English

• 0.   Introduction

  It is common knowledge that Salen and its many different kinds of analogues (R - CH=N -(CH₂) ₂ - N=CH -R) have been extensively investigated in modern coor- dination chemistry and organometallic chemistry for several decades^[1-5]. They are one of the most versatile multidentate chelating ligands and could form stable mono- or multi-nuclear metal complexes^[6-9] with alkaline earth, rare earth and transition metal ions, and their potential applications have been explored in bio- logical system^[10-15]. Moreover, they have certain advan- tages in luminescent^[16-22] and magnetic^[23] materials, ion recognitions^[24-26], electrochemical fields^[27-30], supramo- lecular constructions^[31-37], and so on.

  In recent years, our research mostly concentrated on the syntheses of salamo - like ligands as derivatives of Salen ^[38-46]. These compounds have been investigated in forming transition metal complexes with interest- ing properties^[47-49]. Some works have been devoted to synthesize and characterize mono-, di- and multi-nuclear metal complexes bearing salamo -like ligand and its derivatives^[50-53]. However, there are few researches on unsymmetric salamo-like ligands, and it is expected to obtain multi-nuclear transition metal complexes by introducing some groups such as alkoxy or hydroxyl substitute at 3- positions of salicylaldehyde derivatives in the salamo-like ligands. Herein, as part of our ongo- ing interest in salamo-like transition metal complexes, X-ray crystal structures, spectroscopic properties and Hirshfeld surfaces analyses of two newly designed and synthesized transition metal complexes, {[Ni₂(L) (μ-OAc) (CH₃OH)]₂·4CH₃OH (1) and [Zn₂(L) (μ-OAc) (CH₃CH₂OH)]₂ (2), derived from an unsymmetrical sala-mo-like N₂O₄-donor ligand (H₃L=6-hydroxy-6′- me- thoxy-2, 2′-(ethylenediyldioxybis(nitrilomethylidyne))di- phenol) have been investigated in detail.

  1.   Experimental

  1.1   Materials and methods

  3-Hydroxysalicylic aldehyde of 99% purity and 3- methoxysalicylaldehyde of 98% purity were purchased from Alfa Aesar and used without further purification. The other reagents and solvents were analytical grade reagents from Tianjin Chemical Reagent Factory.

  C, H and N analyses were obtained using a GmbH VarioEL Ⅴ3.00 automatic elemental analyzer. Elemen- tal analysis for Ni and Zn were conducted using an IRIS ER/S·WP-1 ICP atomic emission spectrometer.¹H NMR spectra were recorded using a Bruker AVANCE DRX - 400 spectrometer. The melting points were determined by a microscopic melting point instru- ment made in Beijing Tektronix Instrument Limited Company and were uncorrected. IR spectra were recorded on a VERTEX70 FT-IR spectrophotometer, with samples prepared as KBr (500~4 000 cm^-1) and CsI (100~500 cm^-1) pellets. UV-Vis absorption spectra were recorded on a Shimadzu UV - 2550 spectrometer. Fluorescent spectra were recorded on F - 7000 spectro- photometer. X - ray single crystal structure determina- tions were carried out on a SuperNova, Dual Eos four- circle diffractometer. Hirshfeld surfaces analyses and two-dimensional fingerprint plots of complexes 1 and 2 were calculated using Crystal Explorer program.

  1.2   Synthesis of H₃L

  The unsymmetric salamo-like ligand H₃L was syn- thesized by a modified method reported in the earlier literature (Scheme 1)^[54].

  Scheme 1

  

  Scheme 1.  Synthetic route of H₃L

  下载: 全尺寸图片 幻灯片

  1.3   Synthesis of complex 1

  A methanol solution (3.0 mL) of nickel acetate tetrahydrate (4.92 mg, 0.02 mmol) was added to a ace-tone solution (2.0 mL) of H₃L (3.46 mg, 0.01 mmol) at room temperature. After stirring for 2 h, the mixture was filtered off. The resulting filtrate was left undis-turbed for about a week to form block-like clear yellow- ish green crystals suitable for X-ray crystallographic analysis. Yield: 45.8%. Anal. Calcd. for C₄₄H₆₀N₄Ni₄O₂₂ (%): C, 42.91; H, 4.91; N, 4.55; Ni, 19.06. Found(%): C, 43.16; H, 4.98; N, 4.47; Ni, 18.87.

  1.4   Synthesis of complex 2

  A solution of zinc acetate tetrahydrate (4.96 mg, 0.02 mmol) in ethanol (2.5 mL) was added drop- wise to a solution of H₃L (3.5 mg, 0.01 mmol) in dichlo- romethane (3 mL) at room temperature. The color of the mixing solution turned yellow immediately, and was stirred continually for 1 h at room temperature. The mixture was filtered and the filtrate was allowed to stand at room temperature for about two weeks. The sol- vent was partially evaporated, and several clear yellow- ish single crystals suitable for X-ray crystallographic analysis were obtained. Yield: 47.3%. Anal. Calcd. for C₄₂H₄₈N₄Zn₄O₁₈(%): C 43.55; H 4.18; N 4.84; Zn 22.58. Found(%): C 43.68; H 4.32; N 4.74; Zn 22.31.

  1.5   Crystal structure determinations of complexes 1 and 2

  Suitable crystals of complexes 1 and 2 with approximate dimensions of 0.18 mm×0.15 mm×0.12 mm and 0.11 mm×0.10 mm×0.08 mm, respectively, were mounted on glass rod for determining single crys- tal structures. X - ray diffraction data of complexes 1 and 2 were collected on a Bruker APEX Ⅱ CCD diffractometer with a graphite monochromated Cu Kα radiation source (λ =0.154 184 nm) at 173.20(10) K, and SuperNova (Dual, Cu at zero, Eos) diffractometer using a graphite monochromated Mo Kα radiation source (λ =0.071 073 nm) at 100 K, respectively. The semi-empirical absorption corrections were applied using the SADABS program. The structures were solved by the direct methods (SHELXS-2014). All non- hydrogen atoms were refined anisotropically; the hydroxyl hydrogen atoms in the methanol molecules were located in difference Fourler maps, all other hydrogen atoms were generated geometrically and allowed to ride on their parent carbon atoms^[55]. The crystal data and experimental parameters relevant to the structure determinations are listed in Table 1.

