Dinuclear Copper-Dipyridyl Water Cluster Complex with Host Dragonfly-Like Structure

E Liu Xiaoguang Dong Xiaojing Liu Aiquan Jia Ziyu Guo Huiling Liu Xiaoshuang Guo Qianfeng Zhang

Citation:  E Liu, Xiaoguang Dong, Xiaojing Liu, Aiquan Jia, Ziyu Guo, Huiling Liu, Xiaoshuang Guo, Qianfeng Zhang. Dinuclear Copper-Dipyridyl Water Cluster Complex with Host Dragonfly-Like Structure[J]. Chemistry, 2021, 84(1): 58-62. shu

Dinuclear Copper-Dipyridyl Water Cluster Complex with Host Dragonfly-Like Structure

    通讯作者: 刘娥, 798233143@haust.edu.cn
    张千峰, zhangqf@ahut.edu.cn
摘要: This paper introduces a simple method to synthesize[Cu2(bipy)2(H2P2O7)(OH)2]·7H2O binuclear copper water cluster complex. The crystal structure analysis indicated that seven crystal waters form a two-dimensional water cluster polymer[(H2O)7]n, and the water cluster then forms a strong hydrogen bond with the hydroxyl group in the core structure. The structure of the whole complex resembles a dragonfly. Through the research of this kind of water cluster polymer, it is helpful for improving the modelling of some of the unexplained properties of water and better understanding the structure and behaviour of water molecules in chemical and biological process.

English

  • Water is the most abundant compound on Earth, and plays a very important role in many biological and chemical processes[1~3]. Structural studies on discrete water clusters within the lattice of a crystal host have significantly advanced our understanding of the behavior of bulk water[4, 5]. Elucidating the assembly of discrete water aggre-gates and understanding how water aggregates interact with a crystal host are still challenging scientific endeavors[6~9]. The aggregation of lattice water molecules in crystals into hydrogen-bonded clusters as well as infinite networks has generated considerable interest[10]. The presence of water molecules in the structure can play an important role in stabilizing some supramolecular species since the number of hydrogen bond acceptors and donors can differ significantly from those of the anhydrous compounds[11]. Many biological systems such as proteins, membranes, RNA, and DNA show func-tions related to multiple H-bonded frames[12]. Structural studies on discrete water clusters within the lattice of a crystal host have significantly advanced our knowledge toward the first step of understanding the behavior of bulk water[13].Growth of larger water clusters and how the clusters link to form a large network, which is the bridge between clusters and bulk water, is still a challenging scientific endeavor. Until now, a number of water oligomers have been well studied by X-ray diffraction methods[14]. Infantes et al.[15] have examined about 1400 hydrated structures retrieved from the Cambridge Structural Database (CSD), and made classifications of water/water motifs with statistics as to their relative frequency, and established classification system as follows: D (discrete chain), R (discrete rings), C (infinite chains), T (infinite tapes), and L (infinite layers). In another report[16], they have shown that a proper analysis should be done when reporting any new water morphology in a crystal lattice. With this in mind, we performed a CSD search for our reported water cluster [(H2O)7]n, with the help of the Cambridge Crystallographic Data Centre (CCDC). We did not find this structure-shaped pattern. Therefore, there is no structural information available for a discrete, [(H2O)7]n cluster or its participation in the stabilization of a supramolecular assembly to be reported so far. Moreover, to the best of our kno-wledge, the design of the metal-organic frameworks (MOFs) that act as the hosts and water clusters that act as guests has been reported before[17~19].In this paper, we report the crystal structure data of a discrete, water cluster [(H2O)7]n with an unusual aggregate mode in the crystal host, [Cu2(bipy)2(H2P2O7)(OH)2]. The thermal stability of water cluster in the crystal was also investigated using thermogravimetric analysis.

    All chemicals were of analytical reagent grade and used directly without further purification. The C, H and N elemental analyses were performed on a Perkin-Elmer elemental analyzer. TG and DTG curves were recorded on a NETZSCH -Geratebau GmbH thermoanalyser in the flow of N2, and the temperature range from 20 ℃ to 800 ℃, with a heating rate of 10 ℃/min.

