English

• 0.   Introduction

  Zinc metal complexes have attracted attention due to their diverse structures, low toxicity, and wide applications. A series of zinc metal complexes have been designed, synthesized, and applied to the research on anticancer^[1], antitumor^[2], antibacterial^[3], and other biological activities^[4-5]. In recent decades, research on the antibacterial activities of zinc complexes has received increasing attention. Through the unremitting efforts of scientific workers, some zinc complexes have been developed as a class of important antibacterial agents and are widely used in disease treatment^[6].

  In addition to the biological functions of the zinc element, the ligand also plays an extremely important role in the antibacterial activities of zinc complexes^[7]. Excellent ligands can directly improve the antibacterial activities of zinc complexes, so the design and synthesis of suitable ligands have become a focus and hotspot in the research on the antibacterial activities of zinc complexes. According to the literature reports^[8], various types of zinc complexes have been obtained by the reactions of zinc salts with compounds such as Schiff bases^[9], pyridine derivatives^[10], phenanthroline derivatives^[11], and others^[12]. Compared to the free ligand and zinc salt, the zinc complex demonstrated better antibacterial effects^[13].

  5-Phenyl-1H-pyrazole derivatives are a typical class of heterocyclic aromatic amines that can be used to synthesize zinc metal complexes as a ligand, but there are few research reports on their antibacterial activities. To further investigate the antibacterial activities of the zinc complexes bearing 5-phenyl-1H-pyrazole group, we have designed and synthesized two zinc(Ⅱ) complexes [Zn(HL)₂(NCS)(CH₃COO)] (1) and [Zn₂(L)₂(HL)₂(NCS)₂]₂·2CH₃OH (2) with (H₂L)SCN (5-methyl-3-phenyl-2H-pyrazol-1-ium thiocyanate) (Scheme 1) as a ligand. Simultaneously, the antibacterial activities of the compounds were evaluated in vitro against three bacterial strains Candida albicans (C. albicans), Staphylococcus aureus (S. aureus), and Escherichia coli (E. coli).

  Scheme 1

  

  Scheme 1.  Structure of ligand (H₂L)SCN

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  1.   Experimental

  1.1   Materials and methods

  The whole reagents and solvents of AR grade were purchased commercially and applied in the air without further purification. The bacterial strains were presented by the School of Biology and Food Engineering of Suzhou University. IR spectra (KBr pellet, 400-4 000 cm^-1) were measured on an FTS-40 spectrometer. ¹H NMR and ¹³C NMR spectra studies were carried out on a Bruker Avance 500 spectrometer. Elemental analysis data for C, H, and N were collected by using a Vario EL Ⅲ elemental analyzer. The melting point was recorded on a WRS-1B digital melting point apparatus without correction.

  1.2   Synthesis of ligand (H₂L)SCN

  To a methanol solution (35 mL) of benzoylacetone (0.50 g, 3.08 mmol) was added thiosemicarbazide (0.28 g, 3.08 mmol) slowly. After being stirred under reflux for 36 h, the solution was evaporated to dryness under vacuum. The white powdered residue was dissolved in CH₂Cl₂ (10 mL), and colorless bulk crystals of the ligand were obtained by recrystallization under room temperature after 2 d in an 83% yield. m.p. 93-95 ℃. Anal. Calcd. for C₁₁H₁₁N₃S(%): C, 60.80; H, 5.10; N, 19.34. Found(%): C, 61.02; H, 4.88; N, 19.31. ¹H NMR (500 MHz, CDCl₃): δ 12.80 (br, 1H, NH), 7.82-7.80 (d, J=8.0 Hz, 2H, 2,6-Ar-H), 7.51-7.43 (m, 3H, 3, 4,5-Ar-H), 6.80 (s, 1H, C=CH), 2.36 (s, 3H, CH₃). ¹³C NMR (125 MHz, CDCl₃): δ 147.9, 144.2, 129.5, 129.2, 128.0, 126.2, 112.7, 103.2, 11.8. IR (KBr, cm^-1): 3 125(m), 2 683(s), 2 020(s), 1 994(s), 1 619(s), 1 599(m), 1 540(w), 1 470(m), 1 393(w), 1 363(w), 1 293(m), 1 267(m), 1 217(m), 1 157(m), 1 073(m), 1 002(m), 927(w), 856(m), 830(m), 777(s), 691(s), 512(m), 504(w), 496(w).

