Two Complexes Based on Terpyridine/Benzotricarboxylic Acid Ligands: Synthesis, Structures and Properties

Xiao-Li CHEN Lu SHANG Meng-Ping HUANG Yu-Qing TONG Jia-nan ZHANG Wan-Nian XUE

Citation:  Xiao-Li CHEN, Lu SHANG, Meng-Ping HUANG, Yu-Qing TONG, Jia-nan ZHANG, Wan-Nian XUE. Two Complexes Based on Terpyridine/Benzotricarboxylic Acid Ligands: Synthesis, Structures and Properties[J]. Chinese Journal of Inorganic Chemistry, 2021, 37(2): 340-350. doi: 10.11862/CJIC.2021.037 shu

基于三联吡啶/苯三羧酸类配体构筑的两个配合物的合成、结构和性质

    通讯作者: 陈小莉, chenxiaoli003@163.com
  • 基金项目:

    国家自然科学基金 21763028

    延安大学科研计划项目 YDY2017-07

    国家级大学生创新创业训练计划项目 201910719025

    陕西省教育厅重点科学研究计划项目 20JS154

摘要: 基于H3tbtd、H3bbta和bpy配体在水热条件下合成了配位聚合物{[Co3(tbtd)2(bpy)2(H2O)]·5H2O}n1)和配合物[Cd2(Hbbta)(bpy)3(C2O4)(H2O)](2)(H3tbtd=4-(2,4,6-三羧基苯基)-2,2',6',2″-三联吡啶,H3bbta=1-氟-2,4,6-苯三酸,bpy=2,2'-联吡啶),并用元素分析、红外光谱、X射线单晶衍射等对其进行了表征。配聚物1为二维网状结构,基于丰富的氢键作用扩展形成三维超分子网结构。配合物2为双核结构,相邻的双核结构通过吡啶环之间的ππ堆积作用和氢键作用扩展为二维超分子网状结构。配聚物1在紫外光照射下对染料甲基橙(MO)的降解具有光催化活性,对紫外光催化具有良好的稳定性。此外还研究了配合物2的荧光性质和配合物1~2的热稳定性。

English

  • The crystal engineering of coordination polymers (CPs) has attracted extensive attention because controlling the molecular organization in the solid state can lead to materials with intriguing structural motifs and promising properties in luminescence sensing, magnetism, catalysis, gas absorption, separation, and so on[1-10].

    Although a variety of metal CPs with desired structures and functions have been synthesized to date, rational control in the construction of polymers remains a great challenge in crystal engineering. In order to prepare CPs with desired structures and functionalities, judicious selection of appropriate polydentate organic ligands and metal ions could be the key factors of effective and facile approach[11-14]. So many multidentate ligand contain multi-oxygen, nitrogen and halogen atoms donor are often employed as bridging ligands to construct CPs, due to their extension ability both in covalent bonding and in supramolecular interactions (H -bonding and aromatic stacking)[15-18].

    4-(2, 4, 6-tricarboxylphenyl)-2, 2′, 6′, 2″-terpyridine (H3tbtd) and 1-fluoro-2, 4, 6-phenyltriacid (H3bbta) are such typical example of multidentate N, O and F donor ligand, having three carboxyl groups and one terpyridyl group/fluorine atom attached to the benzene rings. So, they have nine/seven potential donor atoms, which allows the formation of variable structures with different topologies and dimensions constructed from different directions. Furthermore, they have three carboxyl groups that may be completely or partially deprotonated, and can provide hydrogen bond donors and acceptors, which make them a wonderful candidate for the construction of supramolecular networks depending upon the number of deprotonated carboxylate groups. Therefore, they may be an excellent candidate for the construction of multidimensional coordination polymers. However, to the best of our knowledge, tbtd-metal CP and bbta-metal CP have rarely been reported[19].

    With the aim of understanding the coordination chemistry of H3tbtd and H3bbta and studying their properties, we have recently engaged in the research of this kind of CPs. Luckily, we have now obtained one CP, {[Co3(tbtd)2(bpy)2(H2O)] ·5H2O}n (1), and one complex, [Cd2(Hbbta)(bpy)3(C2O4) (H2O)] (2). Herein we described their syntheses, structures, luminescence, thermal stabilities and photocatalytic behaviors.

    All chemicals and reagents were used as received from commercial sources without further purification. All reactions were carried out under hydrothermal conditions. Elemental analyses (C, H, N) were determined with a Elementar Vario EL Ⅲ elemental analyser. IR spectra were recorded as KBr pellets on a Bruker EQUINOX55 spectrophotometer in the 4 000~400 cm-1 region. Thermogravimetric analyses (TGA) were performed in a nitrogen atmosphere with a heating rate of 10 ℃·min-1 with a NETZSCHSTA 449C thermogravimetric analyzer. Powder X-ray diffraction patterns (PXRD) were recorded with a Rigaku D/Max Ⅲ diffractometer operating at 40 kV and 30 mA using Cu radiation (λ=0.154 18 nm) at a scanning rate 2 (°)· min-1 from 5° to 50°.

