Syntheses and spectroscopic studies of volatile low symmetry lanthanide(III) complexes with monodentate 1H-indazole and fluorinated β-diketone

Synthesis, photoluminescence, 4f-4f absorption, and NMR studies of highly volatile nine-coordinate complexes [Ln(hfaa)(3)(L)(3)] (Ln = La, Pr, Nd, and Sm; hfaa is the anion of 1,1,1,5,5,5-hexafluoro-2,4-pentanedione and L = 1H-indazole) are described. NMR spectra reveal that three L are attached to the metal. The chemical shifts of beta-diketonate and Hind protons are in opposite directions and the lanthanide induced paramagnetic shifts are dipolar. The low molecular symmetry of the complexes leads to intense luminescence with prominent Stark splitting of the bands and high oscillator strength of the hypersensitive transition. The band shape of the (4)G(5/2), (2)G(7/2) <- I-4(9/2) transition of neodymium is similar to that of nine-coordinate complexes. Coordinating solvents have pronounced effect on the oscillator strength and band shape. The experimental intensity parameter (eta(Sm)) for the samarium complex is calculated and analyzed. The complexes could be used as precursors for high-performance lanthanide-based materials through chemical vapor deposition.