English

• Coordination polymers (CPs) are crystalline materials constructed by conformationally rigid or flexible organic ligands with different inorganic metal centers^[1-3]. Typically, the self-assembly process of CPs is controllable to achieve targeting CPs with intriguing topologies, high thermal stabilities and desirable attributes through rational design of rigid organic components^[4-5]. So, rigid ligands with aromatic multi-carboxyl, pyridyl or imidazolyl moieties are employed widely, yielding prolific production of CPs^[6-10]. And the self-assembly process becomes challengeable when the flexible organic components are used^[11-12]. As we all known, molecular flexibility is derived from the sp³-hybridized carbon atom, allowing rotation about C-C single bond and different conformational preference^[13]. In terms of CPs, the ultimate conformations of flexible ligands are sensitive to many factors, such as the versatile coordination geometries of metal ions, co-existing substituent groups, auxiliary rigid ligands, counter ions, pH value and temperature^[14-17]. Indeed, it has been demonstrated that conformational freedom may provide rare opportunities to generate CPs with structural diversity which is inaccessible from rigid ligands, chiral centers and dynamic behavior^[18-21].

  Particularly, others and our team have endeav-ored to the investigations of CPs assembled from homophthalic acid (H₂hmph)^[22-30]. As an asymmetric flexible ligand possessing both rigid -COOH group and flexible -CH₂COOH group, homophthalic acid has been used to construct CPs with structures from discrete, 1D chain, 2D lamella, 2D thick-layer, 3D microporous framework to 3D→3D self-penetrated net. And these limited studies have proven that homophthalic acid is an efficient flexible ligand, which can provide strong coordination capability and versatile coordination modes. To broaden our knowledge of the coordination chemistry of homoph-thalic acid ligand, 1, 4-bis(1-imidazolyl)benzene (bib) and 3, 5-bis(1-imidazolyl)pyridine (bip) were intro-duced into the assembled systems of CPs. As novel diimidazolyl-type ligands, two imidazolyl rings in their structures are spaced by phenyl ring and pyridiyl ring, respectively. Additionally, the places of imidazolyl rings attached to phenyl ring and pyridiyl ring are different from each other. Distinct electronic cloud densities and spatial effects can influence the structures and properties of the resulted CPs.

  In this work, we obtained three coordination polymers, namely {[Ni₂(hmph)₂(bib)₂(H₂O)₂]·3H₂O}_n (1), [Cd(hmph)(bib)]_n (2) and {[Zn(hmph)(bip)]·H₂O}_n (3). And the preparations, crystal structures, thermal stabilities, magnetic property for complex 1 and fluorescent properties for 2 and 3 are described as below.

  1.   Experimental

  1.1   Materials and methods

  All chemical reagents were purchased from reagent companies and used directly without any purification. Elemental analyses (C, H and N) were performed on a Flash EA 2000 elemental analyzer. Infrared spectra (IR) were measured by a Nicolet 6700 FT-IR spectrophotometer. The powder X-ray diffraction determinations (PXRD) were recorded by using a Bruker AXS D8 Advance diffractometer with mono-chromated Cu Kα radiation (λ=0.154 18 nm; generator current: 40 mA; generator voltage: 40 kV; scanning range: 5°~50°). The thermogravimetric analysis experi-ments (TGA) were carried out on a SII EXStar6000 TG/DTA6300 analyzer at a heating rate of 10 ℃·min^-1 under N₂ atmosphere. Variable-temperature magnetic susceptibility measurement was performed on a Quantum Design SQUID MPMS XL-7 instrument from 2.5 to 300 K under an applied magnetic field of 2 000 Oe. Luminescence spectra were performed on a Hitachi F-7000 spectrophotometer at room temperature.

  1.2   Preparation of the complexes

  All three complexes were realized through facile solvothermal method. Starting materials were placed in a 7 mL penicillin bottle and sealed in 23 mL PTFE-lined stainless steel autoclave. The reactor was heated to given temperature (120 ℃ for 1 and 2, 160 ℃ for 3) under autogenous pressure for 3 days and then cooled naturally to room temperature. The crystals were dried and collected after they were washed with distilled water and ethanol. The phase purities of all three complexes were confirmed by PXRD measure-ments at room temperature. Each PXRD pattern of the as-synthesized sample agrees well with the simulated one based on the structure solutions, indicative of the purity of the bulk sample (Supporting information, Fig. S1, S2 and S3).

