| Amino acids are important physiological active substance. They are the basic structural unit of the protein and enzyme in many living organisms and involve in various biochemical processes in vivo. Amino acids Schiff base and their metal complexes have been proved having such biological activities as anti-virus, antibacterial, anti-cancer, and they have also good oxygen-carrying and catalytic properties. At the same time they have a wide range of applications such as agriculture, medicine, catalysis, materials, biological science and so on, which have received extensive attention by the people. Therefore, the synthesis of many novel amino acid Schiff bases and their metal complexes through the introduction of some other groups with different structures and activities by the chemical reaction, and the studies such as structures, properties and bioactivities, which is very significant for guiding the synthesis and application of complexs.In this paper, carbonyl compounds with multiple structures have been used to react with L-methionine to synthesize five novel Schiff base ligands, at the same time, eighty coordination compounds of transition ions or rare earth ions with these ligands have been prepared. All these complexes are the first time reported by the author. The single crystals of two coordination compounds have been also obtained. These ligands and complexes were characterized by elemental analysis, TG-DTG analysis, 1HNMR, and so on. The suggested structures of the powder of metal complexes were concluded. The fine structures of two single crystals were detected by X-ray crystal diffraction. Fluorescence properties of Schiff base ligands and their complexes have been studied. The mode of interaction between part complexes and DNA has been tested, too. The inhibition and inducing apoptosis of the amino acid Schiff base copper complexes on tumor cells have been also studied by targeting the cellular proteasome. The main works of the article are as follows:(1) Ten metal complexes with Schiff base ligand (KHL1) derived from O-vanillin and methionine were synthesized. The single crystals of coordination polymer {[CuL1(H2O)2]·[CuL1(H2O)]3·4H2O}n and tetranuclear coordination complex [Cd4(L1)4(H2O)2]·3H2O have been also obtained. Crystal structure showed that:The crystal of [CuL1(H2O)2]·[CuL1(H2O)]3·4H2O}n belongs to the triclinic crystal system, space group Pīwith the cell parameter a =5.2027(5)(?), b = 16.6916(16)(?), c = 20.237(2)(?),α= 88.895(10)°,β= 84.127(1)°,γ=83.577(10)°, V = 1737.2(3)(?)3, F(000) = 848, Dc = 1.561 g/cm3, R1 = 0.0760, wR2 = 0.2095. The title copper (Ⅱ) complex is a kind of coordination polymer, which contains two independent units with different coordination environments. The independent unit 1 consists of one copper ion, two uncoordinated water molecules and one Schiff base ligand and the Cu (1) has a slightly distorted square pyramidal coordination geometry. On the other hand, the independent unit 2 is a one-dimensional chain coordination polymer bridged by carboxyl, and the Cu (2) possess coordination geometry as similar as the Cu (1). The crystal of [Cd4(L1)4(H2O)2]·3H2O belongs to the monoclinic crystal system, space group P2(1)/c with the cell parameter a = 22.035(2) (?), b = 14.362(6) (?), c = 20.237(2)(?),α= 90(?),β=104.8940(10)°,γ=90°, V = 7037(?)3, F(000) = 3416, Dc = 1.605 g/cm3, R1 = 0.1993, wR2 = 0.4536. The [Cd4(L1)4(H2O)2]·3H2O is a tetranuclear coordination complex consisting of four Cd (Ⅱ) ions, two coordinated water molecules, four Schiff base ligands, and three uncoordinated water molecules. A two-dimensional network of molecule is formed by the interaction of the intramolecular and intermolecular hydrogen bonds (O-H…O).The possible chemical compositions of the remaining eight metal complexes are confirmed to be: [ML1(H2O)2]·nH2O (M=Zn,Co,Ni, n=1; M=Mn, n=2), [LnL1 (NO3)(H2O)2]·nH2O (Ln=La,Pr, n=1; Ln= Sm,Yb, n=2 ) (where L1 = C13H15NO4S).(2) Ten metal complexes with Schiff base ligand (KHL2) derived from 2-hydroxy-1-naphthaldehyde and methionine were synthesized. The possible chemical compositions of these complexes are confirmed to be: [ML2(H2O)2]·nH2O (M=Zn, n=0; M=Cu, Mn, n=1; M=Co, Ni, n=2), [LnL2(NO3)(H2O)2]·nH2O (Ln=Er, Sm, n=1; Ln=La, Pr, n=2), [YbL2(NO3)(H2O)2]·2CH3OH (where L2 = C16H15NO3S).