  1.3   Synthesis of complex 1

  To a methanol solution (35 mL) of the ligand (0.60 g, 2.76 mmol) was added Zn(OAc)₂·2H₂O (0.30 g, 1.38 mmol) slowly. After being stirred under reflux for 24 h, the hot solution was filtered to discard the insoluble substances, and the solvent was evaporated to dryness under vacuum. The white viscous residue was dissolved in a co-solvent of ethanol and dichloromethane (7 mL, V_ethanol/V_{dichloromethane}=1/4), and colorless needle-like crystals of complex 1 were obtained by recrystallization at 25 ℃ after 3 d in 73% yield. m.p. 157-158 ℃. Anal. Calcd. for C₂₃H₂₃N₅O₂SZn(%): C, 55.37; H, 4.65; N, 14.04. Found(%): C, 55.31; H, 4.67; N, 13.77. IR (KBr, cm^-1): 3 505(w), 3 032(m), 2 370(w), 2 070(vs), 1 810(m), 1 750(w), 1 511(m), 1 320(w), 1 220(m), 1 160(m), 1 060(s), 960(m), 915(w), 814(m), 762(m), 703(m), 676(s), 643(m), 523(w), 481(w).

  1.4   Synthesis of complex 2

  To a methanol solution (35 mL) of the ligand (0.60 g, 2.76 mmol) was added ZnCl₂ (0.19 g, 1.38 mmol) slowly. After being stirred under reflux for 24 h, the hot solution was filtered to discard the insoluble substances, and the solvent was evaporated to dryness under vacuum. The white viscous residue was dissolved in a co-solvent of methanol and n-hexane (8 mL, V_methanol/V_n-hexane=3/1), and colorless needle-like crystals of complex 2 were obtained by recrystallization at 25 ℃ after 2 d in 69% yield. m.p. 124-125 ℃. Anal. Calcd. for C₄₄H₄₆N₁₀O₂S₂Zn₂(%): C, 56.11; H, 4.92; N, 14.87. Found(%): C, 55.87; H, 5.16; N, 15.02. IR (KBr, cm^-1): 3 411(s), 3 050(m), 2 083(vs), 1 572(m), 1 500(m), 1 428(s), 1 234(m), 1 209(w), 1 140(m), 1 070(s), 981(m), 920(w), 812(m), 765(s), 698(s), 643(m), 545(w), 498(w).

  1.5   Crystal structure determination

  Crystallographic data measurements were conducted on a Bruker D8 VENTURE diffractometer for complex 1 and a SuperNova Dual diffractometer for the ligand and complex 2 with Mo Kα radiation (λ= 0.071 073 nm). The SADABS program was used to correct the empirical absorption effect on the data of complex 1. The empirical absorption correction using spherical harmonics on the data of the ligand and complex 2 was performed in the SCALE3 ABSPACK scaling algorithm. The crystal structures were solved directly with the SHELXT program, and refined by full-matrix least-squares with SHELXL 2018/3 program. All non-hydrogen atoms were refined anisotropically and hydrogen atoms were added in the geometrically idealized positions. In complex 1, two carbon atoms of the benzene ring and one sulfur atom of the isothiocyanato group from the ligand were found to be disordered in two different orientations. Table 1 shows the crystallographic data of the compounds, Table 2 lists the selected bond lengths and bond angles, and Table S1 and S2 (Supporting information) give the structural parameters of the hydrogen bonds and π…π stacking interactions.

