由醚氧桥联羧酸配体构筑的铜(Ⅱ)、锌(Ⅱ)和锰(Ⅱ)配位聚合物的合成、晶体结构、荧光及光催化性质
English
Syntheses, Crystal Structures, Luminescence and Photocatalytic Activity of Cu(Ⅱ), Zn(Ⅱ) and Mn(Ⅱ) Coordination Polymers Based on Ether-Bridged Carboxylic Acids
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0. Introduction
During the past decades, the design and construc-tion of functional coordination polymers have caught enormous attention of chemical researchers, not only because of their charming architectures and topologies, but also for their various potential applications in gas storage and separation, catalysis, magnetism, lumines-cence, and biomedicine[1-12]. However, the design and composition of crystalline complexes with target struc-tures as well as multifunction are of great importance topics and are still the tremendously challenges. The assembly of coordination polymers is mainly affected by many factors, such as metal ions, organic ligands and auxiliary ligands, metal-to-ligand ratio, solvent, and the reaction temperature[13-22]. The metal ions and organic ligands are the key to get intriguing topologies and functional materials. Multicarboxylate ligands are frequently used for the construction of coordination polymers because they can satisfy the charge-balance and can provide diverse ligands and coordination modes[5-6, 14, 16-17, 23-24]. Among such polycarboxylate blocks, semirigid biphen ligands are particularly intriguing, since they enable the formation of uncommon metal-organic networks or even topologically unique nets; at the same time, such ligands can also show interesting properties along with flexibility and conformational diversity[6, 14, 16-17, 25].
Currently, the water pollutant is becoming one serious environment problem in the world. Much effort has been devoted to developing new photocatalytic ma-terials for the green degradation of organic pollutants. Some coordination polymers show good photocatalytic activity for the decomposition of organic dyes[25-28].
Following our interest in the exploration of novel and poorly investigated multicarboxylic acids for the design of coordination polymers[5-6, 14, 17, 25, 29], in the pres-ent study we selected 5-(3, 4-dicarboxylphenoxy)nicotic acid (H3dpna) or 2, 3, 2', 3'-diphenyl ether tetracarboxyl-ic acid (H4deta) as a main building block. The selec-tion of H3dpna and H4deta has been governed by the following reasons. (1) Both ligands contain two aromat-ic rings that are interconnected by a rotatable O -ether group providing a subtle conformational adaptation. (2) They show three different types of functionalities (i. e., -COOH, O-ether or N-pyridyl) and have eight or nine potential coordination sites, which can result in diverse coordination patterns and high dimensionalities, espe-cially when acting as a multiply bridging spacer. (3) Two carboxylic acid blocks remain poorly used for the generation of coordination polymers.
Herein, we report the synthesis, crystal structures, and luminescence and photocatalytic properties of Cu(Ⅱ), Zn(Ⅱ) and Mn(Ⅱ) coordination polymers with H3dp-na or H4deta ligands.
1. Experimental
1.1 Reagents and physical measurements
All chemicals and solvents were of AR grade and used without further purification. The content of carbon, hydrogen and nitrogen were determined using an Elementar Vario EL elemental analyzer. IR spectra were recorded using KBr pellets and a Bruker EQUINOX 55 spectrometer. Thermogravimetric analysis (TGA) data were collected on a LINSEIS STA PT1600 ther-mal analyzer with a heating rate of 10 ℃·min-1. Excita-tion and emission spectra were recorded on an Edin-burgh FLS920 fluorescence spectrometer using the solid samples at room temperature. Powder X-ray diffraction (PXRD) patterns were measured on a Rigaku-Dmax 2400 diffractometer using Cu Kα radia-tion (λ =0.154 06 nm); the X -ray tube was operated at 40 kV and 40 mA; the data collection range was be-tween 5° and 45°.
1.2 Synthesis of {[Cu3(μ4-dpna)2(2, 2′-bipy)2]4H2O}n (1)
A mixture of CuCl2·H2O (0.046 g, 0.3 mmol), H3dpna (0.061 g, 0.2 mmol), 2, 2' - bipy (0.047 g, 0.3 mmol), NaOH (0.024 g, 0.6 mmol), and H2O (10 mL) was stirred at room temperature for 15 min, and then sealed in a 25 mL Teflon - lined stainless steel vessel, and heated at 120 ℃ for 3 d, followed by cooling to room temperature at a rate of 10 ℃ ·h-1. Blue block - shaped crystals were isolated manually, and washed with distilled water. Yield: 45% (based on H3dpna).Anal. Calcd. for C48H36Cu3N6O18(%): C 49.05, H 3.09, N 7.15; Found(%): C 48.93, H 3.07, N 7.16. IR (KBr, cm-1): 3 518w, 3 074w, 1 625m, 1 586s, 1 572s, 1 498w, 1 472w, 1 446m, 1 384s, 1 362s, 1 318w, 1 292w, 1 253w, 1 226w, 1 195w, 1 160w, 1 138w, 1 103w, 1 059w, 1 033w, 989w, 927w, 822w, 795w, 765m, 730w, 699w, 651w, 615w.
1.3 Synthesis of {[Zn3(μ4-dpna)2(2, 2′-bipy)2(H2O)2]·6H2O}n (2)
Synthesis of 2 was similar to 1 except using ZnCl2 (0.041 g, 0.3 mmol) instead of CuCl2·H 2O. Colourless block-shaped crystals of 2 were isolated manually, and washed with distilled water. Yield: 50% (based on H3dpna). Anal. Calcd. for C48H44Zn3N6O22(%): C 46.01, H 3.54, N 6.71; Found(%): C 45.86, H 3.55, N 6.74. IR (KBr, cm-1): 3 083w, 1 600s, 1 581s, 1 564s, 1 492w, 1 475w, 1 444m, 1 391s, 1 319w, 1 302w, 1 257w, 1 231w, 1 200w, 1 159w, 1 063w, 1 027w, 987w, 943w, 917w, 828w, 805w, 823w, 774m, 735w, 704w, 655w.
