Solution studies of lanthanide (III) complexes based on 1,1,1,5,5,5-hexafluoro-2,4-pentanedione and 1,10-phenanthroline Part-I: Synthesis, 1H NMR, 4f-4f absorption and photoluminescence

Solution studies on the complexes of the type [Ln(hfaa)(3)(phen)(2)] (Ln = La, Pr and Nd) and [Ln(hfaa)(3)phen] (Ln = Nd, Ho, Er and Yb; hfaa stands for the anion of 1,1,1,5,5,5-hexafluoro-2,4-pentanedione and phen stands for 1,10-phenanthroline) are presented. These complexes are synthesized in high yields by an in situ method in which hfaa, ammonium hydroxide, lanthanide chlorides and phen were allowed to react in 3:3:1:1 molar ratio in ethanol. In the case of neodymium both eight- and ten-coordinate complexes are isolated. The paramagnetic shifts of the methine protons of beta-diketone have their sign opposed to those of paramagnetic shifts of phen protons and the shifts are dominated by dipolar interactions. The inter-and intramolecular shift ratios have been calculated and discussed. The 4f-4f absorption spectra of the complexes of Pr, Nd, Ho and Er are analyzed. The eight-and ten-coordinate neodymium complexes display distinctively different band shapes of the (4)G(5/2),(2)G(7/2) <- I-4(9/2) hypersensitive transition. The efficient energy transfer from ligand to Pr(III) is reflected by strong red luminescence of this complex at room temperature. (C) 2010 Elsevier B.V. All rights reserved.