A New 1d Chained Coordination Polymer: Synthesis, Crystal Structure, Antitumor Activity and Luminescent Property

A new 1D chained coordination polymer of Zn(II), {[Zn(L)2(4,4′-bipy)]·(H2O)}n(1) (HL = N-acetyl-L-phenylalanine; 4,4′-bipy = 4,4′-bipyridine) has been synthesized and characterized by elemental analysis, IR and X-ray single crystal diffraction analysis. Theresults show that each asymmetric unit of Zn(II) complex belongs to monoclinic, space group P21 with −3 , µ = 0.857 mm −1 , F(000) = 696, and final R1 = 0.0439, ωR2 = 0.1013. The molecules form one-dimensional chained structure by its the bridging 4,4′-bipyridine ligands. The antitumor activities and luminescent properties of Zn(II) coordination polymer have also been investigated.

Based on the above investigation, in this paper, a new 1D chained coordination polymer of Zn(II), {[Zn(L)2(4,4′-bipy)]•(H2O)}n, has been synthesized using N-acetyl-L-phenylalanine and 4,4′-bipyridine as ligands.The Zn(II) complex was characterized by elemental analysis, infrared spectroscopy, single-crystal X-ray crystallography and thermogravimetric analyses.The antitumor activities and luminescent properties of Zn(II) coordination polymer have also been investigated.

IR Spectra
The IR spectra of N-acetyl-L-phenylalanine ligand and complex 1are shown in Figure 5.As shown in Figure 5, the free N-acetyl-L-phenylalanine ligand exhibits two sharp bands at 1695 cm −1 and 1552 cm −1 , and in complex 1, they appear at 1602 cm −1 and 1433 cm −1 , respectively.This shows that the O atoms of COO − are coordinated to Zn(II) ion [31].

AntitumorActivity
The antitumor activities of N-acetyl-L-phenylalanine ligand and complex 1 were tested against human hepatoma SMMC-7721 cells, human lung adenocarcinoma A549 cells and human colon carcinomaWiDrcells based on MTT method according to the literature procedure [32].The results of antitumor activities of N-acetyl-L-phenylalanine ligand and complex 1 are given in Table 1.It can be seen that complex 1exerted cytotoxic effect against human hepatoma SMMC-7721 cells and human colon carcinoma WiDrcells, and N-acetyl-L-phenylalanine ligand exerted cytotoxic effect against human lung adenocarcinoma A549 cells and human colon carcinoma WiDr cells.The antitumor effect against human hepatoma SMMC-7721 of complex 1 is better than that of N-acetyl-L-phenylalanine ligand, and the antitumor effect against human colon carcinoma WiDr cells of N-acetyl-L-phenylalanine ligand is better than that of complex 1.Table 1.Antitumor activities of complex 1 and N-acetyl-L-phenylalanine ligand.

Luminescent Property
The luminescent spectrum of complex 1 was investigated in the solid state at room temperature.As shown in Figure 6, the ligand displays emission peak at 439 nm with excitation at 349 nm, which may be attributed to the π*-π or π-n transition.However, the N-acetyl-L-phenylalanine ligand does not display any emissions with excitation from 200 to 400 nm.

Data Collection, Structural Determination,and Refinement
A colorless single crystal of the complex 1 with dimensions of 0.32 mm × 0.26 mm × 0.22 mm was selected and mounted on a glass fiber for data collection.The X-ray diffraction data were measured at 293(2) K on a Bruker smart CCD diffractometer with a graphite-monochromatized MoKα (λ = 0.71073 Å) radiation.The structure was solved by direct methods with SHELXL-97 [33] and refined on F 2 by full-matrix least-squares procedures with SHELXTL-97 [33].The non-hydrogen atoms were located refined anisotropically, and hydrogen atoms were added according to theoretical models.The crystal data of 1 are given in Table 2.

Conclusions
In summary, we have synthesized and characterized a new 1D chained coordination polymer of Zn(II).The results show that the molecules form one-dimensional chained structure by its the bridging 4,4′-bipyridine ligands.The antitumor activities and luminescent properties of Zn(II) coordinationpolymer have also been investigated.Based on the above results, more and more coordination polymers containing N-acetyl-L-phenylalanine and 4,4′-bipyridine ligands will be synthesized to study their novel structures and properties.

Table 2 .
Summary of crystalresult for Mg(II) complex.