1.4 Syntheses of {[M2(μ4-deta)(phen)2(H2O)]·3H2O}n (M=Mn (3), Zn (4))
A mixture of MCl2·xH2O (x=4 for 3 and x=0 for 4, 0.20 mmol), H4deta (0.035 g, 0.10 mmol), phen (0.040 g, 0.20 mmol), NaOH (0.016 g, 0.40 mmol), and H2O (10 mL) was stirred at room temperature for 15 min, and then sealed in a 25 mL Teflon-lined stainless steel vessel, and heated at 160 ℃ for 3 d, followed by cool-ing to room temperature at a rate of 10 ℃ ·h-1. Yellow (3) or colourless (4) block-shaped crystals were isolated manually, and washed with distilled water. Yield: 52% for 3 and 42% for 4 (based on H4deta). Anal. Calcd. for C40H30Mn2N4O13 (3, %): C 54.31, H 3.42, N 6.33; Found (%): C 54.10, H 3.44, N 6.30. IR (KBr, cm-1): 3 407w, 3 061w, 1 627w, 1 565s, 1 516w, 1 466w, 1 421m, 1 380s, 1 293w, 1 244w, 1 195w, 1 141w, 1 099w, 1 067w, 1 001w, 927w, 902w, 848w, 770w, 729m, 700w, 667w, 639w. Anal. Calcd. for C40H30Zn2N4O13 (4, %): C 53.06, H 3.34, N 6.19; Found(%): C 53.27, H 3.32, N 6.23. IR (KBr, cm-1): 3 439w, 3 066w, 1 648s, 1 625s, 1 581m, 1 516w, 1 494w, 1 450w, 1 423w, 1 384s, 1 305w, 1 265w, 1 226w, 1 191w, 1 160w, 1 142w, 1 103w, 1 024w, 984w, 905w, 853w, 804w, 774w, 725m, 707w, 642w, 607w.
Four compounds are insoluble in water and com-mon organic solvents, such as methanol, ethanol, ace-tone, and DMF.
1.5 Structure determinations
The data for single crystals of compounds 1~4 was collected at 293(2) K on a Bruker SMART APEX Ⅱ CCD diffractometer with Cu Kα radiation (λ=0.154 178 nm). The structures were solved by direct methods and refined by full matrix least-square on F2 using the SHELXTL-2014 program[30]. All non - hydrogen atoms were refined anisotropically. All the hydrogen atoms were positioned geometrically and refined using a riding model. Some lattice solvent molecules in 1 are highly disordered and were removed using the SQUEEZE routine in PLATON[31]. The number of solvent H2O molecules was obtained on the basis of elemental and thermogravimetric analyses. A summary of the crystallography data and structure refinements for 1~4 is given in Table 1. The selected bond lengths and angles for compounds 1~4 are listed in Table 2. Hydrogen bond parameters of compounds 2~4 are given in Table 3~5.
Table 1
Compound 1 2 3 4 Chemical formula C48H36Cu3N6O18 C48H44Zn3N6O22 C40H30Mn2N4O13 C40H30Zn2N4O13 Molecular weight 1 175.47 1 253.00 884.56 905.42 Crystal system Monoclinic Monoclinic Monoclinic Monoclinic Space group P21/c C2/c P21/n P21/n a/nm 1.813 04(17) 2.024 50(6) 1.268 98(8) 1.246 22(3) b/nm 1.003 29(8) 0.767 93(2) 1.718 33(12) 1.720 14(5) c/ nm 1.353 58(11) 3.322 33(10) 1.739 32(14) 1.725 40(7) β/(°) 91.443(9) 100.782(3) 100.857(7) 100.085(3) V/nm3 2.461 4(4) 5.074 0(3) 3.724 7(5) 3.641 5(2) Z 2 4 4 4 F(000) 1 114 2 560 1 808 1 848 Crystal size / mm 0.21×0.20×0.18 0.26×0.24×0.23 0.22×0.21×0.20 0.23×0.19×0.18 θrange for data collection /(°) 4.880~66.600 4.446~69.920 3.648~69.924 3.657~69.969 Limiting indices -17 ≤ h ≤ 21, -24 ≤ h ≤ 20, -13 ≤ h ≤ 15, -11 ≤ h ≤ 15, -11 ≤ k ≤ 11, -9 ≤ k ≤ 4, -17 ≤ k ≤ 20, -20 ≤ k ≤ 20, -14 ≤ l ≤ 16 -38 ≤ l ≤ 40 -20 ≤ l ≤ 20 -20 ≤ l ≤ 20 