    Photocatalytic experiments in aqueous solutions were carried out in typical processes. A suspension containing CP 1 (15 mg) and 25 mL of methylene orange (MO) (10 mg·L-1) solution was stirred in the dark for about 30 min to ensure the establishment of adsorption equilibrium before irradiation. They were then conducted on an XPA-7 type photochemical reactor equipped with a 100 W mercury lamp and the reaction temperature was maintained at about 25 ℃ by circulating cooling water. Every 15 min, a certain volume of samples was collected and separated by centrifugation to remove residual catalyst particles. Then the solution was analyzed by using Shimadzu UV-Vis spectrometer. The concentration of MO was estimated by the absorbance at 463 nm, characteristic of MO.

    A mixture of Co(Ac)2·4H2O (24.9 mg, 0.1 mmol), H3tbtd (44.1 mg, 0.1 mmol), bpy (15.6 mg, 0.1 mmol) and water (10 mL) was stirred and adjusted to pH=6.5 with 0.5 mol·L-1 NaOH solution, then sealed in a 25 mL Telfon - lined stainless steel container, which was heated to 140 ℃ for 72 h. Then the mixture was cooled to room temperature at a rate of 5 ℃·h-1. Red crystals were obtained in ca. 57% yield based on Co. Anal. Calcd. for C68H52Co3N10O18(%): C, 55.41; H, 3.56; N, 9.50; Found(%): C, 55.46; H, 3.52; N, 9.45. FT - IR (KBr, cm-1) for 1: 3 405(s), 2 995(w), 1 603(s), 1 581(s), 1 480(m), 1 349(s), 1 268(w), 1 070(w), 922(w), 811 (m), 696(w).

    A mixture of CdCO3 (17.2 mg, 0.1 mmol), H3bbta (28.8 mg, 0.1 mmol), bpy (15.6 mg, 0.1 mmol) and water (10 mL) was stirred and adjusted to pH=6.0 with 0.5 mol·L-1 Na2C2O4 solution, then sealed in a 25 mL Telfon-lined stainless steel container, which was heated to 160 ℃ for 96 h. Then the mixture was cooled to room temperature at a rate of 5 ℃·h-1. White crystals were obtained in ca. 53% yield based on Cd. Anal. Calcd. for C41H28Cd2FN6O11(%): C, 48.07; H, 2.75; N, 8.20; F, 1.85; Found(%): C, 48.05; H, 2.80; N, 8.22; F, 1.83. FT-IR (KBr, cm-1) for 2: 3 426(s), 3 056(w), 1 703 (m), 1 606(s), 1 568(s), 1 437(s), 1 268(m), 1 099(w), 1 006(w), 859(m), 761(m), 696(m).

    Intensity data were collected on a Bruker Smart APEX Ⅱ CCD diffractometer with graphite-monochromated Mo Kα radiation (λ=0.071 073 nm) at room temperature. Empirical absorption corrections were applied using the SADABS program. The structures were solved by direct methods and refined by the fullmatrix least-squares based on F2 using SHELXTL2014/2016 program[20]. All non - hydrogen atoms were refined anisotropically and hydrogen atoms of organic ligands were generated geometrically. Crystal data and structural refinement parameters for 1~2 are summarized in Table 1. Selected bond distances and bond angles are listed in Table 2, and hydrogen parameters are listed in Table 3.

    Table 1

    Table 1.  Crystal data and structural refinement parameters for 1~2
    下载: 导出CSV
    Complex 1 2
    Empirical formula C68H52Co3N10O18 C41H28Cd2FN6O11
    Formula weight 1 473.98 1 024.49
    Crystal system Monoclinic Triclinic
    Space group P21/c P1
    a / nm 2.288 21(10) 1.189 6(5)
    b / nm 1.712 09(8) 1.324 3(5)
    c / nm 1.751 49(7) 1.525 5(6)
    α / (°) 107.522(6)
    β / (°) 110.845 0(10) 106.013(6)
    γ / (°) 99.915(6)
    V / nm3 6.412 6(5) 2.115 7(14)
    Z 4 2
    Dc / (g·cm-3) 1.527 1.608
    θ range for data collection / (°) 1.71~25.01 1.494~30.811
    Absorption coefficient / mm-1 0.850 1.075
    Crystal size / mm 0.32×0.19×0.12 0.26×0.21×0.14
    F(000) 2 996 1 018
    Reflection collected 11 336 10 632
    Limiting-indices -26 ≤ h ≤ 27, -20 ≤ k ≤ 20, -20 ≤ l ≤ 12 -13 ≤ h ≤ 16, -14 ≤ k ≤ 18, -19 ≤ l ≤ 18
    Goodness-of-fit (on F2) 0.940 1.034
    R1, wR2a [I>2σ(I)] 0.055 5, 0.149 7 0.034 5, 0.099 4
    R1, wR2a (all data) 0.072 5, 0.162 9 0.057 2, 0.113 8
    a R1=∑||Fo|-|Fc||/∑|Fo|, wR2=[∑w(Fo2-Fc2)2/∑w(Fo2)2]1/2

