Blue to near infra-red photoluminescence from distorted SAP (C4V) tris(hexafluoroacetylacetonato)Ho(III) and Tm(III) complexes with indazole

Abstract

A sensitizer ligand, 1,1,1,5,5,5-Hexafluoro-2,4-pentandione (Hhfaa) is employed to synthesize two new ternary–lanthanide(III) complexes, [Ho(hfaa)3(Hind)2] and [Tm(hfaa)3(Hind)2], in which the monodentate N-donor indazole (Hind) was used as the antenna ligand. Both the complexes were characterised thoroughly. The single-crystal XRD suggests that the complexes are eight-coordinate where the metal ions are coordinated to three hfaa̶ and two Hind ligands making the coordination polyhedra as LnO6N2 with distorted square antiprismatic geometries. The one- and two-dimensional NMR analyses confirm the eight-coordinate structures and show that the complexes are isostructural in the solution. The complexes are thermally stable up to 200 °C, which is quite suitable to find the potential application in the optoelectronic devices. Furthermore, the UV-excitation of the complexes led to characteristic emission transitions in the visible and NIR regGive a space between NIR and region on from the [Ho(hfaa)3(Hind)2] and [Tm(hfaa)3(Hind)2] complexes. The NIR luminescence, particularly 1.5 μm from the Ho complex and 1.4 μm from the Tm complex makes them potential candidates for optical communications and of broadening amplification band from C– band (1530–1560 nm) to S + band (1450–1500 nm) in optical fibre, respectively.