Significance of Engineering the MnO6 Octahedral Units to Promote the Oxygen Reduction Reaction of Perovskite Oxides.

The electronic structure and geometric configuration of catalysts play a crucial role to design novel perovskite-type catalysts for oxygen reduction reaction (ORR). Nowadays, many studies are more concerned with the influence of electronic structure and ignore the geometric effect, which plays a nonnegligible role in enhancing catalytic performances. Herein, this work regulates the MnO6 octahedral tilting degree of LaMnO3 by modulating the concentration of Y3+, excluding the electronic effect from the valence state of manganese. Plotting the MnO6 octahedral tilting degree as a function of concentration of Y3+ produces a volcano-shaped plot. The octahedral tilting can reduce the Mn-O covalency, generating more highly active Mn3+ and oxygen vacancies during ORR process. The specific activity has a positive correlation with octahedral tilting degree. Meanwhile, the octahedral tilting stabilizes Mn-O interactions during ORR process and promote stability. Based on experimental results and DFT calculations, octahedral tilting alters the rate-determining step (RDS) and decrease the energy barrier. Subsequent extended experiment confirms that octahedral tilting is the key factor to affect the catalytic performances.

Synthesis and activity of novel indirubin derivatives.

A series of indirubin derivatives hydrochloride were obtained using a convenient and mild method from indirubin. The newly synthesized compounds and their derivatives were characterized by 1 H NMR, 13 C NMR, and MS. Furthermore, we tested their IDO1 enzyme inhibitory activity and anti-proliferative activities in K562 tumor cells. The experimental results revealed that some of the compounds showed potential anti-enzyme and anti-tumor activity. Among of them, compound 4b exhibited certain inhibitory activity on IDO1 (IC50 : 29.52 µmol/L), and compound 4a displayed activity similar to indirubin in K562 tumor cells (IC50 : 24.96 µmol/L). This type of indirubin derivative is expected to have the potential to act as an immunologically active anti-tumor drug, indicating that further research will be worthwhile.