  Table 1

  

  Table 1.  Crystallographic data of the compounds

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  Parameter	(H2L)SCN	1	2
  Formula	C11H11N3S	C23H23N5O2SZn	C44H46N10O2S2Zn2
  Formula weight	217.29	498.89	941.77
  Temperature/ K	150	193	150
  Crystal system	Triclinic	Triclinic	Monoclinic
  Space group	P1	P1	P21/n
  a / nm	0.705 60(9)	0.880 78(8)	1.480 32(11)
  b / nm	0.950 34(9)	1.068 36(9)	0.821 02(7)
  c / nm	1.781 97(9)	1.332 09(12)	1.845 95(13)
  α / (°)	86.174(6)	79.059(4)
  β / (°)	80.023(7)	81.485(3)	97.135(7)
  γ / (°)	73.268(9)	79.586(4)
  Volume / nm3	1.126 8(2)	1.202 00(19)	2.226 1(3)
  Z	4	2	2
  Dc / (g·cm-3)	1.281	1.378	1.405
  μ / mm-1	0.257	1.137	1.220
  F(000)	456	516	976
  Reflection collected	8 064	10 311	9 775
  Unique reflection (Rint)	3 971 (0.039)	5 318 (0.068)	3 918 (0.032)
  Goodness-of-fit on F2	1.074	0.995	1.071
  Final R indices [I > 2σ(I)]	R1=0.063 4, wR2=0.152 8	R1=0.072 8, wR2=0.201 3	R1=0.035 4, wR2=0.076 0
  R indices (all data)	R1=0.085 2, wR2=0.167 9	R1=0.085 9, wR2=0.219 6	R1=0.042 8, wR2=0.080 3

  Table 2

  

  Table 2.  Selected bond lengths (nm) and bond angles (°) of the compounds

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  (H2L)SCN
  N1—N2	0.135 2(4)	N1—C7	0.134 6(4)	N2—C9	0.133 6(4)
  C7—C8	0.139 1(5)	C8—C9	0.1383 (5)	S1—C21	0.161 9(4)
  N6—C21	0.117 4(5)	C1—C7	0.146 7(4)	C9—C10	0.148 4(5)
  N2—N1—C7	108.9(3)	N1—N2—C9	109.8(3)	N1—C7—C8	106.8(3)
  N2—C9—C8	107.0(3)	N2—C9—C10	121.6(3)	N1—C7—C1	122.2(3)
  1
  Zn1—O1	0.194 0(3)	Zn1—N1	0.201 2(3)	Zn1—N3	0.199 9(3)
  Zn1—N5	0.193 7(4)	N1—N2	0.136 1(4)	N3—N4	0.134 3(4)
  O1—Zn1—N1	108.84(12)	O1—Zn1—N3	113.12(12)	O1—Zn1—N5	107.86(14)
  N1—Zn1—N3	107.57(12)	N1—Zn1—N5	111.47(14)	N3—Zn1—N5	108.03(15)
  2
  Zn1—N2	0.197 46(19)	Zn1—N3	0.197 6(2)	Zn1—N4	0.204 02(18)
  Zn1—N1ⅰ	0.198 50(18)	N1—N2	0.137 9(3)	N4—N5	0.136 1(3)
  N2—Zn1—N	3107.87(8)	N2—Zn1—N4	118.38(7)	N1i —Zn1—N2	112.08(8)
  N3—Zn1—N4	98.33(9)	N1(i)—Zn1—N3	116.28(9)	N1i—Zn1—N4	103.56(7)
  Symmetry code: ⅰ 1-x, 1-y, 1-z for 2.

  1.6   Antibacterial activity

  The antibacterial activities of the synthesized compounds were evaluated in vitro against different bacterial strains by the agar diffusion method. The compounds were separately dissolved in DMSO to prepare the solutions of 5.00 mg·mL^-1, which were further diluted to obtain two different mass concentrations of 2.50 and 1.25 mg·mL^-1. Three bacteria including C. albicans, S. aureus, and E. coli were selected as the test bacteria. After being impregnated in the solution for 2 h, the sterilized filter papers of 6 mm in diameter were placed on the culture medium inoculated with the bacterial strains, and then the culture medium was incubated for 24 h at 37 ℃. By measuring the inhibition zone diameters, the antibacterial activities of the compounds were determined and evaluated.