    Table 2

    Table 2.  Selected bond distances (nm) and bond angles (°) for 1~2
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    1
    Co1—O3A 0.200 9(3) Co1—N6 0.205 2(3) Co1—O6 0.206 4(3)
    Co1—N5 0.215 7(4) Co1—N7 0.217 8(4) Co1—O5 0.237 2(3)
    Co2—O7B 0.197 4(3) Co2—N9 0.203 5(3) Co2—O9 0.208 4(3)
    Co2—N8 0.213 1(4) Co2—N10 0.216 7(4) Co2—O10 0.229 7(3)
    Co3—N4 0.213 8(4) Co3—N1 0.208 3(4) Co3—O12 0.208 5(3)
    Co3—O13 0.208 7(4) Co3—N3 0.212 6(4) Co3—N2 0.213 0(4)
    O3A—Co1—N6 122.97(13) O3A—Co1—O6 89.81(13) N6—Co1—O6 145.78(12)
    O3A—Co1—N5 94.84(14) N6—Co1—N5 76.36(13) O6—Co1—N5 113.49(16)
    O3A—Co1—N7 101.85(14) N6—Co1—N7 75.72(13) O6—Co1—N7 89.09(15)
    N5—Co1—N7 152.02(13) O3A—Co1—O5 146.47(12) N6—Co1—O5 90.44(12)
    O6—Co1—O5 58.06(12) N5—Co1—O5 90.30(14) N7—Co1—O5 88.06(13)
    O7B—Co2—N9 121.02(14) O7B—Co2—O9 90.819(13) N9—Co2—O9 146.23(13)
    O7B—Co2—N8 95.64(15) N9—Co2—N8 76.95(13) O9—Co2—N8 113.50(15)
    O7B—Co2—N10 96.06(15) N9—Co2—N10 76.34(13) O9—Co2—N10 90.37(15)
    N8—Co2—N10 153.19(14) O7B—Co2—O10 147.25(13) N9—Co2—O10 91.32(11)
    O9—Co2—O10 59.08(11) N8—Co2—O10 86.24(13) N10—Co2—O10 96.65(13)
    N1—Co3—O12 95.78(15) N1—Co3—O13 90.84(16) O12—Co3—O13 92.84(14)
    N1—Co3—N3 99.35(17) O12—Co3—N3 87.42(14) O13—Co3—N3 169.76(16)
    N1—Co3—N2 77.70(15) O12—Co3—N2 170.90(14) O13—Co3—N2 87.39(15)
    N1—Co3—N4 176.05(18) O12—Co3—N4 83.01(16) O13—Co3—N4 92.97(17)
    N3—Co3—N4 76.87(17) N2—Co3—N4 103.07(16)
    2
    Cd1—O7 0.224 1(7) Cd2—O1 0.231 1(2) Cd1—O5 0.229 4(3)
    Cd2—O2 0.230 2(3) Cd1—O4 0.228 5(2) Cd2—N4 0.232 1(3)
    Cd1—O3 0.234 1(2) Cd2—N5 0.230 2(3) Cd1—N1 0.229 2(3)
    Cd2—N6 0.232 6(3) Cd1—N2 0.237 1(3) Cd2—N3 0.232 7(3)
    O7—Cd1—O5 92.35(10) O1—Cd2—N4 94.44(10) O7—Cd1—O4 95.36(10)
    O1—Cd2—N3 97.51(10) O7—Cd1—O3 95.03(10) O1—Cd2—N6 91.09(10)
    O7—Cd1—N1 103.37(10) O2—Cd2—O1 71.92(9) O7—Cd1—N2 170.22(10)
    O2—Cd2—N4 150.60(9) O5—Cd1—O3 167.89(9) O2—Cd2—N5 88.29(10)
    O5—Cd1—N2 80.75(10) O2—Cd2—N3 84.57(11) O4—Cd1—O5 98.06(10)
    O2—Cd2—N6 108.69(11) O4—Cd1—O3 71.73(8) N4—Cd2—N3 71.22(11)
    O4—Cd1—N1 154.65(9) N4—Cd2—N6 97.21(11) O4—Cd1—N2 92.49(10)
    N5—Cd2—O1 148.44(10) O3—Cd1—N2 92.97(10) N5—Cd2—N4 113.49(10)
    N1—Cd1—O5 98.09(10) N5—Cd2—N3 104.98(11) N1—Cd1—O3 89.53(9)
    N5—Cd2—N6 71.83(11) N1—Cd1—N2 71.04(9) N3—Cd2—N6 166.00(11)
    Symmetry codes: A: -x-1, y+1/2, -z-1/2; B: -x, y-1/2, -z+1/2 for 1.

