Liu Zhenzhen,Shen Zhongquan,Zhang Ning,Zhong Wei,Liu Xiaoming
Abstract Homogeneous Cu(I)/NMI/TEMPO catalyst system (TEMPO = 2,2,6,6-tetramethylpiperidine-N-oxyl) has been investigated for its catalysis on the aerobic oxidation of 1-octanol and other alcohols into aldehydes under room temperature. The catalytic species was found to be a Cu(I) centre coordinated by two NMI molecules and other two weakly bound solvent molecules, [Cu(NMI) 2 (Sol) 2 ] + (Sol = solvent). When CuI was used, this species could be [Cu(NMI)I(Sol) 2 ]. Not like being speculated previously, NMI in this system acts solely as a ligand and its role coordinated to the copper centre enhanced the electron density on the metal centre which promoted the O 2 binding in the catalysis. The labile solvent binding to the Cu(I) centre is essential to ensure both oxygen and substrate binding. The catalyst system is suitable for the oxidation of various alcohols using a simple reaction setup and workup. In particular, the system possesses strong oxidizing capability in quantitative conversion of benzylic alcohols regardless of the substituents on the phenyl ring and allylic alcohols into aldehydes. A plausible mechanism was also proposed for the catalysis. Graphical Abstract The aerobic oxidation of primary alcohols at room temperature to corresponding aldehydes was achieved by the catalyst composed by Cu(I) and methyl imidazole (NMI) mediated by TEMPO in acetonitrile. The catalytic species is proposed to be such a Cu(I) complex that two of its four coordinating sites are occupied by a strong ligand(s) and the rest two are weakly bound by solvent molecules.
Magnetic resonance imaging (MRI)/nuclear medicine imaging (NMI) dual-modality imaging based on radiolabeled nanoparticles has been increasingly exploited for accurate diagnosis of tumor and cardiovascular diseases by virtue of high spatial resolution and high sensitivity. However, significant challenges exist in pursuing truly clinical applications, including massive preparation and rapid radiolabeling of nanoparticles. Herein, we report a clinically translatable kit for the convenient construction of MRI/NMI nanoprobes relying on the flow-synthesis and anchoring group-mediated radiolabeling (LAGMERAL) of iron oxide nanoparticles. First, homogeneous iron oxide nanoparticles with excellent performance were successfully obtained on a large scale by flow synthesis, followed by the surface anchoring of diphosphonate-polyethylene glycol (DP-PEG) to simultaneously render the underlying nanoparticles biocompatible and competent in robust labeling of radioactive metal ions. Moreover, to enable convenient and safe usage in clinics, the DP-PEG modified nanoparticle solution was freeze-dried and sterilized to make a radiolabeling kit followed by careful evaluations of its in vitro and in vivo performance and applicability. The results showed that 99mTc labeled nanoprobes are effectively obtained with a labeling yield of over 95% in 30 minutes after simply injecting Na[99mTcO4] solution into the kit. In addition, the Fe3O4 nanoparticles sealed in the kit can well stand long-term storage even for 300 days without deteriorating the colloidal stability and radiolabeling yield. Upon intravenous injection of the as-prepared radiolabeled nanoprobes, high-resolution vascular images of mice were obtained by vascular SPECT imaging and magnetic resonance angiography, demonstrating the promising clinical translational value of our radiolabeling kit.
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