Synthesis, Characterization And Antibacterial Activity Of Coordination Complexes Of Y(â…¢) With Pyridine Ring Derivatives

In supramolecular chemistry, molecular self-assembly has become an important subject. Supramolecular coordination complexes can be prepared by the weak interactions such as coordination bonds and hydrogen bonds to form one-dimensional or multi-dimensional structures with novel and unique properties, thus to provide a new approach for the preparation of new materials with special functions. In this paper, a series of coordination complexes containing rare earth metal yttrium (III) were firstly synthesized by using Y3+ ions as central metal ions and pyridine ring derivatives as ligands. Their structures, thermal properties and antibacterial activities against gram-negative bacteria Bacillus coli (B. coli) and gram-positive bacteria Staphylococcus aureus (S. aureus) were investigated. The main research methods, contents and results are as follows:Four rare earth metal-organic coordination complexes of Na3Y(pydc)3·12H2O, Y2(pydc)(OH)4-3H2O, Y2(pydc)3-9H2O and Y(pydcH)3-2H2O (pydc= 2,6-pyridinedicarboxylate) were synthesized by the reactions of yttrium nitrate (Y(NO3)3) and pydcH2 in aqueous solution with different pH values, and the crystal coordination complex Na3Y(pydc)3·12H2O was obtained. The structure of Na3Y(pydc)3·12H2O was characterized by X-ray single crystal diffraction analysis. The crystal of coordination complex Na3Y(pydc)3·12H2O belongs to monoclinic system with space group P21/c, and the coordination geometry configuration of Y3+ center is nine-coordinated by three pydc2" groups as tridentate ligands through two oxygen atoms of two carboxylate groups and one nitrogen donor atom of pyridine ring. The method of synthesis and structure identification of crystal coordination complex Na3Y(pydc)3·12H2O has made a substantial basis for subsequent research of the coordination complexes containing rare earth metal Y3+ ions and pyridine ring derivatives ligands.Another four rare earth metal-organic coordination complexes of Y2(py)(pydc)3-4H2O, Y2(py)2(pydc)3-2H2O, Y(pyH)(pydc)2-H2O and Y(pyH)3(pydc)3-4H2O (py=pyridine), containing pyridine ligands, were synthesized by the reaction of Y(NO3)3 with pydcH2 in pyridine aqueous solution. The structures and thermal properties of above-mentioned four metal-organic coordination complexes were characterized and measured by elemental analyses, infrared spectrum (IR), nuclear magnetic resonance (NMR) and thermal analyzer. The antibacterial activities tested results indicated that the antibacterial activities of above-mentioned four metal-organic coordination complexes against B. coli and S. aureus were in the sequence of Y2(py)(pydc)3-4H2O, Y2(py)2(pydc)3-2H2O> Y(pyH)(pydc)2-H2O, Y(pyH)3(pydc)3-4H2O.A novel coordination complex Y(phen)2(NO3)3 (phen=1,10-phenanthroline) was synthesized by the reaction of Y(NO3)3 with phen in ethanol solution in order to improve the antibacterial activity of rare earth metal-organic coordination complexes. The antibacterial activities results tested by nutrient broth dilution method revealed that the minimal inhibitory concentration (MIC) of complex Y(phen)2(NO3)3 against B. coli and S. aureus was about 40 mg-L-1 and 100 mg·L-1, respectively. It showed that the coordination complex Y(phen)2(NO3)3 could be used for a strong antibacterial agent.In order to farther explore the antibacterial activity of hydrogen bonding rare earth metal-organic complex containing phen ligand, a hydrogen bonding rare earth metal-organic complex Y2(phenH)2(pydc)3(NO3)2·6H2O was synthesized by the reaction of Y(NO3)3 with proton transfer compound (phenH+)2(pydc2-), which was synthesized from pydcH2 and phen in aqueous solution by reflux method. The antibacterial activities of proton transfer compound (phenH+)2(pydc2") and rare earth metal-organic complex Y2(phenH)2(pydc)3(NO3)2·6H2O were tested by culture medium diffusion method. The results showed that the inhibition zone diameter of proton-transfer compound (phenH+)2(pydc2") against B. coli and S. aureus was about 26 mm and 19 mm, and the inhibition zone diameter of complex Y2(phenH)2(pydc)3(NO3)2·6H2O was about 28 mm and 22 mm, respectively. It showed that the proton transfer compound (phenH+)2(pydc2-) and rare earth metal-organic complex Y2(phenH)2(pydc)3(NO3)2·6H2O could be used for antibacterial agents.In this paper, synthesis methods and antibacterial activitives of other hydrogen bonding rare earth metal-organic coordination complexes were studied. A proton transfer compound (pydaH2)2+(pydc2-) was firstly synthesized from the reaction of pydcH2 with pyda (pyda= 2,6-pyridinediamine) under ultrasonic. The major influence factors of proton transfer compound (pydaH2)2+(pydc2-) on yields were investigated. The characterization and analyses of structure for proton transfer compound (pydaH2)2+(pydc2") revealed that (pydaH2)2+(pydc2-) could be successfully obtained by ultrasonic method. The rare earth metal-organic coordination complex (pydaH2)Y2(pydc)4·10H2O was synthesized by the reaction of Y(NO3)3 with proton transfer compound (pydaH2)2+(pydc2") in aqueous solution. The thermal properties and antibacterial activities of proton transfer compound (pydaH2)2+(pydc2-) and rare earth metal-organic coordination complex (pydaH2)Y2(pydc)4·10H2O were determined respectively. The results disclosed that the thermal stability of proton transfer compound (pydaH2)2+(pydc2") was higher than that of rare earth metal-organic coordination complex (pydaH2)Y2(pydc)4·10H2O, and both of (pydaH2)2+(pydc2") and (pydaH2)Y2(pydc)4·10H2O belonged to the weak antibacterial agents.From the studies on synthesis, characterization and antibacterial activity of coordination complexes of Y(Ⅲ) containing pyridine ring derivatives, some useful conclusions are as follow:(a) The molar ratio of metal ion and ligands, ligand species, kinds and pH values of solvent are the major factors affecting the structure and properties of coordination complexes. (b) The antibacterial activities of ligands play a dominant role in the antibacterial activities of coordination complexes, and rare earth metal Y3+ ions have a synergistic enhancement effect on antibacterial activities with ligands in coordination complexes. (c) The proton transfer compound (phenH+)2(pydc2-) and metal-organic coordination complexes Y(phen)2(NO3)3 and Y2(phenH)2(pydc)3(NO3)2·6H2O can be used for antibacterial agents.