Reflection collected, unique (Rint) 8 795, 4 331 (0.076 5) 9 067, 4 708 (0.027 9) 6 746, 4 196 (0.052 0) 6 769, 4 606 (0.050 5) Dc/ (g·cm-3) 1.586 1.640 1.577 1.651 μ / mm-1 2.116 2.439 6.171 2.289 Data, restraint, parameter 4 331, 0, 322 4 708, 0, 357 4 196, 0, 534 4 606, 0, 532 Goodness-of-fit on F2 0.964 1.022 1.031 1.023 Final R indices[I≥2σ(I)]R1, wR2 0.068 1, 0.150 8 0.044 2, 0.120 4 0.062 9, 0.154 5 0.075 4, 0.183 9 R indices(all data)R1, wR2 0.110 4, 0.186 8 0.058 8, 0.129 8 0.105 6, 0.191 1 0.109 6, 0.206 8 Largest diff. peak and hole/(e·nm-3) 614 and -824 921 and -772 708 and -578 2 058 and -1 275 Table 2
1 Cu(1)-O(6)A 0.194 3(4) Cu(1)-O(6)B 0.194 3(4) Cu(1)-N(1) 0.203 6(5) Cu(1)-N(1)C 0.203 6(5) Cu(2)-O(1) 0.195 7(4) Cu(2)-O(4)D 0.195 5(5) Cu(2)-N(2) 0.200 1(5) Cu(2)-N(3) 0.197 2(5) O(6)A-Cu(1)-N(1)C 91.72(19) O(6)B-Cu(1)-N(1)C 88.28(19) O(6)A-Cu(1)-N(1) 88.27(19) O(6)B-Cu(1)-N(1) 91.73(19) O(4)D-Cu(2)-O(1) 94.31(19) O(4)D-Cu(2)-N(3) 94.8(2) N(3)-Cu(2)-O(1) 159.2(2) O(4)D-Cu(2)-N(2) 158.4(2) N(2)-Cu(2)-O(1) 96.15(19) N(2)-Cu(2)-N(3) 81.8(2) 2 Zn(1)-O(1) 0.202 4(2) Zn(1)-O(6)A 0.217 1(3) Zn(1)-O(7)A 0.241 5(4) Zn(1)-N(1)B 0.219 1(3) Zn(1)-N(2) 0.211 2(3) Zn(1)-N(3) 0.217 8(3) Zn(2)-O(3) 0.232 9(3) Zn(2)-O(3)C 0.232 9(3) Zn(2)-O(4) 0.204 8(3) Zn(2)-O(4)C 0.204 8(3) Zn(2)-O(8) 0.201 2(3) Zn(2)-O(8)C 0.201 2(3) O(1)-Zn(1)-N(2) 97.45(10) O(6)A-Zn(1)-O(1) 86.61(11) N(2)-Zn(1)-O(6)A 89.09(13) N(3)-Zn(1)-O(1) 165.24(11) N(2)-Zn(1)-N(3) 75.66(12) O(6)A-Zn(1)-N(3) 106.07(12) O(1)-Zn(1)-N(1)B 91.52(10) N(2)-Zn(1)-N(1)B 132.67(11) O(6)A-Zn(1)-N(1)B 137.95(12) N(3)-Zn(1)-N(1)B 84.10(11) O(7)A-Zn(1)-O(1) 102.35(12) O(7)A-Zn(1)-N(2) 138.00(12) O(6)A-Zn(1)-O(7)A 56.00(12) O(7)A-Zn(1)-N(3) 91.20(13) O(7)A-Zn(1)-N(1)B 83.67(11) O(8)C-Zn(2)-O(8) 99.0(2) O(8)-Zn(2)-O(4) 103.74(14) O(8)C-Zn(2)-O(4) 97.33(14) O(4)C-Zn(2)-O(4) 147.35(18) O(8)-Zn(2)-O(3) 87.29(12) O(8)-Zn(2)-O(3)C 156.47(14) O(4)-Zn(2)-O(3) 59.14(10) O(3)-Zn(2)-O(4)C 97.84(11) O(3)-Zn(2)-O(3)C 95.92(15) 3 Mn(1)-O(2) 0.222 3(4) Mn(1)-O(4) 0.208 8(4) Mn(1)-O(8)A 0.208 0(4) Mn(1)-N(1) 0.224 2(4) Mn(1)-N(2) 0.220 2(5) Mn(2)-O(1) 0.231 7(4) Mn(2)-O(2) 0.223 9(4) Mn(2)-O(7)A 0.209 6(4) Mn(2)-O(10) 0.218 9(4) Mn(2)-N(3) 0.223 0(5) Mn(2)-N(4) 0.227 2(5) O(4)-Mn(1)-O(8)A 150.42(17) N(2)-Mn(1)-O(8)A 99.62(17) O(4)-Mn(1)-N(2) 109.80(16) O(2)-Mn(1)-O(8)A 89.27(17) O(2)-Mn(1)-O(4) 84.63(15) O(2)-Mn(1)-N(2) 96.36(16) N(1)-Mn(1)-O(8)A 105.16(18) O(4)-Mn(1)-N(1) 86.16(17) N(1)-Mn(1)-N(2) 74.34(17) N(1)-Mn(1)-O(2) 163.81(15) O(10)-Mn(2)-O(7)A 84.84(16) N(3)-Mn(2)-O(7)A 103.63(16) N(3)-Mn(2)-O(10) 99.51(17) O(2)-Mn(2)-O(7)A 100.13(15) O(2)-Mn(2)-O(10) 97.90(16) N(3)-Mn(2)-O(2) 151.59(17) N(4)-Mn(2)-O(7)A 93.82(15) N(4)-Mn(2)-O(10) 172.85(16) N(4)-Mn(2)-N(3) 73.95(16) N(4)-Mn(2)-O(2) 89.24(15) O(1)-Mn(2)-O(7)A 154.45(15) O(1)-Mn(2)-O(10) 87.24(16) N(3)-Mn(2)-O(1) 101.62(16) O(2)-Mn(2)-O(1) 57.01(14) N(4)-Mn(2)-O(1) 96.82(16) Mn(1)-O(2)-Mn(2) 133.88(18) 4 Zn(1)-O(1) 0.215 7(4) Zn(1)-O(2) 0.229 4(5) Zn(1)-O(6)A 0.205 6(4) Zn(1)-O(10) 0.212 7(5) Zn(1)-N(1) 0.217 1(5) Zn(1)-N(2) 0.210 5(6) Zn(2)-O(1) 0.223 6(4) Zn(2)-O(3) 0.198 