title: Ln(III) complexes of a bis(5-(pyridine-2-yl)-1,2,4-triazol-3-yl)methane ligand: synthesis, structure and fluorescent properties.
abstract: The new tetradentate ligand H2L bis(5-(pyridine-2-yl)-1,2,4-triazol-3-yl)methane ligand H2L has been used to prepare corresponding Ln(III) complexes [Ln(L)(HL)H2O]·6H2O where Ln(III) is Tb(III), Sm(III), Eu(III), Gd(III), Nd(III). The resulting complexes were investigated by various means including elemental- and thermogravimetric analysis and IR-, UV-, VIS spectroscopy. The complexes form an isostructural series in the solid state according to X-ray diffraction. The optimal value of triple state energy of the ligand sensitizes both fluorescent visible and near-IR emissions of the lanthanides. However, the overall emission is moderate as a result of the quenching action of coordinated water molecules. The displacement of water molecules from the inner coordination sphere both in solid samples and the solutions results in a significant increase of the efficiency of the luminescence. The best value of the quantum yield was obtained for the Tb(III) complex with 41%. Luminescence titrations demonstrate that [Tb(L)(HL)H2O] is a pH-sensitive emitter which is able to detect pH values in both near neutral pH and acidic pH ranges.
authors.affiliation: Taurida National V.I. Vernadsky University, Simferopol, 95007 Ukraine. galex0330@rambler.ru
authors.forename: Alexey N
authors.initials: AN
authors.lastname: Gusev
authors.forename: Miki
authors.initials: M
authors.lastname: Hasegawa
authors.forename: Galyna A
authors.initials: GA
authors.lastname: Nishchymenko
authors.forename: Victor F
authors.initials: VF
authors.lastname: Shul'gin
authors.forename: Svetlana B
authors.initials: SB
authors.lastname: Meshkova
authors.forename: Pavel
authors.initials: P
authors.lastname: Doga
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Linert
mesh_terms: D056831:Coordination Complexes / Q000138:chemical synthesis* / Q000737:chemistry; D018360:Crystallography, X-Ray; D006863:Hydrogen-Ion Concentration; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D008024:Ligands; D008697:Methane / Q000737:chemistry*; D008968:Molecular Conformation; D011725:Pyridines / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
chemical_list: D056831:Coordination Complexes; D028581:Lanthanoid Series Elements; D008024:Ligands; D011725:Pyridines; C023666:pyridine; D008697:Methane