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

Lanthanide doping in bismuth-based oxides and coordination polymers is known to modify the materials properties significantly while preserving their principal structure. Herein we report a series of lanthanide doped bismuth oxido nanoclusters (BiO-NCs) of the type [Bi 38 O 45 (NO 3 ) 24 (dmso) y ]:Ln ( C-1:Ln ; Ln 3+ = La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu; y = 26–28) including isostructural host and doped structures. The dopants are statistically distributed on the lattice position of Bi 3+ and changing the optical and magnetic properties of the BiO-NCs host material. Successful doping of the BiO-NCs was demonstrated by electrospray ionization mass spectrometry (ESI-MS) and exemplarily by single crystal X-ray diffraction (SC XRD) analysis for C-1:Gd and C-1:Dy . The respective amount of doping (≈ 1 ω %) was determined using inductive coupled plasma optical emission spectroscopy (ICP-OES). Altered optical properties in the UV–vis absorption and photoluminescence (PL) emission were demonstrated with special focus on C-1:Er , C-1:Yb and C-2 d :Dy . PL emission studies showed dual emission based on Bi 3+ and the Ln 3+ specific emissions, resulting in characteristic emission combinations over a wide wavelength range from visible to the NIR region. Starting from C-1:Gd and C-1:Dy the methacrylate substituted BiO-NCs [Bi 38 O 45 (OMc) 24 (EtOH) 14 ]:Gd ( C-2 E :Dy ) and [Bi 38 O 45 (OMc) 24 (EtOH) 14 ]:Dy ( C-2 E :Dy ) were synthesized to finally give solvent-free [Bi 38 O 45 (OMc) 24 ]:Ln ( C-2 d :Gd, C-2 d :Dy ) after drying. The introduction of paramagnetic behavior in the BiO-NC diamagnetic host structure was confirmed by superconducting quantum interference device (SQUID) measurements, with molar susceptibilities of χ mol T = 5.10 cm 3 ·K·mol –1 for C-2 d :Gd and χ mol T = 10.00 cm 3 ·K·mol –1 for C-2 d :Dy . The core composition aligns well with the data obtained by ICP-OES analysis. We further investigated the suitability of Gd 3+ in C‑2 d :Gd as polarization agent (PA) for dynamic nuclear polarization (DNP)-enhanced magic-angle spinning nuclear magnetic resonance (MAS-NMR) experiments, which resulted in a proton enhancement of approximately 10.