Atomically Precise Bismuth Oxido Nanoclusters as Hosts for Ln³⁺: Effects of Doping on Optical and Magnetic Properties of a Soluble Metal Oxide

A series of lanthanoid-doped bismuth oxido nanoclusters (BiO-NCs) of the type [Bi₃₈O₄₅(NO₃)₂₄(dmso)y]:Ln (C-1:Ln; Ln³⁺ = La – Lu, ≠ Pm; y = 26–28) including isostructural host and doped structures is reported. Successful doping with ≈1 ω% of the BiO-NCs was demonstrated by ICP-OES, ESI-MS, and exemplarily by SC XRD analysis for C-1:Gd and C-1:Dy. The dopants are statistically albeit nonuniformly distributed on the lattice position of Bi³⁺ and change the optical and magnetic properties of the BiO-NC host material. Altered optical properties (UV–vis and PL) were demonstrated with special focus on C-1:Er, C-1:Yb, and C-2d:Dy showing dual Bi³⁺ and the Ln³⁺ specific PL emissions, resulting in characteristic emission combinations over a wide wavelength range from visible to the NIR region and lifetimes up to 0.5 ms. Starting from C-1:Gd and C-1:Dy the methacrylate-substituted BiO-NCs [Bi₃₈O₄₅(OMc)₂₄(EtOH)₁₄]:Gd (C-2E:Gd) and [Bi₃₈O₄₅(OMc)₂₄(EtOH)₁₄]:Dy (C-2E:Dy) were synthesized to finally give solvate-free [Bi₃₈O₄₅(OMc)₂₄]:Ln (C-2d:Gd, C-2d:Dy) after drying. The introduction of paramagnetic behavior in the BiO-NC diamagnetic host structure was confirmed by SQUID measurements. We further investigated the suitability of Gd³⁺ in C-2d:Gd as a polarization agent for dynamic nuclear polarization (DNP)-enhanced MAS NMR experiments, which resulted in a proton enhancement factor of approximately 10.