    Crystals data were collected on an Enraf-Nonius CAD-4 diffractometer with graphite monochromated Mo Kα radiation (λ=0.71073 Å). Intensities were corrected for Lorentz and polarization effects and empirical absorption, and data reduction was carried out. The structure was analyzed by the direct method. These data can be observed at CCDC via www.ccdc.cam.ac.uk/data-request/cif. The CCDC number is 689109.

    To a 100mL flask were added Cu3(PO4)2·3H2O (4.35 g, 0.01 mol), NaOH (0.80 g, 0.02 mol) and 40 mL deionized water, and then 3.20 g (0.20 mol) 2, 2-bipyridine in 20 mL of ethanol was added while stirring at 90 ℃. The reaction was maintained for 4 to 5 hours, and then the mixture was filtered, and the obtained filtrate was allowed to stand at room temperature until a deep blue single crystal suitable for X-ray measurement was obtained. From the element analysis and the single crystal X-ray, we concluded that the compound is [Cu2(bipy)2(H2P2O7)(OH)2]·7H2O. Anal. Calc. for C20H36Cu2N4O16P2: C, 30.87%; H, 4.63%; N, 7.20%. Found: C, 30.32%; H, 4.50%; N, 7.68%.

    The structure unit of the compound contains host [Cu2(bipy)2(H2P2O7)(OH)2]complex and guest water cluster [(H2O)7]n. The coordination environments of two Cu(Ⅱ) atoms are similar. Each Cu(Ⅱ) atom is pentacoordinated with two N atoms from two 2, 2′-bipyridine ligands and two O atoms from H2P2O7 anions and one OH anion in a distorted square pyramidal geometry (Fig. 1). Two nitrogen atoms from bipyridine and two oxygen atoms from H2P2O7 anions occupy the basal sites with Cu-N distances of 2.006(9) Å, 2.009(9) Å and Cu-O distances of 1.921(8) Å, 1.933(9) Å for Cu(1), Cu-N 2.004(9) Å, 2.009(9) Å, and Cu-O 1.930(8) Å, 1.967(9) Å for Cu(2). The hydroxyl anions occupy the apical position, and H2P2O72- bridges two Cu atoms to form dinuclear structure. The Cu-N and Cu-O bond lengths in the compound are all in the normal range.

    Figure 1

    图 1.  配合物的分子结构图
    Figure 1.  The molecular structure with the atomic numbering for complex

    Seven discrete water molecules form strong H-bond action (as shown in Fig. 2) with the donor-acceptor of distance ranging from 2.668 to 2.800 Å (average: 2.737 Å), which are comparable to the values in ice Ih[20]. The water cluster [(H2O)7]n in the compound forms 2D polymer along the c axis (showed in Fig. 3). According to the established classification system of water cluster by Infantes et al., [15, 21] this aggregate mode has not been predicted theoretically nor previously reported exp-erimentally. Therefore, there is no structural infor-mation available for this structure-shaped pattern or its participation in the stabilization of a supra-molecular assembly to be reported so far.

    Figure 2

    图 2.  沿c轴方向水聚簇聚合物[(H2O)7]n的堆积图, 代表颜色: O1w, 红色; O2w, 橙色; O3w, 黄色; O4w, 亮绿色; O5w, 绿色; O6w, 蓝色; O7w, 紫色
    Figure 2.  Packing of water clusters polymer, [(H2O)7]n, along the c axis. Colours are as follows: red, O1w; orange, O2w; yellow, O3w; light green, O4w; green, O5w; blue, O6w; purple, O7w

    Figure 3

    图 3.  沿c轴方向的水团簇[(H2O)7]n二维结构图
    Figure 3.  The water cluster [(H2O)7]n in compound form 2D polymer along the c axis

    The hydroxyl group in host forms strong H-bond actions with water cluster, which are held together by O-HO interactions. The two terminal hydroxyl groups (O3 and O7) in bridging ligand (H2P2O7)2- of host [Cu2(bipy)2(H2P2O7)(OH)2] connect water cluster [(H2O)7]n through O-HOw hydrogen bonds. Tab. 1 and Tab. 2 list the hydrogen bonds and π-π interactions, respectively. Fig. 4 shows that the water cluster and the host [Cu2(bipy)2(H2P2O7)][OH]2 adjacent molecular groups are arranged in reverse order. Fig. 5 shows the reverse interconnection mode between the molecular chain of adjacent host Cu2(bipy)2(H2P2O7)[(OH)2 groups and the water molecules.

