English

• 0.   Introduction

  Photochromic materials with colour change induced by light have received widespread attention because of their important application in optical infor mation storages, optical switches, optical control mate rials and so on^[1-4]. Among the materials, inorganic polyoxometalate (POM) is one of the notable photochromic compounds due to its exceptional redox properties, pho toactivities, and thermal stabilities^[5-9]. However, it is still difficult to synthesize the pure POM with improved photochromic performance^[10]. On the other hand, pure organic photochromic materials often show poor fatigue resistance and high-temperature resistance despite they have fast response time and rich colours. In con trast, organic-inorganic hybrid photochromic materials can not only maintain the advantages of the organic and inorganic components but also generate new prop erties due to the synergistic effect between the organic and inorganic units^[11-16].

  As an important photochromic material, viologen compounds usually act as electron acceptors and show a potential application in the fields of photochemical devices, optoelectronics, and inkless printing^[17-21]. Recently, viologen-POM hybrids as a new kind of photochromic materials have garnered increasing atten tion due to their structural diversities and good photo thermal stabilities^[22-25]. For example, in 2021, Zheng et al. reported a novel metalloviologen-POM hybrid, [Co (H₂O)₆]₂[Co₃(bpdo)₄(H₂O)₁₀] [Co₄(H₂O)₂(B-α-PW₉O₃₄)₂] · 2bpdo·14H₂O (bpdo=4, 4′-bipyridyl-N, N′-dioxide), which exhibits tunable thermochromic properties and reversible structural transformations in single-crystal-to-single-crystal fashion and can be used as a nonvolatile memristor with unique temperature-regulated resis tive switching behaviours^[26]. In 2020, Zhang et al. syn thesized a new viologen-POM hybrid, (Pbpy)(Me₂NH₂)₃ [PW₁₁ZnO₄₀] (Pbpy=1, 1′-[1, 4-phenylene-bis(methy lene)]bis(4, 4′-bipyridinium)), which can be used as a multifunctional material for rapid solar ultraviolet (UV) light detection, photoluminescence-based UV probing and inkless and erasable printing^[27]. In 2022, Wang et al. synthesized three viologen-POM hybrids, [Ag(bmypd)_0.5(β-Mo₈O₂₆)_0.5] (bmypd=1, 1′-[biphenyl-4, 4′-bis(methylene)]bis(4, 4′-bipyridyinium)), [Ag₂(bypy)₄ (HSiW₁₂O₄₀)₂] ·14H₂O and [Ag(bypy) (γ-Mo₈O₂₆)_0.5] (bypy=1-benzyl-4, 4′-bipyridyinium), which can be used as the photochromic materials for UV probing, amine detecting and inkless and erasable printing^[28]. Furthermore, POMs can be integrated into the frame work of Prussian blue through various interactions including ionic electrostatic attraction, π···π stacking and hydrogen bonding. These integrations can provide rich structural tunable methods for preparation of the functional hybrid materials. Moreover, the combination of viologen and POMs can promote electron transfers, which will not only enhance the photochromic perfor mance but also expand the application fields of the cor responding hybrid materials^[29-31].

  Based on the above consideration, herein, by using the cations of 1, 1′-dimethyl-4, 4′-bipyridinium (MV) dichloride (MV·2Cl) and 1, 1′-diethyl-4, 4′-bipyri-dinium (EV) dibromide (EV·2Br) to combine with the different POM anions, two new viologen-POM hybrid materials: (MV)₂[HPW₂^ⅤW₁₀^ⅥO₄₀] ·2H₂O (1) and (EV)₂ [Mo₈O₂₆] (2) have been synthesized successfully. Single-crystal structural analyses revealed that there are rich hydrogen bond interactions between the cations and the anions in 1 and 2. Intriguingly, 2 exhibits sensitive photochromic properties with a response time of 1 min. In addition, both 1 and 2 display good catalytic activi ties in the photocatalytic degradation of several organic dyes such as methylene blue (MB), pararosaniline hydrochloride (PH), and rhodamine 6G (R6G).