  Table 1

  

  Table 1.  Crystal data and structure refinement parameters for complexes 1 and 2

  下载: 导出CSV

  Complex	1	2
  Formula	C44H60N4Ni4O22	C42H48N4Zn4O18
  Formula weight	1 231.8	1 158.32
  Crystal system	Triclinic	Triclinic
  Space group	P1	P1
  a /nm	0.966 71(4)	0.976 37(6)
  b / nm	1.135 94(6)	1.041 21(7)
  c / nm	1.454 37(10)	1.214 10(9)
  α/(°)	112.312(6)	89.010(6)
  β/(°)	95.582(5)	73.275(6)
  γ/(°)	106.259(4)	74.235(6)
  V / nm3	13.806 7(15)	11.351 0(14)
  Z	1	1
  Dc / (g·cm-3)	1.481	1.695
  μ / mm-1	2.203	2.169
  F(000)	640	592
  θ range /(°)	4.312~66.598	2.037~27.099
  Index ranges	-11 ≤ h ≤ 11, -10 ≤ k ≤ 13, -17 ≤ l ≤ 16	-12≤ h ≤ 12, -11 ≤ k ≤ 13, -15 ≤ l ≤ 15
  Reflections collected	8 899	9 115
  Independent reflection	4 871	4 917
  Rint	0.020 6	0.042 2
  Completeness / %	99.76	98
  Data, restraint, parameter	4 871, 1, 344	4 917, 0, 310
  GOF	1.044	1.048
  Final R1, wR2 indices [I > 2σ(I)]	0.028 8, 0.075 1	0.051 2, 0.106 2
  R1, wR2 indices (all data)	0.031 6, 0.077 4	0.076 2, 0.115 9
  a R1=∑||Fo|-|Fc||/∑|Fo||; b wR2={∑w(Fo2-Fc2)2/∑[w(Fo2)]2}1/2.

  CCDC: 1984199, 1; 1984198, 2.

  2.   Results and discussion

  2.1   IR spectra

  The FT - IR spectra of H₃L with its corresponding complexes 1 and 2 exhibited various bands in the 400~ 4 000 cm^-1 region (Table 2). The hydroxyl group of H₃L exhibited a characteristic absorption band at approxi- mate 3 436 cm^-1. An absorption band of the coordinat- ed and crystallized methanol molecules was observed at approximate 3 387 cm^-1 in complex 1, and an absorp- tion band of the coordinated ethanol molecules was observed at approximate 3 428 cm^-1 in complex 2, indi- cating that the Ni and Zn ions are coordinated to oxygen atoms in phenoxy groups of the fully deprotonat- ed ligand L^3- moieties. The results are in accordance with the elemental analysis results. A characteristic strong C=N stretching band of H₃L emerged at approxi- mate 1 613 cm^-1, and those of complexes 1 and 2 emerged at approximate 1 602 and 1 597 cm^-1, respec- tively^[56]. The changes in the spectra of complexes 1 and 2 shows that the oxime nitrogen atoms of the ligand H₃L have coordinated with the Ni and Zn ions. The expected Ar-O vibration band of H₃L was observed at approximate 1 253 cm^-1; nevertheless, this band occurred at approximate 1 234 and 1 213 cm^-1 in com- plexes 1 and 2, respectively. The Ar - O stretching fre- quencies of phenoxy groups are shifted to low frequen- cies, which could be evidence of the Ni - O or Zn - O bond formation between the Ni or Zn ions and the oxygen atoms of phenoxy groups^[57].

  Table 2

  

  Table 2.  FT-IR spectra of H₃L and complexes 1 and 2 cm^-1

  下载: 导出CSV

  Compound	νO-H	νC=N	νAr-O	νM-N	νM-O
  H3L	3 436	1 613	1 253	—	—
  1	3 387	1 602	1 234	516	426
  2	3 428	1 597	1 213	512	423

  The far-IR spectra (500~100 cm^-1) of complexes 1 and 2 were also obtained to identify the bonds of M-O and M - N frequencies. The ν_M-O bands at approximate 426 and 423 cm^-1 in complexes 1 and 2 can be assigned to ν_Ni-O and ν_Zn-O, while the ν_M-N bands at approximate 516 and 512 cm^-1 are attributed to ν_Ni-N and ν_Zn-N, respectively^[52]. The results mentioned above are in accordance with the results of X-ray crystal dif- fractions.

  2.2   UV-Vis spectra

  The UV - Vis absorption spectra of the free ligand H₃L with its corresponding complexes 1 and 2 in the ethanol solutions (10 μmol·L^-1) at 298 K are shown in Fig. 1.

  Figure 1

  

  Figure 1.  UV-Vis spectra of H₃L and complexes 1 and 2

  下载: 全尺寸图片 幻灯片

  Obviously, the absorption peaks of the free ligand H₃L differ from those of complexes 1 and 2. The UV - Vis spectra of ligand H₃L and its complexes 1 and 2 in the ethanol solutions are shown in Fig. 1. From the Fig. 1, we can see that the free ligand H₃L showed two strong absorption peaks near 271 and 319 nm. The ab- sorption peak at ca. 271 nm can be assigned to the π- π* transitions of phenyl rings, and the absorption peak at ca. 319 nm can be assigned to the intra-ligand π -π* transition of oxime group. Upon coordination of the free ligand, the π-π* transitions of phenyl rings in complex- es 1 and 2 are bathochromically shifted to 274 and 278 nm, respectively, which indicates the coordination of ligand L^3- moieties with Ni and Zn ions^[49]. Mean- while, new absorption peaks appeared at 374 and 349 nm in complexes 1 and 2 may be accounted for the n- π* charge transfer transition from the filled p orbital of bridging phenoxo oxygen atoms to the vacant d-orbital of corresponding metal ions.

