CAO Shu-Hua TAI Xi-Shi XIN Chun-Ling

Synthesis, Crystal Structure and Antitumor Activity of a Ca(II) Coordination Polymer Based on 4-Acetylphenoxyacetate Ligands①

CAO Shu-Hua TAI Xi-Shi②XIN Chun-Ling

(261061)

A novel Ca(II) coordination polymer, [CaL2(H2O)2]n(1, HL=4-acetylphenoxyacetic acid) has been synthesized with 4-acetylphenoxyacetic acid, Ca(ClO4)2·4H2O and NaOH as raw materials.Complex 1 was characterized by elemental analysis and single-crystal X-ray diffraction analysis.The results show that the Ca(II) ion is eight-coordinated in a distorted triangular dodecahedral geometric configuration with six carboxylate O atoms of four L ligands and two O atoms of two coordinated water molecules.Complex 1 formsa one-dimensional chained structure by the bridging effect of carboxylate O atoms.The antitumor activity of HL ligand and complex 1 has also been investigated.

4-acetylphenoxyacetic acid,Ca(II) coordination polymer, synthesis,crystal structure,antitumor activity;

1 INTRODUCTION

The design and synthesis of metal coordination polymers have received considerable attention during the past decades because they show not only structural diversity[1], but also potential widespread applications as functional materials, such as molecular recognition[2], gas storage[3], magneto- caloric effect[4], luminescence[5-7], catalysis[8], magnetic property[9], bioactivity[10], magnetorefrigerant[11], and so on.To our knowledge, many studies on coordination polymers have focused on transition metals in the past years[12-16].However, few investigations have been done on calcium coordination polymers.In our previous work, some calcium coordination polymers have been synthesized and struc- turally characterized[17-20].In order to extend the investiga- tion of novel structures and properties of calcium coordina- tion polymer, in this work, we successfully designed and synthesized a novel 1D Ca(II) coordination polymer, [CaL2(H2O)2]n(HL = 4-acetylphenoxyacetic acid), by 4-acetylphenoxyacetic acid, Ca(ClO4)2·4H2O and NaOH as raw materials.And its antitumor activity against human hepatoma-7721 cells, human colon carcinomacells and human lung adenocarcinomacells has been investigated.The coordination mode of Ca(II) ion is shown in Fig.1.

Fig.1.Coordination mode of Ca(II) ion

2 EXPERIMENTAL

2.1 Materials and measurements

4-Acetylphenoxyacetic acid, NaOH, Ca(ClO4)2·4H2O and ethanol solvent were of analytical grade and used directly without further purification.Carbon, hydrogen and nitrogen were determined using an Elementar Vario III EL elemental analyzer.IR spectra were recorded using KBr discs on a Nicolet AVATAR 360 FTIR spectrophotometer (Nicolet Instrument Inc., Madison, WI, USA) (range 4,000～400 cm–1).Single-crystal X-ray diffraction data of [CaL2(H2O)2]nwere collected on a Bruker Smart CCD diffractometer (Bruker, Billerica, MA, USA).

2.2 Synthesis of [CaL2(H2O)2]n (1)

4-Acetylphenoxyacetic acid (0.1941 g, 1.0 mmol) and sodium hydrate (0.040 g, 1.0 mmol) were dissolved into 10 mL ethanol solution at room temperature.Then 5 mL of aqueous solution containing 0.1195 g Ca(ClO4)2·4H2O (0.5 mmol) was dropped into the above solution.The mixture was heated at 70°C for 6.5 h with stirring, cooled to room temperature and filtered.Colourless crystals of [CaL2(H2O)2]nwere obtained in 25 days by slowly volatilizing the filtrate at room temperature.Anal.Calcd.for C20H22O10Ca: C, 51.90; H, 4.76%.Found: C, 51.65; H, 5.09.IRmax(cm–1):(COO–): 1675 cm−1.

2.3 Antitumor activity

The culture of tumor cells (Human hepatoma7721 cells, human colon carcinomacells and human lung adenocarcinoma549 cells) and the test procedure for the antitumor activity are consistent with the literature[21, 22].

2.4 Crystal data and structure determination

A single crystal of 1 (0.12mm × 0.11mm × 0.10mm) was placed on a Bruker SMART APEX CCD X-ray diffractometer equipped with graphite-monochromated Moradiation (= 0.71073 Å) at 99.99(10) K.4441 reflections (int= 0.0245) were independent for 1.The structure was solved by direct methodsusing-2014/7 program[23].The[24]program was used to refine the structure.The non-hydrogen atoms were refined anisotropically and the hydrogen atoms were generated by theoretical calculations.Crystal data for complex 1: monoclinic system, space group2/with= 24.4894(11),= 11.3416(5),= 7.7164(4)Å,= 94.750(5)º,= 2135.88(17) Å3,= 4, C20H22O10Ca,M= 462.45,D= 1.438 Mg/m3,(000) = 968 and(Mo) = 0.348 mm–1.The final= 0.0319,= 0.0753 (= 1/[2(F2) + (0.0342)2+ 1.4584], where= (F+ 2F2)/3),= 1.067.The maximum and minimum peaks are 0.229 and –0.333 e/Å3, respectively.