  1.   Experimental

  1.1   Materials and methods

  All the chemicals were received as AR grade and used without further purification. IR spectra were recorded on a Varian 640 FT-IR spectrometer with KBr pellets in a range of 4 000-400 cm^-1. Powder X-ray diffraction (PXRD) pattern was collected on a DX-2600 spectrometer with Mo Kα radiation (λ=0.071 073 nm) at room temperature (U=40 kV, I=30 mA, 2θ=5°-50°). Thermogravimetric analyses (TGA) were carried out under N₂ flow on an SDT 2960 differential thermal ana lyzer with a rate of 10 ℃·min^-1. Solid-state UV-Vis diffused reflection spectra were conducted using a Cary5000 UV-Vis spectrophotometer. Electron spin resonance (ESR) spectra were performed with a Bruker EMX spectrometer at an X-band frequency (100 kHz) under a high pure N₂ atmosphere.

  1.2   Synthesis of compound 1

  MV·2Cl (12.8 mg, 0.05 mmol) and H₃PW₁₂O₄₀· xH₂O (71.4 mg, 0.025 mmol) in a 5 mL solution of methanol and water were added to a 15 mL Teflonlined autoclave. After 30 min of ultrasonic vibration, the closed reactor was placed in an oven and heated at 160 ℃ for 72 h. After cooling to room temperature, black square crystals were filtered and washed with ethanol and deionized water to obtain compound 1. Yield: 37.6% based on MV·2Cl. Anal. Calcd. for C₂₄H₃₃N₄O₄₂PW₁₂ (%): C, 8.77; H, 1.01; N, 1.71. Found (%): C, 8.64; H, 0.92; N, 1.56. IR (KBr disc, cm^-1): 3 447 (m, br), 3 054 (w), 2 917 (w), 1 639 (m), 1 187 (w), 1 061 (s), 957 (s), 884 (s), 802 (vs), 671 (m).

  1.3   Synthesis of compound 2

  EV·2Br (18.7 mg, 0.05 mmol), (NH₄)₆Mo₇O₂₄· 4H₂O (37 mg, 0.3 mmol) and AgNO₃ (3.4 mg, 0.02 mmol) in 20 mL water were added to a 25 mL Teflonlined autoclave, and the pH value of solution was adjusted to 5 by using NH₃·H₂O. After heating at 160 ℃ for 72 h, yellow square crystals of compound 2 were obtained. Yield: 67.4% based on EV·2Br. Anal. Calcd. for C₂₈H₃₆Mo₈N₄O₂₆ (%): C, 20.86; H, 2.25; N, 3.48. Found (%): C, 20.90; H, 2.37; N, 3.59. IR (KBr disc, cm^-1): 3 423 (m, br), 3 059 (m), 1 635 (s), 1 448 (m), 1 169 (m), 932 (vs), 837 (s), 798 (s), 661 (s).

  1.4   X-ray crystallography

  The single-crystal X-ray diffraction data of compound 1 were collected on a Bruker D8 QUEST instrument equipped with graphite-monochromated Cu Kα radiation (λ =0.154 184 nm) at 296 K. The single-crystal data of compound 2 were collected on an Oxford Diffraction Gemini R Ultra diffractometer with graphite monochromated Mo Kα (λ=0.071 073 nm) at 296.15 K. Structures were solved by SHELXS (direct methods) and refined by SHELXL (full-matrix least-squares techniques) in the Olex2 package. Crystal data and structure refinements of 1 and 2 are provided in Table S1 (Supporting information). Selected bond lengths and angles are listed in Table S2 and S3.

