Preparation, Structures and Thermal Stabilities of Four Transition Metal Complexes Constructed by 3, 7-Di(3-pyridyl)-1, 5-dioxa-3, 7-diazacyclooctane Bipyridine Ligand

Li LI

Citation:  LI Li. Preparation, Structures and Thermal Stabilities of Four Transition Metal Complexes Constructed by 3, 7-Di(3-pyridyl)-1, 5-dioxa-3, 7-diazacyclooctane Bipyridine Ligand[J]. Chinese Journal of Inorganic Chemistry, 2021, 37(1): 121-130. doi: 10.11862/CJIC.2021.009 shu

双吡啶化合物3,7-di(3-pyridyl)-1,5-dioxa-3,7-diazacyclooctane构建的四个过渡金属配合物的合成、结构及热稳定性

    通讯作者: 李理, leeleaa@163.com
  • 基金项目:

    苏州科技大学青年基金(No.XKQ201512)资助

    苏州科技大学青年基金 XKQ20151

摘要: 采用准刚性的双吡啶化合物3,7-di(3-pyridyl)-1,5-dioxa-3,7-diazacyclooctane(L),合成了4个过渡金属配合物[Co(NO3)(H2O)2(L)2]NO31)、[Co2Cl4(L)2]·CH2Cl22)、[Cd2(AcO)4(L)2]·4CH3OH(3)和[Cd2(NO32(CH3OH)2(H2O)2(L)2](NO32·2H2O(4)。单晶衍射分析表明,配合物1是单核结构,配合物2是24-元环状双核结构,而配合物34为多边形双核结构。在这些配合物中,双吡啶配体分别采用了单齿、trans-和cis-桥连3种不同配位方式。配合物经过了元素分析、红外、热重和X射线单晶结构分析表征。

English

  • Pyridine ligands have been employed extensively in constructing functional materials with transition metal[1-13]. They have shown many advantages containing appropriate coordination capability, uncharged property, easy structural design as well as versatile coordination mode.N, N'-bidentate bipyridine has drawn much attention during these decades. Those ligands with larger spacer have been used to construct porous metallocyclic architectures, metal - organic frameworks (MOFs), optical complexes and so on, such as bis(4-(pyridine-4-yl)phenyl)amine[3], N, N' - (1, 2 - phenylene)diisonicotinamide[4], 3-bis(4-pyridyl) propane[7], 1, 2-dimethoxy-4, 5-bis(2 - pyridylethynyl)benzene[8], 1, 8 - bis(4 - pyridylethynyl)anthracene[9], ((pyridinyl) - 1H - pyrazolyl)pyridine[10], 4, 6-bis(4'-pyridylsulfide)dibenzofuran[11], 4, 6-bis(methylsulfanylmethyl) dibenzofuran[11], 1, 1' - bis(4-pyridyl) ferrocene[13] and the others[14-16]. To date, most of those ligands are flexible.

    In our previous research, a clamplike bipyridine ligand 3, 7-di(3- pyridyl)-1, 5- dioxa -3, 7 - diazacyclooctane (L) has been synthesized. We have measured the 1H NMR spectra of L in CDCl3 in a range of - 10 to 50 ℃. Along with the change of temperature, the rotation of the N-C bonds accompany with alternate between "up, up" and "down, down" conformations in ligand would take place. The bipyridine ligand has shown quasirigid characteristics under room temperature. During the coordinating with copper salts, it acted as a cis-bridge ligand[17]. Herein, as part of continuing studies on its coordination chemistry, we have built four transition metal complexes [Co(NO3)(H 2O)2(L)2]NO 3 (1), [Co2Cl4(L) 2] · CH 2Cl2 (2), [Cd2(AcO)4(L)2]·4CH3OH (3) and [Cd2 (NO3)2(CH3OH)2(H2O)2(L)2] (NO3)2·2H2O (4). They have shown diverse coordination chemistry. X-ray single-crystal structure analysis displays that 1 is a mononuclear complex, while 2~ 4 are dinuclear complexes. The ligand molecule in these complexes has exhibited three types of coordination mode including mono-dentate, trans-bridge and cis-bridge. All of these complexes have been characterized by elemental analysis, IR spectra, thermal gravity analysis and X-ray single-crystal structure analysis. The intra-/inter- molecular hydrogen interactions of these complexes have also been discussed.

    The ligand L has been prepared and characterized previously[17]. Other reagents were purchased from commercial sources and used as received without further purification. Carbon, hydrogen and nitrogen analysis were carried out by direct combustion on an EA1110 - CHNSO elemental analyzer. FT-IR spectra were recorded on a Perkin Elmer Spectrum BX Ⅱ spectrometer. Thermal stability analysis was measured on a PRT -1A Thermogravimetric Analyzer. Powder X-ray diffraction (PXRD) determination was performed on an X-ray diffractometer (X' Pert PRO MPOCPW 3040/60, Panalytical) with Cu radiation (λ =0.154 06 nm). The operating voltage and current were 40 kV and 40 mA, and the measurement was carried out over a 2θ range of 5° to 50° in continuous scanning mode.

    Complex 1: To a Pyrex tube (6 mm inner diameter) was added 5.0 mL CH 2 Cl2 solution of L (1.0 mmol, 290 mg), then was slowly layed onto 5.0 mL CH3OH solution of Co(NO3) 2·6H2O (1.0 mmol, 291 mg). The tube was sealed at room temperature for 4 d, and red block crystals of complex 1 were afforded. Yield: 481 mg (63% based on Co). Anal. Calcd. for C28H36CoN10O12 (%): C 44.04, H 4.75, N 18.34; Found(%): C 44.12, H 4.68, N 18.15. FT-IR (KBr, cm-1): 3 412(m), 3 042(w), 2 963(w), 2 935(w), 2 902(w), 1 602(w), 1 578(m), 1 522 (s), 1 496(vs), 1 464(w), 1 443(w), 1 426(w), 1 369(vs), 1 309(s), 1 261(s), 1 229(vs), 1 193(m), 1 167(w), 1 136 (s), 1 058(s), 1 029(vs), 1 015(s), 991(s), 942(m), 888 (m), 828(w), 799(m), 781(w), 745(w), 696(m), 665(m), 621(w), 569(w), 487(w), 416(w).