    Table 1

    表 1  水团簇氢键的几何参数
    Table 1.  Geometrical parameters of hydrogen bonds (Å, deg) for the water cluster
    下载: 导出CSV
    Donor-HAcceptor HA DA D-HA
    O(3)-H(3A)O(5W)a 1.9251 2.7442 176.77
    O(7)-H(7A) O(7W)b 1.9455 2.7338 160.98
    O(8)-H(8B)O(6W) 2.0211 2.7497 147.76
    O(9)-H(9B)O(1W) 2.0538 2.8060 152.33
    O(1W)-H(11W)O(5)c 2.1592 2.9616 157.31
    O(3W)-H(13W)-O(1)c 2.3327 3.0490 142.18
    O(2W)-H(22W)O(7W)c 2.3246 2.7596 111.66
    O(4W)-H(14W)O(7)d 2.1247 2.8141 137.67
    O(6W)-H(16W)O(7)d 1.9218 2.7285 159.45
    O(3W)-H(23W)O(6W) 2.3711 2.7961 111.19
    O(5W)-H(25W)O(2)d 1.9866 2.8354 177.39
    O(6W)-H(26W)O(8) 2.4347 2.7497 102.65
    O(7W)-H(27W)O(7)d 2.4091 2.7338 103.19
    O(7W)-H(27W)O(9) 2.4345 2.7392 101.74
    C(1)-H(1A)O(2) 2.4402 2.9523 114.71
    C(2)-H(2A)O(3W)e 2.5682 3.3492 141.85
    C(3)-H(3B)O(6W)f 2.4954 3.3929 162.21
    C(4)-H(4A)O(3)g 2.4471 3.3614 167.62
    C(10)-H(10A)O(3W)h 2.5892 3.4934 164.22
    C(13)-H(13A)O(1W)i 2.5104 3.3958 159.19
    C(14)-H(14A)O(7W)i 2.4989 3.4053 164.86
    Symmetry code: a, 1+x, 1+y, z; b, x, 1+y, z; c, -1+x, y, z; d, x, -1+y, z; e, x, 1+y, z; f, 1-x, 2-y, -z; g, 2-x, 2-y, -z; h, 1+x, y, z; i, 2-x, 1-y, 1-z.x, 1-y, 1-z.

    Table 2

    表 2  在配合物中π-π键长以及相关参数
    Table 2.  π-π interactions (face-to-face) in complexea
    下载: 导出CSV
    Ring(i)→
    Ring(j)/C
    Distance between
    the (i, j) Ring
    Centroids/Å
    Dihedral
    Angle
    (i, j)/(°)
    Distance of
    Centroid(i)
    from Ring
    (j)/Å
    R1→R4i 3.509 7.75 3.477
    R2→R6ii 3.478 10.86 3.412
    R3→R4i 3.891 27.66 3.446
    R4→R1i 3.509 7.65 3.477
    R4→R3i 3.891 26.24 3.446
    R5→R5iii 3.902 28.71 3.422
    R6→R2ii 3.478 11.16 3.412
    R6→R6ii 3.866 27.83 3.419
    ASymmetry code: (i)=2-x, 2-y, -z; (ⅱ)=2-x, 2-y, 1-z; (ⅲ)=2-x, 1-y, 1-z; R(i)/R(j) denotes the ith/jth rings of bipy: R(1)=Cu(1)/N(1)/C(5)/C(6)/N(2); R(2)=Cu(2)/N(3)/C(15)/C(16)/N(4); R(3)=N(1)/C(1)/C(2)/C(3)/C(4)/C(5); R(4)=N(2)/C(6)/C(7)/C(8)/C(9)/C(10); R(5)=N(3)/C(11)/C(12)/C(13)/C(14)/C(15); R(6)=N(4)/C(16)/C(17)/C(18)/C(19)/C(20).