3 RESULTS AND DISCUSSION

3.1 Structural description of [CaL2(H2O)2] n (1)

Single-crystal X-ray structural analyses show that complex 1 crystallizes inmonoclinicspace group2/.Selected bond distances and bond angles of complex 1 are shown in Table 1.The average distance of the Ca–O bonds is 2.465 Å (ranging from 2.3384(12) to 2.6308(12) Å), which are consistent with those reported[16-21].And the bond angles of O–Ca–O vary from 50.82(4) to 157.67(4)°.

Table 1.Selected Bond Lengths (Å) and Bond Angles (°)

Symmetry transformation: A: 1 –,, 1/2 –; B: 1 –, 1 –, 1 –; C:, 1 –, –1/2 +

The asymmetric unit of complex 1 is shown in Fig.2.The fundamental unit of 1 contains one Ca(II) ion, two 4-acetylphenoxyacetate ligands and two coordinated water molecules.Each Ca(II) ion is eight-coordination with six O atoms (O(3B), O(3C), O(4), O(4A), O(4B) and O(4C)) from four 4-acetylphenoxyacetate ligands and two O atoms (O(5) and O(5A)) from two coordinated water molecules, resulting in a distorted triangular dodecahedral geometric configuration.In complex 1, thecarboxylate O atoms of 4-acetylphenoxyacetate ligand adopt different coordination modes with Ca(II) ion (Fig.3): one O atom adopts a bidentate chelating mode to coordinate to different Ca(II) ions, and the other O atom adopts a monodentate chelating mode to coordinate to the Ca(II) ion.The complex forms a one-dimensional (1D) chain structure by the bridging effect of carboxylate O atoms with adjacent Ca(II) ions (Fig.4).The 3D network structure is also formed by the interactions of 1D chain (Fig.5).In addition, four uncoordinated water molecules also exist in the crystal structure.

Fig.2.Asymmetric unit of [CaL2(H2O)2]n

Fig.3.Coordination mode of carboxylate O atoms

Fig.4.One-dimension chained structure

Fig.5.3D supramolecular network structure

3.2 Antitumor activity

The antitumor activity of 4-acetylphenoxyacetic acid and [CaL2(H2O)2]nwas tested against human hepatoma7721 cells, human colon carcinomacells and human lung adenocarcinoma549 cells.The data of antitumor activity are given in Table 2.The results show that both 4-acetylphenoxyacetic acid and [CaL2(H2O)2]nexhibit considerable cytotoxicity, but the antitumor effect of [CaL2(H2O)2]nis better than that of 4-acetylphenoxyacetic acid.The antitumor effect of [CaL2(H2O)2]nagainst WiDr cell is better than that reported[22], while the antitumor effect of [CaL2(H2O)2]nagainst SMMC-7721 and A549 cells is weaker than that in document[22].

Table 3.Antitumor Activity of 4-Acetylphenoxyacetic Acid and [CaL2(H2O)2]n

4 CONCLUSION

In summary, we have synthesized and structurally characterized a new eight-coordinated Ca(II) coordination polymer, [CaL2(H2O)2]n(1).The antitumor activities of 4-acetylphenoxyacetic acid and theCa(II) coordination polymer have also been tested.The above resultsprovide a good idea for the synthesis of Ca(II) complexeswith antitumor activity in the future.

(1) Lee, E.; Seo, S.; Lee, S.S.; Lindoy, L.F.Assembling latter d-block heterometal coordination polymers: synthetic strategies and structural outcomes.2017, 348, 121–170.

(2) Yao, S.L.; Liu, S.J.; Tian, X.M.; Zheng, T.F.; Cao, C.; Niu, C.Y.; Chen, Y.Q.; Chen, J.L.; Huang, H.P.; Wen, H.R.A ZnII-based metal-organic framework with a rare tcj topology as a turn-on fluorescent sensor for acetylacetone.2019, 58, 3578–3581.

(3) Ma, S.Q.; Zhou, H.C.Gas storage in porous metal-organic frameworks for clean energy applications.2010, 46, 44–53.

(4) Liu, S.J.; Cao, C.; Xie, C.C.; Zheng, T.F.; Tong, X.L.; Liao, J.S.; Chen, J.L.; Wen, H.R.; Chang, Z.; Bu, X.H.Tricarboxylate-based GdIIIcoordination polymers exhibiting large magnetocaloric effects.2016, 45, 9209–9215.

(5) Song, J.; Duan, B.F.; Lu, J.F.; Ge, H.G.Three new lanthanide coordination polymers constructed from 2,6-bis(pyrazin-2-yl)pyridine-4- carboxylate: syntheses, structures and luminescence.2020, 39, 793–800.

(6) Wang, Y.S.; Zhou.Z.M.Utilization of mixed ligands to construct two new coordination polymers: syntheses, structures and properties.2015, 228, 117–123.