  Synthesis of {[Ni₂(hmph)₂(bib)₂(H₂O)2]·3H₂O}_n (1): In the presence of aqueous NaOH solution (0.5 mol·L^-1, 0.1 mL), the mixture of homophthalic acid (0.1 mmol, 18.0 mg), 1, 4-bis(1-imidazolyl)benzene (0.1 mmol, 21.0 mg), Ni(OAc)₂·4H₂O (0.2 mmol, 49.8 mg) was suspended in distilled water (6.0 mL), giving green sheet crystals after solvothermal reaction (56% based on Ni). Anal. Calcd. for C₄₂H₄₂Ni₂N₈O₁₃(%): C, 51.25; H, 4.30; N, 11.39. Found(%): C, 51.22; H, 4.36; N, 11.34. IR (cm^-1): 3 427(w), 3 130(w), 1 551(s), 1 521(s), 1 379(s), 1 303(m), 1 228(w), 1 062(s), 960(m), 934(m), 863(w), 829(m), 814(m), 728(s), 651(s).

  Synthesis of [Cd(hmph)(bib)]_n (2). In the presence of aqueous HAc solution (0.5 mol·L^-1, 0.2 mL), the mixture of homophthalic acid (0.1 mmol, 18.0 mg), 1, 4-bis(1-imidazolyl)benzene (0.2 mmol, 42.0 mg), Cd(OAc)₂ ·2H₂O (0.2 mmol, 53.3 mg) and H₂O (6.0 mL) gave colourless blocked crystals after solvothermal reaction (72% based on Cd). Anal. Calcd. for C₂₁H₁₆CdN₄O₄(%): C, 50.37; H, 3.22; N, 11.19. Found(%): C, 50.32; H, 3.25; N, 11.27. IR (cm^-1): 3 119(w), 1 576(s), 1 524(s), 1 490(m), 1 384(s), 1 302(s), 1 271(m), 1 133(s), 1 103(s), 1 065(s), 1 051(s), 955(s), 928(m), 839(s), 821(s), 732(s), 701(m), 667(s).

  Synthesis of {[Zn(hmph)(bip)]·H₂O}_n (3). The mixture of homophthalic acid (0.1 mmol, 18.0 mg), 3, 5-bis(1-imidazolyl)pyridine (0.2 mmol, 42.0 mg), Zn(OAc)₂ ·2H₂O (0.2 mmol, 43.9 mg) was suspended in H₂O-methanol solution (6 mL, 2:1, V/V), giving colourless blocked crystals after solvothermal reaction (54% based on Zn). Anal. Calcd. for C₂₀H₁₇ZnN₅O₅(%): C, 50.81; H, 3.62; N, 14.81. Found(%): C, 50.77; H, 3.65; N, 14.76. IR (cm^-1): 3 441(w), 3 128(w), 1 634(s), 1 585(s), 1 559(s), 1 503(s), 1 383(s), 1 361(s), 1 312(m), 1 256(s), 1 110(s), 1 061(s), 1 005(m), 956(m), 941(m), 878(s), 840(s), 728(s), 691(s), 646(s).

  1.3   X-ray crystallography

  Single-crystal X-ray diffraction data for complexes 1~3 were collected on a Bruker SMART APEX Ⅱ CCD diffractometer equipped with graphite-monochromated Mo Kα radiation (λ=0.071 073 nm). Using Olex2 software, all three structures were solved by direct method and refined with SHElXL-2015 refinement package by least squares minimisation^[31-33]. Hydrogen atoms were fixed at their calculated positions with the riding model. The Uiso values for H atoms of organic ligands were 1.2 times U_eq of their attached carbon atoms, and they were 1.5 times U_eq of their attached oxygen atoms for the hydrogen atoms at water. The details of the structure solution and final refinements are listed in Table 1.