8(4) Zn(2)-O(9) 0.194 7(4) Zn(2)-N(3) 0.207 3(5) Zn(2)-N(4) 0.215 4(6) O(6)A-Zn(1)-N(2) 105.8(2) O(6)A-Zn(1)-O(10) 86.98(19) N(2)-Zn(1)-O(10) 95.4(2) O(6)A-Zn(1)-O(1) 98.87(18) N(2)-Zn(1)-O(1) 153.6(2) O(1)-Zn(1)-O(10) 95.00(19) O(6)A-Zn(1)-N(1) 93.18(18) N(2)-Zn(1)-N(1) 78.1(2) O(10)-Zn(1)-N(1) 173.24(19) O(1)-Zn(1)-N(1) 91.65(18) O(6)A-Zn(1)-O(2) 155.56(18) O(2)-Zn(1)-N(2) 98.2(2) O(10)-Zn(1)-O(2) 86.66(19) O(1)-Zn(1)-O(2) 58.29(17) N(1)-Zn(1)-O(2) 95.86(19) Symmetry codes: A:x, -y+3/2, z-1/2; B: -x+1, y-1/2, -z+1/2; C: -x+1, -y+1, -z; D: x, -y+3/2, z+1/2 for 1; A: -x, -y+1, -z; B: -x+1, -y+2, -z; C: -x, -y, -z+1/2 for 2; A: -x+1, -y, -z+1 for 3; A: -x+1, -y, -z+1 for 4. Table 3
D-H…A d(D-H) / nm d(H…A) / nm d(D…A) / nm ∠DHA / (°) O(8)-H(1W)…O(9) 0.082 0 0.200 6 0.264 2 133.86 O(8)-H(2W)…O(10)A 0.084 5 0.185 1 0.265 9 159.74 O(9)-H(3W)…O(6)B 0.085 0 0.217 7 0.302 7 179.52 O(9)-H(4W)…O(2)A 0.085 0 0.196 4 0.281 5 179.54 O(10)-H(5W)…O(3) 0.085 0 0.195 1 0.280 1 179.05 O(11)-H(7W)…O(2)A 0.085 5 0.213 2 0.298 7 179.08 Symmetry codes: A: x, y-1, z; B: -x, -y+1, -z. Table 4
D-H…A d(D-H) / nm d(H…A) / nm d(D…A) / nm ∠DHA / (°) O(10)-H(1W)…O(6)A 0.085 0 0.183 9 0.268 8 179.42 O(11)-H(3W)…O(12)B 0.085 0 0.188 7 0.273 6 179.28 O(11)-H(4W)…O(4)C 0.088 2 0.213 0 0.280 5 132.73 O(12)-H(5W)…O(3)C 0.085 6 0.192 0 0.274 8 162.66 O(12)-H(6W)…O(6)C 0.085 4 0.197 6 0.277 2 154.70 O(13)-H(7W)…O(10)D 0.068 1 0.209 3 0.277 3 176.73 O(13)-H(8W)…O(11)E 0.084 6 0.216 1 0.280 9 133.27 Symmetry codes: A: x+1/2, -y+3/2, z-1/2; B: -x+2, -y+1, -z+1; C: x+1, y, z; D: -x+1/2, y-1/2, -z+1/2; E: x-1, y, z. Table 5
D-H…A d(D-H) / nm d(H…A) / nm d(D…A) / nm ∠DHA / (°) O(10)-H(1W)…O(13) 0.082 0 0.213 5 0.277 5 134.94 O(10)-H(2W)…O(6)A 0.086 6 0.180 9 0.267 5 179.01 O(11)-H(3W)…O(3)B 0.086 6 0.199 4 0.286 0 179.47 O(11)-H(4W)…O(12)C 0.085 4 0.189 7 0.275 1 179.72 O(12)-H(5W)…O(4)D 0.085 0 0.186 2 0.271 2 179.69 O(12)-H(6W)…O(7)D 0.086 0 0.192 2 0.278 2 178.37 O(13)-H(7W)…O(8)D 0.085 1 0.191 9 0.277 0 179.00 O(13)-H(8W)…O(11)E 0.084 6 0.204 2 0.288 8 179.14 Symmetry codes: A: x-1/2, -y+1/2, z+1/2; B: x-1, y, z; C: x-1, y-1, z; D: -x+2, -y+1, -z; E: -x+1/2, y+1/2, -z+1/2. CCDC: 2004109, 1; 2004110, 2; 2004481, 3; 2004482, 4.
1.6 Photocatalytic activity studies
Photocatalytic degradation of methylene blue (MB) in the presence of catalysts 1 ~4 was investigated using a Cary 5000 UV-Vis-NIR spectrophotometer.The catalytic reactions were performed as follows: cata-lyst (0.04 mmol·L-1) was dispersed in 100 mL aqueous solution of MB (0.031 mmol·L-1) under stirring for 30 min in the dark, aiming to ensure an adsorption-desorp-tion equilibrium. The obtained mixture was then ex-posed to a continuous UV irradiation using an Hg lamp (125 W) with continuous stirring for 150 min. Reaction samples (5 mL) were taken out every 15 min, centri-fuged, and then analyzed by UV - Vis spectrophotome-try, monitoring an intensity decrease of the MB absorp-tion band at 668 nm. A control experiment was also performed under the same reaction conditions, showing that no MB degradation took place in the absence of catalyst.
