Current Organic Chemistry - Volume 21, Issue 28, 2017

Polyhedral oligomeric silsesquioxanes (POSS) with a rigid inorganic Si-O-Si core and flexible and reactive and/or inert organic coronae have attracted much attention. Their unique structures, in addition to their physical properties, e.g. low dielectric constant or high thermal stability, are especially interesting. The well-defined organization of silsesquioxanes is important due to their possible use as precursors and components of versatile inorganic/organic hybrid materials. This paper presents a short overview of the two parallel paths in current research on double-decker silsesquioxanes (DDSQ), i.e. the synthesis and properties of both molecular and macromolecular compounds based on a DDSQ core. Over the last decade the number of publications concerning DDSQ based compounds has increased showing the growing interest in this field. Several reviews on different aspects of POSS have been prepared; however, because of the relatively “young age” of the double-decker silsesquioxane there has not been a review of the above topic.

Background: Cyclic oligomeric silsesquioxanes (COSSs) composed of an inorganic Si-O-Si cycle with different silicon atom number from 3 to 12 and organic substituent groups are the promising precursors for organic-inorganic hybrids. COSSs includes two categories: metallic cyclic oligomeric silsesquioxanes (mCOSSs) and macrocyclic oligomeric silsesquioxanes (MOSSs). Since pioneer works were done by Russian scientists, including Zhdanov, Shchegolikhina, and Lindeman, et al. in the 1990s, COSS chemistry has emerged as a new research field in organic silicon chemistry. Methods: Three major methods, including cation exchange strategy, ligand exchange strategy and cleavage of polymetallasiloxane strategy, have been used to prepare a variety of COSSs. Objective: The aim of this article is to present a comprehensive understanding of mCOSSs and MOSSs in synthesis and potential applications. Results: mCOSSs and MOSSs have exhibited excellent performances when they are employed as the precursors of magnetic, organic-inorganic, and porous materials. Conclusion: The article reviews the major developments of COSSs in synthesis, characterization, functionalization, and excellent performances over the last decades. Future research will focus on the synthesis advance and various applications of COSSs.

Background: Polyhedral oligomeric silsesquioxanes are one subclass of silsesquioxanes characterized by a cage-like nanostructure. They are one of the most popular organic and inorganic hybrid molecules. As one of derivatives of polyhedral oligomeric silsesquioxanes, metal-containing silsesquioxane is a new type of organometallic compound which is becoming attractive. Its properities may be affected deeply due to the different type of metal containing silsesquioxanes. Nowadays, they are increasingly promising in the field of catalytic materials, hybrid materials, medical materials and functional materials and so on. Objective: In this review, we reviewed progress in the synthesis of metal-containing silsesquioxanes in the past 5 years and the applications of metal-containing silsesquioxanes in which the literatures are not limited by the most recent 5 years in order to convery the lastest research progress to readers. Conclusion: Metal-containing silsesquioxanes were synthesized either by the main group metal or transition metal complexes with silsesquioxane silanolate ligands, or by condensed cage-like silsesquioxanes with other functional groups such as hydroxyl, amino and carboxyl. As for latter, by introducing functional groups, a variety of novel metal-containing silsesquioxane compounds will be created. Therefore, metal-containing silsesquioxanes for its unique properties and well defined structures could be used widely in the study of catalysts in chemical processes, building blocks for high performance materials, functional materials and medical materials.

Background: Polyhedral oligomeric silsesquioxane (POSS)-based amphiphiles can be divided into two types: traditional and shape amphiphiles, which are often composed of hydrophobic cage-like POSS moiety and hydrophilic/hydrophobic linear polymer segment, mainly exhibiting tadpole-, dumbbell- and starshaped structures. Objective: The aim of this review will give an overall understanding of POSS-based amphiphiles in synthesis, characterization and potential applications. Method: Combined click reaction with living (controlled) polymerization techniques, two main strategies, “POSS first” strategy and “polymer first” strategy, have been used to prepare POSS-based amphiphiles. Results: POSS-based amphiphiles can be self-assembly in specific solution and they have been widely applied in organic-inorganic materials, proton exchange membranes, catalyst supports, nanotechnologies, dyeencapsulation, and photoluminescence devices, etc. Conclusion: In this review, we majorly focus on the advances in the synthesis, self-assembling, and potential applications of POSS-based amphiphiles reported over the last decade.

Contamination by aflatoxins affects food; especially cereal grains are affected by aflatoxin AfB1, while AfM1 affects milk. Many efforts have been addressed to face the problem. In a recent study, we have experimentally showed that the biopolymer chitosan is capable to adsorb the AfB1; however, more sensing and capturing studies are required. In this work, the aflatoxins mentioned above and their interaction with chitosan is computationally investigated. Density Functional Theory as implemented in the GAUSSIAN 09 code is employed. The B3LYP functional together with the 6-31g(d) basis set are enough to model these interactions. Through a total energy calculation, it was found that the more negative charge is on the oxygen atoms of aflatoxins, being the preferred site to interact with chitosan. According to the adsorption energy, aflatoxins are physisorbed which is confirmed by the simulated IR spectra. Modification onto the HOMO-LUMO gap as well as a little shift on the simulated infrared spectra suggests sensing applications of chitosan for these aflatoxins.

The chemoselective catalytic reduction of nitro compounds represents the most important and prevalent process in manufacturing functionalized anilines. Consequently, the development of selective catalysts for the reduction of nitro compounds in the presence of other reducible groups is a major crucial challenge. Herein, a novel, simple, and metal-free, S8 or CS2 mediated reduction of nitroarenes is used to provide the corresponding amine or amide with H2O or acids as solvents and hydrogen sources. Different reaction conditions were optimized and a series of amines and amides were obtained with good yields. The present method provides effective and convenient approaches to synthesize amines and amides.