    Complex 2 : To a Pyrex tube was added 5.0 mL CH2Cl 2 solution of L (1.0 mmol, 290 mg), then was slowly layed onto 5.0 mL CH3CN solution of CoCl2 (1.0 mmol, 130 mg). The tube was sealed at room temperature for 6 d, and blue block crystals of complex 2 were afforded. Yield: 231 mg (52% based on Co). Anal. Calcd. for C29H34Cl6Co2N8O4(%): C 39.17, H 3.85, N 12.60; Found(%): C 40.12, H 3.97, N 12.95. FT - IR (KBr, cm-1): 3 413(w), 3 112(w), 3 077(w), 3 048(w), 2 980(w), 2 940(w), 2 903(w), 1 600(s), 1 577(s), 1 495 (vs), 1 438(s), 1 368(vs), 1 305(s), 1 258(m), 1 223(s), 1 197(m), 1 171(w), 1 136(s), 1 063(s), 1 038(vs), 1 015 (s), 991(s), 944(s), 889(m), 807(s), 730(m), 692(s), 663 (s), 620(w), 568(w), 496(w), 419(w).

    Complex 3: It was prepared as the method for complexes 1 and 2 except that 5.0 mL CH3OH solution of Cd(AcO)2·2H2O (1.0 mmol, 267 mg) was used. The tube was sealed at room temperature for 5 d, and colorless block crystals of complex 3 were afforded. Yield: 329 mg (58% based on Cd). Anal. Calcd. for C40H60Cd2N8O16(%): C 42.37, H 5.33, N 9.88; Found (%): C 42.12, H 5.08, N 9.70. FT-IR (KBr, cm-1): 3 440(vs), 2 967(w), 2 963(w), 2 933(w), 1 560(vs), 1 498(s), 1 420(s), 1 364(s), 1 306(s), 1 261(m), 1 231(s), 1 199 (w), 1 166(w), 1 134(s), 1 063(s), 1 033(vs), 1 016(s), 995(s), 942(s), 876(m), 803(m), 790(w), 697(m), 670 (m), ), 642(w), 620(w).

    Complex 4: It was prepared the method for 1~3 except that 5.0 mL CH3 OH solution of Cd(NO 3)2·4H2O (1.0 mmol, 308 mg) was used. After one week, colorless block crystals of complex 4 were afforded. Yield: 830 mg (72% based on Cd). Anal. Calcd. for C30H48Cd2N12O22 (%): C 31.23, H 4.19, N 14.57; Found(%): C 31.12, H 4.02, N 14.30. FT-IR (KBr, cm-1): 3 450(vs), 2 901(w), 1 602(m), 1 498(m), 1 384(vs), 1 305(s), 1 261(m), 1 233(s), 1 198(m), 1 167(w), 1 135(m), 1 062(m), 1 033 (s), 997(m), 942(m), 900(w), 881(w), 799(m), 692(m), 641(w).

    The single crystals with dimensions of 0.50 mm×0.40 mm×0.35 mm (1), 0.25 mm×0.22 mm×0.20 mm (2), 0.35 mm×0.25 mm×0.22 mm (3) and 0.40 mm×0.20 mm×0.20 mm (4) were mounted on a glass fiber, relatively. Single-crystal X-ray diffraction measurements were performed on a Bruker APEX Ⅱ 4K CCD area detector equipped with a graphite monochromated Mo radiation (λ=0.071 073 nm) by using the ω - scan mode on all observed reflections in a θ range of 3.06° ~ 25.35°(1), 3.07° ~ 26.00°(2), 3.05° ~ 25.02°(3) and 3.16°~24.24°(4). All absorption corrections were applied using the SADABS program[18]. The structures were solved by direct methods and refined on F2 by full-matrix least-squares using the SHELXTL-97 program package[19]. Metal atoms were located from the e-maps, and other non-hydrogen atoms were derived from the successive difference Fourier peaks. The nitrate anion was disordered about a twofold rotation axis in complex 4[20]. Hydrogen atoms were placed in geometrically idealized positions (C—H 0.095~0.098 nm) and were constrained to ride on their parent atoms with Uiso(H)=1.2~ 1.5Ueq(C). Summary of the crystallographic data for 1~4 are given in Table 1. Selected bond lengths and angles are given in Table 2. Hydrogen bonds geometries are listed in Table 3.