    Table 3

    Table 3.  Hydrogen bond parameters for 1 and 2
    下载: 导出CSV
    D—H…A d(D—H) / nm d(H…A) / nm d(D…A) / nm ∠DHA / (°)
    1
    O14D—H14a…O3C 0.084 8(2) 0.208 14(2) 0.288 6(3) 158.81(3)
    O14D—H14b…O15D 0.085 6(3) 0.205 4(4) 0.289 5(5) 166.84(3)
    O15D—H15a…O14H 0.086 7(3) 0.269 6(2) 0.283 5(4) 101.80(3)
    O15D—H15b…O16E 0.086 2(3) 0.217 9(3) 0.294 9(3) 148.66(3)
    O17G—H17a…O9C 0.085 0(3) 0.322 0(3) 0.300 4(3) 97.01(3)
    2
    O5A—H5a…O4B 0.090 3(3) 0.109 0(5) 0.275 7(3) 157.78(7)
    C1A—H1a…O9C 0.093 0(6) 0.267 4(6) 0.325 8(8) 121.43(6)
    C19D—H19a…O3D 0.093 0(2) 0.247 8(3) 0.321 6(6) 136.47(8)
    C18E—H18a…O8D 0.093 1(7) 0.241 0(6) 0.318 8(6) 141.04(9)
    Symmetry codes: C: 1+x, 2.5-y, 0.5+z, D: -x, 2-y, -z; E: -x, 1-y, -z; F: 1+x, 2+y, 1+z; G: 1-x, 1.5+y, 0.5-z; H: 1+x, 1+y, 1+z for 1; A: x, y, -1+z; B: -x, -y, -1-z; C: 1-x, 1-y, 1-z, D: x, 1+y, z; E: x, 1+y, z for 2.

    CCDC: 1986403, 1; 2004223, 2.

    The asymmetric unit of 1 contains three independent Co(Ⅱ)ions, two tbtd3- ligands, two coordinated bpy ligands, one coordinated water molecule and five lattice water molecules. As shown in Fig. 1, Co1 is surrounded by three nitrogen atoms (N5, N6 and N7) from one chelating tbtd3- ligand (Co1—N5 0.215 7(4) nm, Co1—N6 0.205 2(3) nm, Co1—N7 0.217 8(4) nm), three oxygen atoms (O3A, O5 and O6) from two carboxylate groups of two tbtd3- ligand. The coordination geometry of Co1 center can be described as a distorted octahedral geometry. Similar to Co1, Co2 lies in a general position and coordinates to three oxygen atoms from two carboxylate groups of two tbtd3- ligands, three nitrogen atoms from a chelating tbtd3- ligand. The bond lengths of Co2—N are comparable to the reported ones[21], varying from 0.203 5(3) to 0.216 7(4) nm. The Co2—O distances fall in a range of 0.197 4(3)~ 0.229 7(3) nm. Whereas Co3 center is ligated by four nitrogen atoms from two chelating bpy ligands (Co3— N1 0.208 3(4) nm, Co3—N2 0.213 0(4) nm, Co3—N3 0.212 6(4) nm, Co3—N4 0.213 8(4) nm), one bridging oxygen atom from carboxylate group of a tbtd3- ligand and one oxygen atom (O13A) from an aqua ligand to complete a distorted octahedral geometry. The Co3—O distances fall in a range of 0.208 3(3)~0.208 7(3) nm, similar to those found in other Co-MOFs[22].

    Figure 1

    Figure 1.  Coordination environment of Co(Ⅱ)ion in 1

    Ellipsoid probability is drawn at 30% and all H atoms are omitted for clarity; Symmetry codes: A:-1-x, 0.5+y, -0.5-z; B:-x, -0.5+y, 0.5-z

    It noteworthy that the completely deprotonated tbtd3- ligand adopts a septadentate chelating and bridging coordination mode (Scheme 1a). Two carboxylate groups coordinate with two Co(Ⅱ)ions monodentately. One carboxylate group chelate with one Co(Ⅱ)ions bidentately. On the other hand, three nitrogen atoms on terpyridine ring coordinates with a Co(Ⅱ)ion by tridentately. In order to adapt to the formation of coordination bond, the terpyridine ring and benzene ring of tbtd3- ligand are distorted. The dihedral angle of the terpyridine ring and benzene ring of two tbtd3- ligand is 67.81°. On the basis of the connection mode, the neighboring two Co1 and Co2 centers are bridged by two tbtd3- anions to form an 18-atom ring [Co2O2N2C12], which contains a type of micropore with size of ca. 0.707 7 nm×0.883 1 nm (based on the distances of Co1 …Co2 and C7…C29). Each 18-atom ring unit is connected to the other four units though tbtd3- anions to generate a novel 2D network (Fig. 2). The adjacent 2D network are recognized each other to generate a 3D supramolecular network via hydrogen bonding interactions (Fig. 3). Then the layers superimpose under the directions of C—H… π interactions between the bpy protons and a phenyl ring (C16—H16…π 0.285 1 nm, C45—H45…π 0.269 7 nm), as well as ππ stacking interactions with a centroid-to-centroid distance of 0.336 8 nm, which are ultimately extended into a 3D supramolecular structure.

