Air-Stable Gadolinium Precursors for the Facile Microwave-Assisted Synthesis of Gd₂O₃ Nanocontrast Agents for Magnetic Resonance Imaging

Using metal organic precursors in materials synthesis remains a challenge due to their high moisture susceptibility. In this work, we describe a facile methodology for the synthesis of Gd₂O₃-based contrast agents from two new gadolinium-based complexes. [Gd­(PyTFP)₄] (PyH) 1 (PyTFP = C₈H₅NOF₃, Py = C₅H₅N) and [Gd­(DMOTFP)₃Py] 2 (DMOTFP = C₈H₇NO₂F₃) were synthesized via a classical ligand exchange reaction of [Gd­{N­(SiMe₃)₂}₃] under inert conditions. As a result, X-ray diffraction analysis revealed a distorted square antiprismatic coordination and an augmented triangular prismatic arrangement of ligands around gadolinium atoms in 1 and 2, respectively. It also showed that 1 is an anionic complex of formula [Gd­(PyTFP)₄]­(PyH), while a neutral tris-compound, [Gd­(DMOTFP)₃Py], was obtained as a pyridine adduct in 2. Fast and reproducible microwave-assisted decomposition of 1 and 2 provided homogeneous Gd­(OH)₃ nanorods at mild temperature without using any surfactant or capping reagent. As-synthesized nanorods were easily transformed into a cubic phase of Gd₂O₃ nanoparticles by thermal treatment under ambient conditions. The magnetic measurement showed the typical paramagnetic behavior of the Gd₂O₃ nanoparticles (NPs). The cytotoxicity profile demonstrates the biocompatibility and negligible toxicity of the as-synthesized nanoprobes. The suggested approach provides a new class of gadolinium-based precursors which allows facile synthesis of highly crystalline Gd₂O₃ NPs.