Preparationct, Structure, Thermal Chemical Properties And Antibaerial Activities Of Lanthanide Complexes With Aromatic Carboxylic Acids

Eighteen novel complexes ([Ln（3,5-Dipr-2-OHBA）₃（phen）]₂([Ln（3,5-Dipr-2-OHBA）₃（phen）]₂(Ln=La（1）, Nd（2）, Sm（3）, Eu（4）, Tb（5）, Dy（6）, Er（7）, Yb（8）;Ho（3,5-Dipr-2-OHBA）₃（phen）₂·C2H5OH（9）;[Ln（3,5-DmeoxBA）₃（phen）]₂（Ln=Pr（10）, Nd（11）,Sm（12）, Eu（13）, Tb（14）, Dy（15）, Ho（16）, Er（17）, Yb（18）;3,5-Dipr-2-OHBA=3,5-diisopropylsalicylic acid;3,5-DmeoxBA=3,5-Dimethoxybenzoic acid; phen=1,10-phenanthroline）weresynthesized.The structures of some complexes ([Ln（3,5-Dipr-2-OHBA）₃（phen）]₂（Ln=Dy（6）, Yb（8））;Ho（3,5-Dipr-2-OHBA）₃（phen）₂·C₂H₅OH（9）;[Ln（3,5-DmeoxBA）₃（phen）]₂（Ln=Pr（10）, Nd（11）,Sm（12）, Eu（13）, Ho（16）） were obtained by single crystal X-ray diffraction. The two binuclearcomplexes6and8are isostructural. Each Ln³+ion is octa-coordinated, yielding atrigondodecahedron comformation. The the coordination number of the mononuclear complex9is nine, adopting a distorted mono-capped square anti-prismatic geometry. The complexes10,11,12,13,16are isostructural. Each Ln3+ion is octa-coordinated, yielding a distortedsquare-antiprism comformation. Besides, we characterized the seventeen powdery complexesby elemental analysis, IR spectra,1HNMR spectra, powder X-ray diffraction （XRD） andTG/DSC-FTIR technology. The fluorescent property of complexes3、4、5、6、13、14、15were also studied.The thermal properties of the title complexes were investigated by simultaneousTG/DSC-FTIR techniques. The thermoanalysis and the TG-FTIR spectra of gaseous productsof the complexes showed that:1,10-phenanthroline escape firstly in the form of gaseousaromatic macromolecules. The coordinated aromatic carboxylic acids decompose into CO2,H₂O and other gaseous organic small molecules. The activation energy E values of the firstdecomposition stage for complexes6、8、10、11、12、13、16were calculated by integralisoconversional non-linear （NL-INT） and Starink methods. Heat capacities of the fifteencomplexes ([Ln（3,5-Dipr-2-OHBA）₃（phen）]₂（Ln=La（1）, Nd（2）, Eu（4）, Tb（5）, Dy（6）, Yb（8））;[Ln（3,5-DmeoxBA）₃（phen）]₂（Ln=Pr（10）, Nd（11）, Sm（12）, Eu （13）, Tb（14）, Dy（15）, Ho（16）,Er（17）, Yb（18））were measured by differential scanning calorimetry （DSC）. The values of theexperimental heat capacities were fitted to a polynomial equation with the least-squares method. Besides, the smoothed heat capacities and thermodynamic functions （H_T-H₂98.15K）,（S_T-S₂98.15K）, and （G_T-G₂98.15K） were calculated.The antibacterial action of the complexes14、15、17、18on bacteria and fungus such asEscherichia coli, Staphylococcus aureus and Candida albicans were studied by filter paperapproach. The results show that the four complexes shown good anti-microbial activitiesagainst E. coli, S. aureus and C. albicans.