  1.5   Photocatalytic degradation of organic dyes

  The hybrid materials 1 and 2 (30 mg) were added into the 50 mL aqueous solution of MB, PH and R6G (6 mg·L^-1), then the obtained suspensions were magnetically stirred in the dark for about 30 min to ensure the equilibrium of working solution. The solution was then exposed to UV irradiation from a 100 W Hg lamp (λ= 365 nm). The solution was kept stirring during irradiation. At given time intervals, 2 mL of the sample was taken out for analysis.

  2.   Results and discussion

  2.1   Structure description

  Single-crystal structural analysis reveals that compound 1 crystallizes in a triclinic P1 space group, and the asymmetric unit comprises two MV²⁺ cations, two [H_0.5P_0.5W^ⅤW₅^ⅥO₂₀]^2- units and two lattice water molecules (Fig. 1a). A lot of hydrogen bonding interactions have been observed between the MV²⁺ cations and the [HPW₂^ⅤW₁₀^ⅥO₄₀]^4- anions with the C—H···O distances in a range of 0.318-0.355 nm (Table 1). The water molecules are linked to the POM anions by four kinds of O—H···O hydrogen bonds (Fig. 2a and Table 1). These hydrogen bonding interactions connect the MV²⁺ cations and POM anions to form a 2D plane (Fig. 2b) and finally a 3D supramolecular network (Fig. 2c).

  Figure 1

  

  Figure 1.  Structures of the asymmetric units of compounds 1 (a) and 2 (b)

  All hydrogen atoms except water and the disordered atoms are omitted for clarity.

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  Figure 2

  

  Figure 2.  (a) Hydrogen-bond interactions in compound 1; (b) View of a 2D layer; (c) 3D network along the a-axis

  Symmetry codes: ^ⅰ 1-x, -y, 1-z; ^ⅱ-x, -y, -z; ^ⅲ -x, 2-y, 1-z; ^ⅳ x, 1+y, 1+z; ^ⅴ 1 -x, 1-y, 1-z; ^ⅵ x, y, 1+z; ^ⅶ x, 1+y, z; ^ⅷ 1+x, y-1, z.

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  Table 1

  

  Table 1.  Hydrogen-bonding parameters of compound 1

  下载: 导出CSV

  D—H···A	d(D—H) / nm	d(H···A) / nm	d(D···A) / nm	∠D—H···A / (°)
  O1W—H1WA···O5	0.085	0.221	0.301(4)	157
  O1W—H1WB···O7ⅰ	0.085	0.244	0.327(4)	166
  O2W—H2WA···O27	0.085	0.201	0.284(4)	166
  O2W—H2WB···O29ⅱ	0.085	0.217	0.295(5)	151
  C2—H2···O11ⅲ	0.093	0.236	0.328(4)	171
  C3—H3···O2Wⅳ	0.093	0.269	0.345(6)	140
  C5—H5···O2	0.093	0.239	0.331(4)	171
  C6—H6···O1	0.093	0.257	0.318(5)	123
  C7—H7A···O37ⅴ	0.096	0.255	0.345(5)	157
  C7—H7B···O36ⅵ	0.096	0.259	0.322(4)	123
  C9—H9···O27ⅳ	0.093	0.242	0.317(4)	138
  C11—H11···O2	0.093	0.252	0.343(4)	167
  C12—H12···O32ⅰ	0.093	0.265	0.339(4)	137
  C13—H13C···O32ⅶ	0.096	0.264	0.346(4)	144
  C15—H15···O16ⅴ	0.093	0.245	0.330(4)	152
  C17—H17···O38	0.093	0.262	0.355(4)	177
  C19—H19A···O12ⅷ	0.096	0.252	0.332(4)	141
  C19—H19C···O3ⅰ	0.096	0.248	0.320(5)	132
  C20—H20···O14ⅷ	0.093	0.264	0.330(4)	128
  C21—H21···O5	0.093	0.265	0.341(4)	139
  C23—H23···O38	0.093	0.247	0.333(4)	154
  C24—H24···O39	0.093	0.250	0.323(3)	136
  Symmetry codes: ⅰ 1-x, -y, 1-z; ⅱ -x, -y, -z; ⅲ -x, 2-y, 1-z; ⅳ x, 1+y, 1+z; ⅴ 1-x, 1-y, 1-z; ⅵ x, y, 1+z; ⅶ x, 1+y, z; ⅷ 1+x, y-1, z.

