Current Organic Chemistry - Volume 21, Issue 22, 2017

Background: Silicon-based thin films produced by remote microwave hydrogen plasma chemical vapor deposition (RP-CVD) from 1,1,4,4-tetramethyldisilaethylene, 1,1,3,3-tetramethyldisiloxane and 1,1,3,3- tetramethyldisilazane precursors are compared. The structure of these compounds differs in atomic composition of the central unit which links the two dimethylhydrosilane moieties. Objective: The effect of temperature on the kinetics of film growth rate induced by RP CVD process, chemical composition and structure as well as same characteristic parameters of resulting amorphous hydrogenated silicon carbide (a-SiC:H), silicon oxycarbide (a-SiOC:H), and silicon carbonitride (a-SiCN:H) films is discussed. Conclusion: It was found that RP CVD process is controlled by adsorption, in which there are two temperature ranges for the formation of the CVD layers. At low-temperature range soft polymer-like material is formed containing organic groups whereas at high-temperature range a transformation to high-density ceramic- like material occurs. Based upon the results of the studies, mechanisms of the initiation step, as well as growth and crosslinking steps in the film formation during RP CVD deposition are proposed. The films were also characterized in terms of their representative properties, such as density, refractive index and biocompatibility. Owing to the high density, defect-free surface and excellent optical parameters the films may be useful as coatings for optoelectronics applications and in medicine for steel implants.

Background: Cu-catalyzed azide–alkyne cycloaddition (CuAAC), as the most exemplary click reaction, plays an important role in attaching a probe or substrate of interest to a specific bio-macromolecule or small molecule. So CuAAC has attracted many chemists and biologists interest. Objective: Click reaction provides a powerful tool to solve tremendous questions in chemical biology. Using CuAAC, chemists and biologists dug into plentiful chemical and biological problems. Conclusion: This review focuses on the CuAAC and its recent applications in different fields. The applications of CuAAC are dispersing to the field of detecting hydrazoic acids, fluoride ions, and labeling proteins, nucleic acids or other biological molecules and even in material science. Both in small molecular and biological macromolecular detection, CuAAC plays an important role and provides a lot of methods to investigate biological processes. The promoted CuAAC reaction is studied well and the applications of CuAAC in solid phase synthesis are described. In addition, more applications of CuAAC can be developed.

Background: Coupling reactions, commonly can be achieved via a wide range of organometallic reagents and electrophiles, representing an important class of synthetic transformation, namely “cross-coupling reaction. It is frequently catalyzed by various palladium (Pd) as species. The synthesis and characterization of an N-heterocyclic carbine (NHC) was accomplished in 1991. In 1991, the first synthesis of a stable NHC was achieved and reported. Objective: This development literally invigorated the interest and attention for this novel species being examined as a ligand for the synthesis of Pd Complexes. Conclusion: In this review, we tried to give a full account on the development of NHC–Pd chemistry intended being used as catalyst under non-conventional conditions. In this light, those carbon-carbon bond formations being successfully achieved in aqueous systems, using immobilized NHC-Pd complexes under nonconventional strategies, such as being conducted under microwave irradiations (MWI) are supported and solvent- free conditions are discussed.

Objective: In the present work, the possibility of using UV-LED curing processes for the design of “smart” nanocoatings showing enhanced thermal, thermo-mechanical and barrier properties was thoroughly investigated. Method: A commercially available ethoxylated bisphenol A diacrylate resin, chosen as a model system, was added to 5 wt.% of an organophilic nanoclay (Cloisite 30B) and a photoinitiator (2,4,6-Trimethylbenzoyldiphenyl- phosphineoxide), suitable for the UV-LED curing process. The system was then exposed to UV-LED radiation and the obtained coatings were characterized. Results: As assessed by infrared spectroscopy and differential scanning calorimetry, a quick exposure (i.e. 5 s) to the UV-LED radiation in dynamic conditions was enough to achieve the completeness of the photocuring reaction. The morphology of the obtained coatings was characterized using X-ray diffraction and scanning electron microscopy: in particular, a clear increase in the interlayer distance was observed, hence indicating the occurrence of intercalation phenomena of the nanofiller into the curable resin. Furthermore, the good interactions taking place between the clay nanoplatelets and the polymer network were responsible for: i) an increase of the glass transition values of the polymer network, ii) enhanced thermal and thermo-oxidative stability of the nanocoatings and iii) improved barrier properties towards oxygen diffusion. Conclusion: The UV-LED curing process was found very suitable for obtaining nanostructured coatings showing decreased oxygen permeability, as well as improved thermal and thermo-mechanical features.