  Table 1

  

  Table 1.  Crystal and structure refinement data for complexes 1~3

  下载: 导出CSV

  	1	2	3
  Empirical formula	C42H42Ni2N8O13	C21H16CdN4O4	C20H17ZnN5O5
  Formula weight	984.25	500.78	472.76
  Crystal system	Monoclinic	Triclinic	Triclinic
  Space group	P21/n	P1	P1
  a / nm	1.328 32(11)	0.787 9(6)	0.893 56(5)
  b / nm	0.902 68(7)	0.991 7(7)	1.046 85(6)
  c / nm	1.810 85(15)	1.326 1(9)	1.121 85(6)
  α / (°)		73.638(15)	67.482 0(10)
  β / (°)	105.115(2)	78.862(17)	81.466 0(10)
  γ/ (°)		73.637(15)	73.942 0(10)
  V / nm3	2.096 2(3)	0.946 6(12)	0.930 51(9)
  Z	2	2	2
  Dc / (g·cm-3)	1.559	1.757	1.687
  μ / mm-1	0.976	1.192	1.367
  F(000)	1 020	500	484
  θ range / (°)	3.414~50.122	3.226~50.602	3.934~51
  Reflection collected, unique	13 126, 3 711	6 178, 3 396	6 257, 3 452
  Rint	0.041 6	0.020 0	0.013 8
  Completeness to θ / %	99.9	98.9	99.7
  Data, restraint, parameter	3 711, 12, 298	3 396, 0, 271	3 452, 0, 280
  Goodness-of-fit	1.038	1.061	1.056
  R1	0.035 9	0.020 7	0.023 2
  wR2 [I>2σ(I)]	0.087 0	0.051 1	0.061 0
  R1 (all data)	0.047 1	0.022 7	0.024 7
  wR2 (all data)	0.094 1	0.053 2	0.061 9
  (Δρ)max and (Δρ)min / (e·nm-3)	410, -530	360, -330	260, -360

  CCDC: 1935595, 1; 1935596, 2; 1935599, 3.

  2.   Results and discussion

  2.1   Crystal structure

  2.1.1   Structural description of {[Ni₂(hmph)₂(bib)₂ (H₂O)₂]·3H₂O}_n (1)

  Complex 1 belongs to the monoclinic crystal system of P2₁/n space group. The asymmetric unit consists of one Ni(Ⅱ) cation, one completely deproto-nated hmph^2- dianion, one bib molecule, one coor-dinating water molecule and one and a half guest water molecules, as shown in Fig. 1a. The unique Ni atom displays a [NiO4N₂] octahedral geometry with the coordination sphere defined by three oxygen atoms from two symmetry related hmph^2- moieties, the last one oxygen atom from one coordinating water and two N atoms from two bib. The Ni-O bond lengths range from 0.206 17(19) to 0.209 57(17) nm, while the Ni-N bond lengths are 0.206 3(2) and 0.207 5(2) nm. The [NiO₄N₂] units are connected by the flexible -CH₂COO^- groups in bridging bidentate mode to form a metal-carboxylate chain with the intrachain Ni…Ni separa-tion of 0.533 83(5) nm, wherein the O-C-C-C-C-C-O-Ni eight-membered rings are fabricated by the coop-eration of the rigid -COO^- groups in monodentate mode and the -CH₂COO^- groups (Fig. 1b). And the 1D motifs are further bridged by the bib molecules along c direction to generate an irregular metal-organic monolayer paralleling to bc plane, in which the Ni…Ni separations are 1.361 95(9) nm and 1.356 28(10) nm (Fig. 1c). This monolayer employs the mentioned eight-membered rings acting as pendent arms above and below. Moreover, the adjacent bib bridges are of certain angle and every other bib bridges are parallel, probably because of the spatial effect resulting from the eight-membered rings. Particularly, the presence of coordinated and free water molecules leads to the formation of abundant H-bonding interactions. Through the cooperations of O(5W)-H(5WB)…O(6W) (O…O 0.280 3(3) nm, ∠O-H…O=173.1°) with O(6W)- H(6WA)…O(4)^ⅲ (O…O 0.326 0(4) nm, ∠O-H…O=150.8°), O(6W)-H(6WB…O(3)^ⅲ (O…O 0.282 3(4) nm, ∠O-H…O=128.2°), O(7W)-H(7WA)…O(6W) (O…O 0.298 3(8) nm, ∠O-H…O=152.6°) and O(7W)- H(7WB) …O(3)^ⅲ (O…O 0.278 2(7) nm, ∠O-H…O=159.3°), individual layers are stacked to create the whole 3D supramolecular structure (Fig. 1d).