  Compound 2 crystallizes in a monoclinic P2₁/n space group. The asymmetric unit contains a half of [Mo₈O₂₆]^4- unit and an EV²⁺ cation (Fig. 1b). The Mo₈ unit exhibits a classic α-type [Mo₈O₂₆]^4- anion. As shown in Fig. 3a, each EV²⁺ cation is connected to six neighbouring [Mo₈O₂₆]^4- ions via the C—H···O hydrogen bonding interactions (Table 2). These hydrogen bonding interactions connect the EV²⁺ cations and [Mo₈O₂₆]^4- anions to form a 3D supramolecular network (Fig. 3b).

  Figure 3

  

  Figure 3.  (a) Hydrogen bonding interactions of compound 2; (b) 3D network along the a-axis

  Symmetry codes: ^ⅰ x-0.5, 1.5-y, 0.5+z; ^ⅱ x-1, y, z; ^ⅲ 1-x, 1-y, 2-z; ^ⅳ 1-x, 2-y, 2-z; ^ⅴ x, 1+y, z; ^ⅵ 1.5-x, 0.5+y, 1.5-z; ^ⅶ x-0.5, 1.5-y, z-0.5.

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  Table 2

  

  Table 2.  Hydrogen-bonding parameters of compound 2

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  D—H···A	d(D—H) /nm	d(H···A) /nm	d(D···A) /nm	∠D—H···A /(°)
  C2—H2A···O8ⅰ	0.097	0.253	0.325(3)	131
  C2—H2B···O5ⅱ	0.097	0.243	0.324(2)	141
  C3—H3···O4ⅲ	0.093	0.238	0.309(2)	133
  C4—H4···O11	0.093	0.242	0.332(2)	161
  C5—H5···O9ⅳ	0.093	0.269	0.338(3)	132
  C6—H6···O8ⅰ	0.093	0.258	0.331(3)	136
  C9—H9···O10	0.093	0.244	0.318(3)	136
  C10—H10···O9	0.093	0.269	0.350(2)	146
  C11—H11···O13ⅴ	0.093	0.253	0.346(2)	177
  C12—H12···O12ⅴ	0.093	0.251	0.310(2)	122
  C13—H13B···O8ⅵ	0.097	0.248	0.338(3)	154
  C14—H14A···O9ⅵ	0.096	0.248	0.327(3)	139
  C14—H14C···O4ⅶ	0.096	0.249	0.334(3)	148
  Symmetry codes: ⅰ x-0.5, 1.5-y, 0.5+z; ⅱ x-1, y, z; ⅲ 1-x, 1-y, 2-z; ⅳ 1-x, 2-y, 2-z; ⅴ x, 1+y, z; ⅵ 1.5-x, 0.5+y, 1.5-z; ⅶ x-0.5, 1.5-y, z-0.5.

  It is noticeable that the bipyridyl rings in compound 1 are almost in a plane with the dihedral angles of 12.5(2)° and 14.2(2)° for the bipyridyl with N3/N4 and N1/N2 atoms, respectively, while the bipyridyl rings in compound 2 are non-planar due to a large dihedral angle of 58.5(2)°.