    Table 1

    Table 1.  Crystallographic and structural refinement details for 1~4
    下载: 导出CSV
    Complex 1 2 3 4
    Empirical formula C28H36CoN10O12 C29H34Cl6Co2N8O4 C40H60Cd2N8O16 C30H48Cd2N12O22
    Formula weight 763.60 889.20 1 133.76 1 153.60
    Crystal system Monoclinic Monoclinic Triclinic Triclinic
    Space group P2/c C2/c P1 P1
    a / nm 1.072 8(2) 0.955 91(5) 0.958 04(4) 0.937 13(19)
    b / nm 0.866 88(17) 2.753 00(14) 1.165 02(5) 1.070 0(2)
    c / nm 1.870 9(6) 1.406 73(8) 1.203 89(4) 1.270 2(3)
    α/(°) 107.496(3) 109.52(3)
    β/(°) 108.80(3) 105.324(5) 106.103(3) 108.64(3)
    γ/(°) 100.170(3) 99.59(3)
    V / nm3 1.647 1(7) 3.570 4(3) 1.180 67(8) 1.082 8(4)
    Z 2 4 1 1
    Dc/ (g·cm-3) 1.540 1.654 1.595 1.769
    F(000) 794 1 808 580 584
    μ / mm-1 0.600 1.426 0.977 1.079
    θ range /(°) 3.06~25.35 3.07~26.00 3.05~25.02 3.16~25.00
    Limiting indices -10 ≤ h ≤ 12 -11 ≤ h ≤ 11 -11 ≤ h ≤ 11 -10 ≤ h ≤ 10
    -10 ≤ k ≤ 10 -33 ≤ k ≤ 26 -12 ≤ k ≤ 13 -12 ≤ k ≤ 12
    -22 ≤ l ≤ 21 -12 ≤ l ≤ 17 -14 ≤ l ≤ 14 -14 ≤ l ≤ 14
    Total reflection 15 226 8 321 11 193 8 377
    Data, restraint, parameter 3 024, 0, 305 3 506, 0, 222 4 175, 3, 302 3 392, 29, 383
    Initial R indices [I > 2σ(I)] R1=0.034 8, R1=0.033 0, R1=0.025 1, R1=0.052 9,
    wR2=0.074 2 wR2=0.069 5 wR2=0.059 2 wR2=0.121 2
    R indices (all data) R1=0.039 6, R1=0.044 5, R1=0.028 9, R1=0.062 7,
    wR2=0.076 5 wR2=0.074 4 wR2=0.061 4 wR2=0.132 1
    Goodness-of-fit 1.095 1.022 1.069 1.063
    Largest diff. peak and hole / (e·cm-3) 210, -275 289, -325 446, -410 539, -767

    Table 2

    Table 2.  Selected bond lengths (nm) and angles (°) for complexes 1~4
    下载: 导出CSV
    Complex 1
    Co(1)—O(7) 0.210 28(17) Co(1)—O(7)#1 0.210 28(17) Co(1)—N(1) 0.211 21(16)
    Co(1)—N(1)#1 0.211 21(16) Co(1)—O(3) 0.214 00(15) Co(1)—O(3)#1 0.214 00(15)
    O(7)—Co(1)—O(7)#1 172.06(10) O(7)—Co(1)—N(1) 93.67(7) O(7)#1—Co(1)—N(1) 91.79(6)
    O(7)—Co(1)—N(1)#1 91.79(6) O(7)#1—Co(1)—N(1)#1 93.67(7) N(1)—Co(1)—N(1)#1 93.23(9)
    O(7)—Co(1)—O(3) 88.45(7) O(7)#1—Co(1)—O(3) 84.67(7) N(1)—Co(1)—O(3) 103.40(6)
    N(1)#1—Co(1)—O(3) 163.32(6) O(7)—Co(1)—O(3)#1 84.67(7) O(7)#1—Co(1)—O(3)#1 88.45(7)
    N(1)—Co(1)—O(3)#1 163.32(6) N(1)#1—Co(1)—O(3)#1 103.40(6) O(3)—Co(1)—O(3)#1 60.01(8)
    Complex 2
    Co(1)—N(1) 0.204 42(19) Co(1)—N(2) 0.202 1(2) Co(1)—Cl(1) 0.223 38(7)
    Co(1)—Cl(2) 0.223 74(6)
    N(1)—Co(1)—Cl(1) 105.13(6) N(2)—Co(1)—N(1) 107.60(8) N(1)—Co(1)—Cl(2) 108.56(6)
    N(2)—Co(1)—Cl(1) 107.40(6) N(2)—Co(1)—Cl(2) 107.46(5) Cl(1)—Co(1)—Cl(2) 120.12(3)
    Complex 3
    Cd(1)—N(2)#1 0.230(2) Cd(1)—N(1) 0.232(2) Cd(1)—O(3) 0.243(2)
    Cd(1)—O(4) 0.237(2) Cd(1)—O(5) 0.243(2) Cd(1)—O(6) 0.236(2)
    Cd(1)—O(6)#1 0.248(2)
    N(2)#1—Cd(1)—N(1) 173.9(8) N(2)#1—Cd(1)—O(6) 89.2(7) N(1)—Cd(1)—O(6) 87.0(7)
    N(2)#1—Cd(1)—O(4) 91.4(7) N(1)—Cd(1)—O(4) 89.3(7) O(6)—Cd(1)—O(4) 146.9(7)
    N(2)#1—Cd(1)—O(5) 88.0(7) N(1)—Cd(1)—O(5) 87.4(7) O(6)—Cd(1)—O(5) 92.4(7)
    O(4)—Cd(1)—O(5) 54.6(7) N(2)#1—Cd(1)—O(3) 91.7(7) N(1)—Cd(1)—O(3) 94.3(8)
    O(6)—Cd(1)—O(3) 123.7(7) O(4)—Cd(1)—O(3) 89.4(7) O(5)—Cd(1)—O(3) 143.9(7)
    N(2)#1—Cd(1)—O(6)#1 94.4(7) N(1)—Cd(1)—O(6)#1 88.9(7) O(6)—Cd(1)—O(6)#1 71.2(8)
    O(4)—Cd(1)—O(6)#1 141.6(7) O(5)—Cd(1)—O(6)#1 163.3(7) O(3)—Cd(1)—O(6)#1 52.6(6)
    Complex 4
    Cd(1)—N(2) 0.225 4(5) Cd(1)—N(3) 0.225 4(5) Cd(1)—O(1) 0.246 0(5)
    Cd(1)—O(1)#1 0.244 7(5) Cd(1)—O(5) 0.235 8(6) Cd(1)—O(7) 0.234 4(5)
    N(2)—Cd(1)—N(3) 176.53(17) N(2)—Cd(1)—O(5) 93.05(19) N(3)—Cd(1)—O(5) 90.49(17)
    N(2)—Cd(1)—O(4) 88.0(2) N(3)—Cd(1)—O(4) 92.0(2) O(5)—Cd(1)—O(4) 87.5(3)
    N(2)—Cd(1)—O(1)#1 88.07(17) N(3)—Cd(1)—O(1)#1 90.78(17) O(5)—Cd(1)—O(1)#1 112.9(2)
    O(4)—Cd(1)—O(1)#1 159.4(2) N(2)—Cd(1)—O(1) 89.25(17) N(3)—Cd(1)—O(1) 87.30(17)
    O(5)—Cd(1)—O(1) 177.3(2) O(4)—Cd(1)—O(1) 94.1(2) O(1)#1—Cd(1)—O(1) 65.6(2)
    Symmetry codes: #1: -x, y, -z+1/2 for 1; #1: -x+2, -y, -z+1 for 3; #1 -x+1, -y+1, -z+2 for 4.