  Figure 1

  

  Figure 1.  (a) View of coordination environment of Ni(Ⅱ) in complex 1; (b) View of Ni-carboxylate chain spaced by carboxylate ligands; (c) View of monolayer structure lying in bc plane; (d) 3D supramolecular structure fabricated by H-bonding interactions labeled as dark dotted lines

  Symmetry codes: ^ⅰ-x+1/2, y-1/2, -z+1/2; ^ⅱ-x, -y+2, -z+1; ^ⅲ -x+1, -y+2, z; Displacement ellipsoids are drawn at the 50% probability level and all hydrogen atoms of carbon atoms are omitted for clarity

  下载: 全尺寸图片 幻灯片

  2.1.2   Structural description of [Cd(hmph)(bib)]_n (2)

  Complex 2 crystallizes in the triclinic crystal system of P1 space group. The asymmetric unit is comprised of one Cd(Ⅱ) cation, one completely deprotonated hmph^2- dianion and one bib molecule, as shown in Fig. 2a. The center Cd ion displays a [CdO₄N₂] octahedral geometry with the coordination sphere defined by four oxygen atoms from three symmetry related hmph^2- dianions, and two terminal N atoms from two bib molecules. All Cd-O bond lengths fall in a range from 0.224 9(2) to 0.277 39(14) nm, while the Cd-N bond lengths are 0.228 0(2) and 0.230 2(2) nm. Two Cd octahedra are double bridged by two -CH₂COO^- groups to form one dinuclear kernel with the Cd…Cd separation of 0.398 31(21) nm (Fig. 2b). These adjacent dinuclear units are further connected to generate a double-stranded chain along a direction through μ₂-hmph^2- dianion with -COO^- groups in chelating coordination mode and -CH₂COO^- groups in bridging bidentate mode. And in such manner, an alternating arrangement of 8-membered and 16-membered metal-organic ring is fabricated. Furthermore, the 1D chains are bridged by μ₂-bib ligands to produce a 2D bilayer (Fig. 2c). Individual layers are stacked to create the ultimate 3D supra-molecular structure by weak van der Waals forces since there are only intralayer π-π stacking interac-tions between the phenyl rings of bib molecules with the centroid-centroid distances of 0.378 33(19) nm.

  Figure 2

  

  Figure 2.  (a) View of coordination environment of Cd(Ⅱ) in complex 2; (b) View of Cd-carboxylate chain containing an alternating arrangement of 8-membered and 16-membered rings; (c) View of 2D bilayer with intralayer π-π interactions

  Symmetry codes: ^ⅰ x-1, y, z+1; ^ⅱ x+1, y, z; ^ⅲ-x+1, -y+1, -z+1; Displacement ellipsoids are drawn at the 50% probability level and all hydrogen atoms of carbon atoms are omitted for clarity

  下载: 全尺寸图片 幻灯片

  2.1.3   Structural description of {[Zn(hmph)(bip)]·H₂O}_n (3)

  Complex 3 also crystallizes in the triclinic crystal system of P1 space group. The asymmetric unit comp-rises one Zn(Ⅱ) cation, one completely deprotonated hmph^2- dianion, one bip molecule and one uncoor-dinated water molecule, as shown in Fig. 3a. The centre Zn ion exhibits a [ZnN₂O₂] tetrahedral geometry with the coordination sphere defined by two oxygen atoms from two symmetry related hmph^2- dianions, and two N atoms from two bip molecules. The Zn-O bond lengths are 0.194 06(13) and 0.194 72(12) nm. The Zn-N bond lengths are 0.200 76(14) and 0.204 89(14) nm. Two neighbor tetrahedra are double bridged by two μ₂-hmph^2- dianions adopting monodentate mode to form one dinuclear unit with the Zn…Zn separation of 0.537 52(2) nm (Fig. 3b). Meanwhile, one 16-membered metal-organic ring is observed. The ancillary μ₂-bip ligand molecules link adjacent dinuclear units to form a double-stranded chain structure. Individual chains are propagated to 2D layer structure through only two kinds of H-bonds originating from the uncoordinated water molecules and organic ligands (Fig. 3c). Moreover, there are obvious intralayer π-π stacking interactions between the pyridine rings of bip molecules with the centroid-centroid distances of 0.390 97(2) nm (Fig. 3d). So, the ultimate 3D supramolecular structure of complex 3 is maintained by weak van der Waals forces only.

