Synthesis and Characterization of Novel Silylated Sm3+ and Eu3+ Complexes Incorporated Into Mesoporous Silica Nanoparticles

Novel Sm³⁺ and Eu³⁺ silylated complexes were synthesized and incorporated into mesoporous silica nanoparticles (MSNs), yielding luminescent probes with potential applications in biolabeling and theranostics. Silylated ligands were used as coupling agents to form covalent bonds between the complexes and an oxide matrix via a conventional sol–gel process. The new silylated complexes were characterized by ¹H nuclear magnetic resonance spectroscopy (¹H NMR), Fourier transform infrared spectroscopy (FTIR), luminescence spectroscopy, and luminescence decay. The hybrid nanoparticles were synthesized by covalent bonding between the silylated complexes and MSNs. Nanoparticles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), luminescence spectroscopy, small-angle X-ray scattering (SAXS), X-ray diffraction (XRD), and porosimetry measures. Additionally, surface area (by Brunauer–Emmett–Teller [BET] method), luminescence spectroscopy, and the cytotoxicity in cancer cells were also evaluated. Novel luminescent complexes (Eu(tta-Si)₃(phen) and Sm(tta-Si)₃(phen)₂) were synthesized and covalently incorporated into MSNs. This strategy prevented complex leaching and preserved their intrinsic optical properties. Comprehensive characterization confirmed successful nanoparticle formation. Preliminary studies of the silylated complexes and nanoparticles demonstrated cytotoxicity toward cancer cells, with minimal cytotoxic effect on nontumor cells. These results suggest the potential use of silylated Sm³⁺ and Eu³⁺ complex and hybrid nanoparticles functionalized with the silylated complex for bioimaging and targeted cancer therapy.