Structural Characterization, Magnetic and Luminescent Properties of Praseodymium(III)-4,4,4-Trifluoro-1-(2-Naphthyl)Butane-1,3-Dionato(1-) Complexes

Abstract

Four new Pr(III) mononuclear complexes of formula [Pr(ntfa)3(MeOH)2] (1), [Pr(ntfa)3(bipy)2] (2), [Pr(ntfa)3(4,4`-Mt2bipy)] (3) and [Pr(ntfa)3(5,5`-Me2bipy)] (4), where ntfa = 4,4,4-trifuoro-1-(naphthalen-2-yl)butane-1,3-dionato(1-), 5,5`-Me2bipy = 5,5`-dimethyl-2,2`-dipyridine, 4,4`-Mt2bipy = 4,4′-dimethoxy-2,2`-dipyridine, have been synthesized and structurally characterized. The complexes display the coordination numbers 8 for 1, 3 and 4, and 10 for 2. Magnetic measurements of complexes 1–4 were consistent with a magnetically uncoupled Pr3+ ion in the 3H4 ground state. The solid state luminescence studies showed that the ancillary chelating bipyridyl ligands in the 2–4 complexes greatly enhance the luminescence emission in the visible and NIR regions through efficient energy transfer from the ligands to the central Pr3+ ion; behaving as “antenna” ligands.

Diverse Coordination Numbers and Geometries in Pyridyl Adducts of Lanthanide(III) Complexes Based on β-Diketonate

“…Studying the luminescence of the tris(β-ketonato) Tb ( 9) and tetrakis(β-ketonato) Eu (10) complexes revealed efficient energy transfer in the visible region from the ligands to the central Ln(III) ion. Similar luminescent emission trend was observed in the UV and visible regions in other related β-ketonate derivatives [24][25][26][57][58][59][60][61]. However, it should be mentioned that incorporating strong chelating polypyridyl ligands into the Ln(III)-tris(βketonato) significantly enhances the emission luminescent properties of the compounds in the visible and NIR regions [25,62].…”

“…The purity of the ten compounds was confirmed by elemental microanalyses (see experimental section) and also with checking their X-ray powder diffractions (Figures S1-S10, Supplementary Material Section) as well as X-ray structural analysis. The IR spectra of the complexes under investigation display general characteristic pattern that is similar to most Ln(III) compounds containing tris-and tetrakis(βketonato) anions [24][25][26]. The strong vibrational band observed over the frequency range 1604-1614 cm −1 of the complexes 1-10 is assigned to the stretching frequency of the coordinated carbonyl, ν(C=O) [24][25][26].…”

“…The IR spectra of the complexes under investigation display general characteristic pattern that is similar to most Ln(III) compounds containing tris-and tetrakis(βketonato) anions [24][25][26]. The strong vibrational band observed over the frequency range 1604-1614 cm −1 of the complexes 1-10 is assigned to the stretching frequency of the coordinated carbonyl, ν(C=O) [24][25][26]. The weak broad band observed around 3460 cm −1 reveals the ν(O-H) stretching frequency of the coordinated aqua ligands in 1.…”

“…When excess Hfta is used, the tetrakis(β-ketonato) anionic complex (Hpy)[Eu(btfa) 4 ] (10) was isolated. This trend in reactions of Ln(III) salts and β-diketonate derivatives seems to be universal, where many compounds and pyridyl adducts of similar structural formulas have been isolated and structurally characterized [24][25][26]31,[57][58][59][60][61].…”

“…Following Pearson's HSAB theory, lanthanide cations are hard Lewis acids, and thus exhibit strong binding affinity for Lewis bases derived from O-donor and N-containing ligands. A large number of Ln(III) complexes have been isolated and structurally characterized with the indicated ligands and specifically with β-diketonate species [21][22][23][24][25][26][27][28][29][30]. Herein, we report the synthesis, structural characterization of a novel series of La(III), Eu(III) and Tb(III) complexes based on 4,4,4trifluoro-1-phenyl-butane-1,3-dione (Hbtfa) and their pyridine derivatives (4,4 -Mt 2 bipy = 4,4 -dimethoxybipyridine, 4,4 -Me 2 bipy = 4,4 -dimethylbipyridine, 5,5 -Me 2 bipy = 5,5dimethylbipyridine, phen = 1,10-phenanthrolinene, terpy = 2,2 :6 , 2 -terpyridine, 2-benzpy = 2-(2-pyriyl)-benzimidazole) as well as the photoluminescent properties of Tb(III) and Eu(III) compounds.…”