English

• The chemistry of organotin carboxylates has flourished for decades, owing to their remarkable stru-ctural diversity^[1] and significant biological activity^[2-3], for example as antibacterial and antitumor agents, as well as other potential applications in catalysis^[4-5]. Recently, carboxylic acids with additional donor atoms have proved their values in the capability of affecting the coordination modes of tin atom as well as decent bioactivities, and therefore attracted a great deal of attention. Lots of organotin carboxylates derived from S- or N-functionalized carboxylic acids have been synthesized and characterized in recent years, which displayed fascinating structural features^[6-11] and excellent biological activities^[12-15]. On the other hand, tetrazole has been extensively exploited as ligand in coordination chemistry because of its variable coor-dination modes, and its derivatives have prominent versatile biological activities^[16-17]. Our previous work showed that organotin derivatives of tetrazolyl-1-acetic acid exhibited considerable structural diversity and good antifungal activity^{[12, 18]}. As an extension of our investigations on biologically active organotin deriva-tives, we herein report the syntheses, structures and antitumor activities in vitro of organotin 5-substituted 1H-tetrazolyl-1-acetates.

  1.   Experimental

  NMR spectra were obtained with a Bruker 400 spectrometer, and the chemical shifts were reported with respect to reference standards (internal SiMe₄ for ¹H and ¹³C NMR spectra, external SnMe₄ for ¹¹⁹Sn NMR). IR spectra were obtained from a Tensor 27 spectrometer as KBr discs. Elemental analyses were carried out on an Elementar Vario EL analyzer. Melting points were measured with an X-4 digital micro melting-point apparatus and were uncorrected. 5-Methyl-1H-tetrazolyl-1-acetic acid (L¹) and 5-amino-1H-tetrazolyl-1-acetic acid (L²)^[19] were prepared accor-ding to the published methods. Organotin oxide and organotin hydroxide are commercially available and used as received without further purification.

  1.1   Synthesis of 1

  The mixture of 5-methyl-1H-tetrazolyl-1-acetic acid (0.28 g, 2 mmol) and (Ph₃Sn)₂O (0.72 g, 1 mmol) in anhydrous benzene (40 mL) was stirred and heated at reflux for 8 h. The reaction mixture was filtered off while hot, and the filtrate was concentrated to give the crude product, which was recrystallized from benzene/hexane to afford colorless crystals of 1. Yield: 80% (0.79 g), m.p. 96~98 ℃. ¹H NMR (CDCl₃): δ 2.34 (s, 3H, CH₃), 5.08 (s, 2H, CH₂), 7.45~7.55 (m, 9H, C₆H₅), 7.60~7.74 (m, 6H, C₆H₅). ¹³C NMR (CDCl₃): δ 8.8 (CH₃), 48.5 (CH₂), 128.5, 129.0 (³J(¹³C-^119/117Sn)=64.3 Hz), 130.9, 136.9 (²J(¹³C-^119/117Sn)=48.9 Hz) (C₆H₅), 152.6 (CN₄), 169.9 (COO). ¹¹⁹Sn NMR (CDCl₃): δ -82.7. IR (cm^-1): ν_as(COO) 1 674, ν_s(COO) 1 393. Anal. Calcd. for C₂₂H₂₀N₄O₂Sn(%): C 53.80, H 4.10, N 11.41; Found(%): C 53.99, H 4.31, N 11.07.

  1.2   Synthesis of 2

  This complex was obtained similarly using tricyclohexyltin hydroxide instead of (Ph₃Sn)₂O as described above for 1, but in a 1:1 molar ratio. Yield: 68%, m.p. 133~135 ℃. ¹H NMR (CDCl₃): δ 1.24~1.42 (m, 9H), 1.60~1.73 (m, 15H), 1.81~1.98 (m, 9H) (C₆H₁₁), 2.55 (s, 3H, CH₃), 5.06 (s, 2H, CH₂). ¹³C NMR (CDCl₃): δ 8.9 (CH₃), 26.8, 28.8 (³J(¹³C-^119/117Sn)=63.8 Hz), 30.9 (²J(¹³C-^119/117Sn)=14.6 Hz), 34.5, 48.7 (CH₂), 152.3 (CN₄), 168.8 (COO). ¹H NMR (acetone-d₆): δ 1.11 ~1.20 (m, 9H), 1.46~1.58 (m, 16H), 1.73~1.80 (m, 8H)(C₆H₁₁), 2.41 (s, 3H, CH₃), 5.10 (s, 2H, CH₂). ¹³C NMR (acetone-d₆): δ 7.3 (CH₃), 47.8 (CH₂), 26.0 (⁴J(¹³C-^119/117Sn)=7 Hz), 28.1, 30.1 (²J(¹³C-^119/117Sn)=18 Hz), 34.4 (¹J(¹³C-^119/117Sn)=359, 343 Hz) (C₆H₁₁), 151.9 (CN₄), 168.7 (COO). ¹¹⁹Sn NMR (acetone-d₆): δ 17.7. IR (cm^-1): ν_as(COO) 1 663, ν_s(COO) 1 351. Anal. Calcd. for C₂₂H₃₈N₄O₂Sn(%): C 51.88, H 7.52, N 11.00; Found(%): C 51.60, H 7.55, N 10.78.