  2.3   Descriptions of crystal structures

  X - ray crystallographic analyses reveal that com- plexes 1 and 2 form two different crystal structures, which are different from common tetra - nuclear struc- tures of salamo-like complexes reported earlier^[40].

  2.3.1   Crystal structure of complex 1

  As shown in Fig. 2 and Table 3, in the crystal structure of complex 1, there are four Ni ions, two fully deprotonated L^3- moieties, two coordinated MeOH molecules, two μ - acetate ligands and four crystallized MeOH molecules. Complex 1 possesses a highly sym- metrical tetra-nuclear structure. The hexa -coordinated central Ni ion (Ni1) is surrounded by four oxygen atoms (O1, O1#1, O2 and O5) from the fully deproton- ated L^3- moiety, one oxygen atom (O7) of the μ-acetate ligand and one oxygen atoms (O6) from the coordinated methanol molecule adopting a twisted octahedral geom- etry. The hexa-coordinated terminal Ni ion (Ni2) lies in the N₂O₂ -donor coordination sphere (N1, N2, O2 and O5) of the fully deprotonated L^3- unit, and coordinates further to one oxygen atom (O8) from the μ - acetate ligand and one oxygen atoms (O9) from the coordinated methanol molecule adopting a twisted octahedral geometry.

  Figure 2

  

  Figure 2.  (a) Molecular structure of complex 1 with 30% probability displacement ellipsoids; (b) Coordination polyhedra for Ni ions of complex 1

  Hydrogen atoms are omitted for clarity; Symmetry code: #1: 2-x, 1-y, 1-z

  下载: 全尺寸图片 幻灯片

  Table 3

  

  Table 3.  Selected bond lengths (nm) and angles (°) for complex 1

  下载: 导出CSV

  Ni1-O1	0.208 68(15)	Ni1-O7	0.204 17(14)	Ni2-O8	0.206 33(13)
  Ni1-O2	0.200 25(14)	Ni1-O1#1	0.204 14(12)	Ni2-O9	0.211 58(14)
  Ni1-O5	0.200 69(14)	Ni1-O2	0.201 32(14)	Ni2-N1	0.211 21(17)
  Ni1-O6	0.218 97(14)	Ni2-O5	0.202 22(13)	Ni2-N2	0.209 30(18)
  O1-Ni1-O2	80.68(6)	O5-Ni1-O7	89.25(6)	O5-Ni2-O8	91.69(5)
  O1-Ni1-O5	161.72(5)	O1#1-Ni1-O5	100.61(5)	O5-Ni2-O9	86.90(5)
  O1-Ni1-O6	121.26(6)	O6-Ni1-O7	83.53(5)	O5-Ni2-N1	164.56(6)
  O1-Ni1-O7	88.70(6)	O1#1-Ni1-O6	91.87(5)	O5-Ni2-N2	86.34(6)
  O1-Ni1-O1#1	84.11(5)	O1#1-Ni1-O7	167.88(6)	O8-Ni2-O9	178.16(6)
  O2-Ni1-O5	81.38(6)	O2-Ni2-O5	80.74(6)	O8-Ni2-N1	90.09(6)
  O2-Ni1-O6	157.81(6)	O1-Ni2-O8	91.38(5)	O8-Ni2-N2	87.55(6)
  O2-Ni1-O7	94.48(5)	O2-Ni2-O9	89.56(6)	O9-Ni2-N1	91.59(6)
  O1#1-Ni1-O2	93.96(5)	O1-Ni2-N1	83.88(6)	O9-Ni2-N2	91.17(6)
  O5-Ni1-O6	76.51(6)	O1-Ni2-N2	167.01(6)	N1-Ni2-N2	109.06(7)
  Symmetry code: #1: 2-x, 1-y, 1-z.

  As illustrated in Fig. 3 and Table 4, there are two intra-molecular hydrogen bonding inter -actions (C8-H8A…O9 and C20-H20B…O5) in the crystal struc- ture of complex 1.

  Figure 3

  

  Figure 3.  View of intra-molecular hydrogen bondings of complex 1

  Hydrogen atoms are omitted for clarity except those forming hydrogen bonds

  下载: 全尺寸图片 幻灯片

  Table 4

  

  Table 4.  Hydrogen bonding interaction parameters for complex 1

  下载: 导出CSV

  D-H…A	d(D-H) / nm	d(H…A) / nm	d(D…A) / nm	∠D-H…A / (°)
  C8-H8A…O9	0.097	0.244	0.329 0(3)	146
  C20-H20B…O5	0.096	0.257	0.312 8(3)	177

  2.3.2   Crystal structure of complex 2

  X - ray crystallographic analysis reveals that com- plex 2 is a symmetric trinuclear structure. It crystalliz- es in the triclinic system, space group P1. As shown in Fig. 4, the obtained complex 2 includs four Zn ions, two fully deprotonated L^3- moieties, two coordinated ethanol molecules and two μ-acetate ligands. The penta - coordinated central Zn ion (Zn1) is surrounded by three oxygen atoms (O6, O6 and O5) from the fully deprotonated L^3- moiety, one oxygen atom (O8) of the μ - acetate ligand and one oxygen atom (O9) from the coordinated ethanol molecule, forming a square pyra- mid geometry. Unlike the center Zn ion, the penta - coordinated terminal Zn ion (Zn2) lies in the N₂O₂ - donor coordination sphere (N1, N2, O1 and O5) of the fully deprotonated L^3- unit, and coordinates further to one oxygen atom (O7) from the μ-acetate ligand, adopt- ing a twisted triangular bipyramidal geometry. Herein, we have synthesized a novel structural tetranuclear complex 2, where all the Zn ions are penta- coordinated with distorted tetragonal pyramidal and trigonal bipyramidal symmetries. In order to get the geometries adopted by Zn1 and Zn2, the τ values were estimated to be τ₁=0.143 and τ₂=0.725^[58-59], respectively.