2. Results and discussion
2.1 Description of the structure
2.1.1 {[Cu3(μ4-dpna)2(2, 2'-bipy)2]·4H2O}n (1)
X-ray crystallography analysis reveals that com-pound 1 crystallizes in the monoclinic system space group P21/c. As shown in Fig. 1, the asymmetric unit of 1 bears two crystallographically unique Cu(Ⅱ) ions (Cu1 with half occupancy; Cu2 with full occupancy), one μ4 - dpna3- block, one 2, 2'-bipy moiety, and two lattice wa-ter molecules. The tetra-coordinated Cu1 atom exhibits a planar tetragonal {CuN2O2} environment, which is occupied by two carboxylate O and two N donors from four different μ4 -dpna3- blocks. The Cu2 center is also tetra-coordinated and forms a distorted tetrahedral {CuN2O2} geometry. It is completed by two carboxylate O atoms from two μ4 - dpna3- blocks and two N atoms from the 2, 2'-bipy moiety. The Cu-O and Cu-N bond distances are 0.194 3(4)~0.259 9(5) and 0.197 2(5)~ 0.203 6(5) nm, respectively; these are within the nor-mal ranges observed in related Cu(Ⅱ) compounds[5, 32]. In 1, the dpna3- ligand adopts coordination mode Ⅰ (Scheme 1) with carboxylate groups being monoden-tate. In the dpna3- ligand, a dihedral angle (between two aromatic rings) and a C - Oether- C angle are 86.88° and 115.49°, respectively. The μ4 - dpna3- ligands con-nect Cu1 and Cu2 atoms to give a 2D sheet (Fig. 2).
Figure 1
Scheme1
Figure 2
2.1.2 {[Zn3(μ4-dpna)2(2, 2'-bipy)2(H2O)2]·6H2O}n (2)
The asymmetric unit of compound 2 contains two crystallographically unique Zn(Ⅱ) ions (Zn1 with full occupancy and Zn2 with half occupancy), one μ4 -dpna3-block, one 2, 2'-bipy moiety, one H2O ligand, and three lattice water molecules. As depicted in Fig. 3, six-coordinated Zn1 atom features a distorted octahedral {ZnN3O3} environment, which is filled by three carbox-ylate O and one N atom of three μ4 - dpna3- blocks and two N atoms of one 2, 2'-bipy moiety. The Zn2 center is also six - coordinated and displays a distorted octahe-dral {ZnO6} geometry. It is taken by four carboxylate O atoms from two μ4-dpna3- blocks and two O donors from two H2O ligands. The bond lengths of Zn-O are in a range of 0.201 2(3)~0.241 5(4) nm, while the Zn-N bonds are 0.211 2(3)~0.219 1(3) nm, being comparable to those found in some reported Zn compounds[14, 29, 32]. The pyridyl N atom acts as an N-donor for Cu(Ⅱ)/Zn(Ⅱ)centers in both compounds. In 2, the dpna3- block acts as a μ4-linker (mode Ⅱ, Scheme 1), in which three car-boxylate groups adopt monodentate or bidentate modes. Besides, μ4-deta4-ligand is considerably bent showing a dihedral angle of 80.43° (between two aromatic rings) and the C-Oether-C angle of 117.16°. The μ4-dpna3- ligands link Zn(Ⅱ) centers to furnish a 2D sheet (Fig. 4). Compounds 1 and 2 were isolated under the same con-ditions, except for the type of Cu(Ⅱ)/Zn(Ⅱ) chloride start-ing material (CuCl2·H2O for 1 and ZnCl2 for 2). Hence, structural difference between two products indicate that the assembly process is metal ion-dependent.
Figure 3
Figure 4
2.1.3 {[M2(μ4-deta)(phen)2(H2O)]·3H2O}n (M=Mn (3)and Zn (4))
Compounds 3 and 4 are isostructural (Table 1) and the structure of 3 is discussed in detail as an exam-ple (Fig. 5 and 6). X-ray crystallography analysis reveals that compound 3 crystallizes in the monoclinic system space group P21/n. As shown in Fig. 5, the asymmetric unit of 3 bears two crystallographically unique Mn(Ⅱ) ions (Mn1 and Mn2), one μ4-deta4- block, two phen moi-eties, one H2O ligand and three lattice water mole-cules. The five-coordinated Mn1 atom exhibits a dis-torted trigonal bipyramide {MnN2O3} environment, which is occupied by three carboxylate O donors from two different μ4-deta4- blocks and two N atoms from the phen moiety. The Mn2 center is six - coordinated and forms a distorted octahedral {MnN2O4} geometry. It is completed by three carboxylate O atoms from two μ4-deta4- blocks, one O atom for the H 2 O ligand, and two N atoms from the phen moiety. The Mn - O and Mn - N bond distances are 0.208 0(4)~0.231 7(4) and 0.220 2(5) ~0.227 2(5) nm, respectively; these are within the nor-mal ranges observed in related Mn(Ⅱ) compounds[14, 17]. In 3, deta4- ligand adopts μ4 - coordination mode (mode Ⅲ, Scheme 1) with carboxylate groups being monoden-tate, bidentate or tridentate. In deta4- ligand, a dihedral angle (between two aromatic rings) and a C - Oether - C angle are 81.81° and 119.51°, respectively. The μ4-deta4- ligands connect Mn1 and Mn2 atoms to give a 1D chain (Fig. 6).