  2.   Results and discussion

  2.1   IR spectra analysis

  The FTIR spectrum for the free ligand had an obvious absorption peak at 1 073 cm^-1, which is assigned to the stretching vibration of N—N in the pyrazole group, while for complex 1 the peak was shifted to 1 060 cm^-1 and for complex 2 the peak was shifted to 1 070 cm^-1, confirming that the nitrogen atom from the pyrazole group is involved in the coordination reaction. Compared with the stretching vibration absorption peak (2 020 cm^-1) of C≡N in the free ligand, a protruding infrared absorption peak appeared at 2 070 cm^-1 for complex 1 and 2 083 cm^-1 for complex 2, confirming that the nitrogen atom from the thiocyanate anion is coordinated to the zinc cation from Zn(OAc)₂·2H₂O and ZnCl₂. The appearance of a new characteristic absorption peak at 523 cm^-1 in the spectrum of complex 1 could be referred to as the stretching vibration of Zn—N. Similarly, the characteristic peak of the stretching vibration of Zn—N in complex 2 was observed at 545 cm^-1. All those are further evidence of the coordination reactions between zinc cations from Zn(OAc)₂·2H₂O and ZnCl₂ and the nitrogen atoms from the pyrazole group and isothiocyanato.

  2.2   Structural description

  2.2.1   Structure of ligand (H₂L)SCN

  The asymmetric unit of ligand (H₂L)SCN consists of one crystallographically independent H₂L⁺ cation and one thiocyanate anion (Fig.1). The thiocyanate anion balances the valence charge of the H₂L⁺ cation as the counter anion. As shown in Table 2, the bond lengths and bond angles in the benzene ring and pyrazole ring agree well with the values of similar compounds^[14]. The bond length of C1—C7 is 0.134 6(4) nm, longer than the normal value of the C=C double bond but shorter than that of the C—C single bond, which is due to the π…π conjugation effect between the benzene ring and pyrazole ring. The bond length of C21≡N6 is 0.117 4(5) nm, which exhibits the typical triple bond character. The dihedral angle between the benzene ring plane composed of atoms (C1 to C6) and the pyrazole ring composed of atoms (N1, N2, C5, C9, C8, and C7) is 5.281(13)°, indicating that the two planes are nearly coplanar. This is also further confirmed by the torsion angles of C6—C1—C7—C8 being -4.5(6)° and C2—C1—C7—N1 being -5.5(6)°.

  Figure 1

  

  Figure 1.  Crystal structure of ligand (H₂L)SCN with 30% probability ellipsoids for non-hydrogen atoms

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  As shown in Fig.2, there exists an abundance of hydrogen bonds and π…π stacking interactions in the crystal structure. The nitrogen atoms (N6, N3) from the thiocyanate anion serve as H-acceptors to the nitrogen atoms (N1, N4) from the pyrazole group of the ligand, forming two types of intramolecular hydrogen bonds N1…N6 of 0.281 1(4) nm (N1—H1…N6) and N4…N3 of 0.278 9(4) nm (N4—H4A…N3), which further increase the structure stability of the ligand. In addition, the nitrogen atoms (N2, N5) from the pyrazole group serve as H-donors to the nitrogen atoms (N3, N6) from the thiocyanate anion, forming two types of intermolecular hydrogen bonds N2…N3 of 0.284 3(4) nm (N2—H2…N3) and N5…N6 of 0.275 9(4) nm (N5—H5A…N6), by which two neighboring ligand molecules are connected into a bimolecular structure. Meanwhile, three types of π…π stacking interactions with centroid…centroid distances in a range of 0.350 6(2)-0.382 4(2) nm and dihedral angles in a range of 1.77°-5.28° are observed among the neighboring ligands. By the above-mentioned hydrogen bonds and π…π stacking interactions, an infinite 2D network structure is constructed.