    Table 3

    Table 3.  Hydrogen bond geometries for complexes 1~4
    下载: 导出CSV
    D—H…A d(D—H) / nm d(H…A) / nm d(D…A) / nm ∠D—H…A / (°)
    Complex 1
    O(7)—H(7a)…O(5)#3 0.079 0.203 0.281 52 175
    O(7)—H(7b)…N(2)#3 0.091 0.183 0.273 98 176
    C(1)—H(1)…O(7)#1 0.095 0.257 0.313 76 118
    C(9)—H(9)…O(5)#4 0.097 0.248 0.326 90 138
    C(12)—H(12A)…O(1)#5 0.097 0.252 0.335 89 144
    C(14)—H(14B)…O(3)#6 0.099 0.247 0.314 70 125
    Complex 2
    C(11)—H(11A)…Cl(2)#3 0.097 0.278 0.361 28 145
    C(12)—H(12B)…Cl(1)#4 0.097 0.283 0.364 75 143
    Complex 3
    C(1)—H(1)…O(2) 0.093 0.247 0.297 37 114
    C(6)—H(6)…O(2) 0.093 0.251 0.307 62 119
    C(12)—H(12B)…O(4)#2 0.097 0.258 0.344 48 149
    C(13)—H(13B)…O(8)#3 0.097 0.243 0.338 69 170
    C(16)—H(16B)…O(1)#4 0.096 0.259 0.349 20 157
    C(16)—H(16C)…O(1)#5 0.096 0.250 0.338 50 153
    Complex 4
    O(4)—H(5')…O(2) 0.072 0.248 0.304 3 136
    O(4)—H(5')…O(11A) 0.072 0.247 0.281 111
    O(15)—H(15A)…O(11A) 0.096 0.206 0.274 6 127.1
    O(5)—H(2')…O(3)#1 0.074 0.257 0.309 0 128.7
    O(5)—H(2')…O(8A)#2 0.074 0.244 0.279 8 111.5
    O(12)—H(3')…O(7)#4 0.085 0.233 0.303 1 140
    O(12)—H(3')…O(11A)#5 0.085 0.259 0.317 127
    O(12)—H(4')…O(5)#5 0.085 0.204 0.271 7 136
    O(4)—H(5')…O(10)#3 0.072 0.214 0.274 1 142
    C(1)—H(1)…O(3)#1 0.101 0.256 0.341 0 142
    C(1)—H(1)…O(6)#1 0.101 0.249 0.298 8 110
    C(13)—H(12)…O(8A)#2 0.095 0.255 0.318 6 124
    C(13)—H(13A)…O(10)#3 0.093 0.250 0.342 5 175
    C(13)—H(13B)…O(8A)#6 0.111 0.220 0.326 5 160
    Symmetry codes: #1: -x, y, -z+1/2; #3: -x, y-1, -z+1/2; #4: x, y-1, z; #5: -x+1, -y, -z+1; #6: -x, -y, -z+1 for 1; #3: -x+1, -y, -z+1; #4: -x+1/2, -y+1/2, -z+1 for 2; #1: -x+2, -y, -z+1; #2: x, y+1, z; #3: -x+1, -y+1, -z; #4: -x+2, -y, -z; #5: x, y-1, z for 3; #1: 1-x, 1-y, 2-z; #2: 1-x, -y, 1-z; #3: -x, 1-y, 1-z; #4: x-1, y, z; #5: x, 1+y, z; #6: 1-x, 1-y, 1 -z for 4.

    CCDC: 940778, 1; 915840, 2; 1446573, 3; 1446574, 4.

    2.1.1   Crystal structure of complex 1

    Single crystal structure reveals that 1 crystallizes in the monoclinic space group P2/c. The asymmetric unit consists of a discrete [Co(NO3) (H2O)2 (L)2] + cation and a free nitrate anion (Fig. 1a). In the coordination unit, the Co center adopts slightly distorted tetragonal biyramid geometry. Two molecules of water occupy the apical sites, and two pyridine nitrogen atoms (from two molecules of ligands) and a chelating nitrate anion are at the ecuatorial plane. Two molecules of L choose a mono - dentated coordination mode in the cation. They lie on the reverse side to avoid steric hindrance. On the equatorial plane, the maximum deviation of Co atom from the mean plane constructed by N1, N1A, O3 and O3A is 0.021 nm. The bite angle of N1—Co1—N1A is 93.23(9)°. It is wider than that of O3—Co1—O3A (60.01(8)°). The average bond lengths for Co—N and Co—O are 0.203 nm and 0.212 nm, separately. They are close with those in [Co(L1) (L2) (H2O)2] ·3H2O (L1= terephthalic acid; L2=2, 2' - dipyridylamine) of 0.207 and 0.214 nm, respectively[21]. The free nitrate anion is stabilized by multiple hydrogen interactions including O…H—C (0.314~0.336 nm) and O…H—O (0.282 nm), as is shown in Fig. 1b.

