Reactivity of the Asymmetric Wells-Dawson Ion: Lanthanide-Containing 34-Tungsto-2-Phosphates [Ln(P(H 4 )W 17 O 61 ) 2 ] 19– (Ln = La 3+ , Ce 3+ , Eu 3+ , Gd 3+ , Yb 3+ , Lu 3+ , Y 3+ )

High Resolution Image Download MS PowerPoint Slide We report on the synthesis of the lanthanide-containing 17-tungsto-1-phosphates [Ln(P(H 4 )W 17 O 61 ) 2 ] 19– (Ln = La 3+, Ce 3+, Eu 3+, Gd 3+, Yb 3+, Lu 3+, Y 3+ ), comprising a lanthanide ion connecting two [P(H 4 )W 17 O 61 ] 11– units in a syn -configuration. The compounds were characterized in the solid state by IR, powder XRD, and TGA, and in solution by 31 P and 183 W NMR. Alternating current magnetic susceptibility investigations revealed the Ce 3+ and Yb 3+ analogues to be single-molecule magnets (SMM), which was further corroborated by sub-kelvin temperature μSQUID studies. For the Eu 3+ analogue, we have observed a strong 5 D 0 → 7 F J ( J = 0–4) emission along with a weaker 5 D J ( J = 1, 2, or 3) → 7 F J emission arising from higher excited state manifolds, upon excitation via the 7 F 0 → 5 L 6 transition at 395 nm. Analysis of the steady-state and time-resolved data suggests a distorted square-antiprismatic coordination geometry around the Eu 3+ center. The presence of water molecules residing in the outer coordination sphere appears to decrease the intrinsic quantum yield (φ Eu ) by providing O–H oscillators as a nonradiative relaxation channel. The observed branching ratio of about 41% for the 5 D 0 → 7 F 4 transition highlights that [Eu(P(H 4 )W 17 O 61 ) 2 ] 19– exhibits a pronounced 5 D 0 → 7 F 4 emission.