  Figure 4

  

  Figure 4.  (a) Molecular structure of complex 2 with 30% probability displacement ellipsoids; (b) Coordination polyhedra for Zn ions of complex 2

  Hydrogen atoms are omitted for clarity; Symmetry code: #1: 1-x, 1-y, z

  下载: 全尺寸图片 幻灯片

  Table 5

  

  Table 5.  Selected bond lengths (nm) and angles (°) for complex 2

  下载: 导出CSV

  Zn1-O5	0.205 4(3)	Zn1-O6#1	0.201 5(3)	Zn2-N1	0.211 8(4)
  Zn1-O6	0.204 1(3)	Zn2-O1	0.195 1(3)	Zn2-N1	0.209 5(4)
  Zn1-O8	0.198 2(3)	Zn2-O5	0.202 6(3)
  Zn1-O9	0.203 4(3)	Zn2-O7	0.197 8(2)
  O5-Zn1-O6	79.33(11)	O8-Zn1-O9	108.61(12)	O5-Zn2-O7	92.37(11)
  O5-Zn1-O8	95.91(12)	O6#1-Zn1-O8	98.56(11)	O5-Zn2-N1	171.13(13)
  O5-Zn1-O9	93.25(11)	O6#1-Zn1-O9	100.40(12)	O5-Zn2-N2	83.69(14)
  O5-Zn1-O6#1	155.75(12)	O1-Zn2-O5	96.09(13)	O7-Zn2-N1	92.14(13)
  O6-Zn1-O8	147.18(12)	O1-Zn2-O7	112.79(12)	O7-Zn2-N2	127.64(14)
  O6-Zn1-O9	104.10(12)	O1-Zn2-N1	89.20(14)	N1-Zn2-N2	87.51(15)
  O6-Zn1-O6#1	77.95(11)	O1-Zn2-N2	119.56(13)
  Symmetry code: #1: 1-x, 1-y, 1-z.

  As illustrated in Fig. 5, there are three intra- molecular (O9 -H9…O1, O9-H9…O2, and C9 -H9A… O7) hydrogen bonding interactions. As shown in Fig. 6 and Table 6, complex 2 molecules are linked into an in- finite 2D supramolecular structure by inter - molecular (C7-H7B…O3, C10-H10A…O4) hydrogen bonding interactions in the crystal structure of complex 2^[60-64].

  Figure 5

  

  Figure 5.  Intra-molecular C-H…O hydrogen bondings of complex 2

  Hydrogen atoms, except those forming hydrogen bonds, are omit-ted for clarity

  下载: 全尺寸图片 幻灯片

  Figure 6

  

  Figure 6.  Two dimensional supramolecular structure linked by inter-molecular C-H…O hydrogen bondings in complex 2

  下载: 全尺寸图片 幻灯片

  Table 6

  

  Table 6.  Hydrogen bonding interaction parameters for complex 2

  下载: 导出CSV

  D-H…A	d(D-H) / nm	d(H…A) / nm	d(D…A) / nm	∠D-H…A /(°)
  O9-H9…O1	0.086(3)	0.188(3)	0.267 5(4)	153
  O9-H9…O2	0.086(3)	0.242(2)	0.308 2(4)	134
  C7-H7B…O3#2	0.096	0.260	0.339 3(6)	141
  C9-H9A…O7	0.097	0.242	0.326 8(6)	146
  C18-H18…O6#1	0.097	0.254	0.325 4(6)	130
  Symmetry codes: #1: 2-x, 1-y, 2-z; #2: -1+x, y, z.

  2.4   Hirshfeld surfaces analyses

  The Hirshfeld surfaces^[65] of complexes 1 and 2 are illustrated in Fig. 7. The surfaces have been mapped over d_norm, and the corresponding location in shape index exists the complementary region of red concave surface surrounded by receptors and the blue convex surface surrounding receptors, further proving that such hydrogen bonding exists. As for the large amount of white region in d_norm surfaces, it is suggested that there is a weaker and farther contact between mole- cules, rather than hydrogen bonding.

  Figure 7

  

  Figure 7.  Hirshfeld surfaces analyses mapped with curvedness, d_norm and shape index of complexes 1 and 2

  下载: 全尺寸图片 幻灯片

  Fig. 8 shows the 2D plots generated^[66] correspond- ing to the O…H, C…H and H…H interactions from the Hirshfeld surfaces of complexes 1 and 2. As shown in Fig. 8a, for complex 1, the H…H interactions appear at (0.115 7 nm, 0.114 7 nm) and account for 67% of the total area of Hirshfeld surfaces. The C…H/H…C interactions are in the range of (0.157 8 nm, 0.106 7 nm) and appear as a pair of symmetrical wings, accounting for 11.4% of the total area of Hirshfeld sur- faces. The proportions of O…H/H…O interactions are comprised of 17.7% of the total Hirshfed surfaces for each molecule of complex 1. As shown in Fig. 8b, for complex 2, the interactions of H…H appear at (0.115 nm, 0.115 nm) accounting for 45.4% of the total area of Hirshfeld surfaces. The C…H/H…C interactions in the range of (0.160 nm, 0.105 nm) account for 24.2% of the total area of Hirshfeld surfaces. The proportions of O…H/H…O interactions are comprised of 24.3% of the total Hirshfed surfaces for each molecule of com- plex 2. It is because of the existence of these weaker hydrogen bonds that complexes 1 and 2 can be stable.

  Figure 8

  

  Figure 8.  Fingerprint plots of complexes 1 (a) and 2 (b)

  Full and resolved into O…H, C…H and H…H contacts show the percentages of contacts contributed to the total Hirshfeld surface area of molecule

  下载: 全尺寸图片 幻灯片

  2.5   Fluorescence properties

  The fluorescence spectra of H₃L and its corre- sponding complexes 1 and 2 were investigated at room temperature and are shown in Fig. 9. The free ligand H₃L exhibited a relatively strong emission peak at ca. 400 nm upon excitation at 370 nm, and it should be assigned to the intraligand π-π* transition. Complex 1 showed a lower photoluminescence with maximum emission at ca. 391 nm. Compared with the ligand H₃L, emission intensity of complex 1 reduced obviously, indicating that the Ni ions have a quality of fluores- cent quenching. On the other hand, complex 2 showed an obvious fluorescence enhancement at ca. 395 nm. The intense peak is likely due to the coordination of H₃L with the Zn ions, which breaks the intramolecu- lar hydrogen-bonding interactions of H₃L and increases the coplanarity of the conjugated system.