  2.2   FTIR and PXRD

  IR spectra of compounds 1 and 2 are shown in Fig. S1. As for 1, a broad peak at 3 447 cm^-1 is attributed to the O—H vibration of water. The weak peak at 2 917 cm^-1 is assigned to the C—H stretching vibration. A band at 1 639 cm^-1 can be attributed to the —C=N stretching vibration of the pyridyl ring. In addition, the four bands at 957, 884, 802 and 671 cm^-1 are the characteristic peaks of the [HPW₂^ⅤW₁₀^ⅥO₄₀]^4- anion. As for 2, the weak peak at 2 978 cm^-1 is assigned to the C—H stretching vibration. A band at 1 636 cm^-1 can be attributed to the —C=N stretching vibration of the pyridyl ring. In addition, the four bands at 932, 837, 798 and 661 cm^-1 are the characteristic peaks of the [Mo₈O₂₆]^4- unit.

  As shown in Fig. S2, the PXRD patterns of as-synthesized samples of compounds 1 and 2 were consistent with the simulated results, demonstrating the high phase purity of the bulk samples.

  2.3   Photochromism

  The photochromic properties of compounds 1 and 2 were studied in detail. When 1 and 2 were exposed to a 300 W mercury lamp at room temperature, the colour of 1 did not change significantly, while 2 showed a sensitive colour change from yellow to grey within 1 min to give sample 2g (Fig. 4). When the sample 2g was heated at 120 ℃ for 1 h, its colour turned into a faint yellow (2-decoloured). The sample 2-decoloured can change back to 2g after being illuminated again. These changes have been demonstrated by solid-state UV-Vis spectra (Fig. 5a). In addition, at the same illumination under the nitrogen atmosphere, 2 can also show the same colour change, indicating that the photochromism of 2 is not affected in the presence of oxygen (Fig.S4).

  Figure 4

  

  Figure 4.  Transformation among samples 2, 2g and 2-decoloured and their colour changes

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  Figure 5

  

  Figure 5.  (a) Solid-state UV-Vis spectra of 2 and 2g; (b) ESR spectra of 2 and 2g

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  To clarify the photochromic mechanism of compound 2, ESR spectra and theoretical calculations were carried out. Before illumination, 2 did not show any ESR signal. However, when 2 was exposed to a mercury lamp, an obvious ESR peak appeared immediately with g=2.005 7, which can be attributed to EV⁺· radical (Fig. 5b) ^[32], revealing that there is an electron transfer between the cation and anion. As we know from the crystal structure analysis, the most favourable electron transfer path between the [Mo₈O₂₆]^4- anion and the EV²⁺ cation is from the O atom of POM to the N atom of pyridine. As shown in Fig. 6a, there is a strong p···π interaction between the O2 of POM and the pyridyl (py) ring with a distance of 0.291 nm for O2^ⅴ···π (N2-py) and 0.309 nm for O2^ⅲ···π (N1-py), which is significantly shorter than the known distance (0.382 nm) of the related electron donor and acceptor^[33]. Moreover, further evidence can be obtained from the theoretical calculation of electrostatic potential on the surface of molecules. As shown in Fig. 6b, the red region around the EV²⁺ cation and the blue region around the POM anion represent the electron-deficient and electron-rich units, respectively^{[22, 34-35]}. This result indicated that the POM anion is a good electron donor, the EV²⁺ cation is a good electron acceptor, and electron transfer can occur easily between the anion and cation under light. Therefore, the photochromic mechanism of 2 is due to the photo-induced electron transfer.

  Figure 6

  

  Figure 6.  (a) p···π interactions between the O2 of POM and the py ring in compound 2; (b) Surface electrostatic potential diagram of 2

  Symmetry codes: ^ⅲ 1-x, 1-y, 2-z; ^ⅴ x, 1+y, z; Materials Studio 2020 version; the GGA‑ PBE function was used to calculate the electrostatic potential of the system on the DNP basis set, with other settings set to the default Fine accuracy of the system.