    Figure 1

    Figure 1.  (a) Coordination structural unit with 30% probability ellipsoids in complex 1, where H atoms are omitted for clarify and the symmetry code is #1: -x, y, 1/2-z; (b) Interactions of nitrate anion in complex 1 where the symmetry code is #1: -1+x, -1+y, z
    2.1.2   Crystal structure of complex 2

    Complex 2 crystallizes in the monoclinic space group C2/c. The asymmetric unit consists of a neutral [Co(L)Cl2] unit and half a CH2Cl2 solvent molecule, as shown in Fig. 2a. In the coordination unit, each Co atom is coordinated by two nitrogen atoms from pyridine rings and two Cl atoms, adopting a tetrahedral [CoN2Cl2] coordination geometry. The angle of N2—Co1—N1 is 107.60(8)°. It is smaller than that reported in [Co2Cl4(L3)2] (L3=1, 2-dimethoxy-4, 5-bis(2-pyridylethynyl)benzene) of 117.53(9)°[8]. This might be due to the tension of octagonal ring in ligand. Two pyridine rings in ligand L arrange in an opposite direction. Ligand L acts as a trans - bridge, and they wrap around two cobalt atoms producing a helical 24-membered macrocycle. The Co…Co distance is 0.700 nm. The distance between the center of heterooctane is 1.019 nm. The average bond lengths for Co—N (0.203 nm) and Co—Cl (0.224 nm) are in agreement with those in [Co2Cl4(L4)2] (L4=N, N'- (1, 2 - phenylene)diisonicotinamide) (Co—N 0.203 nm, Co—Cl 0.223 nm) [4] and [Co2Cl4(L3)2] (Co—N 0.203 nm, Co—Cl 0.224 nm)[8]. The free solvent molecule CH2Cl2 is not eclipsed in the macrocycle, and it is stabilized by three adjacent coordination molecules as is illustrated in Fig. 2b. It might result from the gentle reaction condition as well as the intermolecular hydrogen interactions of Cl…H—C (Cl…C 0.305 nm) and O…H—C (O…C 0.277 nm).

    Figure 2

    Figure 2.  (a) Coordination structural unit with 30% probability ellipsoids in complex 2, where H atoms and solvent molecule are omitted for clarify; (b) Interactions of CH 2Cl2 solvent molecule in complex 2, where the symmetry codes are #1: -x+1, -y, -z+1; #2: 1/2-x, 1/2-y, 1-z; #3: -1/2+x, 1/2-y, 1/2+z
    2.1.3   Crystal structure of complex 3

    Complex 3 crystallizes in the triclinic space group P1. The asymmetric unit consists of a discrete [Cd(L)( μ -OAc) (OAc)] (Fig. 3a) and two molecules of methanol. The Cd center is seven - coordinated by two separate pyridine ligands, two bridged acetates and another chelated acetate anion forming a distorted pentagonal bipyramidal geometry. The N atoms of the bipyridine occupy the apical sites and the O atoms of the acetate units lie in the equatorial plane. In complex 3, pyridine rings in ligand L arrange parallel to each other. Two molecules of ligand L act as cis-bridge, and link with two Cd (NO3) 2 units forming two rectangle cavities. The Cd…Cd separation is 0.393 nm. The mean Cd—N (0.231 nm) and Cd—O (0.241 nm) bond lengths are in agreement with those in [Cd2(L5)4(L6)2] (L5=bis(4-bromobenzoate), L6=1, 3 - bis(4 - pyridyl)propane) (0.231, 0.242 nm) [22]. Four free methanol molecules are stabilized by multiple hydrogen interactions of O…H—O (O…O 0.271~ 0.273 nm) and O…H—C (O…C 0.297~0.349 nm, Fig. 3b).

    Figure 3

    Figure 3.  (a) Coordination structural unit with 30% probability ellipsoids in complex 3, where H atoms and solvent molecules are omitted for clarify and the symmetry code is #1: 2-x, -y, 1-z; (b) Interactions of CH3OH solvent molecules in complex 3, where the symmetry code is #1: 1-x, 1-y, 1-z
    2.1.4   Crystal structure of complex 4

    Complex 4 crystallizes in the triclinic space group P1. The asymmetric unit consists of a [Cd(L) ( μ -NO3) (CH3OH)(H2O)]+ cation (Fig. 4a), one disordered nitrate anion and one molecule of water. The Cd center is six- coordinated by two separate pyridine ligands, two bridged nitrate anions, one water molecule and one methanol molecule forming a distorted tetragonal bipyramidal geometry. The bipyridine ligand L in complex 4 adopts a similar coordination mode with that in complex 3. The Cd…Cd separation is 0.412 nm. The average bond lengths for Cd—N and Cd—Onitrate are 0.226 and 0.246 nm, separately. They are comparable to those reported in complexes [Fe(η5-C5H4-1-C5H4N)2]2Cd2 (NO3) 4·CH3OH·0.5C6H6 (0.224 and 0.249 nm) [23] and [Cd4(L7)4(NO3)6(MeOH)6]2+ (L7=4, 4'-bis(4-pyridyl)biphenyl) (0.226 and 0.249 nm)[13]. One water molecule and a disordered nitrate anion are stabilized by multiple hydrogen interactions of O…H—O (O…O 0.272~0.317 nm) and O…H—C (O…C 0.299~0.341 nm) (Fig. 4b).

    Figure 4

    Figure 4.  (a) Coordination structural unit with 30% probability ellipsoids in complex 4, where H atoms, counter nitrate anions and solvent molecules are omitted for clarify and the symmetry code is #1: -x+1, y, -z+1/2; (b) Hydrogen bond interactions in complex 4

    In complexes 1~4, the average torsion angles of two pyridyl rings varied from 42.88°(2) to 19.34°(4). The corresponding centre distances of two pyridyl rings range from 0.497 9(2) to 0.382 0 nm (4) (Table 4). Through rotation of the N—C bonds and broaden or compress of two pyridine rings, the ligand L molecule has displayed considerable flexibility to adjust itself to adapt different coordination environment.

