Silicon Derivatives Research Articles

GC‐MS Profiling and Therapeutic Potentials of Prosopis juliflora (Sw.) DC: Cytotoxic and Antimicrobial Insights

Plants belonging to the genus Prosopis L. (family Fabaceae, subfamily Mimosoideae) have gained significant popularity in traditional medicine due to their potential as anticancer, antidiabetic, anti‐inflammatory, and antibacterial compounds. The primary objective of this work was to determine the phytochemical composition of the ethanolic extract derived from Prosopis juliflora leaves, as well as to assess its antibacterial and cytotoxic properties. The phytochemical screening using GC‐MS revealed the presence of phytosteroids, ketone, esters, diisooctyl phthalate, and triterpenes. Besides, varying amounts of some silicon derivatives, which were reported to have antimicrobial activity, were detected with octasiloxane, which showed the highest amount (18.47%). 6‐Ethoxy‐6‐methyl‐2‐cyclohexenone (antioxidant, antidiabetic, antiobesity, and antimicrobial) was detected in considerable quantity. Cytotoxic activity was seen in human breast cancer (MCF‐7), human ovary adenocarcinoma (A2780), and human colon adenocarcinoma (HT‐29) cell lines, as well as in normal human fetal lung fibroblasts (MRC‐5), when subjected to the MTT assay. The plant extract exhibited the highest level of activity (5.75 μg/mL) against the A2780 cell line, with the MCF‐7 cell line showing a somewhat lower level of activity (18.49 μg/mL). The antibacterial effect of the plant extracts was evaluated against four standard Gram‐positive and four standard Gram‐negative. The antimicrobial potential was observed only against Staphylococcus aureus which recorded a 14.5 ± 0.05 mm inhibition zone. The present study has demonstrated the identification of bioactive constituents in P. juliflora plant extracts, which exhibit significant cytotoxic activity against breast and colon malignancies. The study also highlighted P. juliflora extract as an antibacterial against S. aureus.

Tuning the Lewis Acidity of Neutral Silanes Using Perfluorinated Aryl‐ and Alkoxy Substituents

AbstractThe emerging field of Lewis acidic silanes demonstrates the versability of molecular silicon compounds for catalytic applications. Nevertheless, when compared to the multifunctional boron Lewis acid B(C6F5)3, silicon derivatives still lack in terms of reactivity. In this regard, we demonstrate the installation of perfluorotolyl groups (TolF) on neutral silicon atoms to obtain the respective tetra‐ and trisubstituted silanes Si(TolF)4 and HSi(TolF)3. These compounds were fully characterized including SC‐XRD analysis but unexpectedly showed no significant Lewis acidity. By using strongly electron‐withdrawing perfluorocresolato groups (OTolF) the tetrasubstituted silane Si(OTolF)4 was obtained, bearing an 8 % increased Δδ(31P) shift when applying the Gutmann‐Beckett method, compared to literature‐known Si(OPhF)4. Ultimately the heteroleptic Si(PhF)2pinF was successfully synthesized and fully characterized including SC‐XRD analysis, introducing a highly Lewis acidic silicon atom holding two silicon‐carbon bonds.

Synergistic Palladium/Lewis acid-Catalyzed Regio- and Stereo-divergent Bissilylation of Alkynoates: Scope, Mechanism, and Origin of Selectivity.

Transition metal-catalyzed bissilylation reactions of alkynes with disilane reagents have become one of the most straightforward and efficient protocols to rapidly produce structurally diverse alkenyl silicon derivatives. In these reactions, the utilization of unsymmetrical disilane reagents provided the possibilities for reactivity enhancement as well as the synthetic merits in contrast to symmetrical disilane reagents. However, a major yet challenging objective is achieving precise control over the selectivity including the regioselectivity and thecis/trans-selectivity. Herein we realized the first divergent bissilylation of alkynoates with our developed air-stable disilane reagent TMDQ by means of synergistic Pd/Lewis acid catalytic system. The catalytic system precisely dictates the selectivity, resulting in the divergent synthesis of 1,2-bissilyl alkenes. The power of these 1,2-bissilyl alkenes serving as the key synthetic intermediates has been clearly demonstrated by rapid construction of diverse motifs and densely functionalized biologically active compounds. In addition, the origins of the switchable selectivities were well elucidated by experimental and computational studies on the reaction mechanism and were mainly attributed to different ligand steric effects, the use of the specific disilane reagent TMDQ and the different coordination modes of different Lewis acid with alkynoates.