  Figure 2

  

  Figure 2.  Two-dimensional network structure of ligand (H₂L)SCN

  Symmetry codes: ^ⅰ 1-x, 1-y, -z; ^ⅱ-x, 1-y, 1-z; ^ⅲ 1-x, 1-y, 1-z; Cg1: N1, N2, C9, C8, C7; Cg2: C1-C6; Cg3: N4, N5, C12, C13, C14; Cg4: C15-C20.

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  2.2.2   Structure of complex 1

  The asymmetric unit of complex 1 consists of two HL molecules, one acetate anion, one isothiocyanato, and one central Zn(Ⅱ) cation. As shown in Fig.3, the H₂L⁺ cation in the ligand releases an H⁺ ion with the process of reaction, generating one HL molecule coordinated to the Zn(Ⅱ) cation in an η¹ mode. The Zn1 cation is four-coordinated by two nitrogen atoms (N1 and N2) from two different pyrazole groups, one oxygen atom (O1) from one acetate anion, and one nitrogen atom (N5) from one isothiocyanato, resulting in a distorted tetrahedral [ZnN₃O] coordination geometry. The Zn1 cation lies approximately in the center of the tetrahedron, and the three nitrogen atoms (N1, N3, and N5) and one oxygen atom (O1) occupy the four vertices of the tetrahedron. Three Zn1—N bond lengths are 0.201 2(3), 0.199 9(3), and 0.193 7(4) nm respectively, which are comparable to the reported values in related Zn(Ⅱ) complexes^[15]. None of the Zn1—N bond lengths is equal to the Zn1—O1 bond of 0.194 0(3) nm. The six bond angles O1—Zn1—N1 of 108.84(12)°, O1—Zn1—N3 of 113.12(12)°, O1—Zn1—N5 of 107.86(14)°, N1—Zn1—N3 of 107.57(12)°, N1—Zn1—N5 of 111.47(14)°, and N3—Zn1—N5 of 108.03(15)° are unequal to each other and deviate significantly from the regular tetrahedral angle of 109.5°. All these data confirm that the Zn1 cation is located in an imperfect tetrahedron environment.

  Figure 3

  

  Figure 3.  Crystal structure of complex 1 with 30% probability ellipsoids for non-hydrogen atoms

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  As shown in Fig.4, two types of hydrogen bonds are observed in the crystal structure which benefit the structure stability of complex 1 and the formation of a 1D chain structure. The oxygen atom (O2) from the acetate anion serves as an H-acceptor to the nitrogen atom (N4) from the pyrazole group in the same asymmetric unit, forming the intramolecular hydrogen bond N4…O2 of 0.273 8(4) nm (N4—H4…O2), and the oxygen atom (O2^ⅰ) from the acetate anion serves as an H-acceptor to the nitrogen atom (N2) from the pyrazole group in another asymmetric unit, forming the intermolecular hydrogen bond N2…O2^ⅰ of 0.276 9(4) nm (N2—H2…O2^ⅰ). Another noticeable characteristic of complex 1 is that the abundant π…π stacking interactions and C—H…π weak interactions exist in the crystal structure. Two types of C—H…π weak interactions (C18…Cg3^ⅱ of 0.384 6(5) nm and C22…Cg2^ⅲ of 0.347 5(5) nm) and the face-to-face Cg2…Cg4^ⅳ stacking interaction with the centroid-centroid distance of 0.371 7(4) nm and the dihedral angle of 5.74° further enhance the structural stability of complex 1. By the above-mentioned hydrogen bonds and weak interactions, the asymmetric units are extended into an infinite 1D chain structure.

