Slow magnetic relaxation and luminescence properties in neodymium(iii)-4,4,4-trifluoro-1-(2-naphthyl)butane-1,3-dionato complexes incorporating bipyridyl ligands

Abstract

Five new eight-coordinated Nd(III) mononuclear complexes with the formulae [Nd(ntfa)₃(EtOH)₂] (1), [Nd(ntfa)₃(phen)] (2), [Nd(ntfa)₃(bipy)] (3), [Nd(ntfa)₃(5,5′-Me₂bipy)] (4) and [Nd(ntfa)₃(4,4′-Mt₂bipy)] (5), where ntfa = 4,4,4-trifluoro-1-(naphthalen-2-yl)butane-1,3-dionate, phen = phenanthroline, bipy = 2,2′-dipyridine, 5,5′-Me₂bipy = 5,5′-dimethyl-2,2′-dipyridine, and 4,4′-Mt₂bipy = 4,4′-dimethoxy-2,2′-dipyridine, were synthesized and structurally characterized. Magnetic measurements were carried out on complexes 2–5. Dynamic magnetic studies revealed single-molecule magnet (SMM) behavior for complexes 2, 4 and 5 with anisotropy energy barriers and preexponential factors of U_eff = 18 cm⁻¹, τ₀ = 2.2 × 10⁻⁷ s; U_eff = 31 cm⁻¹, τ₀ = 1.0 × 10⁻⁹ s and U_eff = 19 cm⁻¹, τ₀ = 8.7 × 10⁻⁸ s, respectively. The ancillary chelating bipyridyl ligands in complexes 2–5 greatly enhance the solid state luminescence emission in the visible and NIR regions through efficient energy transfer from the ligands to the central Nd³⁺ ion. This study highlights the bifunctionality of the Nd(III) complexes.