  1.3   Synthesis of 3

  The mixture of 5-amino-1H-tetrazolyl-1-acetic acid (0.29 g, 2 mmol) and (Ph₃Sn)₂O (0.72 g, 1 mmol) in anhydrous benzene (40 mL) was stirred and heated at reflux for 8 h. After cooling to room temperature, the solid was filtered off and recrystallized from acetone/benzene to afford white crystals of 3. Yield: 66% (0.65 g), m.p. 165~166℃. ¹H NMR (DMSO-d₆): δ 4.79 (s, 2H, CH₂), 6.59 (s, 2H, NH₂), 7.39~7.48 (m, 9H), 7.70~7.92 (m, 6H) (C₆H₅). ¹³C NMR (DMSO-d₆): δ 47.4 (CH₂), 128.3 (³J(¹³C-^119/117Sn)=70 Hz), 129.0, 136.2 (²J(¹³C-^119/117Sn)=47 Hz), 142.5 (C₆H₅), 155.8 (CN₄), 168.8 (COO). ¹¹⁹Sn NMR (DMSO-d₆): δ -262.2. IR (cm^-1): ν(NH₂) 3 403 and 3 192, ν_as(COO) 1 624, ν_s(COO) 1 384. Anal. Calcd. for C₂₁H₁₉N₅O₂Sn(%): C 51.25, H 3.89, N 14.23; Found(%): C 51.13, H 4.14, N 14.18.

  1.4   Synthesis of 4

  This complex was obtained similarly using 5-amino-1H-tetrazolyl-1-acetic acid and (ⁿBu₃Sn)₂O instead of 5-methyl-1H-tetrazolyl-1-acetic acid and (Ph₃Sn)₂O as described above for 1. Yield: 69%, m.p. 113~116 ℃. ¹H NMR (acetone-d₆): δ 0.74 (t, J=7.3 Hz, 9H, CH₃), 1.09~1.23 (m, 12H, CH₂CH₂CH₂CH₃), 1.40~1.56 (m, 6H, SnCH₂), 4.78 (s, 2H, CH₂), 5.98 (s, 2H, NH₂). ¹³C NMR (acetone-d₆): δ 13.1 (CH₃), 17.5 (¹J(¹³C-^119/117Sn)=412, 394 Hz) (SnCH₂), 26.7 (³J(¹³C-^119/117Sn)=72 Hz) (CH₂CH₃), 27.7 (²J(¹³C-^119/117Sn)=26 Hz) (SnCH₂CH₂), 47.4(CH₂), 156.0(CN₄), 169.7(COO). ¹¹⁹Sn NMR (acetone -d₆): δ 69.9. IR (cm^-1): ν(NH₂) 3 372 and 3 202, ν_as(COO) 1 647, ν_s(COO) 1 376. Anal. Calcd. for C₁₅H₃₁N₅O₂Sn(%): C 41.69, H 7.23, N 16.21; Found(%): C 41.37, H 6.81, N 16.70.