    Figure 4

    图 4.  同一平面水团簇与相邻配位化合物[Cu2(bipy)2(H2P2O7)(OH)2]的分子基团反向排列图
    Figure 4.  The planar water cluster and coordination compound [Cu2(bipy)2(H2P2O7)(OH)2] adjacent molecular groups are arranged in reverse order

    Figure 5

    图 5.  配位化合物[Cu2(bipy)2(H2P2O7)(OH)2]·7H2O相邻分子链反向互连图
    Figure 5.  The reverse interconnection of the molecular chains of adjacent coordination compound [Cu2(bipy)2(H2P2O7)(OH)2]·7H2O

    Interestingly, if considered from the perspective of bionics, the compound is like a dragonfly flying in the sky, as shown in Fig. 6. Two 2, 2′-bipy ligands make up the dragonfly's wings, and the [Cu2(H2P2O7)] core forms the dragonfly's body, and the 7 water molecules can be regarded as insects. In addition, the face-to-face and edge-to-face π-π interactions among the aromatic bipyridine ligands and Cu atom in compounds are also responsible for the formation of the crystal building. The centre Cu atoms with bipyridine ring are all nearly in the same plane, with the maximum atom deviation of 0.056 Å from the mean plane, respectively.

    Figure 6

    图 6.  整个配合物类似在天空中飞翔的蜻蜓
    Figure 6.  The whole complex resembles a dragonfly flying in the sky

    To get more insight into the properties relative to water cluster, the dehydration behavior of the compound was investigated using thermogravimetric analysis. The TG and DTG curves of the compound are shown in Fig. 7. The weight loss begins at 62.1 ℃, and shows an obvious inflexion at about 150.7 ℃. The first step corresponds to the loss of six water molecules with three heat-absorption peaks (found 14.80% calc. 13.90%), the residue was [Cu2(bipy)2(H2P2O7) (OH)2]·H2O. Or, the compound lost 6.5 water molecules, and the residue was {[Cu2(bipy)2(H2P2O7)] (OH)2}2·H2O (calc. 15.04%). From 150.2 ℃ to 327.0 ℃, no weight loss was observed, indicating the residue is very stable. At 327.0 ℃, there is an intense endothermic phenomenon, and the weight loss of 31.71% corresponds to the loss of [(bipy)(H3PO4)] groups (calc.32.66%). The residue is [Cu2(bipy)(OH)2(HPO4)]. As the temperature continues to rise, the weight-lose of (16.42% + 10.29% + 7.47%) indicates that [Cu2(bipy)(OH)2(HPO4)] gradually decomposes. The final residual compound should be CuO (Calc. 20.45%, Found 19.31%).

    Figure 7

    图 7.  化合物的TG和DTG分析图
    Figure 7.  TG and DTG analysis for compound

    In summary, we have shown that the water in the crystal host [Cu2(bipy)2(H2P2O7)(OH)2]can form water cluster structure. The present aggregate mode has been first reported experimentally. The precise structure information of this water cluster complex is helpful for improving the modelling of some of the unexplained properties of water and better understanding the structure and behaviour of water molecules in chemical and biological process.