Synergistic Palladium/Lewis Acid‐Catalyzed Regio‐ and Stereo‐divergent Bissilylation of Alkynoates: Scope, Mechanism, and Origin of Selectivity

AbstractTransition metal‐catalyzed bissilylation reactions of alkynes with disilane reagents have become one of the most straightforward and efficient protocols to rapidly produce structurally diverse alkenyl silicon derivatives. In these reactions, the utilization of unsymmetrical disilane reagents provided the possibilities for reactivity enhancement as well as the synthetic merits in contrast to symmetrical disilane reagents. However, a major yet challenging objective is achieving precise control over the selectivity including the regioselectivity and the cis/trans‐selectivity. Herein we realized the first divergent bissilylation of alkynoates with our developed air‐stable disilane reagent 8‐(2‐substituted‐1,1,2,2‐tetramethyldisilanyl)quinoline (TMDQ) by means of synergistic Pd/Lewis acid catalytic system. The catalytic system precisely dictates the selectivity, resulting in the divergent synthesis of 1,2‐bissilyl alkenes. The power of these 1,2‐bissilyl alkenes serving as the key synthetic intermediates has been clearly demonstrated by rapid construction of diverse motifs and densely functionalized biologically active compounds. In addition, the origins of the switchable selectivities were well elucidated by experimental and computational studies on the reaction mechanism and were mainly attributed to different ligand steric effects, the use of the specific disilane reagent TMDQ and the different coordination modes of different Lewis acid with alkynoates.

Electrooxidation of Hypercoordinated Derivatives of Silicon and Reactivity of Their Electrogenerated Cation Radicals: 1-Substituted Silatranes.

Electrochemical oxidation of 1-R-substituted silatranes 1 (R = Me, vinyl, (CH2)2CN, CH2Ph, CH2(C10H7), Ph, C6H4Me, p-Cl-C6H4, Cl)-classical representatives of pentacoordinated silicon compounds-and the formation of their short living cation radicals upon reversible or quasi-reversible one-electron withdrawal were studied by means of cyclic and square-wave voltammetry, faradaic impedance spectroscopy and real-time temperature-dependent EPR spectroelectrochemistry supported by DFT B3PW91/6-311++G(d,p) (C-PCM, acetonitrile) calculations. The main reaction responsible for the decay of 1+• is shown to be their deprotonation, and ways of increasing the stability of these species are proposed.

Direct Synthesis of Silicon Compounds—From the Beginning to Green Chemistry Revolution

This paper discusses the historical beginnings and the current state of knowledge of the synthesis of organosilicon compounds and chlorine derivatives of silicon. The key importance of these compounds for modern industry, including the semiconductor industry (photovoltaic cells, microprocessors, memory chips and many other electronic elements) is highlighted. Significant environmental threats related to the production of these compounds and the research challenges aimed at their elimination are discussed. The complexity of the catalytic mechanism of direct reaction of silicon with CH3Cl and alcohols is presented in an accessible way. In the last part of the work, the directions of the development of direct synthesis technology in line with the principles of green chemistry are indicated.

Electrochemical performance of aqueous hybrid supercapacitor based on LiFePO4/Si/graphene composite