  Figure 3

  

  Figure 3.  (a) View of coordination environment of Zn(Ⅱ) in complex 3; (b) View of Zn-organic chain based on dinuclear units containing 16-membered rings; (c) View of 2D layer structure propagated through only two kinds of H-bonds labeled as dark dotted lines; (d) Intralayer π-π stacking interaction between the pyridine rings of bip molecules

  Symmetry codes: ^ⅰ-x+2, -y+2, -z; ^ⅱ x+1, y-1, z; Displacement ellipsoids are drawn at the 50% probability level and all hydrogen atoms of carbon atoms are omitted for clarity

  下载: 全尺寸图片 幻灯片

  2.2   Thermogravimetric analyses

  TGA experiments for complexes 1~3 were carried out to monitoring their thermal stability, as shown in Fig. 4. For complex 1, the TGA curve illustrated one distinct weight loss from 160 to 197 ℃, equivalent to two and a half water molecules (Calcd. 9.14%, Obsd. 8.70%). And the succeeding weight-loss between 267 and 402 ℃ can be assigned to the decomposition of organic components. The final residue is attributed to NiO phase (Calcd. 15.18%, Obsd. 16.29%). Complex 2 can survive before 304 ℃ and then decomposed with a two-step weight loss until 515 ℃. The residue weighing 25.49% of the total sample corresponds to the CdO component (Calcd. 25.64 %). The TGA curve of complex 3 showed the removal of one guest water molecule from 155 to 227 ℃ with a slight weight loss (Calcd. 3.81%, Obsd. 3.59%). And two sharp weight-loss processes were obseved within a range of 292 to 545 ℃, which are attributed to the collapse of the framework. The remnant holding a weight of 25.37% may be the mixture of ZnO (Calcd. 17.21%) and unburned carbon^[34].

  Figure 4

  

  Figure 4.  TGA curves for complexes 1~3

  下载: 全尺寸图片 幻灯片

  2.3   Magnetic property

  In the metal-carboxylate chain structure of complex 1, the separation distance between two adjacent Ni(Ⅱ) ions is 0.533 83(5) nm, indicating that there are magnetic interactions exchanged by carboxylate bridges of the -CH₂COO^- groups along the chain. So the temperature-dependent magnetic susceptibility was measured at an applied magnetic field of 2 000 Oe from 2.5 to 300 K. And the curves of χ_MT vs T and χ_M vs T are shown in Fig. 5. The observed χ_MT at 300 K was 1.05 cm³·K·mol^-1, which was near to the expected spin-only product of 1.00 cm³·mol^-1·K for a uncoupled Ni(Ⅱ) ion. Upon cooling, it kept almost the same level in a wide temperature range of 76 to 300 K. Below 76 K, the χ_MT increased dramatically and reached to a maximum of 1.86 cm³·mol^-1·K at 2.5 K. And similar change occurred in the curve of χ_M vs T. Because complex 1 can magnetically be handled as infinite uniform chains, the magnetic interaction (J) between two adjacent Ni(Ⅱ) ions can be estimated by using the classical spin expression derived from isotropic Heisenberg spin Hamiltonian chains^[35-36]:

  $ \begin{array}{l} {\hat{H}=-J \sum S_{i} S_{i+1}} \\ {\chi_{\mathrm{M}}=\left[N g^{2} \beta^{2} S(S+1) / 3(k T)\right][(1+u) /(1-u)]} \end{array} $

  (1)

  Figure 5

  

  Figure 5.  Temperature dependences of magnetic susceptibility χ_M (○) and χ_MT (□) for complex 1

  下载: 全尺寸图片 幻灯片

  In Eq.(1), u is the Langevin function defined as u=coth[JS(S+1)/(kT)]-kT/[JS(S+1)] with S=1, while other parameters represent their usual meanings. The magnetic data of complex 1 fitted well with Eq.(1) in the whole temperature range. And the best fit led to fitting parameters as following: J=1.01 cm^-1, g=2.04 and R=2.8×10^-4. Furthermore, these magnetic data obey the Curie-Weiss law χ_M=C/(T-θ) from 2.5 to 300 K with Weiss constant θ=0.992 2 K, Curie constant C=1.044 3 cm³·K·mol^-1 and R=0.999 96. The positive J value and θ value, together with the increase of χ_MT value indicate that there are typical ferromagnetic exchange coupling between two adjacent Ni(Ⅱ) ions in uniform chain^[37].

