Iridium-phosphine ligand complexes as an alternative to rhodium-based catalysts for the efficient hydroformylation of propene.

Expensive rhodium (Rh)-based catalysts have been widely used for the hydroformylation of propene. To find a cheaper and effective alternative to these Rh-based catalysts, herein, a series of phosphine ligands were used to coordinate with iridium, and their catalytic reactivities for the hydroformylation of propene were systematically investigated in this study. The effects of different phosphine ligands, pressures, temperatures, and catalyst dosages on the hydroformylation of propene were investigated. Tripyridyl phosphine iridium Ir2(cod)2Cl2-P(3-py)3 (Ir(I)-L5) and its derivatives exhibit the highest catalytic reactivity. Surprisingly, the catalytic reactivity of Ir(I)-L5 is higher than that of Rh2(cod)2Cl2-P(3-py)3 (Rh(I)-L5). When the Ir(I)-L5 complex is used as the catalyst, reactions performed in a polar solvent gave higher turnover number (TON) values than those in a non-polar solvent. Up to a TON of 503 can be obtained. Different n-butyraldehyde/iso-butyraldehyde (n/i) ratios can be obtained by adjusting the phosphine ligands or the proportion of gas pressure. The catalyst showed good reusability in five recycling experiments. Furthermore, based on DFT theoretical calculations, a probable reaction mechanism was proposed. It is reliable that an Ir-based catalyst can be considered as a highly effective catalyst for the hydroformylation of propylene with CO.

Controlling the Lewis Acidity and Polymerizing Effectively Prevent Frustrated Lewis Pairs from Deactivation in the Hydrogenation of Terminal Alkynes.

Two strategies were reported to prevent the deactivation of Frustrated Lewis pairs (FLPs) in the hydrogenation of terminal alkynes: reducing the Lewis acidity and polymerizing the Lewis acid. A polymeric Lewis acid (P-BPh3) with high stability was designed and synthesized. Excellent conversion (up to 99%) and selectivity can be achieved in the hydrogenation of terminal alkynes catalyzed by P-BPh3. This catalytic system works quite well for different substrates. In addition, the P-BPh3 can be easily recycled.

Paramagnetic albumin decorated CuInS2/ZnS QDs for CD133+ glioma bimodal MR/fluorescence targeted imaging.

Glioma stem cells (GSCs) are considered the key to the occurrence, development, invasion, recurrence and sensitivity to treatment of brain tumors. Precise molecular imaging of GSCs by means of probes in vivo has therefore become a premise of solving the above problems. Herein, a sensitive, specific, accurate and biocompatible molecular nanoprobe is reported with MR/fluorescence imaging modalities for CD133+ glioma tumor bimodal targeted imaging. Cd-free high quality CuInS2/ZnS core/shell quantum dots (QDs) were synthesized for fluorescence imaging; DTPA-coupled BSA with Gd3+ chelation (BSA-DTPAGd) were prepared and used both for phase transfer of hydrophobic CuInS2/ZnS QDs and MR imaging modality. The resulting hydrophilic paramagnetic QDs (pQDs) were then linked with anti-CD133 monoclonal antibody, pQDs-CD133mAb denoting the framework of the entire molecular probe, for tumor targeting. The obtained pQDs-CD133mAb has a proper size (ca. 45 nm) and good colloidal stability. It exhibits a high quality fluorescent emission (ca. 630 nm) together with high longitudinal relaxivity (r1 = 15.2 mM-1 s-1) compared with that of commercial Magnevist (r1 = 3.12 mM-1 s-1). Dual modal imaging in vitro and in vivo shows potent tumor enhancement with administration of pQDs-CD133mAb. A biodistribution study indicates hepatobiliary and renal processing of pQDs-CD133mAb with no obvious toxicity. It could be therefore concluded, with a dual-modal imaging and targeting strategy, pQDs-CD133mAb presents a great potential as an alternative for accurate diagnosis of glioma.

Albumin-Mediated Biomineralization of Paramagnetic NIR Ag2S QDs for Tiny Tumor Bimodal Targeted Imaging in Vivo.

Bimodal imaging has captured increasing interests due to its complementary characteristics of two kinds of imaging modalities. Among the various dual-modal imaging techniques, MR/fluorescence imaging has been widely studied owing to its high 3D resolution and sensitivity. There is, however, still a strong demand to construct biocompatible MR/fluorescence contrast agents with near-infrared (NIR) fluorescent emissions and high relaxivities. In this study, BSA-DTPA(Gd) derived from bovine serum albumin (BSA) as a novel kind of biotemplate is employed for biomineralization of paramagnetic NIR Ag2S quantum dots (denoted as Ag2S@BSA-DTPA(Gd) pQDs). This synthetic strategy is found to be bioinspired, environmentally benign, and straightforward. The obtained Ag2S@BSA-DTPA(Gd) pQDs have fine sizes (ca. 6 nm) and good colloidal stability. They exhibit unabated NIR fluorescent emission (ca. 790 nm) as well as high longitudinal relaxivity (r1 = 12.6 mM(-1) s(-1)) compared to that of commercial Magnevist (r1 = 3.13 mM(-1) s(-1)). In vivo tumor-bearing MR and fluorescence imaging both demonstrate that Ag2S@BSA-DTPA(Gd) pQDs have pronounced tiny tumor targeting capability. In vitro and in vivo toxicity study show Ag2S@BSA-DTPA(Gd) pQDs are biocompatible. Also, biodistribution analysis indicates they can be cleared from body mainly via liver metabolism. This protein-mediated biomineralized Ag2S@BSA-DTPA(Gd) pQDs presents great potential as a novel bimodal imaging contrast agent for tiny tumor diagnosis.