  1.5   Synthesis of 5

  This complex was obtained similarly using 5-amino-1H-tetrazolyl-1-acetic acid and tricyclohexyltin hydroxide instead of 5-methyl-1H-tetrazolyl-1-acetic acid and (Ph₃Sn)₂O as described above for 1, but in a 1:1 molar ratio. Yield: 72%, m.p. 164~166 ℃. ¹H NMR (acetone-d₆): δ 1.11~1.22 (m, 9H), 1.46~1.61 (m, 16H), 1.72~1.82 (m, 8H) (C₆H₁₁), 4.86 (s, 2H, CH₂), 5.91 (s, 2H, NH₂). ¹³C NMR (acetone-d₆): δ 27.6, 29.9, 31.6 (²J(¹³C-^119/117Sn)=17 Hz), 35.7 (¹J(¹³C-^119/117Sn)=357, 341 Hz) (C₆H₁₁), 48.0 (CH₂), 156.9 (CN₄), 171.0 (COO). ¹¹⁹Sn NMR (DMSO-d₆): δ -89.9. IR (cm^-1): ν(NH₂) 3 390 and 3 202, ν_as(COO) 1 644, ν_s(COO) 1 367. Anal. Calcd. for C₂₁H₃₇N₅O₂Sn(%): C 49.43, H 7.31, N 13.73; Found(%): C 49.27, H 7.37, N 14.15.

  1.6   Crystal structure determination

  Crystals of 2, 4 and 5 suitable for X-ray analysis were obtained by slowly cooling their hot acetone/hexane solutions. All intensity data were collected with a Rigaku Saturn diffractometer using Mo Kα radiation (λ=0.071 073 nm). The structures were solved by direct methods and difference Fourier map using SHELXS of the SHELXTL package and refined with SHELXL^[20] by full-matrix least-squares on F². All non-hydrogen atoms were refined with anisotropic displacement parameters. Hydrogen atoms were added geometrically and refined with riding model position parameters. The partial cyclohexyl carbons in 2 were disordered, and their occupancy factors were refined to 0.457 for C(18), C(19), C(21) and C(22) as well as 0.543 for C(18)′, C(19)′, C(21)′ and C(22)′. The butyl carbons of C(4)-C(15) in 4 were also disordered, satisfactory results were obtained when they were given occupancy factor of 0.5. A summary of the fundamental crystal data for these three complexes is listed in Table 1.

  Table 1

  

  Table 1.  Crystallographic data and refinement parameters for complexes 2, 4 and 5

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  Complex	2	4	5
  Formula	C22H38N4O2Sn	C15H31N5O2Sn	C21H37N5O2Sn
  Formula weight	509.25	432.14	510.27
  Crystal size / mm	0.20×0.20×0.20	0.20×0.18×0.06	0.20×0.20×0.20
  Crystal system	Monoclinic	Monoclinic	Monoclinic
  Space group	C2/c	C2/c	C2/c
  a / nm	1.653 7(1)	1.663 4(3)	1.639 7(2)
  b / nm	1.626 0(1)	1.451 4(3)	1.623 7(2)
  c / nm	1.967 0(2)	1.835 5(4)	1.950 1(2)
  β / (°)	113.223(1)	114.72(3)	114.665(7)
  T / K	293(2)	113(2)	293(2)
  V / nm3	4.860 6(7)	4.025 4(2)	4.718 4(9)
  Z	8	8	8
  Dc / (g·cm-3)	1.392	1.426	1.437
  θ range / (°)	1.835~25.005	1.945~25.02	3.37~25.01
  F(000)	2 112	1 776	2 112
  μ / mm-1	1.075	1.285	1.108
  Measured reflection	12 647	14 425	17 242
  Unique reflection (Rint)	4 292 (0.070 1)	3 550 (0.091 9)	4 156 (0.068 0)
  Observed reflection with [I≥2σ(I)]	3 420	2 429	3 119
  Parameter	276	318	270
  GOF	1.005	1.073	1.024
  Residuals R1, wR2	0.035 7, 0.089 1	0.077 4, 0.221 4	0.048 9, 0.097 9

  CCDC: 1854152, 2; 1854153, 4; 1854154, 5

  2.   Results and discussion

  2.1   Syntheses of complexes 1~5

  Triorganotin 5-substituted 1H-tetrazolyl-1-acetates (1~5) were easily obtained by the reaction of organotin oxide or organotin hydroxide with 5-methyl-1H-tetrazolyl-1-acetic acid or 5-amino-1H-tetrazolyl-1-acetic acid in anhydrous benzene (Scheme 1). The complexes showed significantly different solubility in organic solvents. Complexes 1 and 2 were moderate soluble in chlorinated solvents, while complexes 3~5 were slightly soluble in these solvents. All complexes were soluble in acetone, and very soluble in strong polar solvents such as DMF and DMSO. The complexes have been characterized by IR and NMR (¹H, ¹³C and ¹¹⁹Sn) spectra as well as elemental analyses.