    Table 4

    Table 4.  Torsion angles and centre distances between two pyridyl rings of ligand L in complexes 1~4
    下载: 导出CSV
    Compound L[17] 1 2 3 4
    Torsion angle between two pyridyl rings / (°) 45.77 40.52 42.88 22.43 19.34
    Centre distance between two pyridyl rings / nm 0.494 2 0.467 3 0.497 9 0.386 6 0.382 0

    In the IR spectra of complexes 1~4 (Fig. 5), bands around 1 602, 1 578, 1 495 cm-1 (1), 1 600, 1 577, 1 495 cm-1 (2), 1 560, 1 498, 1 420 cm-1 (3) and 1 602, 1 578, 1 499 cm-1 (4) are assigned to the stretching vibrations of pyridine groups, separately. The strong peaks around 1 136 cm-1 in all complexes are attributed to the stretching vibrations of the C—O—C bond. The symmetric and antisymmetric stretchings of C—H bonds (—CH2—units in ligand) in complexes 1~ 4 are also in agreement with each other. They were in the region of 2 902~3 042 cm-1 (1), 2 903~3 077 cm-1 (2), 2 901~2 967 cm-1 (3) and 2 901~2 974 cm-1 (4), respectively. Strong vibrations of 1 370, 1 309 cm-1 (1) and 1 364, 1 303 cm-1 (4) are attributed to the NO3-anions[24]. The isolated peak of 731 cm-1 in complex 2 is assigned as antisymmetric stretching of C—Cl bonds in CH2Cl2[25]. The broad bands at 3 440 cm-1 (3) and 3 408 cm-1 (4) are attributed the stretching of O—H. The infrared spectra of these complexes are in good accordance with their structural features.

    Figure 5

    Figure 5.  IR spectra of complexes 1~4

    Thermogravimetric analyses (TGA) of ligand L and complexes 1~4 were carried out under air atmosphere from 30 to 700 ℃ with a heating rate of 10 ℃·min-1 using crystalline samples, and the resulting curves are shown in Fig. 6. The skeleton of ligand L decomposed at around 194 ℃. Correspondingly, curves in 1 (178 ℃), 2 (174 ℃), 3 (214 ℃) and 4 (207 ℃) have shown dramatic stages of weight loss, which might be attributed to the decomposition of ligand. In complex 1, the fisrt stage of weight loss (150~178 ℃) is attributed to the loss of HNO3 and H2O (Obsd. 15.66%, Calcd. 16.51%), then accompanied by the degradation of ligand gradually. There are two steps of weight loss (in the region of 178~300 ℃ and 400~500 ℃, respectively), the decomposition residue is in accordance with CoO (Obsd. 10.36%, Calcd. 9.81%). For complex 2, dichloromethane was unstable and escaped when exposing to the air, it was removed before thermogravimetric test. Ligand L molecules started to degrade at 174 ℃, and it showed two complicated degradation process (in the region of 174~200 ℃ and 200~375 ℃, separately). The final decompsition residue is suggested to be CoO (Obsd. 17.54%, Calcd. 18.13%). For complex 3, molecules of free methanol were unstable and partially escaped when exposing to the air. The weight loss of the first stage (from 30 to 105 ℃) corresponds to the loss of methanol molecules (Obsd. 7.6%, Calcd. 11.3%). The weight loss of the second stage (214~700 ℃) indicates the decomposition of two molecules of ligand L and CH3COO-. For complex 4, the weight loss of the first stage (from 30 to 100 ℃) corresponds to the loss of free water molecules and methanol (Obsd. 8.54%, Calcd. 8.68%). The skeleton of ligand L began to decompose at 207 ℃, and did not end up to 550 ℃, exhibiting two weight loss platforms in TGA curve. Accompanied by gradually sublimation of CdO, there was almost no residue for complexes 3 and 4. Thermogravimetric analysis indicates that, the bipyridine ligands have shown obvious two steps decomposition in complexes 1, 2 and 4, and the ligands in cis-bridge complexes are more stable than those in mono-dentated and trans-bridge complexes.

    Figure 6

    Figure 6.  TGA curves of L and complexes 1~4 in air

    The phase purity of bulk products of complex 1 was further confirmed by elemental analysis and PXRD. As is illustrated in Fig. 7, the PXRD pattern of the synthesized sample was consistent with the simulated one from single crystal structure.

    Figure 7

    Figure 7.  PXRD patterns of complex 1

    Four transition metal complexes were prepared by utility of a clamplike bipyridine ligand 3, 7-di(3-pyridyl) -1, 5-dioxa-3, 7-diazacyclooctane. Single-crystal structures, IR spectra and thermal stabilities of these complexes have been discussed. The bipyridine ligand molecule has displayed diversity coordination mode in these complexes. All of these architectures have shown considerable stabilties. The study on its coordination chemistry with other metal ions is continuing.


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  • Figure 1  (a) Coordination structural unit with 30% probability ellipsoids in complex 1, where H atoms are omitted for clarify and the symmetry code is #1: -x, y, 1/2-z; (b) Interactions of nitrate anion in complex 1 where the symmetry code is #1: -1+x, -1+y, z

    Figure 2  (a) Coordination structural unit with 30% probability ellipsoids in complex 2, where H atoms and solvent molecule are omitted for clarify; (b) Interactions of CH 2Cl2 solvent molecule in complex 2, where the symmetry codes are #1: -x+1, -y, -z+1; #2: 1/2-x, 1/2-y, 1-z; #3: -1/2+x, 1/2-y, 1/2+z

    Figure 3  (a) Coordination structural unit with 30% probability ellipsoids in complex 3, where H atoms and solvent molecules are omitted for clarify and the symmetry code is #1: 2-x, -y, 1-z; (b) Interactions of CH3OH solvent molecules in complex 3, where the symmetry code is #1: 1-x, 1-y, 1-z

    Figure 4  (a) Coordination structural unit with 30% probability ellipsoids in complex 4, where H atoms, counter nitrate anions and solvent molecules are omitted for clarify and the symmetry code is #1: -x+1, y, -z+1/2; (b) Hydrogen bond interactions in complex 4