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  2.4   Photocatalytic degradation of organic dyes

  It is worthwhile to note that the viologen-POM hybrids have seldom been observed to be used as photocatalysts for the degradations of organic dyes up to now^[16]. Hence, it is interesting to explore the photocatalytic activities of compounds 1 and 2 in the degradations of organic dyes like MB, PH and R6G under light irradiation. Our preliminary experimental results indicated that the absorption peaks of MB, PH and R6G decreased to some extent as time went by (Fig. S5). Based on these results, the time-dependent concentration changes of the dyes with UV irradiation in the presence of 1 and 2 can be calculated and shown in Fig. 7a. As shown in Fig. 7b, after irradiation for 2 h on MB and PH, and 80 min on R6G solution, the degradation rates of MB, PH, R6G by 1 were 96.4%, 40.9% and 94.2%, respectively. The corresponding values by 2 were 83.0%, 96.6% (100 min) and 66.1%, respectively. 1 shows an efficient photodegradation on both MB and R6G dyes, while 2 exhibits an excellent photodegradation performance on the PH solution. Notably, the photocatalytic activities of 1 and 2 are at the top as compared with the other related photocatalysts (Table S4). Furthermore, the structural stabilities of 1 and 2 after the photodegradation are still maintained, as confirmed by the PXRD patterns (Fig.S6).

  Figure 7

  

  Figure 7.  (a) Time-dependent concentration changes of the dye (MB, PH and R6G) solutions with UV irradiation in the presence of compounds 1 and 2; (b) Degradation rates of the dyes by 1 and 2

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  3.   Conclusions

  Two viologen-POM hybrid materials, (MV)₂ [HPW₂^ⅤW₁₀^ⅥO₄₀]2·2H₂O (1) and (EV)₂[Mo₈O₂₆] (2) have been synthesized by using the MV²⁺ and EV²⁺ cations to combine with the POM anions. 2 shows a sensitive photochromic change with a response time of 1 min. 1 indicates an efficient photodegradation on both MB and R6G dyes, while 2 exhibits an excellent photodegradation performance on PH dye. This result may provide a general method to prepare promising organic-inorganic hybrids with good functions.

  
  Supporting information is available at http://www.wjhxxb.cn
  
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  Figure 1  Structures of the asymmetric units of compounds 1 (a) and 2 (b)

  All hydrogen atoms except water and the disordered atoms are omitted for clarity.

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  Figure 2  (a) Hydrogen-bond interactions in compound 1; (b) View of a 2D layer; (c) 3D network along the a-axis

  Symmetry codes: ^ⅰ 1-x, -y, 1-z; ^ⅱ-x, -y, -z; ^ⅲ -x, 2-y, 1-z; ^ⅳ x, 1+y, 1+z; ^ⅴ 1 -x, 1-y, 1-z; ^ⅵ x, y, 1+z; ^ⅶ x, 1+y, z; ^ⅷ 1+x, y-1, z.

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  Figure 3  (a) Hydrogen bonding interactions of compound 2; (b) 3D network along the a-axis

  Symmetry codes: ^ⅰ x-0.5, 1.5-y, 0.5+z; ^ⅱ x-1, y, z; ^ⅲ 1-x, 1-y, 2-z; ^ⅳ 1-x, 2-y, 2-z; ^ⅴ x, 1+y, z; ^ⅵ 1.5-x, 0.5+y, 1.5-z; ^ⅶ x-0.5, 1.5-y, z-0.5.

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  Figure 4  Transformation among samples 2, 2g and 2-decoloured and their colour changes

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  Figure 5  (a) Solid-state UV-Vis spectra of 2 and 2g; (b) ESR spectra of 2 and 2g

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  Figure 6  (a) p···π interactions between the O2 of POM and the py ring in compound 2; (b) Surface electrostatic potential diagram of 2

  Symmetry codes: ^ⅲ 1-x, 1-y, 2-z; ^ⅴ x, 1+y, z; Materials Studio 2020 version; the GGA‑ PBE function was used to calculate the electrostatic potential of the system on the DNP basis set, with other settings set to the default Fine accuracy of the system.

