# Reactivity of the Asymmetric Wells-Dawson Ion: Lanthanide-Containing 34-Tungsto-2-Phosphates [Ln(P(H4)W17O61)2]19– (Ln = La3+, Ce3+, Eu3+, Gd3+, Yb3+, Lu3+, Y3+)

## TL;DR

Scientists synthesized new lanthanide-based compounds with unique magnetic and optical properties, useful for materials science and luminescent applications.

## Contribution

The paper introduces a novel class of lanthanide-containing Wells-Dawson ions with tunable magnetic and luminescent properties.

## Key findings

- Ce3+ and Yb3+ analogues exhibit single-molecule magnet behavior confirmed by magnetic susceptibility and μSQUID studies.
- Eu3+ analogue shows strong 5D0 → 7FJ emission with a distorted square-antiprismatic coordination geometry.
- Water molecules in the coordination sphere reduce quantum yield by enabling nonradiative relaxation.

## Abstract

We report on the synthesis of the lanthanide-containing
17-tungsto-1-phosphates
[Ln­(P­(H4)­W17O61)2]19– (Ln = La3+, Ce3+, Eu3+, Gd3+, Yb3+, Lu3+, Y3+), comprising a lanthanide ion connecting two [P­(H4)­W17O61]11– units in a syn-configuration. The compounds were characterized in the solid state
by IR, powder XRD, and TGA, and in solution by 31P and 183W NMR. Alternating current magnetic susceptibility investigations
revealed the Ce3+ and Yb3+ analogues to be single-molecule
magnets (SMM), which was further corroborated by sub-kelvin temperature
μSQUID studies. For the Eu3+ analogue, we have observed
a strong 5D0 → 7F
J
(J = 0–4) emission along
with a weaker 5D
J
(J = 1, 2, or 3) → 7F
J
emission arising from higher excited state manifolds, upon
excitation via the 7F0 → 5L6 transition at 395 nm. Analysis of the steady-state
and time-resolved data suggests a distorted square-antiprismatic coordination
geometry around the Eu3+ center. The presence of water
molecules residing in the outer coordination sphere appears to decrease
the intrinsic quantum yield (φEu) by providing O–H
oscillators as a nonradiative relaxation channel. The observed branching
ratio of about 41% for the 5D0 → 7F4 transition highlights that [Eu­(P­(H4)­W17O61)2]19– exhibits
a pronounced 5D0 → 7F4 emission.