(3) Twenty metal ions complexes with Schiff base ligand (KL3) derived from pyridine-2-formaldehyde and methionine were synthesized. The possible chemical compositions of these complexes are confirmed to be: [M(L3)2]·nH2O (M= Mn, n=0; M=Ni, Zn, n=1; M= Co, Cu, n=3), [LnL3(NO3)2]·nH2O (Ln=La, Sm, n=1; Ln=Yb, n=2; Ln=Er, Pr, n=3), [M(Phen)L3]·Ac·nH2O (M=Co, Cu, n=1; M=Ni, Zn, n=2; M=Mn, n=3), [Ln(Phen)(NO3)L3]·NO3·nH2O (Ln=La, Sm, Er, n=2; Ln= Pr, Yb, n=3) (where L3 = C11H13N2O2S, Phen = 1,10-Phenanthroline, Ac = CH3COO).(4) Twenty metal complexes with Schiff base ligand (KL4) derived from thiophene-2-formaldehyde and methionine were synthesized. The possible chemical compositions of these complexes are confirmed to be: [M(L4)2(H2O)2]·nH2O (M= Co, Cu, n=1; M=Ni, n=2; M=Zn, Mn, n=3), [LnL4(NO3)2(H2O)]·nH2O (Ln=Er, n=0; Ln=La, Sm, n=2; Ln=Pr, Yb, n=3), [ML4(Phen)(H2O)]·Ac·nH2O (M=Co, Cu, Ni, n=2; M=Zn, Mn, n=3), [LnL4(Phen)(NO3)(H2O)]·NO3·nH2O (Ln=Sm, Pr, Yb, n=1; Ln=La, Er, n=2) (where L4 = C10H12NO2S2, Phen = 1,10-Phenanthroline, Ac = CH3COO).(5) Twenty metal complexes with Schiff base ligand (KL5) derived from 2-acetyl pyridine and methionine were synthesized. The possible chemical compositions of these complexes are confirmed to be: [M(L5)2]·nH2O (M= Zn, n=1; M= Cu, Ni, n=2; M= Co, Mn, n=3), [LnL5(NO3)2]·nH2O (Ln=Sm, Yb, n=2; Ln=La, Er, Pr, n=3) , [M(Phen)L5]·Ac·nH2O (M=Cu, n=0; M=Co, Mn, n=2; M=Ni, Zn, n=3), [Ln(Phen)(NO3)L5]·NO3·nH2O (Ln=Pr, Yb, n=1; Ln=La, Sm, Er, n=2) (where L5 = C12H15N2O2S, Phen = 1,10-Phenanthroline, Ac = CH3COO ).(6) Combinating Achar differential and Coats-Redfern integral method were used to process non-isothermal decomposition kinetics of part of the complexes. The kinetic equations and kinetic parameters of thermal decomposition of the complex in some step were obtained.(7) Fluorescence spectra of all ligands and part of their metal ions complexes were detected. Meanwhile, the related fluorescence properties were studied. The experimental results show that these complexes such as [ZnL1(H2O)2]·H2O, [ZnL2(H2O)2], [LaL2(NO3)(H2O)2]·2H2O, [PrL2(NO3)(H2O)2]·2H2O, [Zn(L3)2]·H2O, [LaL3(NO3)2]·H2O, [Zn(L4)2(H2O)2]·3H2O, [LaL4(NO3)2(H2O)]·2H2, [Zn(L5)2]·H2O, [LaL5(NO3)2]·3H2O, [SmL5(NO3)2]·2H2O, [PrL5(NO3)2]·3H2O have good fluorescence effects. Compared with the corresponding ligand, the excitation and emission peaks of these complexes have shifted to some range. Besides, their fluorescence intensity enhanced significantly, which are two or three times as strong as that of the ligand.(8) The interaction between complexes [CuL2(H2O)2]·H2O, [Zn(L3)2]·H2O and [CuL4(Phen)(H2O)]·Ac·2H2O with Sperm DNA was studied. The experimental results suggest that the interaction modes of [CuL2(H2O)2]·H2O and [CuL4(Phen)(H2O)]·Ac·2H2O with deoxyribonucleic acid are intercalation. However, the interaction of [Zn(L3)2]·H2O with deoxyribonucleic acid belongs to static electricity attraction mode. It has been demonstrated that when ligand has more co-planar, wider flat area and smaller steric hindrance, its interaction with DNA is more significant, simultaneously, ligand is more favorable to interact with DNA in the way of insertion.(9) The antiproliferaion activities of sixteen Schiff base copper(Ⅱ), zinc(Ⅱ) complexes were studied by 3-[4,5-dimethyltiazol-2-yl]-2,5-diphenyl-tetrazolium bromide (MTT method) in prostate cancer PC-3 cells. It was found that [CuL2(H2O)2]·H2O and CuL4(Phen)(H2O)]·Ac·2H2O showed the higher antiproliferation activities than other complexes. So CuL2(H2O)2]·H2O and CuL4(Phen)(H2O)]·Ac·2H2O were chosen for further anticancer studies and it turned out to be that they could inhibit proteasome activity and induce apoptosis in prostate cancer PC-3 cells in a concentration- and time-dependent manner. In addition, antiproliferation activity of CuL4(Phen)(H2O)]·Ac·2H2O for prostate cancer PC-3 cells is higher than that of [CuL2(H2O)2]·H2O. More importantly, anti-tumor activity of metal complexes is closely related to selected metal ions and the structure of the ligands. For the same ligand, anti-tumor activity of copper(Ⅱ) complex is better than that of zinc(Ⅱ) complex. Besides, It was found that the complexe formed by the ligand containing better coplanarity, smaller steric hindrance and heteroatom have much higher anti-tumor activities than that formed by other ligands. |
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