Figure 5
Figure 6
2.2 TGA analysis
To determine the thermal stability of compounds 1~4, their thermal behaviors were investigated under nitrogen atmosphere by thermogravimetric analysis (TGA). As shown in Fig. 7, compound 1 lost its four lattice water molecules in a range of 62~120 ℃ (Obsd. 5.8%, Calcd. 6.1%), followed by the decomposition at 210 ℃. For 2, one weight loss (Obsd. 11.2%, Calcd. 11.5%) in the 38~171 ℃ range corresponds to a remov-al of six lattice water molecules and two H2O ligands; decomposition of the sample occurred only at 236 ℃. TGA curve of compound 3 showed that there was a loss of three lattice water molecules and one H2O ligand between 48 and 155 ℃ (Obsd. 8.3%, Calcd. 8.1%); fur-ther heating above 233 ℃ led to a decomposition of the dehydrated sample. Compound 4 lost its three lattice water molecules and one H2O ligand in a range of 57~ 124 ℃ (Obsd. 7.8%, Calcd. 8.0%), followed by the de-composition at 309 ℃.
Figure 7
2.3 Luminescent properties
The emission spectra of H3dpna, H4 deta and com-pounds 2 and 4 were measured in the solid state at room temperature (Fig. 8). The uncoordinated H3dpna and H4deta showed weak photoluminescence with emis-sion maximums at 412 and 408 nm (λex=320 nm). In contrast, compounds 2 and 4 displayed significantly more intense emission bands with the maxima at 406 or 390 nm (λex=320 nm), respectively. All bands can be assigned to the intraligand (π* →n or π* → π) emis-sion[14, 17]. The luminescence enhancement in coordina-tion compounds 2 and 4 can be attributed to the bind-ing of ligands to the metal centers, which effectively increases the rigidity of the ligand and reduces the loss of energy by radiationless decay[29, 32].
Figure 8
2.4 Photocatalytic activity for dye degradation
To study the photocatalytic activity of 1~4, we selected MB as a model dye contaminant in wastewa-ter. The obtained results (Fig. 9 and 10) indicate that the MB degradation rate attained 81.9% after 150 min in the presence of 4 that is the most active catalyst. For 1~3, the MB degradation rates were inferior, being 58.8%, 78.2% or 55.5%. Under similar conditions, blank tests were also carried out and revealed that the degradation of MB almost did not occur in the absence of catalyst, or using H3dpna, H4deta, 2, 2'-bipy or phen as catalysts. Besides, to evaluate the stability of com-pound 4 during the photocatalytic experiments, the cat-alyst recycling tests were performed (Fig. 11). The obtained results indicated that compound 4 preserved its original catalytic activity even after four reaction cycles, showing only a slight decline of the MB degra-dation efficiency from 82% to 77%. Moreover, the chemical stability of 4 after photocatalytic experiments can be confirmed by the PXRD pattern of the recov-ered catalyst (Fig. 12), which well matched that of as-synthesized sample. These results demonstrate that the photocatalytic activity depends on various factors, such as number of water ligands, coordination environ-ment of metal centers, and optical band gap[25-28, 32].
Figure 9
Figure 10
Figure 11
Figure 12
3. Conclusions
In summary, we have synthesized four Cu(Ⅱ), Zn(Ⅱ) and Mn(Ⅱ) coordination polymers based on two unexplored carboxylate ligands. Compounds 1 and 2 possess two different 2D sheet structures. The structural diversity of compounds 1 and 2 is driven by the Cu(Ⅱ)/ Zn(Ⅱ) node. Compounds 3 and 4 show 1D chain structures.
