Chemists synthesize a new germanium-based, artichoke-resembling compound
A RUDN chemist obtained a new germanium-based artichoke-like substance showing unusual encapsulating properties. The product also demonstrates high catalytic activity both in the course of alcohols amidation and in alkanes oxidation. The work will help develop new catalysts for organic reactions. The article of the researchers was published in the Catalysts journal.
One fundamental problem of modern chemistry is targeted construction of carcass substances. They are chemical systems with policyclical construction and 3-D geometric structure. Numerous ways to use carcass systems are determined by different methods used to obtain them as well as kaleidoscopic variety of synthesized structures. Carcass compounds include 'crowns', 'cups', and 'cells'. Cell-like compounds may contain other molecules, e.g. gas particles or small organic molecules. In such cases a cell may play the role of a molecular vehicle or a reactor.
The choice of ligands—the components of the metal complex that frame metal atoms and therefore control their properties—is of great importance for the synthesis and properties of end products. Previously, scientists were extremely interested in silicon-organic compounds that turned out to be promising ligands for carcass complexes. However the chemistry of similar compounds with germanium atoms remained understudied.
RUDN chemists together with their Russian and foreign colleagues obtained an unusual germanium-organic complex containing copper and sodium atoms. The product was synthesized by means of auto-assembly. In the course of this reaction various fragments combined in a solution and formed a complex chemical structure. The breakage of the germanium-organic oligomer (C6H5GeО1,5)n by sodium hydroxide led to the formation of highly active sodium-containing particles that reacted with copper dichloride. The crystallization of the product in a system of specifically selected solutions helped obtain a carcass structure Cu42Ge24Na4 that was unique due to its high metal content including two identical structural fragments. The construction of each fragment (studied in the course of X-ray structural research) resembled an artichoke, and each of them contained a chloroform molecule within it.
The researchers measured the catalytic activity of the obtained compound in popular organic synthesis reactions. The product turned out to be especially effective in homogenous catalysis of cyclohexane and cis-1,2-dimethylcyclohexane oxidation, as well as in the oxidation of alcohols with peroxides. The 'artichoke' compound remained an active catalyst even in very small quantities—400 ppm in copper.
"Our research shows that the fine-tuning of synthesis leads to very complex molecular architecture. This work features a unique metal cluster in an germanium-organic envelope. The product shows unusual abilities in the encapsulation of small molecules and catalysis of reactions that are promising both in fine and basic organic synthesis," sayd Alexey Bilyachenko, a co-author of the work, a Candidate of Chemistry, and a research associate at RUDN.
More information:
Alena Kulakova et al. Cu42Ge24Na4—A Giant Trimetallic Sesquioxane Cage: Synthesis, Structure, and Catalytic Activity, Catalysts (2018). DOI: 10.3390/catal8100484
Provided by RUDN University