  Figure 4

  

  Figure 4.  One-dimensional chain structure of complex 1

  Symmetry codes: ^ⅰ1-x, 1-y, 1-z; ^ⅱ x, 1+y, z; ^ⅲ 1-x, 1-y, 1-z; ^ⅳ 1-x, 2-y, 1-z; Cg2: N3, N4, C17, C18, C19; Cg3: C1-C6; Cg4: C11-C16.

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  2.2.3   Structure of complex 2

  Complex 2 is a binuclear Zn(Ⅱ) molecule with a double-bridged structure. As shown in Fig.5, the asymmetric unit consists of one lattice methanol molecule, one HL molecule, one deprotonated L^- anion, one isothiocyanato, and one central Zn(Ⅱ) cation. Similar to complex 1, one HL molecule generated from the H₂L⁺ cation is coordinated to the Zn(Ⅱ) cation in an η¹ mode. But interestingly, two HL molecules are deprotonated and then coordinated to the Zn(Ⅱ) cation. The Zn1 cation is four-coordinated by three nitrogen atoms (N4, N2, and N1^ⅰ) from three different pyrazole groups and one nitrogen atom (N3) from one isothiocyanato, displaying a distorted tetrahedral [ZnN₄] coordination geometry. The four nitrogen atoms (N3, N4, N2, and N1^ⅰ) are on the four vertices of the tetrahedron, and the Zn1 cation lies approximately in the center of the tetrahedron. The four Zn1—N bond lengths, which fall in a range of 0.204 02(18)-0.197 46(19) nm, are unequal to each other. The six bond angles around the Zn1 cation are in a range of 98.33(9)°-118.38(7)°, which deviates from the standard value of the tetrahedral angle. Based on these results, the tetrahedron can be inferred to have a slightly distorted structure. The Zn1^ⅰ cation possesses a similar coordination mode and coordination unit with the Zn1 cation, which confirms that complex 2 is a relatively perfect symmetrical structure. The two adjacent Zn(Ⅱ) cations are bridged to form a six-membered ring Zn₂N₄ by two pyrazole groups in a μ²-η¹∶η¹-bridging coordination mode, with a nonbonding Zn…Zn separation of 0.358 43(5) nm.

  Figure 5

  

  Figure 5.  Crystal structure of complex 2 with 30% probability ellipsoids for non-hydrogen atoms

  Symmetry code: ^ⅰ 1-x, 1-y, 1-z.

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  As shown in Fig.6, there are two types of intramolecular hydrogen bonds in the crystal structure. The oxygen atom (O1) from the methanol serves as an H-donor to the sulfur atom (S1) from the isothiocyanato, forming the hydrogen bond O1…S1 of 0.337 1(3) nm (O1—H1…S1), and as an H-acceptor to the nitrogen atom (N5) from the pyrazole group, forming the hydrogen bond N5…O1 of 0.286 2(4) nm (N5—H5…O1). By the intramolecular hydrogen bonding interactions, the crystal structure of complex 2 is further stabilized. In addition, the neighboring asymmetric units are further stabilized by the face-to-face Cg2…Cg4^ⅰ stacking interaction with the centroid-centroid distance of 0.363 65(16) nm and the dihedral angle of 7.43°. Meanwhile, the hydrogen bond C13…Cg2^ⅱ of 0.345 9(3) nm (C13—H13…Cg2^ⅱ) is observed between the hydrogen atom (H13) of the benzene ring and the Cg2 plane, which leads to the construction of an infinite 1D chain structure.

  Figure 6

  

  Figure 6.  One-dimensional chain structure of complex 2

  Symmetry codes: ^ⅰ 1-x, 1-y, 1-z; ^ⅱ 1-x, -y, 1-z; Cg2: N4, N5, C19, C18, C17; Cg4: C1-C6.