Aqueous hybrid supercapacitors (HS) are a viable alternative to achieve low-cost, environmentally friendly, and safer energy storage technologies. Herein, lithium iron phosphate modified silicon and graphene derivatives (LFP/Si/graphene) are constructed as the cathode, and graphene nanoplatelets (GNPs) as the anode for an aqueous HS. The incorporation of GNPs and reduced graphene oxide (rGO), which is the source of graphene derivatives (graphene) in the composite, has played the role of an electronic conductivity enhancer for LFP/Si structure in the framework structure of the rGO film. Therefore, Si is able to perform its role effectively in avoiding surface instability issues and preventing the side reaction of LFP in aqueous electrolyte. The electrochemical performance is evaluated in a 1 M Li2SO4 aqueous electrolyte that has been thoroughly deaerated with high-purified argon (Ar) gas to remove any dissolved oxygen that might interfere with the analysis. The Ar blanketing in the electrolyte intensified the electrochemical performance by 60 % as compared to the Ar-free electrolyte. The coated LFP by 0.5 w/w% Si with incorporation of graphene (LFP/Si0.5/graphene) for electronic conductivity enhancement in Swagelok-type cells has an exceptional specific capacitance of 272.6 F/g and a highly improved cycle life, which shows 87.2 % capacitance retention after 5200 cycles. Moreover, a different assembly of a close-to-current commercial format of roll-type cell is also studied, and it exhibits slightly higher in specific capacitance of 301.3 F/g with energy and power density of 35.62 Wh kg−1 with 922.53 W kg−1, respectively. Therefore, both cell configurations using LFP/Si0.5/graphene display promising applications of the HS, which have the potential to slowly build themselves into a vital role in hybrid-electric technology.

Silicon derivatives induced host plant resistance against Tetranychus urticae (Acari: Tetranychidae) in eggplants farms

Silicon derivatives induced host plant resistance against Tetranychus urticae (Acari: Tetranychidae) in eggplants farms

Physical Layer Security: About Humans, Machines and the Transmission Channel

In an increasingly interconnected and globalized world in which the volume but also the confidentiality of transmitted content is becoming ever more important, trust, confidence and trustworthiness are of fundamental importance. Particularly in human societies, this trust is established, sustained and strengthened by personal relationships and experiences. But, in a globally connected world with Cyber-Physical Production Systems (CPPS), Industrial Internet of Things (IIoT) and Digital Twins (DTs), these personal relationships do not longer exist. (Remote) access to systems is possible from anywhere on the globe. However, this implies that there have to be technical solutions to detect, identify and acknowledge entities -people and machines- in the networks and thus to establish an initial level of trust.
 Especially since the proliferation of appropriate use-cases, Physical Layer Security (PhySec) is becoming increasingly popular in the scientific community. Using systems' intrinsic information for security applications provides a lightweight but secure alternative to traditional computationally intensive and complex cryptography. PhySec is therefore not only suitable for the IIoT and the multitude of resource-limited devices and sensors, it also opens up alternatives in terms of scalability and efficiency. Moreover, it provides security aspects regarding the entropy H and Perfect Forward Secrecy (PFS).
 Therefore, this work provides insight into three major branches of PhySec: i) Human - Physically Unclonable Functions (PUFs) ii) silicon/electrical - PUFs, and iii) Channel-PUFs. Based on the PUF operating principle, the silicon derivatives consider the electrical properties of semiconductors. Individual and uninfluenceable deviations during the manufacturing process result in component-specific behavior, which is described in particular for Static- and Dynamic Random Access Memory (S-/DRAM). Following this PUF principle, human characteristics -biological, physiological and behavioral features-, are used to recognize and authenticate them. With respect to the wireless channel, the characteristic properties of electromagnetic wave propagation and the influences on the wireless channel -diffraction, reflection, refraction and scattering-, are used to achieve symmetric encryption of the channel.
 In addition to the "conventional" wireless PhySec, especially the development of the Sixth Generation (6G) Wireless Systems, opens up a wide range of possibilities in terms of PhySec, for example in relation to Visible Light Communication (VLC), Reconfigurable Intelligent Surfaces (RIS) and in general the application of frequencies in the (sub)THz range.
 Thus, the work provides an overview of PhySec fields of application in all areas of the IIoT: in terms of humans, machines, and the transmission channel.

Synthesis and Reactivity of Martin's Spirosilane-Derived Chloromethylsilicate.

