Ln(iii) complexes of a bis(5-(pyridine-2-yl)-1,2,4-triazol-3-yl)methane ligand: synthesis, structure and fluorescent propertiesElectronic supplementary information (ESI) available. CCDC 911405. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c3dt50297j

• Main Authors: Gusev, Alexey N, Hasegawa, Miki, Nishchymenko, Galyna A, Shul'gin, Victor F, Meshkova, Svetlana B, Doga, Pavel, Linert, Wolfgang
• Format: Article
• Language: English
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c3dt50297j

The new tetradentate ligand H 2 L bis(5-(pyridine-2-yl)-1,2,4-triazol-3-yl)methane ligand H 2 L has been used to prepare corresponding Ln( iii ) complexes [Ln(L)(HL)H 2 O]·6H 2 O 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)H 2 O] is a pH-sensitive emitter which is able to detect pH values in both near neutral pH and acidic pH ranges. The new tetradentate ligand H 2 L bis(5-(pyridine-2-yl)-1,2,4-triazol-3-yl)methane ligand H 2 L has been used to prepare corresponding Ln( iii ) complexes [Ln(L)(HL)H 2 O]·6H 2 O where Ln( iii ) is Tb( iii ), Sm( iii ), Eu( iii ), Gd( iii ), Nd( iii ).