    Scheme 1

    Scheme 1.  Coordination modes of tbtd3- (a) and Hbbta2- (b) ligand in 1~2

    Figure 2

    Figure 2.  View of 2D network of 1 along a axis

    Figure 3

    Figure 3.  View of 3D supramolecular architecture of 1 based on hydrogen bonding interaction along b axis

    Symmetry codes: C: 1+x, 2.5-y, 0.5+z; D:-x, 2-y, -z; E:-x, 1-y, -z; F: 1+x, 2+y, 1+z; G: 1-x, 1.5+y, 0.5-z; H: 1+x, 1+y, 1+z

    The asymmetric unit of 2 contains two Cd(Ⅱ)ions, one Hbbta2- ligand, three bpy ligands, one C2O42- ion and one coordinated water molecule (Fig. 4). Each Cd1 is six coordinated by two nitrogen atoms (Cd1—N1 0.229 2(3) nm; Cd1—N2 0.237 1(3) nm) from one bpy ligand, one carboxylate group oxygen atoms from one Hbbta2- ligands, two oxygen atoms from one C2O42- ion and one water molecule. The Cd1—O distances fall in a range of 0.228 5(2)~0.234 1(3) nm and are similar to those found in other cadmium carboxylate complexes[23]. The coordination geometry of Cd1 center can be described as a distorted octahedral geometry. While Cd2 is surrounded by four nitrogen atoms from two chelating bpy ligands, two oxygen atoms from one C2O42- ion. The bond lengths of Cd2—N are comparable to the reported ones, varying between 0.230 2(3) and 0.232 1(3) nm. The partially deprotonated Hbbta2- ligand adopts a monodentate bridging mode (Scheme 1b). Each C2O42- ion connects two Cd(Ⅱ)ions in η2:η2:μ2 bridging coordination mode. Based on the connection mode, each pair of Cd(Ⅱ)ions are bridged by one C2O42- ion to form a binuclear structure with the Cd1…Cd1 distances of 0.595 7 nm. The binuclear structure is linked by the hydrogen bonding interactions and ππ stacking interactions generating a 1D double-chain (Fig. 5). The ππ stacking interactions occurs between the pyridine rings of bpy ligands (R1…R2, R1: C11—C12—C13— C14—N3—C15, R2: C11—C12—C13—C14—N— C15, symmetry code: -x, 1-y, -1-z, centroid distance: 0.399 5 nm, dihedral angle: 0°) and pyridine rings of the bpy and phenyl ring of Hbbta2- ligands (R3…R4, R3: C16—C17—C18—C19—N4—C20, R4: C34— C35—C36—C37—C38—C39, symmetry code: x, y, -1+z, centroid distance: 0.407 9 nm, dihedral angle: 12.84°). The adjacent double-chains are recognized each other to generate a 2D supramolecular network via hydrogen bonding interactions (C—H…O, Fig. 6).

    Figure 4

    Figure 4.  Coordination environment of Cd(Ⅱ)ion in 2

    Ellipsoid probability is drawn at 30% and all H atoms are omitted for clarity

    Figure 5

    Figure 5.  View of double-chain in crystal of 2 by ππ stacking and hydrogen bonding interactions along b axis

    Symmetry codes:-x, -y, -1-z for Cg2; x, y, -1+z for Cg4; A: x, y, -1+z, B: -x, -y, -1-z

    Figure 6

    Figure 6.  View of 2D supramolecular network of 2 along b axis

    Symmetry codes: A: x, y, -1+z, B:-x, -y, -1-z; C: 1-x, 1-y, 1-z, D: x, 1+y, z; E: x, 1+y, z

    In the FT-IR spectra, the absorption bands in the region of 3 405~3 426 cm-1 may be attributed to the stretching vibrations of O—H. The bands in the region of 2 995~3 010 cm-1 can be ascribed to C—H stretching vibrations of the benzene ring[24]. The absence of the absorption bands at 1 730~1 690 cm-1 in 1 indicates the H3tbtd ligand adopts complete deprotonated tbtd3- form, while the characteristic bands at 1 703 cm-1 in 2 indicates the partially deprotonation of carboxylate groups in H3bbta upon reaction with Cd ions. The asymmetric stretching vibrations of the carboxylate groups were observed at 1 603 and 1 606 cm-1, and the symmetric stretching vibration (ms) of the carboxylate groups were observed at 1 480 and 1 437 cm-1, respectively[25]. The separation ΔνCOO between the νas, COO and νs, COO band in 1~2 were 123 and 169 cm-1, which were smaller than 200 cm-1, indicating that the carboxyl groups coordinate with the metal ion in bridging mode[26]. The absorption peaks around 1 006 cm-1 are assigned to C—F stretching vibrations for 2.