  2.4   Fluorescent properties

  The fluorescent properties of complexes 2 and 3 in the solid state were investigated at room temperature, as illustrated in Fig. 6. Under excitation at 305 nm, the maximum emission peak for complex 2 appearred at ~341 nm, and complex 3 exhibited the strongest peak at ~332 nm with excitation wavelength at 275 nm. For comparison, the fluorescent behaviors of H₂hmph, bib and bip ligands were detected. Featureless emissions with the maximum at ~452 nm (λ_ex=390 nm) for H₂hmph, ~385 nm (λ_ex=314 nm) for bib and ~418 nm (λ_ex=290 nm) for bip were observed, respectively. Taking account of the inherent properties of Cd/Zn metal centers and similar emission spectra shapes of the related complexes, the fluorescent properties of complexes 2 and 3 can probably be attributed to the ligand localized emission^[38]. In comparison with the free organic precursors, obvious blue shifts of emission bands for 2 and 3 have been observed, which may be attributed to the deprotonated effect of H₂hmph ligand, and the coordination interactions of the hmph^2- and diimidazolyl-type ligands around the central metal ions^[39].

  Figure 6

  

  Figure 6.  Solid-state emission spectra of complexes 2~3 and the related ligands at ambient temperature

  下载: 全尺寸图片 幻灯片

  3.   Conclusions

  Overall, treating Ni(Ⅱ)/Cd(Ⅱ)/Zn(Ⅱ) acetate with flexible homophthalic acid and diimidazolyl-type ligands yielded three novel coordination polymers under mild solvothermal routes. Complexes 1 and 2 possess 2D monolayer and bilayer structure featuring metal-carboxylate chains cross-linked by bib co-ligands, respectively. Complex 3 is double-stranded chain featuring Zn-carboxylate binuclear units extended by bip co-ligands. All three complexes have high thermal stabilities since their frameworks begin to collapse at 267 ℃ for 1, 304 ℃ for 2 and 292 ℃ for 3. In complex 1, typical ferromagnetic exchange coupling exists between two adjacent Ni(Ⅱ) ions in uniform chain. Moreover, the solid state luminescence of complexes 2 and 3 is attributed to the ligand localized emission with significant blue-shift.

  Supporting information is available at http://www.wjhxxb.cn

  
  
• 1. [1]

     Moulton B, Zaworotko M J. Chem. Rev., 2001, 101:1629-1658 doi: 10.1021/cr9900432
     

  2. [2]

     Zhu Q L, Xu Q. Chem. Soc. Rev., 2014, 43:5468-5512 doi: 10.1039/C3CS60472A
     

  3. [3]

     Xuan W M, Zhu C F, Liu Y, et al. Chem. Soc. Rev., 2012, 41:1677-1695 doi: 10.1039/C1CS15196G
     

  4. [4]

     Kumar G, Kumar G, Gupta R. RSC Adv., 2016, 6:21352-21361 doi: 10.1039/C5RA26283F
     

  5. [5]

     Heine J, Müller-Buschbaum K. Chem. Soc. Rev., 2013, 42:9232-9242 doi: 10.1039/c3cs60232j
     

  6. [6]

     Das D, Biradha K. Cryst. Growth Des., 2018, 18:3683-3692 doi: 10.1021/acs.cgd.8b00498
     

  7. [7]

     Tang Y W, Soares A C, Ferbinteanu M, et al. Dalton Trans., 2018, 47:10071-10079 doi: 10.1039/C8DT02177E
     

  8. [8]

     Yin Z, Zhou Y L, Zeng M H, et al. Dalton Trans., 2015, 44:5258-5275 doi: 10.1039/C4DT04030A
     

  9. [9]

     肖伯安, 陈水生.无机化学学报, 2017, 33(2):347-353XIAO Bo-An, CHEN Shui-Sheng. Chinese J. Inorg. Chem., 2017, 33(2):347-353 
     

  10. [10]

      Miao S B, Li Z H, Xu C Y, et al. CrystEngComm, 2016, 18:1625-1632 doi: 10.1039/C5CE01774B
      

  11. [11]

      Lin Z J, Lü J, Hong M C, Cao R. Chem. Soc. Rev., 2014, 43:5867-5895 doi: 10.1039/C3CS60483G
      

  12. [12]

      Pigge F C. CrystEngComm, 2011, 13:1733-1748 doi: 10.1039/c0ce00417k
      

  13. [13]

      Zhang Z Y, Xu L J, Cao R. New J. Chem., 2018, 42:5593-5601 doi: 10.1039/C7NJ05125E
      

  14. [14]

      Liu T F, Lü J, Cao R. CrystEngComm, 2010, 12:660-670 doi: 10.1039/B914145F
      

  15. [15]

      Zhang X T, Chen H T, Li B, et al. Dalton Trans., 2018, 47:1202-1213 doi: 10.1039/C7DT03761A
      

