Preparation, thermodynamic property and antimicrobial activity of some rare-earth (III) complexes with 3-bromo-5-iodobenzoic acid and 1,10-phenanthroline

• Four new complexes [Ln(3-Br-5-IBA)3phen]2 were synthesized and characterized.
• The non-isothermal kinetics of the first stage for the complexes was studied.
• The heat capacities of the complexes were measured by differential scanning calorimeter.
• The antimicrobial activities for these complexes were tested.
• The fluorescence properties of the complexes 2 and 3 were studied.

Four new rare-earth complexes of general formula [Ln(3-Br-5-IBA)3phen]2 (Ln(III) = Er (1), Tb (2), Dy (3) and Ho (4); 3-Br-5-IBA = 3-bromo-5-iodobenzoate; phen = 1,10-phenanthroline) were synthesized by solution-precipitation method, and investigated using elemental analysis, infrared spectra, ultraviolet spectra and TG/DSC-FTIR technology. The non-isothermal kinetics of the first stage for the complexes was studied by using non-linear integral isoconversional method and double equal-double steps method. The heat capacities of the complexes were measured between 263.15 and 485.55 K by means of differential scanning calorimeter, and the values of the experimental heat capacities were fitted to a polynomial equation with the least-squares method. And the thermodynamic functions [HT − H298.15], [ST − S298.15] and [GT − G298.15] were also derived based on the fitted polynomials and thermodynamic relationships with temperature interval of 10 K. Moreover, the antimicrobial activity test indicated that all these complexes exhibited moderate antimicrobial activity against Candida albicans and Staphylococcus aureus, good antibacterial activity against Escherichia coli. The fluorescence spectra for the complexes 2 and 3 behaved the characteristic transitions of Tb(III) and Dy(III) ions.

Four new rare-earth complexes of general formula [Ln(3-Br-5-IBA)3phen]2 [Ln = Er (1), Tb (2), Dy (3) and Ho (4); 3-Br-5-IBA = 3-bromo-5-iodobenzoate; phen = 1,10-phenanthroline] were synthesized and characterized by elemental analysis, IR, UV and TG/DSC-FTIR technology. Heat capacities of the four complexes were measured by differential scanning calorimetry (DSC). The antimicrobial activity against Escherichia coli, Staphylococcus aureus and Candida albicans were tested using disc diffusion method.Figure optionsDownload as PowerPoint slide