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  • Figure 1  The molecular structure with the atomic numbering for complex

    Figure 2  Packing of water clusters polymer, [(H2O)7]n, along the c axis. Colours are as follows: red, O1w; orange, O2w; yellow, O3w; light green, O4w; green, O5w; blue, O6w; purple, O7w

    Figure 3  The water cluster [(H2O)7]n in compound form 2D polymer along the c axis

    Figure 4  The planar water cluster and coordination compound [Cu2(bipy)2(H2P2O7)(OH)2] adjacent molecular groups are arranged in reverse order

    Figure 5  The reverse interconnection of the molecular chains of adjacent coordination compound [Cu2(bipy)2(H2P2O7)(OH)2]·7H2O

    Figure 6  The whole complex resembles a dragonfly flying in the sky

    Figure 7  TG and DTG analysis for compound

    Table 1.  Geometrical parameters of hydrogen bonds (Å, deg) for the water cluster

    Donor-HAcceptor HA DA D-HA
    O(3)-H(3A)O(5W)a 1.9251 2.7442 176.77
    O(7)-H(7A) O(7W)b 1.9455 2.7338 160.98
    O(8)-H(8B)O(6W) 2.0211 2.7497 147.76
    O(9)-H(9B)O(1W) 2.0538 2.8060 152.33
    O(1W)-H(11W)O(5)c 2.1592 2.9616 157.31
    O(3W)-H(13W)-O(1)c 2.3327 3.0490 142.18
    O(2W)-H(22W)O(7W)c 2.3246 2.7596 111.66
    O(4W)-H(14W)O(7)d 2.1247 2.8141 137.67
    O(6W)-H(16W)O(7)d 1.9218 2.7285 159.45
    O(3W)-H(23W)O(6W) 2.3711 2.7961 111.19
    O(5W)-H(25W)O(2)d 1.9866 2.8354 177.39
    O(6W)-H(26W)O(8) 2.4347 2.7497 102.65
    O(7W)-H(27W)O(7)d 2.4091 2.7338 103.19
    O(7W)-H(27W)O(9) 2.4345 2.7392 101.74
    C(1)-H(1A)O(2) 2.4402 2.9523 114.71
    C(2)-H(2A)O(3W)e 2.5682 3.3492 141.85
    C(3)-H(3B)O(6W)f 2.4954 3.3929 162.21
    C(4)-H(4A)O(3)g 2.4471 3.3614 167.62
    C(10)-H(10A)O(3W)h 2.5892 3.4934 164.22
    C(13)-H(13A)O(1W)i 2.5104 3.3958 159.19
    C(14)-H(14A)O(7W)i 2.4989 3.4053 164.86
    Symmetry code: a, 1+x, 1+y, z; b, x, 1+y, z; c, -1+x, y, z; d, x, -1+y, z; e, x, 1+y, z; f, 1-x, 2-y, -z; g, 2-x, 2-y, -z; h, 1+x, y, z; i, 2-x, 1-y, 1-z.x, 1-y, 1-z.
    下载: 导出CSV

    Table 2.  π-π interactions (face-to-face) in complexea

    Ring(i)→
    Ring(j)/C
    Distance between
    the (i, j) Ring
    Centroids/Å
    Dihedral
    Angle
    (i, j)/(°)
    Distance of
    Centroid(i)
    from Ring
    (j)/Å
    R1→R4i 3.509 7.75 3.477
    R2→R6ii 3.478 10.86 3.412
    R3→R4i 3.891 27.66 3.446
    R4→R1i 3.509 7.65 3.477
    R4→R3i 3.891 26.24 3.446
    R5→R5iii 3.902 28.71 3.422
    R6→R2ii 3.478 11.16 3.412
    R6→R6ii 3.866 27.83 3.419
    ASymmetry code: (i)=2-x, 2-y, -z; (ⅱ)=2-x, 2-y, 1-z; (ⅲ)=2-x, 1-y, 1-z; R(i)/R(j) denotes the ith/jth rings of bipy: R(1)=Cu(1)/N(1)/C(5)/C(6)/N(2); R(2)=Cu(2)/N(3)/C(15)/C(16)/N(4); R(3)=N(1)/C(1)/C(2)/C(3)/C(4)/C(5); R(4)=N(2)/C(6)/C(7)/C(8)/C(9)/C(10); R(5)=N(3)/C(11)/C(12)/C(13)/C(14)/C(15); R(6)=N(4)/C(16)/C(17)/C(18)/C(19)/C(20).
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  • 发布日期:  2021-01-18
  • 收稿日期:  2020-07-08
  • 接受日期:  2020-08-28
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