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  2.3   Antibacterial activity

  Table 3 presents the screening results for the antibacterial experiments of the synthesized compounds. The (H₂L)SCN ligand exhibited relatively good antibacterial activities against C. albicans, S. aureus, and E. coli, which benefited from the biological function of the pyrazole functional group^[16], while DMSO had no inhibitory effects at all. Due to the biological function of the zinc element and the complexation of the ligand to the zinc ion, the complexes exhibited stronger antibacterial activities against the same bacteria than the ligand. As shown in Table 3, there exists a certain mass concentration dependence of the antibacterial activities. With the mass concentration of the compound increasing, the inhibition zone diameter also increased within a certain range. In comparison to complex 1, complex 2 possessed stronger antibacterial activities, which might be mainly related to the different coordination modes of the complexes and the number of 5-phenyl-1H-pyrazole groups in the complexes.

  Table 3

  

  Table 3.  Inhibition zone diameter of the compounds

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  Compound	ρ / (mg·mL-1)	Inhibition zone diameter / mm
  		C. albicans	S. aureus	E. coli
  DMSO		—	—	—
  (H2L)SCN	1.25	8.9	7.7	6.5
  	2.50	9.4	8.1	8.8
  	5.00	10.1	8.9	9.6
  1	1.25	13.1	11.9	13.4
  	2.50	15.0	12.2	15.4
  	5.00	16.3	14.6	17.0
  2	1.25	14.3	11.1	12.9
  	2.50	16.2	12.3	15.0
  	5.00	18.8	14.9	17.7

  3.   Conclusions

  In summary, two tetracoordinated Zn(Ⅱ) complexes [Zn(HL)₂(NCS)(CH₃COO)] (1) and [Zn₂(L)₂(HL)₂(NCS)₂]₂·2CH₃OH (2) bearing 5-phenyl-1H-pyrazole group have been synthesized and characterized. Complex 1 crystallizes in the triclinic system with space group P1, while complex 2 crystallizes in the monoclinic system with space group P2₁/n. By their respective hydrogen bonds and π…π stacking interactions, complexes 1 and 2 are further extended into a stable infinite 1D chain structure. Moreover, examination of their antibacterial activities indicated that the (H₂L)SCN ligand showed relatively good antibacterial activities, while complexes 1 and 2 possessed stronger antibacterial activities than the free ligand.

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

  
  
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  Scheme 1  Structure of ligand (H₂L)SCN

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  Figure 1  Crystal structure of ligand (H₂L)SCN with 30% probability ellipsoids for non-hydrogen atoms

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  Figure 2  Two-dimensional network structure of ligand (H₂L)SCN

  Symmetry codes: ^ⅰ 1-x, 1-y, -z; ^ⅱ-x, 1-y, 1-z; ^ⅲ 1-x, 1-y, 1-z; Cg1: N1, N2, C9, C8, C7; Cg2: C1-C6; Cg3: N4, N5, C12, C13, C14; Cg4: C15-C20.

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  Figure 3  Crystal structure of complex 1 with 30% probability ellipsoids for non-hydrogen atoms

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  Figure 4  One-dimensional chain structure of complex 1

  Symmetry codes: ^ⅰ1-x, 1-y, 1-z; ^ⅱ x, 1+y, z; ^ⅲ 1-x, 1-y, 1-z; ^ⅳ 1-x, 2-y, 1-z; Cg2: N3, N4, C17, C18, C19; Cg3: C1-C6; Cg4: C11-C16.

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  Figure 5  Crystal structure of complex 2 with 30% probability ellipsoids for non-hydrogen atoms

  Symmetry code: ^ⅰ 1-x, 1-y, 1-z.

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  Figure 6  One-dimensional chain structure of complex 2

  Symmetry codes: ^ⅰ 1-x, 1-y, 1-z; ^ⅱ 1-x, -y, 1-z; Cg2: N4, N5, C19, C18, C17; Cg4: C1-C6.