  Figure 9

  

  Figure 9.  Emission spectra of H₃L and complexes 1 and 2

  c=10 μmol·L^-1, λ_ex=370 nm

  下载: 全尺寸图片 幻灯片

  3.   Conclusions

  In summary, we have reported the successful syntheses and characterizations of two newly designed tetra-nuclear metal complexes, [Ni₂(L)(μ-OAc) (CH₃OH)]₂·4CH₃OH (1) and [Zn₂(L) (μ-OAc) (CH₃CH₂OH)]₂ (2), derived from an unsymmetrical sala-mo - like ligand H₃L. All the hexa - coordinated Ni ions in complex 1 adopt slightly twisted octahedral con- figurations. The penta-coordinated Zn ions (Zn1 and Zn1#1) in complex 2 form square pyramid geometries, while the other penta-coordinated Zn ions (Zn2 and Zn2#1) possess twisted triangular bipyramidal geome- tries. The inter-molecular hydrogen bonding interac- tions in crystal structure of 2 result in a self-assembled infinite 2D supramolecular network.

  
  Acknowledgements: This work was supported by the Na- tional Natural Science Foundation of China (Grant No.21968032), the Fundamental Research Funds of Central Uni- versities-Innovation Team Cultivation Project (Grant No.31920190012), the Northwest Minzu University′s Double First-class and Characteristic Development Guide Special Funds-Chemistry Key Disciplines in Gansu Province (Grant No.11080316), and the Teaching Quality and Reform Engineer- ing Project of Gansu University (Grants No.2019GSSYJXSFZX- 01, 2019GSJXCGPY-16), which are gratefully acknowledged.
• 1. [1]

     Dong X Y, Kang Q P, Li X Y, et al. Crystals, 2018, 8:139 doi: 10.3390/cryst8030139

  2. [2]

     Wu H L, Wang C P, Wang F, et al. J. Chin. Chem. Soc., 2015, 62:1028-1034 doi: 10.1002/jccs.201500121

  3. [3]

     Liu Y A, Wang C Y, Zhang M, et al. Polyhedron, 2017, 127:278-286 doi: 10.1016/j.poly.2017.02.007

  4. [4]

     Kang Q P, Li X Y, Wang L, et al. Appl. Organomet. Chem., 2019, 33:e5013

  5. [5]

     Chai L Q, Mao K H, Zhang J Y, et al. Inorg. Chim. Acta, 2017, 457:34-40 doi: 10.1016/j.ica.2016.12.004

  6. [6]

     Akine S, Varadi Z, Nabeshima T. Eur. J. Inorg. Chem., 2013, 35:5987-5998

  7. [7]

     Akine S. J. Incl. Phenom. Macrocycl. Chem., 2012, 72:25-54 doi: 10.1007/s10847-011-0026-3

  8. [8]

     Wu H L, Pan G L, Bai Y C, et al. J. Chem. Res., 2014, 38:211- 217 doi: 10.3184/174751914X13933417974082

  9. [9]

     Wu H L, Pan G L, Bai Y C, et al. Res. Chem. Intermed., 2015, 41:3375-3388 doi: 10.1007/s11164-013-1440-5

  10. [10]

      Zhang Y, Yu M, Pan Y Q, et al. Appl. Organomet. Chem., 2020, 34:e5442

  11. [11]

      Sun S S, Stern C L, Nguyen S T, et al. J. Am. Chem. Soc., 2004, 126:6314-6326 doi: 10.1021/ja037378s

  12. [12]

      Venkataramanan N S, Kuppuraj G, Rajagopal S. Coord. Chem. Rev., 2005, 249:1249-1268 doi: 10.1016/j.ccr.2005.01.023

  13. [13]

      Zhang L W, Zhang Y, Cui Y F, et al. Inorg. Chim. Acta, 2020, 506:119534 doi: 10.1016/j.ica.2020.119534

  14. [14]

      Wu H L, Pan G L, Bai Y C, et al. J. Photochem. Photobiol. B, 2014, 135:33-43 doi: 10.1016/j.jphotobiol.2014.04.005

  15. [15]

      Chen C Y, Zhang J W, Zhang Y H, et al. J. Coord. Chem., 2015, 68:1054-1071 doi: 10.1080/00958972.2015.1007965

  16. [16]

      Ren Z L, Hao J, Hao P, et al. Z. Naturforsch. B, 2018, 73:203 -210 doi: 10.1515/znb-2017-0191

  17. [17]

      Akine S, Taniguchi T, Nabeshima T. Chem. Lett., 2001, 30:682-683 doi: 10.1246/cl.2001.682

  18. [18]

      Zhang L W, Li X Y, Kang Q P. Crystals, 2018, 8:173 doi: 10.3390/cryst8040173

  19. [19]

      Kang Q P, Li X Y, Zhao Q, et al. Appl. Organomet. Chem., 2018, 32:e4379 doi: 10.1002/aoc.4379

  20. [20]

      Dong X Y, Akogun S F, Zhou W M, et al. J. Chin. Chem. Soc., 2017, 64:412-419

  21. [21]

      Song X Q, Peng Y J, Chen G Q, et al. Inorg. Chim. Acta, 2015, 427:13-21 doi: 10.1016/j.ica.2014.12.008

  22. [22]

      Liu L Z, Wang L, Yu M, et al. Spectrochim. Acta Part A, 2019, 222:117209 doi: 10.1016/j.saa.2019.117209

  23. [23]

      Song X Q, Liu P P, Liu Y A, et al. Dalton Trans., 2016, 45:8154-8163 doi: 10.1039/C6DT00212A

  24. [24]

      Pan Y Q, Xu X, Zhang Y, et al. Spectrochim. Acta Part A, 2020, 229:117927 doi: 10.1016/j.saa.2019.117927

  25. [25]

      Wei Z L, Wang L, Wang J F, et al. Spectrochim. Acta Part A, 2020, 228:117775 doi: 10.1016/j.saa.2019.117775

