state
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    The fluorescence titration experiments of H2L1 and H2L2 were performed in DMF solution (25 μmol·L-1) with Cu(OAc)2·H2O and Co(OAc)2·4H2O in methanol solution (1 mmol·L-1), and the results are shown in Fig. 9 and Fig. 10, respectively.

    图 9

    图 9  Fluorescence spectra of H2L1 in DMF solution upon the addition of Cu2+
    Figure 9.  Fluorescence spectra of H2L1 in DMF solution upon the addition of Cu2+
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    图 10

    图 10  Fluorescence spectra of H2L2 in DMF solution upon the addition of Co2+
    Figure 10.  Fluorescence spectra of H2L2 in DMF solution upon the addition of Co2+
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    The fluorescence intensity of H2L1 decreased remarkably upon incremental addition of the Cu2+. When the added amount of the Cu2+ reached 1.0 equiv, the fluorescence emission intensity almost complete quenching and became stable(Fig. 9), which can provide understanding 1:1 stoichiometry between Cu2+ and H2L1. Weakening of fluorescence is due to the coordination of metal(Ⅱ) ion with the ligand[73-74]. Likewise, complex 2 displays weakened emission intensities compared to the corresponding ligand (H2L2) when excited at 432 nm. When the added amount of the Co2+ reached 1.5 equiv, the fluorescence emission intensity almost complete quenching(Fig. 10). The result is corresponding to the crystal structure of complex 2.

    3.   Conclusions

    In summary, we have reported the successful syntheses and characterizations of two newly designed complexes, [Cu(L1)(H2O)] (1) and [Co3(L2)2(μ2-OAc)2(MeOH)2]·3CH2Cl2 (2) derived from Salamo-type N2O2 ligands H2L1 and H2L2. Complex 1 shows a slightly distorted tetragonal pyramid, forming a dimer supramolecular structure by intermolecular hydrogen bond interactions. The supramolecular structure of the complex 2 is formed via intermolecular hydrogen bonds leading to a self-assembly infinite 1D chain structure. The fluorescent properties of H2L1 and H2L2 have been discussed and the structures of complexes 1 and 2 were confirmed by fluorescence titration experiments.

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  • Scheme 1  Synthetic routes to H2L1 and H2L2

    下载: 全尺寸图片 幻灯片

    Figure 1  (a) X-ray crystal structure and atom numbering of complex 1 with 30% probability displacement ellipsoids; (b) Coordination polyhedron for Cu(Ⅱ) ion of complex 1

    下载: 全尺寸图片 幻灯片

    Figure 2  View of a dimer formed by complex 1 molecules via the O-H…O hydrogen bonding interactions

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

    下载: 全尺寸图片 幻灯片

    Figure 3  (a) X-ray crystal structure and atom numberings of complex 2 with 30% probability displacement ellipsoids; (b) Coordination polyhedrons for Co1(Ⅱ) and Co2(Ⅱ) ions of complex 2

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

    下载: 全尺寸图片 幻灯片

    Figure 4  View of the 1D supramolecular structure of complex 2 showing the O-H…O hydrogen bondings

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

    下载: 全尺寸图片 幻灯片

    Figure 5  UV-Vis spectra of the ligands and their complexes 1 and 2

    下载: 全尺寸图片 幻灯片

    Figure 6  Fluorescent spectra of H2L1 and H2L2 in DMF

    c=25 μmol·L-1

    下载: 全尺寸图片 幻灯片

    Figure 7  Luminescence decay curves of H2L1 in the solid state

    下载: 全尺寸图片 幻灯片

    Figure 8  Luminescence decay curves of H2L2 in the solid state

    下载: 全尺寸图片 幻灯片

    Figure 9  Fluorescence spectra of H2L1 in DMF solution upon the addition of Cu2+

    Inset: linear response as a function of cCu2+/cH2L1

    下载: 全尺寸图片 幻灯片

    Figure 10  Fluorescence spectra of H2L2 in DMF solution upon the addition of Co2+