    To study the thermal stabilities of 1~2, thermal gravimetric analysis (TGA) was performed. The TG curves of 1~2 are shown in Fig. 7. CP 1 first lost its coordinated and lattice water molecule below 195 ℃, and the weight loss found of 7.42% was consistent with that calculated (7.33%). Then 1 was relatively stable up to 195~355 ℃. The second weight loss was 80.27% in a temperature range of 365~596 ℃ corresponding to the decomposition of tbtd3- and bpy ligands (Calcd. 80.39%). The TG curve of 2 showed an initial weight loss of 8.43% below 180 ℃ corresponding to the removal of water molecules and C2O42- ions (Calcd. 8.51%). Then 2 was stable up to 240 ℃ and followed by the weight loss in a range of 240~445 ℃, assigned to the decomposition of Hbbta2- and bpy ligands (Calcd. 73.6%; Obsd. 73.1%). The remaining weight of 24.7% was CdO that is in agreement with the calculated value of 25.0%.

    Figure 7

    Figure 7.  TGA curves of 1~2

    In order to confirm the phase purity of the bulk materials, PXRD patterns were measured at room temperature. The PXRD experimental and computersimulated patterns of all of them are shown in Fig. 8. The peaks of the simulated and experimental PXRD patterns were in good agreement with each other, confirming the phase purities of 1~2.

    Figure 8

    Figure 8.  PXRD patterns of 1 (a) and 2 (b)

    The photoluminescence properties of H3bbta and 2 were examined at room temperature, and the emission spectra are shown in Fig. 9. The H3bbta ligand exhibited one emission band at 418 nm upon excitation at 300 nm. Upon the same excitation, 2 showed one intense emission peak at 456 nm, which meant a red shift of ca. 38 nm relative to that of the free ligand (λmax=418 nm). It may be caused by the following reasons: (ⅰ) organic ligands may change their highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels after coordination to metal centers; (ⅱ) charge transfer occurs between organic ligands and metal centers [27]. By comparing the emission spectra of 2 and the free ligand, we can conclude that the enhancement of luminescence in 2 may be attributed to the ligation of ligand to the metal center, which effectively increases the rigidity and reduces the loss of energy by radiationless decay[28-29].

    Figure 9

    Figure 9.  Emission spectra of H3bbta and 2 in solid state at room temperature

    MO was chosen as a model of dye contaminant to evaluate their photocatalytic effectiveness, because it is one of the most widely used dyes in the textile, cosmetic and photographic industries and has become a common organic pollutant[30-31]. Herein, MO was selected for evaluating the activities of photocatalysts in water. Fig. 10a illustrates the time - dependent absorption spectra and concentration change of the MO solution degraded by CP 1. If no photocatalyst existed under UV irradiation, the degradation efficiency of the control experiment was no more than 19.7%. While 81.9% MO were successfully photodegraded with the presence of CP 1 after 120 min. The calculation results indicate that the residual ratio of MO was 18.1% for 1 (Fig. 10b). The result indicated that CP 1 was active for the photodegradation of MO under the ultraviolet light irradiation, which demonstrates that the differences in the structural features and components of the titled complex may affect their photocatalytic performances.

    Figure 10

    Figure 10.  (a) Plots of concentration versus irradiation time for MO in the presence of CP 1; (b) Photocatalytic decomposition of MO solution under UV by CP 1 and the control experiment without any catalyst

    In summary, two new Co/Cd complexes were successfully synthesized based on 4 - (2, 4, 6 - tricarboxyl phenyl)-2, 2′, 6′, 2″-terpyridine (H3tbtd)/1-fluoro-2, 4, 6phenyltriacid (H3bbta) and 2, 2′-bpy ligands through hydrothermal method. 1 shows 2D network structure constructed from Co2+ ion cross-linked by tbtd3- ligands. 2 is binuclear structure, which are linked into 2D supramolecular networks through hydrogen bonding and ππ stack interactions. The photocatalytic activities of CP 1 indicate that it may be good and stable photocatalysts for the photodegradation of MO.