  Scheme 1

  

  Scheme 1.  Syntheses of complexes 1~5

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  The IR spectra of complexes 1~5 showed the absence of the strong and broad band ascribed to the carboxyl group as well as the low carbonyl stretching frequencies, which indicated the removal of the carboxyl proton and the formation of the Sn-O bonds^[21]. The values of Δν(ν_as(COO)-ν_s(COO)) for 1~5 were observed in the region of 240~312 cm^-1, larger than those detected in the corresponding sodium salts of acids L¹ (216 cm^-1) and L² (226 cm^-1), in which the asymmetric and symmetric stretching vibrations of the carboxylate groups appeared at 1 624 and 1 408 cm^-1 for L¹, as well as 1 632 and 1 406 cm^-1 for L², respectively, implying the monodentate manner of the carboxylate groups in the complexes to the tin atom^[22-23]. The ¹H NMR spectroscopic data are also consistent with the suggested structures, exhibiting the expected integral values and chemical shifts. The ¹³C NMR spectra of 1~5 clearly showed the carbonyl carbon resonances at δ 168.8~171.1. The ¹¹⁹Sn NMR chemical shift of triphenyltin complex 1 (δ -82.7) in CDCl₃ solution was in the range of those values for four-coordinated triphenyltin carboxylates^[1], suggesting that this complex should be monomeric four-coordinated structure in non-coordinating solvent. Due to the relatively low solubility of other complexes, their satisfactory ¹¹⁹Sn and ¹³C NMR signals in CDCl₃ solution could not be observed. However, the ¹¹⁹Sn NMR values of tricyclohexyltin complex 2 (δ 17.7) and tributyltin complex 4 (δ 69.9) in the weakly coordinating solvent acetone-d₆ were also compared to those values reported in the corresponding four-coordinated tricyclohexyltin and tributyltin carboxylates^[1]. These results show that the polymeric structures in solid as shown in Fig. 1~3 break down to monomeric structures in solution possibly owing to the weak Sn…N interactions.

  Figure 1

  

  Figure 1.  Molecular structure of 2 with 30% probability displacement ellipsoids

  H atoms are omitted for clarity; Symmetry codes: ^ⅰ 0.5-x, 0.5+y, 0.5-z; ^ⅱ x, 1+y, z

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  Figure 2

  

  Figure 2.  Molecular structure of 4 with 30% probability displacement ellipsoids

  H atoms are omitted for clarity; Symmetry codes: ^ⅰ 0.5-x, 0.5+y, 0.5-z; ^ⅱ 0.5+x, 1+y, z

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  Figure 3

  

  Figure 3.  Molecular structure of 5 with 30% probability displacement ellipsoids

  H atoms are omitted for clarity; Symmetry codes: ^ⅰ 0.5-x, 0.5+y, 0.5-z; ^ⅱ x, 1+y, z

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  2.2   Crystal structures of complexes 2, 4 and 5

  The molecular structures of 2, 4 and 5 have been confirmed by X-ray crystallography, and presented in Fig. 1~3, respectively. The selected bond distances and angles are listed in Table 2. Fig. 1~3 show that the carboxylate group exhibits a monodentate coordination mode in the complexes, as above-mentioned by their IR spectra. Furthermore, the complexes form a similar linkage structure through the intermolecular Sn…N interactions. The Sn…N distance is markedly different in these three complexes. The Sn-N distance is 0.257 2(7) nm in 4, slightly shorter than those in triorganotin derivatives of tetrazolylacetic acid, such as triphenyltin 1H-tetrazolyl-1-acetate (0.260 9(6) nm)^[12]. The Sn…N distances in 2 (0.281 4(4) nm) and 5 (0.298 9(6) nm) are markedly longer than that in 4, but similar to that in tricyclohexyltin 1H-tetrazolyl-1-acetate (0.292 4(9) nm)^[12], indicating that the Sn…N interactions are very weak in 2 and 5. The non-bond Sn…O distances are in the range of 0.333 9~0.338 4 nm, markedly longer than the covalent Sn-O bond distances (0.212 7~0.218 5 nm) in these three compl-exes, but still shorter than the sum of the van der Waals radii for the Sn and O atoms of 0.357 nm^[24], suggesting that some weak interactions possibly exist between these two atoms. It is worth pointing out that complexes 4 and 5 form 3D supramolecular archite-ctures through intermolecular N-H…N, N-H…O or C-H…O hydrogen bonds (Supporting Information) owing to the presence of amino group.