(7) Tian, X.M.; Yao, S.L.; Qiu, C.Q.; Zheng, T.F.; Chen, Y.Q.; Huang, H.; Chen, J.L.; Liu, S.J.; Wen, H.R.Turn-on luminescent sensor toward Fe3+, Cr3+and Al3+based on a Co(II) metal-organic framework with open functional sites.2020, 59, 2803-2810.

(8) Yang, Y.J.; Wang, F.S.; Dong, G.Y.In situ synthesis, structural characterization and catalytic properties of a 2D Cu(I)-cyanide coordination polymer.2019, 38, 811–818.

(9) Zeng, Y.; Liu, S.J.; Liu, C.M.; Xie, Y.R.; Du, Z.Y.Diversified magnetic behaviors in new nickel(II) and copper(II) azido coordination polymers templated by diethyl or triethyl amines.2017, 41, 1212–1218.

(10) Tai, X.S.; Zhao, W.H.Synthesis, crystal structure, and antibacterial activity of magnesium(II) coordination polymers formed by hydrogen bonding.2015, 41, 3471–3478.

(11) Liu, S.J.; Han, S.D.; Zhao, J.P.; Xu, J.; Bu, X.H.In-situ synthesis of molecular magnetorefrigerant materials.2019, 394, 39–52.

(12) Mostafa, M.A.; Ezzatollah, N.; Ali, D.; Seik, W.N.Structure and optical properties of new lead(II) coordination polymers and PbO nanoparticles core of polymer.2015, 1083, 221–228.

(13) Li, G.L.; Liu, G.Z.; Xin, L.Y.; Li, X.L.; Ma, L.F.; Wang, L.Y.Syntheses, structures and fluorescence properties of four Zn/Cd(II) coordination polymers with 3-nitrobenzene-1,2-dicarboxylate and dipyridyl-typed coligands.2015, 25, 694–701.

(14) Liu, Y.Y.; Liu, J.; Song, S.Y.; Wu, H.; Ma, J.F.Two new tetrazamacrocycle based Cu(II) complexes with 2D → 0D single-crystal to single-crystal transformation.2015, 57, 26–28.

(15) Cai, Z.W.; Sun, J.; Pan, Y.T.; Jiang, T.T.; Li, Q.; Cui, P.P.; Zhang, J.Synthesis of a rare doubly-interpenetrating zinc(II) coordination polymer for applications in photocatalysis.2020, 39, 718–726.

(16) Zhou, X.J.; Guo, X.L.; Liu, L.L.; Shi, Z.; Pang, Y.; Tai, X.S.Synthesis, crystal structures, and magnetic properties of three cobalt(II) coordination polymers constructed from 3,5-pyridinedicarboxylic acid or 3,4-pyridinedicarboxylic acid ligands.2019, 9, 166, doi:10.3390/cryst9030166.

(17) Tai, X.S.; Zhao, W.H.Synthesis, crystal structure and antitumor activity of Ca(II) coordination polymer based on 1,5-naphthalenedisulfonate.2013, 23, 1354–1357.

(18) Tai, X.S.; Zhao, W.H.Synthesis, structural characterization, and antitumor activity of a Ca(II) coordination polymer based on 1,6-naphthalenedisulfonate and 4,4′-bipyridyl.2013, 6, 3547–3555.

(19) Tai, X.S.; Wang, X.Synthesis and crystal structure of a 1D chained coordination polymer constructed from Ca2+and 2-[(E)-(2-furoylhydrazono)methyl]benzenesulfonate.2015, 5, 458–465.

(20) Tai, X.S.; Guo, Q.Q.; Li, P.F.; Liu, L.L.A Ca(II) coordination polymer of 2-carboxybenzaldehyde: synthesis, crystal structure, and catalytic activity in oxidation of benzyl alcohol.2018, 8, 150, doi:10.3390/cryst8040150.

(21) Tai, X.S.; Zhou, X.J.; Liu, L.L.Synthesis, crystal structure and antitumor activity of a Na(I) coordination polymer based on 2-propyl-4,5-imidazoledicarboxylic acid and 1,10-phenanthroline ligands.2019,38, 1079–1085.

(22) Tai, X.S.; Wang, X.Synthesis, structural characterization and antitumor activity of a Ca(II) coordination polymer based on 4-formyl-1,3-benzenedisulfonate-2-furoic acid hydrazide ligands.2017, 62, 242–245.

(23) Sheldrick, G.M.-Integrated space-group and crystal-structure determination.2015, A71, 3–8.

(24) Dolomanov, O.V.; Bourhis, L.J.; Gildea, R.J.; Howard, J.A.K.; Puschmann, H.: a complete structure solution, refinement and analysis program.2009, 42, 339–341.

24 April 2020;

29 June 2020 (CCDC 1983480)

① This work was supported by the National Natural Science Foundation of China (No.21171132), the Natural Science Foundation Joint Project of Shandong Province (ZR2017LB025) and Science Foundation of Weifang

.Tai Xi-Shi, born in 1971, professor, majoring in coordination chemistry.E-mail: taixishi@lzu.edu.cn or taixs@wfu.edu.cn

10.14102/j.cnki.0254–5861.2011–2860