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  • Figure 1  Coordination environment of Co(Ⅱ)ion in 1

    Ellipsoid probability is drawn at 30% and all H atoms are omitted for clarity; Symmetry codes: A:-1-x, 0.5+y, -0.5-z; B:-x, -0.5+y, 0.5-z

    Scheme 1  Coordination modes of tbtd3- (a) and Hbbta2- (b) ligand in 1~2

    Figure 2  View of 2D network of 1 along a axis

    Figure 3  View of 3D supramolecular architecture of 1 based on hydrogen bonding interaction along b axis

    Symmetry codes: C: 1+x, 2.5-y, 0.5+z; D:-x, 2-y, -z; E:-x, 1-y, -z; F: 1+x, 2+y, 1+z; G: 1-x, 1.5+y, 0.5-z; H: 1+x, 1+y, 1+z

    Figure 4  Coordination environment of Cd(Ⅱ)ion in 2

    Ellipsoid probability is drawn at 30% and all H atoms are omitted for clarity

    Figure 5  View of double-chain in crystal of 2 by ππ stacking and hydrogen bonding interactions along b axis

    Symmetry codes:-x, -y, -1-z for Cg2; x, y, -1+z for Cg4; A: x, y, -1+z, B: -x, -y, -1-z

    Figure 6  View of 2D supramolecular network of 2 along b axis

    Symmetry codes: A: x, y, -1+z, B:-x, -y, -1-z; C: 1-x, 1-y, 1-z, D: x, 1+y, z; E: x, 1+y, z

    Figure 7  TGA curves of 1~2

    Figure 8  PXRD patterns of 1 (a) and 2 (b)

    Figure 9  Emission spectra of H3bbta and 2 in solid state at room temperature

    Figure 10  (a) Plots of concentration versus irradiation time for MO in the presence of CP 1; (b) Photocatalytic decomposition of MO solution under UV by CP 1 and the control experiment without any catalyst

    Table 1.  Crystal data and structural refinement parameters for 1~2

    Complex 1 2
    Empirical formula C68H52Co3N10O18 C41H28Cd2FN6O11
    Formula weight 1 473.98 1 024.49
    Crystal system Monoclinic Triclinic
    Space group P21/c P1
    a / nm 2.288 21(10) 1.189 6(5)
    b / nm 1.712 09(8) 1.324 3(5)
    c / nm 1.751 49(7) 1.525 5(6)
    α / (°) 107.522(6)
    β / (°) 110.845 0(10) 106.013(6)
    γ / (°) 99.915(6)
    V / nm3 6.412 6(5) 2.115 7(14)
    Z 4 2
    Dc / (g·cm-3) 1.527 1.608
    θ range for data collection / (°) 1.71~25.01 1.494~30.811
    Absorption coefficient / mm-1 0.850 1.075
    Crystal size / mm 0.32×0.19×0.12 0.26×0.21×0.14
    F(000) 2 996 1 018
    Reflection collected 11 336 10 632
    Limiting-indices -26 ≤ h ≤ 27, -20 ≤ k ≤ 20, -20 ≤ l ≤ 12 -13 ≤ h ≤ 16, -14 ≤ k ≤ 18, -19 ≤ l ≤ 18
    Goodness-of-fit (on F2) 0.940 1.034
    R1, wR2a [I>2σ(I)] 0.055 5, 0.149 7 0.034 5, 0.099 4
    R1, wR2a (all data) 0.072 5, 0.162 9 0.057 2, 0.113 8
    a R1=∑||Fo|-|Fc||/∑|Fo|, wR2=[∑w(Fo2-Fc2)2/∑w(Fo2)2]1/2
    下载: 导出CSV