    Inset: linear response as a function of cCo2+/cH2L2

    下载: 全尺寸图片 幻灯片

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

    Complex 1 2
    Empirical formula C2lH20CuN2O8 C57H56Cl6Co3N4O22
    Formula weight 491.93 1 538.54
    Crystal system Triclinic Triclinic
    Space group P1 P1
    a / nm 0.769 19(9) 1.036 3(4)
    b / nm 1.109 66(10) 1.140 7(4)
    c / nm 1.203 52(14) 1.436 9(5)
    β /(°) 79.991(10) 97.421(5)
    V /nm3 1.006 90(19) 1.589 6(10)
    Z 2 1
    Dc / (g·cm-3) 1.623 1.607
    μ/ mm-1 1.139 1.106
    F(000) 506 785
    Crystal size / mm 0.24×0.21×0.17 0.27×0.22×0.19
    θ range / (°) 3.692~26.885 1.892~28.320
    Limiting indices -8≤h≤9, -13≤k≤13, -14≤l≤14 -13≤h≤13, -15≤k≤13, -19≤l≤19
    Independent reflection 3 968 7 712
    Completeness to θ / % 99.8 98.2
    Data, restraint, parameter 3 968, 0, 292 7 712, 67, 453
    G0F on F2 1.039 1.065
    Final R indices [I > 2σ(I)] R=0.043 4, wR=0.092 5 R=0.068 1, wR=0.202 9
    Largest diff. peak and hole / (e·nm-3) 342 and -319 138 and -189.8
    下载: 导出CSV

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

    Cu1-O1 0.191 5(2) Cu1-O8 0.228 9(2) Cu1-N2 0.197 3(2)
    Cu1-O5 0.195 3(2) Cu1-N1 0.201 3(2)
    O1-Cu1-O5 84.18(8) O5-Cu1-O8 94.76(9) N2-Cu1-O8 90.83(9)
    O1-Cu1-O8 93.66(9) O5-Cu1-N1 167.45(10) N2-Cu1-N1 98.21(10)
    O1-Cu1-N1 88.98(9) O5-Cu1-N2 87.77(9)
    O1-Cu1-N2 171.08(9) N1-Cu1-O8 96.17(9)
    下载: 导出CSV

    Table 3.  Hydrogen bonding parameters for complexes 1 and 2

    D-H…A d(D-H) / nm d(H…A) / nm d(D…A) / nm ∠D-H…A/(°)
    1
    O8-H8A…O1#1 0.088 0.255 0.303 6(3) 116
    O8-H8A…O2#1 0.088 0.204 0.291 9(3) 175
    O8-H8B…O5#1 0.088 0.193 0.278 7(3) 166
    2
    O11-H11A…O1#1 0.089 0.182 0.270 8(5) 179
    Symmetry codes: #1: 2-x, 2-y, 1-z for 1; -x, 1-y, 1-z for 2.
    下载: 导出CSV

    Table 4.  Selected bond lengths (nm) and angles (°) for complex 2

    Co1-O3 0.217 4(2) Co2-O11 0.218 4(3) Co2-N2 0.207 2(4)
    Co1-O6 0.215 8(3) Co2-O9 0.206 2(3) Co2-O3 0.203 0(3)
    Co1-O10 0.202 8(3) Co2-N1 0.209 8(3) Co2-O6 0.205 9(3)
    O3#1-Co1-O3 180.0 O10-Co1-O10#1 180.0 O3-Co2-N2 165.36(12)
    O6-Co1-O3#1 102.10(10) O6-Co2-O11 90.08(10) O3-Co2-O6 83.52(10)
    O6-Co1-O3 77.90(10) O9-Co2-N1 92.25(12) O3-Co2-O9 94.31(11)
    O6#1-Co1-O6 180.0 O9-Co2-N2 98.05(13) O3-Co2-O11 86.12(11)
    O10-Co1-O3#1 93.05(10) N1-Co2-O11 87.77(12) O6-Co2-N1 172.03(12)
    O10-Co1-O3 86.95(10) N2-Co2-N1 98.62(13) O6-Co2-N2 88.65(12)
    O10#1-Co1-O6#1 89.58(10) N2-Co2-O11 81.53(13) O6-Co2-O9 89.96(11)
    O10-Co1-O6#1 90.42(10) O3-Co2-N1 88.67(12) O9-Co2-O11 179.57(12)
    Symmetry codes : #1: -x+1, -y+2, -z+1
    下载: 导出CSV

    Table 5.  FT-IR spectra of the ligands and their complexes 1 and 2

    cm-1
    Compound νC=N νAr-O νM-N νM-O νC=O νC=C
    H2L1 1 612 1 261 — — 1 733 1 467
    H2L2 1 613 1 282 — — 1 731 1 450
    Complex 1 1 597 1 221 561 456 1 718 1 408
    Complex 2 1 581 1 220 525 461 1 710 1 400
    下载: 导出CSV
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  • 发布日期:  2018-07-10
  • 收稿日期:  2018-01-22
  • 修回日期:  2018-03-14
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