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Table 1. Crystal data for compounds 1~4
Compound 1 2 3 4 Chemical formula C48H36Cu3N6O18 C48H44Zn3N6O22 C40H30Mn2N4O13 C40H30Zn2N4O13 Molecular weight 1 175.47 1 253.00 884.56 905.42 Crystal system Monoclinic Monoclinic Monoclinic Monoclinic Space group P21/c C2/c P21/n P21/n a/nm 1.813 04(17) 2.024 50(6) 1.268 98(8) 1.246 22(3) b/nm 1.003 29(8) 0.767 93(2) 1.718 33(12) 1.720 14(5) c/ nm 1.353 58(11) 3.322 33(10) 1.739 32(14) 1.725 40(7) β/(°) 91.443(9) 100.782(3) 100.857(7) 100.085(3) V/nm3 2.461 4(4) 5.074 0(3) 3.724 7(5) 3.641 5(2) Z 2 4 4 4 F(000) 1 114 2 560 1 808 1 848 Crystal size / mm 0.21×0.20×0.18 0.26×0.24×0.23 0.22×0.21×0.20 0.23×0.19×0.18 θrange for data collection /(°) 4.880~66.600 4.446~69.920 3.648~69.924 3.657~69.969 Limiting indices -17 ≤ h ≤ 21, -24 ≤ h ≤ 20, -13 ≤ h ≤ 15, -11 ≤ h ≤ 15, -11 ≤ k ≤ 11, -9 ≤ k ≤ 4, -17 ≤ k ≤ 20, -20 ≤ k ≤ 20, -14 ≤ l ≤ 16 -38 ≤ l ≤ 40 -20 ≤ l ≤ 20 -20 ≤ l ≤ 20 Reflection collected, unique (Rint) 8 795, 4 331 (0.076 5) 9 067, 4 708 (0.027 9) 6 746, 4 196 (0.052 0) 6 769, 4 606 (0.050 5) Dc/ (g·cm-3) 1.586 1.640 1.577 1.651 μ / mm-1 2.116 2.439 6.171 2.289 Data, restraint, parameter 4 331, 0, 322 4 708, 0, 357 4 196, 0, 534 4 606, 0, 532 Goodness-of-fit on F2 0.964 1.022 1.031 1.023 Final R indices[I≥2σ(I)]R1, wR2 0.068 1, 0.150 8 0.044 2, 0.120 4 0.062 9, 0.154 5 0.075 4, 0.183 9 R indices(all data)R1, wR2 0.110 4, 0.186 8 0.058 8, 0.129 8 0.105 6, 0.191 1 0.109 6, 0.206 8 Largest diff. peak and hole/(e·nm-3) 614 and -824 921 and -772 708 and -578 2 058 and -1 275 Table 2. Selected bond distances (nm) and bond angles (°) for compounds 1~4
1 Cu(1)-O(6)A 0.194 3(4) Cu(1)-O(6)B 0.194 3(4) Cu(1)-N(1) 0.203 6(5) Cu(1)-N(1)C 0.203 6(5) Cu(2)-O(1) 0.195 7(4) Cu(2)-O(4)D 0.195 5(5) Cu(2)-N(2) 0.200 1(5) Cu(2)-N(3) 0.197 2(5) O(6)A-Cu(1)-N(1)C 91.72(19) O(6)B-Cu(1)-N(1)C 88.28(19) O(6)A-Cu(1)-N(1) 88.27(19) O(6)B-Cu(1)-N(1) 91.73(19) O(4)D-Cu(2)-O(1) 94.31(19) O(4)D-Cu(2)-N(3) 94.8(2) N(3)-Cu(2)-O(1) 159.2(2) O(4)D-Cu(2)-N(2) 158.4(2) N(2)-Cu(2)-O(1) 96.15(19) N(2)-Cu(2)-N(3) 81.8(2) 2 Zn(1)-O(1) 0.202 4(2) Zn(1)-O(6)A 0.217 1(3) Zn(1)-O(7)A 0.241 5(4) Zn(1)-N(1)B 0.219 1(3) Zn(1)-N(2) 0.211 2(3) Zn(1)-N(3) 0.217 8(3) Zn(2)-O(3) 0.232 9(3) Zn(2)-O(3)C 0.232 9(3) Zn(2)-O(4) 0.204 8(3) Zn(2)-O(4)C 0.204 8(3) Zn(2)-O(8) 0.201 2(3) Zn(2)-O(8)C 0.201 2(3) O(1)-Zn(1)-N(2) 97.45(10) O(6)A-Zn(1)-O(1) 86.61(11) N(2)-Zn(1)-O(6)A 89.09(13) N(3)-Zn(1)-O(1) 165.24(11) N(2)-Zn(1)-N(3) 75.66(12) O(6)A-Zn(1)-N(3) 106.07(12) O(1)-Zn(1)-N(1)B 91.52(10) N(2)-Zn(1)-N(1)B 132.67(11) O(6)A-Zn(1)-N(1)B 137.95(12) N(3)-Zn(1)-N(1)B 84.10(11) O(7)A-Zn(1)-O(1) 102.35(12) O(7)A-Zn(1)-N(2) 138.00(12) O(6)A-Zn(1)-O(7)A 56.00(12) O(7)A-Zn(1)-N(3) 91.20(13) O(7)A-Zn(1)-N(1)B 83.67(11) O(8)C-Zn(2)-O(8) 99.0(2) O(8)-Zn(2)-O(4) 103.74(14) O(8)C-Zn(2)-O(4) 97.33(14) O(4)C-Zn(2)-O(4) 147.35(18) O(8)-Zn(2)-O(3) 87.29(12) O(8)-Zn(2)-O(3)C 156.47(14) O(4)-Zn(2)-O(3) 59.14(10) O(3)-Zn(2)-O(4)C 97.84(11) O(3)-Zn(2)-O(3)C 95.92(15) 3 Mn(1)-O(2) 0.222 3(4) Mn(1)-O(4) 0.208 8(4) Mn(1)-O(8)A 0.208 0(4) Mn(1)-N(1) 0.224 2(4) Mn(1)-N(2) 0.220 2(5) Mn(2)-O(1) 0.231 7(4) Mn(2)-O(2) 0.223 9(4) Mn(2)-O(7)A 