  26. [26]

      Wang L, Wei Z L, Chen Z Z, et al. Microchem. J., 2020, 155:104801 doi: 10.1016/j.microc.2020.104801

  27. [27]

      Li J, Zhang H J, Chang J, et al. Crystals, 2018, 8:176 doi: 10.3390/cryst8040176

  28. [28]

      Chai L Q, Zhou L, Zhang K Y, et al. Appl. Organomet.Chem, 2018,32:e4576

  29. [29]

      Ömer S, Ümmühan Ö Ö, Nurgul S, et al. Tetrahedron, 2016, 72:5843-5852

  30. [30]

      Hao J, Li X Y, Wang L, et al. Spectrochim. Acta Part A, 2018, 204:388-402 doi: 10.1016/j.saa.2018.06.074

  31. [31]

      常健, 张宏佳, 贾浩然, 等.无机化学学报, 2018, 34(11):2097-2107 http://www.wjhxxb.cn/wjhxxbcn/ch/reader/view_abstract.aspx?flag=1&file_no=20181119&journal_id=wjhxxbcnCHANG Jian, ZHANG Hong-Jia, JIA Hao- Ran, et al. Chinese J. Inorg. Chem., 2018, 34(11):2097-2107 http://www.wjhxxb.cn/wjhxxbcn/ch/reader/view_abstract.aspx?flag=1&file_no=20181119&journal_id=wjhxxbcn

  32. [32]

      Jia H R, Chang J, Zhang H J, et al. Crystals, 2018, 8:272 doi: 10.3390/cryst8070272

  33. [33]

      Zhou L, Hu Q, Chai L Q, et al. Polyhedron, 2019, 158:102- 116 doi: 10.1016/j.poly.2018.10.052

  34. [34]

      张宏佳, 常健, 贾浩然, 等.无机化学学报, 2018, 34(12):2261-2270 http://www.wjhxxb.cn/wjhxxbcn/ch/reader/view_abstract.aspx?flag=1&file_no=20181217&journal_id=wjhxxbcnZHANG Hong-Jia, CHANG Jian, JIA Hao- Ran, et al. Chinese J. Inorg. Chem., 2018, 34(12):2261-2270 http://www.wjhxxb.cn/wjhxxbcn/ch/reader/view_abstract.aspx?flag=1&file_no=20181217&journal_id=wjhxxbcn

  35. [35]

      Dong X Y, Li X Y, Liu L Z, et al. RSC Adv., 2017, 7:48394- 48403 doi: 10.1039/C7RA07826A

  36. [36]

      Liu C, An X X, Cui Y F, et al. Appl. Organomet. Chem., 2020, 34:e5272

  37. [37]

      Pan Y Q, Zhang Y, Yu M, et al. Appl. Organomet. Chem., 2020, 34:e5441

  38. [38]

      Zhao Q, An X X, Liu L Z, et al. Inorg. Chim. Acta, 2019, 490:6-15 doi: 10.1016/j.ica.2019.02.040

  39. [39]

      Akine S, Taniguchi T, Dong W K, et al. J. Org. Chem., 2005, 70:1704-1711 doi: 10.1021/jo048030y

  40. [40]

      Liu C, Wei Z L, Mu H R, et al. J. Photochem. Photobiol. A, 2020, 397:112569 doi: 10.1016/j.jphotochem.2020.112569

  41. [41]

      Yu M, Zhang Y, Pan Y Q, et al. Inorg. Chim. Acta, 2020, 509:

  42. [42]

      Wang L, Wei Z L, Liu C, et al. Spectrochim. Acta Part A, 2020, 239:118496 doi: 10.1016/j.saa.2020.118496

  43. [43]

      An X X, Zhao Q, Mu H R, et al. Crystals, 2019, 9:101 doi: 10.3390/cryst9020101

  44. [44]

      Mu H R, Yu M, Wang L, et al. Phosphorus Sulfur Silicon Relat. Elem., 2020, 195:1756807

  45. [45]

      Dong X Y, Zhao Q, Kang Q P, et al. Crystals, 2018, 8:23 doi: 10.3390/cryst8010023

  46. [46]

      Li X Y, Kang Q P, Liu L Z, et al. Crystals, 2018, 8:43 doi: 10.3390/cryst8010043

  47. [47]

      于盟, 穆浩冉, 刘玲芝, 等.无机化学学报, 2019, 35 (6):1109-1120 http://www.wjhxxb.cn/wjhxxbcn/ch/reader/view_abstract.aspx?flag=1&file_no=20190622&journal_id=wjhxxbcnYU Meng, MU Hao-Ran, LIU Ling-Zhi, et al. Chinese J. Inorg. Chem., 2019, 35 (6):1109-1120 http://www.wjhxxb.cn/wjhxxbcn/ch/reader/view_abstract.aspx?flag=1&file_no=20190622&journal_id=wjhxxbcn

  48. [48]

      Dong X Y, Zhao Q, Wei Z L, et al. Molecules, 2018, 23:1006 doi: 10.3390/molecules23051006

  49. [49]

      Kang Q P, Li X Y, Wei Z L, et al. Polyhedron, 2019, 165:38- 50 doi: 10.1016/j.poly.2019.03.008

  50. [50]

      Gao L, Liu C, Wang F, et al. Crystals, 2018, 8:77 doi: 10.3390/cryst8020077

  51. [51]

      Hao J, Li X Y, Zhang Y, et al. Materials, 2018, 11:523 doi: 10.3390/ma11040523

  52. [52]

      刘玲芝, 于盟, 李肖妍, 等.无机化学学报, 2019, 35 (7):1283-1294 http://www.wjhxxb.cn/wjhxxbcn/ch/reader/view_abstract.aspx?flag=1&file_no=20190721&journal_id=wjhxxbcnLIU Ling-Zhi, YU Meng, LI Xiao-Yan, et al. Chinese J. Inorg. Chem., 2019, 35 (7):1283-1294 http://www.wjhxxb.cn/wjhxxbcn/ch/reader/view_abstract.aspx?flag=1&file_no=20190721&journal_id=wjhxxbcn

  53. [53]

      Li X Y, Kang Q P, Liu C, et al. New J. Chem., 2019, 43:4605- 4619 doi: 10.1039/C9NJ00014C

  54. [54]

      董秀延, 高垒, 王飞, 等.无机化学学报, 2018, 34 (4):739-749 http://www.wjhxxb.cn/wjhxxbcn/ch/reader/view_abstract.aspx?flag=1&file_no=20180418&journal_id=wjhxxbcnDONG Xiu - Yan, GAO Lei, WANG Fei, et al. Chinese J. Inorg. Chem., 2018, 34 (4):739-749 http://www.wjhxxb.cn/wjhxxbcn/ch/reader/view_abstract.aspx?flag=1&file_no=20180418&journal_id=wjhxxbcn

  55. [55]

      Sheldrick G M. SHELXS - 97, Program for the Solution and Refinement of Crystal Structures, University of GÖttingen, Germany, 1997.