    Table 2.  Selected bond distances (nm) and bond angles (°) for 1~2

    1
    Co1—O3A 0.200 9(3) Co1—N6 0.205 2(3) Co1—O6 0.206 4(3)
    Co1—N5 0.215 7(4) Co1—N7 0.217 8(4) Co1—O5 0.237 2(3)
    Co2—O7B 0.197 4(3) Co2—N9 0.203 5(3) Co2—O9 0.208 4(3)
    Co2—N8 0.213 1(4) Co2—N10 0.216 7(4) Co2—O10 0.229 7(3)
    Co3—N4 0.213 8(4) Co3—N1 0.208 3(4) Co3—O12 0.208 5(3)
    Co3—O13 0.208 7(4) Co3—N3 0.212 6(4) Co3—N2 0.213 0(4)
    O3A—Co1—N6 122.97(13) O3A—Co1—O6 89.81(13) N6—Co1—O6 145.78(12)
    O3A—Co1—N5 94.84(14) N6—Co1—N5 76.36(13) O6—Co1—N5 113.49(16)
    O3A—Co1—N7 101.85(14) N6—Co1—N7 75.72(13) O6—Co1—N7 89.09(15)
    N5—Co1—N7 152.02(13) O3A—Co1—O5 146.47(12) N6—Co1—O5 90.44(12)
    O6—Co1—O5 58.06(12) N5—Co1—O5 90.30(14) N7—Co1—O5 88.06(13)
    O7B—Co2—N9 121.02(14) O7B—Co2—O9 90.819(13) N9—Co2—O9 146.23(13)
    O7B—Co2—N8 95.64(15) N9—Co2—N8 76.95(13) O9—Co2—N8 113.50(15)
    O7B—Co2—N10 96.06(15) N9—Co2—N10 76.34(13) O9—Co2—N10 90.37(15)
    N8—Co2—N10 153.19(14) O7B—Co2—O10 147.25(13) N9—Co2—O10 91.32(11)
    O9—Co2—O10 59.08(11) N8—Co2—O10 86.24(13) N10—Co2—O10 96.65(13)
    N1—Co3—O12 95.78(15) N1—Co3—O13 90.84(16) O12—Co3—O13 92.84(14)
    N1—Co3—N3 99.35(17) O12—Co3—N3 87.42(14) O13—Co3—N3 169.76(16)
    N1—Co3—N2 77.70(15) O12—Co3—N2 170.90(14) O13—Co3—N2 87.39(15)
    N1—Co3—N4 176.05(18) O12—Co3—N4 83.01(16) O13—Co3—N4 92.97(17)
    N3—Co3—N4 76.87(17) N2—Co3—N4 103.07(16)
    2
    Cd1—O7 0.224 1(7) Cd2—O1 0.231 1(2) Cd1—O5 0.229 4(3)
    Cd2—O2 0.230 2(3) Cd1—O4 0.228 5(2) Cd2—N4 0.232 1(3)
    Cd1—O3 0.234 1(2) Cd2—N5 0.230 2(3) Cd1—N1 0.229 2(3)
    Cd2—N6 0.232 6(3) Cd1—N2 0.237 1(3) Cd2—N3 0.232 7(3)
    O7—Cd1—O5 92.35(10) O1—Cd2—N4 94.44(10) O7—Cd1—O4 95.36(10)
    O1—Cd2—N3 97.51(10) O7—Cd1—O3 95.03(10) O1—Cd2—N6 91.09(10)
    O7—Cd1—N1 103.37(10) O2—Cd2—O1 71.92(9) O7—Cd1—N2 170.22(10)
    O2—Cd2—N4 150.60(9) O5—Cd1—O3 167.89(9) O2—Cd2—N5 88.29(10)
    O5—Cd1—N2 80.75(10) O2—Cd2—N3 84.57(11) O4—Cd1—O5 98.06(10)
    O2—Cd2—N6 108.69(11) O4—Cd1—O3 71.73(8) N4—Cd2—N3 71.22(11)
    O4—Cd1—N1 154.65(9) N4—Cd2—N6 97.21(11) O4—Cd1—N2 92.49(10)
    N5—Cd2—O1 148.44(10) O3—Cd1—N2 92.97(10) N5—Cd2—N4 113.49(10)
    N1—Cd1—O5 98.09(10) N5—Cd2—N3 104.98(11) N1—Cd1—O3 89.53(9)
    N5—Cd2—N6 71.83(11) N1—Cd1—N2 71.04(9) N3—Cd2—N6 166.00(11)
    Symmetry codes: A: -x-1, y+1/2, -z-1/2; B: -x, y-1/2, -z+1/2 for 1.
    下载: 导出CSV

    Table 3.  Hydrogen bond parameters for 1 and 2

    D—H…A d(D—H) / nm d(H…A) / nm d(D…A) / nm ∠DHA / (°)
    1
    O14D—H14a…O3C 0.084 8(2) 0.208 14(2) 0.288 6(3) 158.81(3)
    O14D—H14b…O15D 0.085 6(3) 0.205 4(4) 0.289 5(5) 166.84(3)
    O15D—H15a…O14H 0.086 7(3) 0.269 6(2) 0.283 5(4) 101.80(3)
    O15D—H15b…O16E 0.086 2(3) 0.217 9(3) 0.294 9(3) 148.66(3)
    O17G—H17a…O9C 0.085 0(3) 0.322 0(3) 0.300 4(3) 97.01(3)
    2
    O5A—H5a…O4B 0.090 3(3) 0.109 0(5) 0.275 7(3) 157.78(7)
    C1A—H1a…O9C 0.093 0(6) 0.267 4(6) 0.325 8(8) 121.43(6)
    C19D—H19a…O3D 0.093 0(2) 0.247 8(3) 0.321 6(6) 136.47(8)
    C18E—H18a…O8D 0.093 1(7) 0.241 0(6) 0.318 8(6) 141.04(9)
    Symmetry codes: C: 1+x, 2.5-y, 0.5+z, D: -x, 2-y, -z; E: -x, 1-y, -z; F: 1+x, 2+y, 1+z; G: 1-x, 1.5+y, 0.5-z; H: 1+x, 1+y, 1+z for 1; A: x, y, -1+z; B: -x, -y, -1-z; C: 1-x, 1-y, 1-z, D: x, 1+y, z; E: x, 1+y, z for 2.
    下载: 导出CSV
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  • 发布日期:  2021-02-10
  • 收稿日期:  2020-05-20
  • 修回日期:  2020-11-02
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