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Magnetic nanoparticles have had a significant impact on a wide range of advanced applications in the academic and industrial fields. In particular, in nanomedicine, the nanoparticles require specific properties, including hydrophilic behavior, uniform and tunable dimensions, and good magnetic properties, which are still challenging to achieve by industrial-scale synthesis. Here, we report a gram-scale synthesis of hydrophilic magnetic nanoclusters based on a one-pot solvothermal system. Using this approach, we achieved the nanoclusters with controlled size composed of magnetite nanocrystals in close-packed superstructures that exhibited hydrophilicity, superparamagnetism, high magnetization, and colloidal stability. The proposed solvothermal method is found to be highly suitable for synthesizing industrial quantities (gram-per-batch level) of magnetic spheres with unchanged structural and magnetic properties. Furthermore, coating the magnetic spheres with an additional silica layer provided further stability and specific functionalities favorable for biological applications. Using in vitro and in vivo studies, we successfully demonstrated both positive and negative separation and the use of the magnetic nanoclusters as a theragnostic nanoprobe. This scalable synthetic procedure is expected to be highly suitable for widespread use in biomedical, energy storage, photonics, and catalysis fields, among others.

Bis(azido)palladium(ii) complexes Pd(N₃)₂L₂ (L = PMe₃, PMe₂Ph, PEt₃, PMePh₂) reacted with two equivalents of 2,6-dimethylphenyl isocyanide to give the Pd(ii) complexes, trans-Pd[CN₄(R)](N&z.dbd;C&z.dbd;N–R)L₂ (R = 2,6-Me₂C₆H₃, L = PMe₃, 1; PMe₂Ph, 2; PEt₃, 3; PMePh₂, 4) containing a carbodiimido ligand and a C-coordinated 5-membered tetrazolato ligand. X-Ray structures of 1 and 2 identified the formation of palladium(II) complexes with a carbodiimido group, in which a nitrogen of the linear N&z.dbd;C&z.dbd;N moiety is bonded to the metal center, and with a tetrazolato ring formed via 1,3-dipolar cycloaddition of the isocyanide to the coordinated azido bond. Heating the isolated complexes 1 and 3 at 60 °C for 5 h converted them into the bis(carbodiimido)palladium(ii) complexes, trans-Pd[N&z.dbd;C&z.dbd;N–R]₂L₂ (R = 2,6-Me₂C₆H₃, L = PMe₃, 5; PEt₃, 6). The reactions of 2,6-dimethylphenyl isocyanide with Pd(N₃)₂L₂ (L = PMe₃, PEt₃) also gave the same complexes directly. Reaction of Pd(N₃)₂(dppe) with 2,6-dimethylphenyl isocyanide also caused the formation of the bis(carbodiimido) complex Pd[N&z.dbd;C&z.dbd;N–2,6-Me₂C₆H₃]₂(dppe), 7 in 75% yield. However, reactions of M(N₃)₂(PMe₃)₂ (M = Pd or Pt) with tert-butyl isocyanide resulted in the formation of bis(tetrazolato) compounds, M[CN₄(R)]₂(PMe₃)₂ (R = tert-butyl, M = Pd, 8; Pt, 9) by the cycloaddition of isocyanide to the coordinated azido bond. The same reactions with other isocyanides such as cyclohexyl and n-butyl isocyanides afforded bis(tetrazolato) complexes, trans-M[CN₄(R)]₂L₂ (M = Pd, R = C₆H₁₁, L = PMe₃: 10_anti,syn; M = Pd, R = n-Bu, L = PMe₃: 11_anti,syn; M = Pt, R = n-Bu, L = PMe₃: 12_anti,syn; M = Pt, R = n-Bu, L = PEt₃: 13_anti,syn), which show a mixture of syn and anti isomers in solution. Molecular structures of 11_anti, 12_anti, and 13_syn have been determined by X-ray crystallography.