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  Table 1.  Crystallographic data of the compounds

  Parameter	(H2L)SCN	1	2
  Formula	C11H11N3S	C23H23N5O2SZn	C44H46N10O2S2Zn2
  Formula weight	217.29	498.89	941.77
  Temperature/ K	150	193	150
  Crystal system	Triclinic	Triclinic	Monoclinic
  Space group	P1	P1	P21/n
  a / nm	0.705 60(9)	0.880 78(8)	1.480 32(11)
  b / nm	0.950 34(9)	1.068 36(9)	0.821 02(7)
  c / nm	1.781 97(9)	1.332 09(12)	1.845 95(13)
  α / (°)	86.174(6)	79.059(4)
  β / (°)	80.023(7)	81.485(3)	97.135(7)
  γ / (°)	73.268(9)	79.586(4)
  Volume / nm3	1.126 8(2)	1.202 00(19)	2.226 1(3)
  Z	4	2	2
  Dc / (g·cm-3)	1.281	1.378	1.405
  μ / mm-1	0.257	1.137	1.220
  F(000)	456	516	976
  Reflection collected	8 064	10 311	9 775
  Unique reflection (Rint)	3 971 (0.039)	5 318 (0.068)	3 918 (0.032)
  Goodness-of-fit on F2	1.074	0.995	1.071
  Final R indices [I > 2σ(I)]	R1=0.063 4, wR2=0.152 8	R1=0.072 8, wR2=0.201 3	R1=0.035 4, wR2=0.076 0
  R indices (all data)	R1=0.085 2, wR2=0.167 9	R1=0.085 9, wR2=0.219 6	R1=0.042 8, wR2=0.080 3

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  Table 2.  Selected bond lengths (nm) and bond angles (°) of the compounds

  (H2L)SCN
  N1—N2	0.135 2(4)	N1—C7	0.134 6(4)	N2—C9	0.133 6(4)
  C7—C8	0.139 1(5)	C8—C9	0.1383 (5)	S1—C21	0.161 9(4)
  N6—C21	0.117 4(5)	C1—C7	0.146 7(4)	C9—C10	0.148 4(5)
  N2—N1—C7	108.9(3)	N1—N2—C9	109.8(3)	N1—C7—C8	106.8(3)
  N2—C9—C8	107.0(3)	N2—C9—C10	121.6(3)	N1—C7—C1	122.2(3)
  1
  Zn1—O1	0.194 0(3)	Zn1—N1	0.201 2(3)	Zn1—N3	0.199 9(3)
  Zn1—N5	0.193 7(4)	N1—N2	0.136 1(4)	N3—N4	0.134 3(4)
  O1—Zn1—N1	108.84(12)	O1—Zn1—N3	113.12(12)	O1—Zn1—N5	107.86(14)
  N1—Zn1—N3	107.57(12)	N1—Zn1—N5	111.47(14)	N3—Zn1—N5	108.03(15)
  2
  Zn1—N2	0.197 46(19)	Zn1—N3	0.197 6(2)	Zn1—N4	0.204 02(18)
  Zn1—N1ⅰ	0.198 50(18)	N1—N2	0.137 9(3)	N4—N5	0.136 1(3)
  N2—Zn1—N	3107.87(8)	N2—Zn1—N4	118.38(7)	N1i —Zn1—N2	112.08(8)
  N3—Zn1—N4	98.33(9)	N1(i)—Zn1—N3	116.28(9)	N1i—Zn1—N4	103.56(7)
  Symmetry code: ⅰ 1-x, 1-y, 1-z for 2.

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  Table 3.  Inhibition zone diameter of the compounds

  Compound	ρ / (mg·mL-1)	Inhibition zone diameter / mm
  		C. albicans	S. aureus	E. coli
  DMSO		—	—	—
  (H2L)SCN	1.25	8.9	7.7	6.5
  	2.50	9.4	8.1	8.8
  	5.00	10.1	8.9	9.6
  1	1.25	13.1	11.9	13.4
  	2.50	15.0	12.2	15.4
  	5.00	16.3	14.6	17.0
  2	1.25	14.3	11.1	12.9
  	2.50	16.2	12.3	15.0
  	5.00	18.8	14.9	17.7

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