    Figure 5  IR spectra of complexes 1~4

    Figure 6  TGA curves of L and complexes 1~4 in air

    Figure 7  PXRD patterns of complex 1

    Table 1.  Crystallographic and structural refinement details for 1~4

    Complex 1 2 3 4
    Empirical formula C28H36CoN10O12 C29H34Cl6Co2N8O4 C40H60Cd2N8O16 C30H48Cd2N12O22
    Formula weight 763.60 889.20 1 133.76 1 153.60
    Crystal system Monoclinic Monoclinic Triclinic Triclinic
    Space group P2/c C2/c P1 P1
    a / nm 1.072 8(2) 0.955 91(5) 0.958 04(4) 0.937 13(19)
    b / nm 0.866 88(17) 2.753 00(14) 1.165 02(5) 1.070 0(2)
    c / nm 1.870 9(6) 1.406 73(8) 1.203 89(4) 1.270 2(3)
    α/(°) 107.496(3) 109.52(3)
    β/(°) 108.80(3) 105.324(5) 106.103(3) 108.64(3)
    γ/(°) 100.170(3) 99.59(3)
    V / nm3 1.647 1(7) 3.570 4(3) 1.180 67(8) 1.082 8(4)
    Z 2 4 1 1
    Dc/ (g·cm-3) 1.540 1.654 1.595 1.769
    F(000) 794 1 808 580 584
    μ / mm-1 0.600 1.426 0.977 1.079
    θ range /(°) 3.06~25.35 3.07~26.00 3.05~25.02 3.16~25.00
    Limiting indices -10 ≤ h ≤ 12 -11 ≤ h ≤ 11 -11 ≤ h ≤ 11 -10 ≤ h ≤ 10
    -10 ≤ k ≤ 10 -33 ≤ k ≤ 26 -12 ≤ k ≤ 13 -12 ≤ k ≤ 12
    -22 ≤ l ≤ 21 -12 ≤ l ≤ 17 -14 ≤ l ≤ 14 -14 ≤ l ≤ 14
    Total reflection 15 226 8 321 11 193 8 377
    Data, restraint, parameter 3 024, 0, 305 3 506, 0, 222 4 175, 3, 302 3 392, 29, 383
    Initial R indices [I > 2σ(I)] R1=0.034 8, R1=0.033 0, R1=0.025 1, R1=0.052 9,
    wR2=0.074 2 wR2=0.069 5 wR2=0.059 2 wR2=0.121 2
    R indices (all data) R1=0.039 6, R1=0.044 5, R1=0.028 9, R1=0.062 7,
    wR2=0.076 5 wR2=0.074 4 wR2=0.061 4 wR2=0.132 1
    Goodness-of-fit 1.095 1.022 1.069 1.063
    Largest diff. peak and hole / (e·cm-3) 210, -275 289, -325 446, -410 539, -767
    下载: 导出CSV

    Table 2.  Selected bond lengths (nm) and angles (°) for complexes 1~4

    Complex 1
    Co(1)—O(7) 0.210 28(17) Co(1)—O(7)#1 0.210 28(17) Co(1)—N(1) 0.211 21(16)
    Co(1)—N(1)#1 0.211 21(16) Co(1)—O(3) 0.214 00(15) Co(1)—O(3)#1 0.214 00(15)
    O(7)—Co(1)—O(7)#1 172.06(10) O(7)—Co(1)—N(1) 93.67(7) O(7)#1—Co(1)—N(1) 91.79(6)
    O(7)—Co(1)—N(1)#1 91.79(6) O(7)#1—Co(1)—N(1)#1 93.67(7) N(1)—Co(1)—N(1)#1 93.23(9)
    O(7)—Co(1)—O(3) 88.45(7) O(7)#1—Co(1)—O(3) 84.67(7) N(1)—Co(1)—O(3) 103.40(6)
    N(1)#1—Co(1)—O(3) 163.32(6) O(7)—Co(1)—O(3)#1 84.67(7) O(7)#1—Co(1)—O(3)#1 88.45(7)
    N(1)—Co(1)—O(3)#1 163.32(6) N(1)#1—Co(1)—O(3)#1 103.40(6) O(3)—Co(1)—O(3)#1 60.01(8)
    Complex 2
    Co(1)—N(1) 0.204 42(19) Co(1)—N(2) 0.202 1(2) Co(1)—Cl(1) 0.223 38(7)
    Co(1)—Cl(2) 0.223 74(6)
    N(1)—Co(1)—Cl(1) 105.13(6) N(2)—Co(1)—N(1) 107.60(8) N(1)—Co(1)—Cl(2) 108.56(6)
    N(2)—Co(1)—Cl(1) 107.40(6) N(2)—Co(1)—Cl(2) 107.46(5) Cl(1)—Co(1)—Cl(2) 120.12(3)
    Complex 3
    Cd(1)—N(2)#1 0.230(2) Cd(1)—N(1) 0.232(2) Cd(1)—O(3) 0.243(2)
    Cd(1)—O(4) 0.237(2) Cd(1)—O(5) 0.243(2) Cd(1)—O(6) 0.236(2)
    Cd(1)—O(6)#1 0.248(2)
    N(2)#1—Cd(1)—N(1) 173.9(8) N(2)#1—Cd(1)—O(6) 89.2(7) N(1)—Cd(1)—O(6) 87.0(7)
    N(2)#1—Cd(1)—O(4) 91.4(7) N(1)—Cd(1)—O(4) 89.3(7) O(6)—Cd(1)—O(4) 146.9(7)
    N(2)#1—Cd(1)—O(5) 88.0(7) N(1)—Cd(1)—O(5) 87.4(7) O(6)—Cd(1)—O(5) 92.4(7)
    O(4)—Cd(1)—O(5) 54.6(7) N(2)#1—Cd(1)—O(3) 91.7(7) N(1)—Cd(1)—O(3) 94.3(8)
    O(6)—Cd(1)—O(3) 123.7(7) O(4)—Cd(1)—O(3) 89.4(7) O(5)—Cd(1)—O(3) 143.9(7)
    N(2)#1—Cd(1)—O(6)#1 94.4(7) N(1)—Cd(1)—O(6)#1 88.9(7) O(6)—Cd(1)—O(6)#1 71.2(8)
    O(4)—Cd(1)—O(6)#1 141.6(7) O(5)—Cd(1)—O(6)#1 163.3(7) O(3)—Cd(1)—O(6)#1 52.6(6)
    Complex 4
    Cd(1)—N(2) 0.225 4(5) Cd(1)—N(3) 0.225 4(5) Cd(1)—O(1) 0.246 0(5)
    Cd(1)—O(1)#1 0.244 7(5) Cd(1)—O(5) 0.235 8(6) Cd(1)—O(7) 0.234 4(5)
    N(2)—Cd(1)—N(3) 176.53(17) N(2)—Cd(1)—O(5) 93.05(19) N(3)—Cd(1)—O(5) 90.49(17)
    N(2)—Cd(1)—O(4) 88.0(2) N(3)—Cd(1)—O(4) 92.0(2) O(5)—Cd(1)—O(4) 87.5(3)
    N(2)—Cd(1)—O(1)#1 88.07(17) N(3)—Cd(1)—O(1)#1 90.78(17) O(5)—Cd(1)—O(1)#1 112.9(2)
    O(4)—Cd(1)—O(1)#1 159.4(2) N(2)—Cd(1)—O(1) 89.25(17) N(3)—Cd(1)—O(1) 87.30(17)
    O(5)—Cd(1)—O(1) 177.3(2) O(4)—Cd(1)—O(1) 94.1(2) O(1)#1—Cd(1)—O(1) 65.6(2)
    Symmetry codes: #1: -x, y, -z+1/2 for 1; #1: -x+2, -y, -z+1 for 3; #1 -x+1, -y+1, -z+2 for 4.
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    Table 3.  Hydrogen bond geometries for complexes 1~4

