Institute for Advanced Studies in Basic Sciences

About: Institute for Advanced Studies in Basic Sciences is a education organization based out in Zanjān, Iran. It is known for research contribution in the topics: Catalysis & Ionic liquid. The organization has 906 authors who have published 1997 publications receiving 28892 citations.

Synthetic manganese–calcium oxides mimic the water-oxidizing complex of photosynthesis functionally and structurally

Abstract: In the worldwide search for sustainable energy technologies, water oxidation by abundant low-cost materials is of key importance. In nature, this process is efficiently catalyzed by an intricate manganese–calcium (Mn4Ca) complex bound to the proteins of photosystem II (PSII). Recently synthetic manganese–calcium oxides were found to be active catalysts of water oxidation but at the atomic level their structure has remained elusive. To investigate these amorphous catalysts, extended-range X-ray absorption spectroscopy (XAS) at the K-edges of both manganese and calcium was performed. The XAS results reveal striking similarities between the synthetic material and the natural Mn4Ca complex. The oxidation state of manganese in the active oxides was found to be close to +4, but MnIII ions are present as well at a level of about 20%. Neighboring Mn ions are extensively interconnected by two bridging oxygens, a characteristic feature of layered manganese oxides. However, the oxides do not exhibit long-range order, as opposed to canonical, but catalytically inactive MnIII- or MnIV-oxides. Two different Ca-containing motifs were identified. One of them results in the formation of Mn3CaO4 cubes, as also proposed for the natural paragon in PSII. Other calcium ions likely interconnect oxide-layer fragments. We conclude that these readily synthesized manganese–calcium oxides are the closest structural and functional analogs to the native PSII catalyst found so far. Evolutionary implications are considered. From the differences to inactive manganese oxides, we infer structural features facilitating the catalysis of water oxidation in both the protein-bound Mn4Ca complex of PSII and in the synthetic oxides.

Ordered mesoporous organosilica with ionic-liquid framework: an efficient and reusable support for the palladium-catalyzed Suzuki-Miyaura coupling reaction in water.

Abstract: The preparation of a novel palladium-supported periodic mesoporous organosilica based on alkylimidazolium ionic liquid (Pd@PMO-IL) in which imidazoilium ionic liquid is uniformly distributed in the silica mesoporous framework is described. Both Pd@PMO-IL and the parent PMO-IL were characterized by N 2 -adsorption-desorption, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), TEM, and solid-state NMR spectroscopy. We have demonstrated that Pd@PMO-IL is an efficient and reusable catalyst for the Suzuki-Miyaura coupling reaction of various types of iodo-, bromo-, and even deactivated aryl chlorides in water. It was also found that although the PMO-IL nano-structure acts as reservoir for soluble Pd species, it can also operate as a nanoscaffold to recapture the Pd nanoparticles into the mesochannels thus preventing extensive agglomeration of Pd. This observation might be attributed to the isolated ionic liquid units that effectively control the reaction mechanism by preventing Pd agglomeration and releasing and recapturing Pd nanoparticles during the reaction process. The catalyst can be recovered and reused for at least four reaction cycles without significant loss of activity.

Recent Applications of Magnetically Recoverable Nanocatalysts in CC and CX Coupling Reactions

Abstract: Magnetic nanoparticles have emerged recently as an alternative for the easy separation of nanosized catalysts from reaction mixtures by employing an external magnetic field. These magnetic nanoparticles have been used as supports for catalysts and/or as part of an active catalytic site. Herein, special attention is given to identify the main synthetic steps required to develop both precious‐ and nonprecious‐metal‐catalyzed CC and CX coupling reactions by using magnetically separable catalysts.