  Table 2

  

  Table 2.  Selected bond distances (nm) and angles (°) for complexes 2, 4 and 5

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  Complex 2
  Sn1-C5	0.214 4(3)	Sn1-O1	0.214 6(2)	Sn1…O2	0.333 9(2)
  Sn1…N2ⅰ	0.281 4(4)	C4-O1	0.128 8(4)	C4-O2	0.121 9(4)
  O1-Sn1-N2ⅰ	170.6(2)	C5-Sn1-C11	116.7(1)	C5-Sn1-O1	99.6(1)
  C11-Sn1-O1	90.0(1)	O1-C4-O2	126.7(3)	C4-C3-N4	114.0(3)
  Complex 4
  Sn1-C4	0.191(3)	Sn1-O1	0.218 5(6)	Sn1…O2	0.335 0(7)
  Sn1-N3ⅰ	0.257 2(7)	C1-O1	0.126 9(10)	C1-O2	0.122 4(9)
  O1-Sn1-N3ⅰ	174.3(2)	C4-Sn1-C8	133.9(9)	C4-Sn1-O1	83.1(9)
  C8-Sn1-O1	103.4(8)	O1-C1-O2	127.1(8)	C1-C2-N1	114.0(7)
  Complex 5
  Sn1-C4	0.215 0(5)	Sn1-O1	0.212 7(4)	Sn1…O2	0.338 4(4)
  Sn1…N2ⅰ	0.298 9(6)	C3-O1	0.128 2(6)	C3-O2	0.121 3(6)
  O1-Sn1-N2ⅰ	172.2(1)	C4-Sn1-C16	114.9(2)	C4-Sn1-O1	90.3(2)
  C10-Sn1-O1	102.3(2)	O1-C3-O2	127.5(5)	C3-C2-N4	114.9(4)
  Symmetry codes: ⅰ 0.5-x, 0.5+y, 0.5-z for 2, 4 and 5.

  2.3   Cytostatic activity evaluation

  The cytotoxic activity of complexes 1~5 and the free acids (L¹ and L²) for Hela and A549 cells in vitro was assayed by the MTT method^[25], and the data of IC₅₀ are summarized in Table 3. From these results, it is observed that the free acids have scarcely any activity against Hela and A549 cells, but all complexes except 4 display good activity to these two cells. It is also found that the complexes exhibit higher activity against A549 cells than Hela cells. Moreover, complex 3 exhibits promising result. This complex is even more active against A549 cells than cisplatin supported by its smaller IC₅₀ value compared to that of cisplatin.

  Table 3

  

  Table 3.  IC₅₀ values of complexes 1~5 for HeLa and A549 cells

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  μmol·L-1
  Compound	HeLa	A549
  1	12.39±0.38	5.38±0.05
  2	12.60±0.20	6.67±0.14
  3	10.50±0.40	2.46±0.02
  4	84.60±3.77	49.72±1.23
  5	20.47±0.73	6.16±0.18
  L1	>200	>200
  L2	>200	>200
  Cisplatin	6.86±0.18	4.66±0.07

  3.   Conclusions

  In conclusion, five triorganotin 5-methyl-1H-tetrazolyl-1-acetates and 5-amino-1H-tetrazolyl-1-acetates have been synthesized and characterized. The crystal structural analyses of three of them reveal that the carboxylate group acts as a monodentate ligand in the complexes, and the complexes form linkage coordination polymers through the intermolecular Sn…N interactions in solid state. Most of the complexes display good cytotoxicities for Hela and A549 cells in vitro, especially complex 3 exhibits excellent cytotoxicity for A549 cells.