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  Figure 7  (a) Time-dependent concentration changes of the dye (MB, PH and R6G) solutions with UV irradiation in the presence of compounds 1 and 2; (b) Degradation rates of the dyes by 1 and 2

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  Table 1.  Hydrogen-bonding parameters of compound 1

  D—H···A	d(D—H) / nm	d(H···A) / nm	d(D···A) / nm	∠D—H···A / (°)
  O1W—H1WA···O5	0.085	0.221	0.301(4)	157
  O1W—H1WB···O7ⅰ	0.085	0.244	0.327(4)	166
  O2W—H2WA···O27	0.085	0.201	0.284(4)	166
  O2W—H2WB···O29ⅱ	0.085	0.217	0.295(5)	151
  C2—H2···O11ⅲ	0.093	0.236	0.328(4)	171
  C3—H3···O2Wⅳ	0.093	0.269	0.345(6)	140
  C5—H5···O2	0.093	0.239	0.331(4)	171
  C6—H6···O1	0.093	0.257	0.318(5)	123
  C7—H7A···O37ⅴ	0.096	0.255	0.345(5)	157
  C7—H7B···O36ⅵ	0.096	0.259	0.322(4)	123
  C9—H9···O27ⅳ	0.093	0.242	0.317(4)	138
  C11—H11···O2	0.093	0.252	0.343(4)	167
  C12—H12···O32ⅰ	0.093	0.265	0.339(4)	137
  C13—H13C···O32ⅶ	0.096	0.264	0.346(4)	144
  C15—H15···O16ⅴ	0.093	0.245	0.330(4)	152
  C17—H17···O38	0.093	0.262	0.355(4)	177
  C19—H19A···O12ⅷ	0.096	0.252	0.332(4)	141
  C19—H19C···O3ⅰ	0.096	0.248	0.320(5)	132
  C20—H20···O14ⅷ	0.093	0.264	0.330(4)	128
  C21—H21···O5	0.093	0.265	0.341(4)	139
  C23—H23···O38	0.093	0.247	0.333(4)	154
  C24—H24···O39	0.093	0.250	0.323(3)	136
  Symmetry codes: ⅰ 1-x, -y, 1-z; ⅱ -x, -y, -z; ⅲ -x, 2-y, 1-z; ⅳ x, 1+y, 1+z; ⅴ 1-x, 1-y, 1-z; ⅵ x, y, 1+z; ⅶ x, 1+y, z; ⅷ 1+x, y-1, z.

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  Table 2.  Hydrogen-bonding parameters of compound 2

  D—H···A	d(D—H) /nm	d(H···A) /nm	d(D···A) /nm	∠D—H···A /(°)
  C2—H2A···O8ⅰ	0.097	0.253	0.325(3)	131
  C2—H2B···O5ⅱ	0.097	0.243	0.324(2)	141
  C3—H3···O4ⅲ	0.093	0.238	0.309(2)	133
  C4—H4···O11	0.093	0.242	0.332(2)	161
  C5—H5···O9ⅳ	0.093	0.269	0.338(3)	132
  C6—H6···O8ⅰ	0.093	0.258	0.331(3)	136
  C9—H9···O10	0.093	0.244	0.318(3)	136
  C10—H10···O9	0.093	0.269	0.350(2)	146
  C11—H11···O13ⅴ	0.093	0.253	0.346(2)	177
  C12—H12···O12ⅴ	0.093	0.251	0.310(2)	122
  C13—H13B···O8ⅵ	0.097	0.248	0.338(3)	154
  C14—H14A···O9ⅵ	0.096	0.248	0.327(3)	139
  C14—H14C···O4ⅶ	0.096	0.249	0.334(3)	148
  Symmetry codes: ⅰ x-0.5, 1.5-y, 0.5+z; ⅱ x-1, y, z; ⅲ 1-x, 1-y, 2-z; ⅳ 1-x, 2-y, 2-z; ⅴ x, 1+y, z; ⅵ 1.5-x, 0.5+y, 1.5-z; ⅶ x-0.5, 1.5-y, z-0.5.

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