Structure and sensitized near-infrared luminescence of Yb(III) complexes with sulfonylamidophosphate type ligand

A series of new lanthanide complexes with dimethyl(phenylsulfonyl)amidophosphate (HSP) was synthesized ({Na[Ln(SP)4]}n (Ln1), [Ln(SP)3phen] (Ln2) and [Ln(SP)3bpy]·H2O (Ln3) (where Ln = GdIII, ErIII, YbIII and LuIII; phen = 1,10-phenantroline; and bpy = 2,2′-bipyridine) and the crystal structures of [Er(SP)3phen] and [Yb(SP)3bpy]·H2O were resolved. Absorption (at 295, 4 K), emission (at 295, 77, 4 K) and IR (at 295 K) spectra as well as luminescence decay time measurements were used to characterize the photophysical properties of single crystals. Effective energy transfer from a [SP]− ligand to the YbIII ion was demonstrated despite a large energy gap ΔE=Etrip−E2F5/2ΔE=Etrip−E2F5/2. Replacing one molecule of the [SP]− ligand with the phen or bpy molecule caused reduction of the emission decay time from 35 μs for Yb1 to 20 and 15.5 μs for Yb2 and Yb3, respectively at the temperature of 295 K. Using the absorption spectra τrad (1.1 ms—Yb1, 943 μs—Yb2 and 914 μs—Yb3) and QLnLn (3.14%—Yb1, 2.19%—Yb2, 1.64%—Yb3) were estimated. On the basis of low temperature, high-resolution absorption and luminescence spectra, the ligand-field splittings of the excited and ground states of YbIII complexes were determined.