LAUSR

Abstract The synthesis, crystal structure and spectroscopic properties of the neodymium(III) complex [Nd(btpa)Cl 2 ]Cl·5H 2 O with btpa being the octadentate polypyridine ligand 6,6′-bis[bis(2-pyridylmethyl)aminomethyl]-2.2′-bipyridine are reported. The structure shows that the Nd 3+ ion is coordinated to seven nitrogen atoms of btpa and two chloride ions, leaving one uncoordinated pyridine group. The coordination polyhedron is best described as a monocapped cube. The btpa ligand forms a stable 1:1 complex with Nd(CF 3 SO 3 ) 3 and other selected triflates of the lanthanides(III) ions (Ln) in anhydrous acetonitrile. The stability constants of the Ln(btpa) 3+ complexes are quite similar along the series, due to a compensation between ligand-metal interaction and lanthanide desolvation. High resolution absorption spectroscopy at 4 K shows one equivalent crystallographic position of the Nd 3+ ion in the structure. The Nd-btpa complexes in the solid-state and in AN solution upon excitation wavelength from the range of ligands absorption bands display NIR luminescence with the characteristic 4 F 3/2  →  4 I J (J = 9/2, 11/2 and 13/2) transitions of the Nd 3+ ion. The decay times of the 4 F 3/2 state of Nd 3+ equal 1.4 (293 K) and 2.3 μs (77 K) (λ exc  = 350 nm) for the complexes in the solid-state as well as 0.43 (293 K) and 0.46 μs (77 K) (λ exc  = 266 nm) for AN solution.