    D—H…A d(D—H) / nm d(H…A) / nm d(D…A) / nm ∠D—H…A / (°)
    Complex 1
    O(7)—H(7a)…O(5)#3 0.079 0.203 0.281 52 175
    O(7)—H(7b)…N(2)#3 0.091 0.183 0.273 98 176
    C(1)—H(1)…O(7)#1 0.095 0.257 0.313 76 118
    C(9)—H(9)…O(5)#4 0.097 0.248 0.326 90 138
    C(12)—H(12A)…O(1)#5 0.097 0.252 0.335 89 144
    C(14)—H(14B)…O(3)#6 0.099 0.247 0.314 70 125
    Complex 2
    C(11)—H(11A)…Cl(2)#3 0.097 0.278 0.361 28 145
    C(12)—H(12B)…Cl(1)#4 0.097 0.283 0.364 75 143
    Complex 3
    C(1)—H(1)…O(2) 0.093 0.247 0.297 37 114
    C(6)—H(6)…O(2) 0.093 0.251 0.307 62 119
    C(12)—H(12B)…O(4)#2 0.097 0.258 0.344 48 149
    C(13)—H(13B)…O(8)#3 0.097 0.243 0.338 69 170
    C(16)—H(16B)…O(1)#4 0.096 0.259 0.349 20 157
    C(16)—H(16C)…O(1)#5 0.096 0.250 0.338 50 153
    Complex 4
    O(4)—H(5')…O(2) 0.072 0.248 0.304 3 136
    O(4)—H(5')…O(11A) 0.072 0.247 0.281 111
    O(15)—H(15A)…O(11A) 0.096 0.206 0.274 6 127.1
    O(5)—H(2')…O(3)#1 0.074 0.257 0.309 0 128.7
    O(5)—H(2')…O(8A)#2 0.074 0.244 0.279 8 111.5
    O(12)—H(3')…O(7)#4 0.085 0.233 0.303 1 140
    O(12)—H(3')…O(11A)#5 0.085 0.259 0.317 127
    O(12)—H(4')…O(5)#5 0.085 0.204 0.271 7 136
    O(4)—H(5')…O(10)#3 0.072 0.214 0.274 1 142
    C(1)—H(1)…O(3)#1 0.101 0.256 0.341 0 142
    C(1)—H(1)…O(6)#1 0.101 0.249 0.298 8 110
    C(13)—H(12)…O(8A)#2 0.095 0.255 0.318 6 124
    C(13)—H(13A)…O(10)#3 0.093 0.250 0.342 5 175
    C(13)—H(13B)…O(8A)#6 0.111 0.220 0.326 5 160
    Symmetry codes: #1: -x, y, -z+1/2; #3: -x, y-1, -z+1/2; #4: x, y-1, z; #5: -x+1, -y, -z+1; #6: -x, -y, -z+1 for 1; #3: -x+1, -y, -z+1; #4: -x+1/2, -y+1/2, -z+1 for 2; #1: -x+2, -y, -z+1; #2: x, y+1, z; #3: -x+1, -y+1, -z; #4: -x+2, -y, -z; #5: x, y-1, z for 3; #1: 1-x, 1-y, 2-z; #2: 1-x, -y, 1-z; #3: -x, 1-y, 1-z; #4: x-1, y, z; #5: x, 1+y, z; #6: 1-x, 1-y, 1 -z for 4.
    下载: 导出CSV

    Table 4.  Torsion angles and centre distances between two pyridyl rings of ligand L in complexes 1~4

    Compound L[17] 1 2 3 4
    Torsion angle between two pyridyl rings / (°) 45.77 40.52 42.88 22.43 19.34
    Centre distance between two pyridyl rings / nm 0.494 2 0.467 3 0.497 9 0.386 6 0.382 0
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  • 发布日期:  2021-01-10
  • 收稿日期:  2020-02-11
  • 修回日期:  2020-10-27
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