  56. [56]

      Sun Y X, Pan Y Q, Xu X, et al. Crystals, 2019, 9:607 doi: 10.3390/cryst9120607

  57. [57]

      Zhang Y, Liu L Z, Peng Y D, et al. Transit. Met. Chem., 2019, 44:627-639 doi: 10.1007/s11243-019-00325-3

  58. [58]

      Addison A W, Rao T N, Reedijk J, et al. J. Chem. Soc. Dalton Trans., 1984, 7:1349-1356

  59. [59]

      Konno T, Tokuda K, Sakurai J, et al. Bull. Chem. Soc. Jpn., 2000, 73:2767-2773 doi: 10.1246/bcsj.73.2767

  60. [60]

      Chai L Q, Tang L J, Chen L C, et al. Polyhedron, 2017, 122:228-240 doi: 10.1016/j.poly.2016.11.032

  61. [61]

      Chai L Q, Liu G, Zhang Y L, et al. J. Coord. Chem., 2013, 66:3926-3938 doi: 10.1080/00958972.2013.857016

  62. [62]

      Wang P, Zhao L. Spectrochim. Acta A, 2015, 135:342-350 doi: 10.1016/j.saa.2014.06.129

  63. [63]

      An X X, Liu C, Chen Z Z, et al. Crystals, 2019, 9:602 doi: 10.3390/cryst9110602

  64. [64]

      郭建强, 孙银霞, 俞彬, 等.无机化学学报, 2017, 33(8):1481-1488 http://www.wjhxxb.cn/wjhxxbcn/ch/reader/view_abstract.aspx?flag=1&file_no=20170822&journal_id=wjhxxbcnGUO Jian-Qiang, SUN Yin-Xia, YU Bin, et al. Chinese J. Inorg. Chem., 2017, 33(8):1481-1488 http://www.wjhxxb.cn/wjhxxbcn/ch/reader/view_abstract.aspx?flag=1&file_no=20170822&journal_id=wjhxxbcn

  65. [65]

      Rohl A L, Moret M, Kaminsky W, et al. Cryst. Growth Des., 2012, 8:4517-4525

  66. [66]

      Chattopadhyay B, Mukherjee A K, Narendra N, et al. Cryst. Growth Des., 2010, 10:65-68

• 

  Scheme 1  Synthetic route of H₃L

  下载: 全尺寸图片 幻灯片
  

  Figure 1  UV-Vis spectra of H₃L and complexes 1 and 2

  下载: 全尺寸图片 幻灯片
  

  Figure 2  (a) Molecular structure of complex 1 with 30% probability displacement ellipsoids; (b) Coordination polyhedra for Ni ions of complex 1

  Hydrogen atoms are omitted for clarity; Symmetry code: #1: 2-x, 1-y, 1-z

  下载: 全尺寸图片 幻灯片
  

  Figure 3  View of intra-molecular hydrogen bondings of complex 1

  Hydrogen atoms are omitted for clarity except those forming hydrogen bonds

  下载: 全尺寸图片 幻灯片
  

  Figure 4  (a) Molecular structure of complex 2 with 30% probability displacement ellipsoids; (b) Coordination polyhedra for Zn ions of complex 2

  Hydrogen atoms are omitted for clarity; Symmetry code: #1: 1-x, 1-y, z

  下载: 全尺寸图片 幻灯片
  

  Figure 5  Intra-molecular C-H…O hydrogen bondings of complex 2

  Hydrogen atoms, except those forming hydrogen bonds, are omit-ted for clarity

  下载: 全尺寸图片 幻灯片
  

  Figure 6  Two dimensional supramolecular structure linked by inter-molecular C-H…O hydrogen bondings in complex 2

  下载: 全尺寸图片 幻灯片
  

  Figure 7  Hirshfeld surfaces analyses mapped with curvedness, d_norm and shape index of complexes 1 and 2

  下载: 全尺寸图片 幻灯片
  

  Figure 8  Fingerprint plots of complexes 1 (a) and 2 (b)

  Full and resolved into O…H, C…H and H…H contacts show the percentages of contacts contributed to the total Hirshfeld surface area of molecule

