Synthesis of Eu(III) complexes with 2-aminopyridine and 1,10-phenanthroline: Structural, optical, thermal and morphological studies

Three europium complexes [Eu(2-ap)(3)(phen)]Cl-3 (1), [Eu(2-ap)(2)(phen)(2)]Cl-3 (2) and [Eu(2-ap)(phen)(3)]Cl-3 (3) have been synthesized with different molar ratios of ligands 2-ap and phen (where 2-ap is 2-aminopyridine, phen is 1,10-phenanthroline). The structures of the ligands and complexes were well characterized by elemental analysis, Fourier transform infrared spectroscopy (FT-IR) and powder X-ray diffraction studies (XRD). The optical properties of the complexes were investigated by ultraviolet visible absorption spectroscopy (UV-vis) and photoluminescence emission spectroscopy (PL) and photoluminescence lifetime decay measurements. The complexes exhibited intense red emission at 615 nm due to D-5(0) -> F-7(2) transitions of the central Eu(III) ion. It was also observed that with increase in the molar ratio of ligand phen, the relative emission intensity of D-5(0) -> F-7(2) transition at 615 nm was enhanced in complex (3) than in the complex (1) and complex (2), indicating that the complex (3) exhibited good luminescent properties. Furthermore, the complex (3) shows good quantum yield and long luminescence lifetime, hence it can be used as an efficient fluoroprobe. The thermal properties of the obtained complexes were studied by thermogravimetry analysis (TG-DTA) demonstrating the corresponding mass losses due to the ligands 2-ap and phen and the formation of stable oxide Eu2O3 as the final product after decomposition. The morphologies as studied by Scanning Electron Microscopy (SEM) depicted different microstructures for all the three complexes revealing that the change in concentration of ligands leads to the change in morphologies of the complexes. (C) 2015 Elsevier B.V. All rights reserved.