  16. [16]

      王玉芳, 太军慧, 颜小伟, 等.无机化学学报, 2018, 34(6):1121-1126WANG Yu-Fang, TAI Jun-Hui, YAN Xiao-Wei, et al. Chinese J. Inorg. Chem., 2018, 34(6):1121-1126 
      

  17. [17]

      Li X L, Liu G Z, Xin L Y, et al. J. Solid State Chem., 2017, 246:252-257 doi: 10.1016/j.jssc.2016.11.030
      

  18. [18]

      Ju F Y, Li Y P, Li G L, et al. Chin. J. Struct. Chem., 2016, 35:404-412
      

  19. [19]

      Kang H X, Fu Y Q, Ju F Y, et al. Russ. J. Coord. Chem., 2018, 44:340-346 doi: 10.1134/S1070328418050020
      

  20. [20]

      Xin L Y, Liu G Z, Ma L F, et al. Inorg. Chim. Acta, 2016, 443:64-68 doi: 10.1016/j.ica.2015.12.022
      

  21. [21]

      Li G L, Liu G Z, Ma L F, et al. Chem. Commun., 2014, 50:2615-2617 doi: 10.1039/C3CC49106D
      

  22. [22]

      Burrows A D, Harrington R W, Mahon M F, et al. Eur. J. Inorg. Chem., 2003:766-776
      

  23. [23]

      Zhou J H, Wang Y, Wang S N, et al. J. Coord. Chem., 2013, 66:737-747 doi: 10.1080/00958972.2012.762767
      

  24. [24]

      Liu G Z, Xin L Y, Wang L Y. CrystEngComm, 2011, 13:3013-3020 doi: 10.1039/c0ce00873g
      

  25. [25]

      Farnum G A, Wang C Y, Supkowski R M, et al. Inorg. Chim. Acta, 2011, 375:280-289 doi: 10.1016/j.ica.2011.05.019
      

  26. [26]

      Wang Y, Liu Z Q, Zhou J H, et al. Inorg. Chim. Acta, 2013, 400:169-178 doi: 10.1016/j.ica.2013.02.026
      

  27. [27]

      Orhan O, Colak A T, Sahin O, et al. Polyhedron, 2015, 87:268-274 doi: 10.1016/j.poly.2014.11.028
      

  28. [28]

      Liu G Z, Zhang J, Wang L Y. Polyhedron, 2011, 30:1487-1493 doi: 10.1016/j.poly.2011.02.053
      

  29. [29]

      Rogers C M, Wang C Y, Farnum G A, et al. Inorg. Chim. Acta, 2013, 403:78-84 doi: 10.1016/j.ica.2013.01.005
      

  30. [30]

      Kraft P E, Uebler J W, Laduca R L. J. Mol. Struct., 2013, 1038:86-94 doi: 10.1016/j.molstruc.2013.01.045
      

  31. [31]

      Burla M C, Caliandro R, Camalli M, et al. J. Appl. Cryst., 2007, 40:609-613 doi: 10.1107/S0021889807010941
      

  32. [32]

      Dolomanov O V, Bourhis L J, Gildea R J, et al. J. Appl. Cryst., 2009, 42:339-341 doi: 10.1107/S0021889808042726
      

  33. [33]

      Sheldrick G M. Acta Crystallogr. Sect. C:Cryst. Struct. Commun., 2015, C71:3-8
      

  34. [34]

      Li Y P, Ju F Y, Li G L, et al. Russ. J. Coord. Chem., 2018, 44:214-219 doi: 10.1134/S1070328418030028
      

  35. [35]

      Wang W B, Wang R Y, Liu L N, et al. Cryst. Growth Des., 2018, 18:3449-3457 doi: 10.1021/acs.cgd.8b00174
      

  36. [36]

      Wang Y Q, Jia Q X, Wang K, et al. Inorg. Chem., 2010, 49:1551-1560 doi: 10.1021/ic901798y
      

  37. [37]

      Li G L, Yin W D, Liu G Z, et al. J. Solid State Chem., 2014, 220:1-8 doi: 10.1016/j.jssc.2014.08.007
      

  38. [38]

      乔宇, 马博男, 李秀颖, 等.无机化学学报, 2015, 31(6):1245-1251QIAO Yu, MA Bo-Nan, LI Xiu-Ying, et al. Chinese J. Inorg. Chem., 2015, 31(6):1245-1251 
      