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

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• 

  Scheme 1  Syntheses of complexes 1~5

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  Figure 1  Molecular structure of 2 with 30% probability displacement ellipsoids

  H atoms are omitted for clarity; Symmetry codes: ^ⅰ 0.5-x, 0.5+y, 0.5-z; ^ⅱ x, 1+y, z

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  Figure 2  Molecular structure of 4 with 30% probability displacement ellipsoids

  H atoms are omitted for clarity; Symmetry codes: ^ⅰ 0.5-x, 0.5+y, 0.5-z; ^ⅱ 0.5+x, 1+y, z

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  Figure 3  Molecular structure of 5 with 30% probability displacement ellipsoids

  H atoms are omitted for clarity; Symmetry codes: ^ⅰ 0.5-x, 0.5+y, 0.5-z; ^ⅱ x, 1+y, z

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  Table 1.  Crystallographic data and refinement parameters for complexes 2, 4 and 5

  Complex	2	4	5
  Formula	C22H38N4O2Sn	C15H31N5O2Sn	C21H37N5O2Sn
  Formula weight	509.25	432.14	510.27
  Crystal size / mm	0.20×0.20×0.20	0.20×0.18×0.06	0.20×0.20×0.20
  Crystal system	Monoclinic	Monoclinic	Monoclinic
  Space group	C2/c	C2/c	C2/c
  a / nm	1.653 7(1)	1.663 4(3)	1.639 7(2)
  b / nm	1.626 0(1)	1.451 4(3)	1.623 7(2)
  c / nm	1.967 0(2)	1.835 5(4)	1.950 1(2)
  β / (°)	113.223(1)	114.72(3)	114.665(7)
  T / K	293(2)	113(2)	293(2)
  V / nm3	4.860 6(7)	4.025 4(2)	4.718 4(9)
  Z	8	8	8
  Dc / (g·cm-3)	1.392	1.426	1.437
  θ range / (°)	1.835~25.005	1.945~25.02	3.37~25.01
  F(000)	2 112	1 776	2 112
  μ / mm-1	1.075	1.285	1.108
  Measured reflection	12 647	14 425	17 242
  Unique reflection (Rint)	4 292 (0.070 1)	3 550 (0.091 9)	4 156 (0.068 0)
  Observed reflection with [I≥2σ(I)]	3 420	2 429	3 119
  Parameter	276	318	270
  GOF	1.005	1.073	1.024
  Residuals R1, wR2	0.035 7, 0.089 1	0.077 4, 0.221 4	0.048 9, 0.097 9

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  Table 2.  Selected bond distances (nm) and angles (°) for complexes 2, 4 and 5

  Complex 2
  Sn1-C5	0.214 4(3)	Sn1-O1	0.214 6(2)	Sn1…O2	0.333 9(2)
  Sn1…N2ⅰ	0.281 4(4)	C4-O1	0.128 8(4)	C4-O2	0.121 9(4)
  O1-Sn1-N2ⅰ	170.6(2)	C5-Sn1-C11	116.7(1)	C5-Sn1-O1	99.6(1)
  C11-Sn1-O1	90.0(1)	O1-C4-O2	126.7(3)	C4-C3-N4	114.0(3)
  Complex 4
  Sn1-C4	0.191(3)	Sn1-O1	0.218 5(6)	Sn1…O2	0.335 0(7)
  Sn1-N3ⅰ	0.257 2(7)	C1-O1	0.126 9(10)	C1-O2	0.122 4(9)
  O1-Sn1-N3ⅰ	174.3(2)	C4-Sn1-C8	133.9(9)	C4-Sn1-O1	83.1(9)
  C8-Sn1-O1	103.4(8)	O1-C1-O2	127.1(8)	C1-C2-N1	114.0(7)
  Complex 5
  Sn1-C4	0.215 0(5)	Sn1-O1	0.212 7(4)	Sn1…O2	0.338 4(4)
  Sn1…N2ⅰ	0.298 9(6)	C3-O1	0.128 2(6)	C3-O2	0.121 3(6)
  O1-Sn1-N2ⅰ	172.2(1)	C4-Sn1-C16	114.9(2)	C4-Sn1-O1	90.3(2)
  C10-Sn1-O1	102.3(2)	O1-C3-O2	127.5(5)	C3-C2-N4	114.9(4)
  Symmetry codes: ⅰ 0.5-x, 0.5+y, 0.5-z for 2, 4 and 5.

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  Table 3.  IC₅₀ values of complexes 1~5 for HeLa and A549 cells

  μmol·L-1
  Compound	HeLa	A549
  1	12.39±0.38	5.38±0.05
  2	12.60±0.20	6.67±0.14
  3	10.50±0.40	2.46±0.02
  4	84.60±3.77	49.72±1.23
  5	20.47±0.73	6.16±0.18
  L1	>200	>200
  L2	>200	>200
  Cisplatin	6.86±0.18	4.66±0.07

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