Modified pyridine-2,6-dicarboxylate acid ligands for sensitization of near-infrared luminescence from lanthanide ions (Ln3+ = Pr3+, Nd3+, Gd3+, Dy3+, Er3+)

Abstract A detailed study of the ability pyridine-2,6-dicarboxylic acid (1) and its 4-mono- 3,4,5-tri-substituted analogues to sensitize emission from Pr3+, Nd3+, Gd3+, Dy3+ Er3+ is presented. Sensitization Ln3+ was demonstrated via ligands in all complexes, excluding with covering spectral range 500 nm 1850 nm obtained variation ion. From ligand-based photoluminescence Gd3+-complexes, relative ligand other singlet triplet state energies complexes are estimated be at 3.1 eV 2.6 eV respectively whilst for 3,5-dibromo-substituted (4) they 2.9 eV 2.3 eV. Hypersensitivity 4I15/2 → 2H11/2 4I15/2 → 4G11/2 intra-atomic transitions also observed 4-chloro-substituted (3) complex. Enhanced sensitization Nd3+ (ca. 5-fold) 2-fold) near-infrared comparison those (1).