0.209 6(4) Mn(2)-O(10) 0.218 9(4) Mn(2)-N(3) 0.223 0(5) Mn(2)-N(4) 0.227 2(5) O(4)-Mn(1)-O(8)A 150.42(17) N(2)-Mn(1)-O(8)A 99.62(17) O(4)-Mn(1)-N(2) 109.80(16) O(2)-Mn(1)-O(8)A 89.27(17) O(2)-Mn(1)-O(4) 84.63(15) O(2)-Mn(1)-N(2) 96.36(16) N(1)-Mn(1)-O(8)A 105.16(18) O(4)-Mn(1)-N(1) 86.16(17) N(1)-Mn(1)-N(2) 74.34(17) N(1)-Mn(1)-O(2) 163.81(15) O(10)-Mn(2)-O(7)A 84.84(16) N(3)-Mn(2)-O(7)A 103.63(16) N(3)-Mn(2)-O(10) 99.51(17) O(2)-Mn(2)-O(7)A 100.13(15) O(2)-Mn(2)-O(10) 97.90(16) N(3)-Mn(2)-O(2) 151.59(17) N(4)-Mn(2)-O(7)A 93.82(15) N(4)-Mn(2)-O(10) 172.85(16) N(4)-Mn(2)-N(3) 73.95(16) N(4)-Mn(2)-O(2) 89.24(15) O(1)-Mn(2)-O(7)A 154.45(15) O(1)-Mn(2)-O(10) 87.24(16) N(3)-Mn(2)-O(1) 101.62(16) O(2)-Mn(2)-O(1) 57.01(14) N(4)-Mn(2)-O(1) 96.82(16) Mn(1)-O(2)-Mn(2) 133.88(18) 4 Zn(1)-O(1) 0.215 7(4) Zn(1)-O(2) 0.229 4(5) Zn(1)-O(6)A 0.205 6(4) Zn(1)-O(10) 0.212 7(5) Zn(1)-N(1) 0.217 1(5) Zn(1)-N(2) 0.210 5(6) Zn(2)-O(1) 0.223 6(4) Zn(2)-O(3) 0.198 8(4) Zn(2)-O(9) 0.194 7(4) Zn(2)-N(3) 0.207 3(5) Zn(2)-N(4) 0.215 4(6) O(6)A-Zn(1)-N(2) 105.8(2) O(6)A-Zn(1)-O(10) 86.98(19) N(2)-Zn(1)-O(10) 95.4(2) O(6)A-Zn(1)-O(1) 98.87(18) N(2)-Zn(1)-O(1) 153.6(2) O(1)-Zn(1)-O(10) 95.00(19) O(6)A-Zn(1)-N(1) 93.18(18) N(2)-Zn(1)-N(1) 78.1(2) O(10)-Zn(1)-N(1) 173.24(19) O(1)-Zn(1)-N(1) 91.65(18) O(6)A-Zn(1)-O(2) 155.56(18) O(2)-Zn(1)-N(2) 98.2(2) O(10)-Zn(1)-O(2) 86.66(19) O(1)-Zn(1)-O(2) 58.29(17) N(1)-Zn(1)-O(2) 95.86(19) Symmetry codes: A:x, -y+3/2, z-1/2; B: -x+1, y-1/2, -z+1/2; C: -x+1, -y+1, -z; D: x, -y+3/2, z+1/2 for 1; A: -x, -y+1, -z; B: -x+1, -y+2, -z; C: -x, -y, -z+1/2 for 2; A: -x+1, -y, -z+1 for 3; A: -x+1, -y, -z+1 for 4. Table 3. Hydrogen bond parameters of compound 2
D-H…A d(D-H) / nm d(H…A) / nm d(D…A) / nm ∠DHA / (°) O(8)-H(1W)…O(9) 0.082 0 0.200 6 0.264 2 133.86 O(8)-H(2W)…O(10)A 0.084 5 0.185 1 0.265 9 159.74 O(9)-H(3W)…O(6)B 0.085 0 0.217 7 0.302 7 179.52 O(9)-H(4W)…O(2)A 0.085 0 0.196 4 0.281 5 179.54 O(10)-H(5W)…O(3) 0.085 0 0.195 1 0.280 1 179.05 O(11)-H(7W)…O(2)A 0.085 5 0.213 2 0.298 7 179.08 Symmetry codes: A: x, y-1, z; B: -x, -y+1, -z. Table 4. Hydrogen bond parameters of compound 3
D-H…A d(D-H) / nm d(H…A) / nm d(D…A) / nm ∠DHA / (°) O(10)-H(1W)…O(6)A 0.085 0 0.183 9 0.268 8 179.42 O(11)-H(3W)…O(12)B 0.085 0 0.188 7 0.273 6 179.28 O(11)-H(4W)…O(4)C 0.088 2 0.213 0 0.280 5 132.73 O(12)-H(5W)…O(3)C 0.085 6 0.192 0 0.274 8 162.66 O(12)-H(6W)…O(6)C 0.085 4 0.197 6 0.277 2 154.70 O(13)-H(7W)…O(10)D 0.068 1 0.209 3 0.277 3 176.73 O(13)-H(8W)…O(11)E 0.084 6 0.216 1 0.280 9 133.27 Symmetry codes: A: x+1/2, -y+3/2, z-1/2; B: -x+2, -y+1, -z+1; C: x+1, y, z; D: -x+1/2, y-1/2, -z+1/2; E: x-1, y, z. Table 5. Hydrogen bond parameters of compound 4
D-H…A d(D-H) / nm d(H…A) / nm d(D…A) / nm ∠DHA / (°) O(10)-H(1W)…O(13) 0.082 0 0.213 5 0.277 5 134.94 O(10)-H(2W)…O(6)A 0.086 6 0.180 9 0.267 5 179.01 O(11)-H(3W)…O(3)B 0.086 6 0.199 4 0.286 0 179.47 O(11)-H(4W)…O(12)C 0.085 4 0.189 7 0.275 1 179.72 O(12)-H(5W)…O(4)D 0.085 0 0.186 2 0.271 2 179.69 O(12)-H(6W)…O(7)D 0.086 0 0.192 2 0.278 2 178.37 O(13)-H(7W)…O(8)D 0.085 1 0.191 9 0.277 0 179.00 O(13)-H(8W)…O(11)E 0.084 6 0.204 2 0.288 8 179.14 Symmetry codes: A: x-1/2, -y+1/2, z+1/2; B: x-1, y, z; C: x-1, y-1, z; D: -x+2, -y+1, -z; E: -x+1/2, y+1/2, -z+1/2.
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