  39. [39]

      Chang X H, Zhao Y, Feng X, et al. Polyhedron, 2014, 83:159-166 doi: 10.1016/j.poly.2014.05.063
      

• 

  Figure 1  (a) View of coordination environment of Ni(Ⅱ) in complex 1; (b) View of Ni-carboxylate chain spaced by carboxylate ligands; (c) View of monolayer structure lying in bc plane; (d) 3D supramolecular structure fabricated by H-bonding interactions labeled as dark dotted lines

  Symmetry codes: ^ⅰ-x+1/2, y-1/2, -z+1/2; ^ⅱ-x, -y+2, -z+1; ^ⅲ -x+1, -y+2, z; Displacement ellipsoids are drawn at the 50% probability level and all hydrogen atoms of carbon atoms are omitted for clarity

  下载: 全尺寸图片 幻灯片
  

  Figure 2  (a) View of coordination environment of Cd(Ⅱ) in complex 2; (b) View of Cd-carboxylate chain containing an alternating arrangement of 8-membered and 16-membered rings; (c) View of 2D bilayer with intralayer π-π interactions

  Symmetry codes: ^ⅰ x-1, y, z+1; ^ⅱ x+1, y, z; ^ⅲ-x+1, -y+1, -z+1; Displacement ellipsoids are drawn at the 50% probability level and all hydrogen atoms of carbon atoms are omitted for clarity

  下载: 全尺寸图片 幻灯片
  

  Figure 3  (a) View of coordination environment of Zn(Ⅱ) in complex 3; (b) View of Zn-organic chain based on dinuclear units containing 16-membered rings; (c) View of 2D layer structure propagated through only two kinds of H-bonds labeled as dark dotted lines; (d) Intralayer π-π stacking interaction between the pyridine rings of bip molecules

  Symmetry codes: ^ⅰ-x+2, -y+2, -z; ^ⅱ x+1, y-1, z; Displacement ellipsoids are drawn at the 50% probability level and all hydrogen atoms of carbon atoms are omitted for clarity

  下载: 全尺寸图片 幻灯片
  

  Figure 4  TGA curves for complexes 1~3

  下载: 全尺寸图片 幻灯片
  

  Figure 5  Temperature dependences of magnetic susceptibility χ_M (○) and χ_MT (□) for complex 1

  下载: 全尺寸图片 幻灯片
  

  Figure 6  Solid-state emission spectra of complexes 2~3 and the related ligands at ambient temperature

  下载: 全尺寸图片 幻灯片

  Table 1.  Crystal and structure refinement data for complexes 1~3

  	1	2	3
  Empirical formula	C42H42Ni2N8O13	C21H16CdN4O4	C20H17ZnN5O5
  Formula weight	984.25	500.78	472.76
  Crystal system	Monoclinic	Triclinic	Triclinic
  Space group	P21/n	P1	P1
  a / nm	1.328 32(11)	0.787 9(6)	0.893 56(5)
  b / nm	0.902 68(7)	0.991 7(7)	1.046 85(6)
  c / nm	1.810 85(15)	1.326 1(9)	1.121 85(6)
  α / (°)		73.638(15)	67.482 0(10)
  β / (°)	105.115(2)	78.862(17)	81.466 0(10)
  γ/ (°)		73.637(15)	73.942 0(10)
  V / nm3	2.096 2(3)	0.946 6(12)	0.930 51(9)
  Z	2	2	2
  Dc / (g·cm-3)	1.559	1.757	1.687
  μ / mm-1	0.976	1.192	1.367
  F(000)	1 020	500	484
  θ range / (°)	3.414~50.122	3.226~50.602	3.934~51
  Reflection collected, unique	13 126, 3 711	6 178, 3 396	6 257, 3 452
  Rint	0.041 6	0.020 0	0.013 8
  Completeness to θ / %	99.9	98.9	99.7
  Data, restraint, parameter	3 711, 12, 298	3 396, 0, 271	3 452, 0, 280
  Goodness-of-fit	1.038	1.061	1.056
  R1	0.035 9	0.020 7	0.023 2
  wR2 [I>2σ(I)]	0.087 0	0.051 1	0.061 0
  R1 (all data)	0.047 1	0.022 7	0.024 7
  wR2 (all data)	0.094 1	0.053 2	0.061 9
  (Δρ)max and (Δρ)min / (e·nm-3)	410, -530	360, -330	260, -360

  下载: 导出CSV
•