  下载: 全尺寸图片 幻灯片
  

  Figure 9  Emission spectra of H₃L and complexes 1 and 2

  c=10 μmol·L^-1, λ_ex=370 nm

  下载: 全尺寸图片 幻灯片

  Table 1.  Crystal data and structure refinement parameters for complexes 1 and 2

  Complex	1	2
  Formula	C44H60N4Ni4O22	C42H48N4Zn4O18
  Formula weight	1 231.8	1 158.32
  Crystal system	Triclinic	Triclinic
  Space group	P1	P1
  a /nm	0.966 71(4)	0.976 37(6)
  b / nm	1.135 94(6)	1.041 21(7)
  c / nm	1.454 37(10)	1.214 10(9)
  α/(°)	112.312(6)	89.010(6)
  β/(°)	95.582(5)	73.275(6)
  γ/(°)	106.259(4)	74.235(6)
  V / nm3	13.806 7(15)	11.351 0(14)
  Z	1	1
  Dc / (g·cm-3)	1.481	1.695
  μ / mm-1	2.203	2.169
  F(000)	640	592
  θ range /(°)	4.312~66.598	2.037~27.099
  Index ranges	-11 ≤ h ≤ 11, -10 ≤ k ≤ 13, -17 ≤ l ≤ 16	-12≤ h ≤ 12, -11 ≤ k ≤ 13, -15 ≤ l ≤ 15
  Reflections collected	8 899	9 115
  Independent reflection	4 871	4 917
  Rint	0.020 6	0.042 2
  Completeness / %	99.76	98
  Data, restraint, parameter	4 871, 1, 344	4 917, 0, 310
  GOF	1.044	1.048
  Final R1, wR2 indices [I > 2σ(I)]	0.028 8, 0.075 1	0.051 2, 0.106 2
  R1, wR2 indices (all data)	0.031 6, 0.077 4	0.076 2, 0.115 9
  a R1=∑||Fo|-|Fc||/∑|Fo||; b wR2={∑w(Fo2-Fc2)2/∑[w(Fo2)]2}1/2.

  下载: 导出CSV

  Table 2.  FT-IR spectra of H₃L and complexes 1 and 2 cm^-1

  Compound	νO-H	νC=N	νAr-O	νM-N	νM-O
  H3L	3 436	1 613	1 253	—	—
  1	3 387	1 602	1 234	516	426
  2	3 428	1 597	1 213	512	423

  下载: 导出CSV

  Table 3.  Selected bond lengths (nm) and angles (°) for complex 1

  Ni1-O1	0.208 68(15)	Ni1-O7	0.204 17(14)	Ni2-O8	0.206 33(13)
  Ni1-O2	0.200 25(14)	Ni1-O1#1	0.204 14(12)	Ni2-O9	0.211 58(14)
  Ni1-O5	0.200 69(14)	Ni1-O2	0.201 32(14)	Ni2-N1	0.211 21(17)
  Ni1-O6	0.218 97(14)	Ni2-O5	0.202 22(13)	Ni2-N2	0.209 30(18)
  O1-Ni1-O2	80.68(6)	O5-Ni1-O7	89.25(6)	O5-Ni2-O8	91.69(5)
  O1-Ni1-O5	161.72(5)	O1#1-Ni1-O5	100.61(5)	O5-Ni2-O9	86.90(5)
  O1-Ni1-O6	121.26(6)	O6-Ni1-O7	83.53(5)	O5-Ni2-N1	164.56(6)
  O1-Ni1-O7	88.70(6)	O1#1-Ni1-O6	91.87(5)	O5-Ni2-N2	86.34(6)
  O1-Ni1-O1#1	84.11(5)	O1#1-Ni1-O7	167.88(6)	O8-Ni2-O9	178.16(6)
  O2-Ni1-O5	81.38(6)	O2-Ni2-O5	80.74(6)	O8-Ni2-N1	90.09(6)
  O2-Ni1-O6	157.81(6)	O1-Ni2-O8	91.38(5)	O8-Ni2-N2	87.55(6)
  O2-Ni1-O7	94.48(5)	O2-Ni2-O9	89.56(6)	O9-Ni2-N1	91.59(6)
  O1#1-Ni1-O2	93.96(5)	O1-Ni2-N1	83.88(6)	O9-Ni2-N2	91.17(6)
  O5-Ni1-O6	76.51(6)	O1-Ni2-N2	167.01(6)	N1-Ni2-N2	109.06(7)
  Symmetry code: #1: 2-x, 1-y, 1-z.

  下载: 导出CSV

  Table 4.  Hydrogen bonding interaction parameters for complex 1

  D-H…A	d(D-H) / nm	d(H…A) / nm	d(D…A) / nm	∠D-H…A / (°)
  C8-H8A…O9	0.097	0.244	0.329 0(3)	146
  C20-H20B…O5	0.096	0.257	0.312 8(3)	177

  下载: 导出CSV

  Table 5.  Selected bond lengths (nm) and angles (°) for complex 2

  Zn1-O5	0.205 4(3)	Zn1-O6#1	0.201 5(3)	Zn2-N1	0.211 8(4)
  Zn1-O6	0.204 1(3)	Zn2-O1	0.195 1(3)	Zn2-N1	0.209 5(4)
  Zn1-O8	0.198 2(3)	Zn2-O5	0.202 6(3)
  Zn1-O9	0.203 4(3)	Zn2-O7	0.197 8(2)
  O5-Zn1-O6	79.33(11)	O8-Zn1-O9	108.61(12)	O5-Zn2-O7	92.37(11)
  O5-Zn1-O8	95.91(12)	O6#1-Zn1-O8	98.56(11)	O5-Zn2-N1	171.13(13)
  O5-Zn1-O9	93.25(11)	O6#1-Zn1-O9	100.40(12)	O5-Zn2-N2	83.69(14)
  O5-Zn1-O6#1	155.75(12)	O1-Zn2-O5	96.09(13)	O7-Zn2-N1	92.14(13)
  O6-Zn1-O8	147.18(12)	O1-Zn2-O7	112.79(12)	O7-Zn2-N2	127.64(14)
  O6-Zn1-O9	104.10(12)	O1-Zn2-N1	89.20(14)	N1-Zn2-N2	87.51(15)
  O6-Zn1-O6#1	77.95(11)	O1-Zn2-N2	119.56(13)
  Symmetry code: #1: 1-x, 1-y, 1-z.

  下载: 导出CSV

  Table 6.  Hydrogen bonding interaction parameters for complex 2

  D-H…A	d(D-H) / nm	d(H…A) / nm	d(D…A) / nm	∠D-H…A /(°)
  O9-H9…O1	0.086(3)	0.188(3)	0.267 5(4)	153
  O9-H9…O2	0.086(3)	0.242(2)	0.308 2(4)	134
  C7-H7B…O3#2	0.096	0.260	0.339 3(6)	141
  C9-H9A…O7	0.097	0.242	0.326 8(6)	146
  C18-H18…O6#1	0.097	0.254	0.325 4(6)	130
  Symmetry codes: #1: 2-x, 1-y, 2-z; #2: -1+x, y, z.

  下载: 导出CSV
•