Near-infrared and visible luminescence from terphenyl-based lanthanide(III) complexes bearing amido and sulfonamido pendant arms

A series of m-terphenyl-based ligands bearing three coordinating oxyacetate and two amido or two sulfonamido groups, (1a-b)H-3 and (2)H-3, respectivel y, have been synthesized and characterized. The structures of the correspon ding neutral complexes have been studied using H-1-NMR spectroscopy and lum inescence experiments. The photophysical proper ties of the (1a-b)Eu, (2)Eu , (1a)Tb, and (2)Tb complexes have been studied to determine the structure of the first coordination sphere in methanol. The first coordination sphere consists of eight donor atoms provided by the Ligand (three chelating oxya cetate groups and two amide or sulfonamide oxygens), and one methanol molec ule. The (1a)Dy and (1a)Sm complexes exhibited sensitized luminescence in t he visible spectral region, but the luminescence intensity was very sensiti ve to quenching by C-H groups. The near-infrared emitting (1a)Ln and (2)Ln complexes exhibited sensitized luminescence at wavelengths (at 880, 1060, a nd 1330 nm for Nd3+, at 980 nm for Yb3+, and at 1550 nm for Er3+) Of intere st for applications in optical telecommunication devices. The luminescence lifetimes of these complexes in DMSO and [D-6]DMSO are in the range of micr oseconds. The luminescent state of the NIR emitting lanthanide ions is very efficiently quenched by high frequency oscillators (such as C-H groups) in the solvent and the ligand.