Pentacoordinate silicon derivatives with a chloromethyl ligand are versatile compounds that are usually obtained from the corresponding tetravalent trialkoxy- or trihalogeno(chloromethyl)silane. We describe herein the synthesis of a chloromethylsilicate bearing two Martin’s ligands readily obtained by addition of in situ generated chloromethyllithium to a spirosilane. The reactivity of this new species was evaluated and it has been established that the chloride is displaced by strong nucleophiles such as alkyllithiums and (hetero)aryllithiums. In Lewis acidic conditions, the pentacoordinate silicon species rearranges through a formal insertion of a methylene into one Si–C bond, to form a new tetravalent spirosilane with a six-membered ring. The same kind of rearrangement can be triggered also by addition of a Lewis base. The mechanism of the rearrangement in both conditions has been studied by means of DFT calculations.

Persistent Planar Tetracoordinate Carbon in Global Minima Structures of Silicon-Carbon Clusters

Recently, we reported a series of global minima whose structures consist of carbon rings decorated with heavier group 14 elements. Interestingly, these structures feature planar tetracoordinate carbons (ptCs) and result from the replacement of five or six protons (H+) from the cyclopentadienyl anion (C5H5−) or the pentalene dianion (C8H62−) by three or four E2+ dications (E = Si–Pb), respectively. The silicon derivatives of these series are the Si3C5 and Si4C8 clusters. Here we show that ptC persists in some clusters with an equivalent number of C and Si atoms, i.e., Si5C5, Si8C8, and Si9C9. In all these species, the ptC is embedded in a pentagonal C5 ring and participates in a three-center, two-electron (3c-2e) Si-ptC-Si σ-bond. Furthermore, these clusters are π-aromatic species according to chemical bonding analysis and magnetic criteria.

Boron, silicon, nitrogen and sulfur-based contemporary precursors for the generation of alkyl radicals by single electron transfer and their synthetic utilization.

Recent developments in the use of boron, silicon, nitrogen and sulfur derivatives in single-electron transfer reactions for the generation of alkyl radicals are described. Photoredox catalyzed, electrochemistry promoted or thermally-induced oxidative and reductive processes are discussed highlighting their synthetic scope and discussing their mechanistic pathways.

SYNTHESIS AND PROPERTIES OF ORGANOSILICON EPISULFIDES

A study was made of the interaction of thiourea with saturated and unsaturated organosilicon oxiranes in absolute methyl alcohol in a medium of potassium hydroxide, and methods were developed for the synthesis of unsaturated and unsaturated organosilicon silicides with a yield of 65–75%.The studies carried out revealed that the synthesized organosilicon episulfides are very reactive compounds and can react with nucleophilic and electrophilic reagents, while forming the corresponding silicon derivatives. The IR- spectra of the products were studied. It should be noted that, when comparing the IR- spectra of oxiranes and episulfides, it was revealed that the stretching vibrations of the CH2 group of the episulfide ring are underestimated by 50–70 cm-1 in comparison with the oxirane ring

Synthesis and Optical Resolution of Configurationally Stable Zwitterionic Pentacoordinate Silicon Derivatives

AbstractStereogenic silicon centres in functionalised tetracoordinated organosilanes generally exhibit very high configurational stability under neutral conditions. This stability drops completely when higher coordination states of the silicon centre are reached due to rapid substituent exchange. Herein we describe the synthesis of chiral and neutral pentacoordinate silicon derivatives with high configurational stability. The zwitterionic nature of these air‐ and water‐tolerant species allows for the first time their direct and efficient optical resolution using chiral HPLC techniques. By means of this method, pentacoordinate silicon compounds exhibiting high Si‐inversion have been obtained as single enantiomers. A rationalisation of the enantiomerisation pathways has been also carried out using DFT calculations.

Synthesis and Optical Resolution of Configurationally Stable Zwitterionic Pentacoordinate Silicon Derivatives.

Stereogenic silicon centres in functionalised tetracoordinated organosilanes generally exhibit very high configurational stability under neutral conditions. This stability drops completely when higher coordination states of the silicon centre are reached due to rapid substituent exchange. Herein we describe the synthesis of chiral and neutral pentacoordinate silicon derivatives with high configurational stability. The zwitterionic nature of these air- and water-tolerant species allows for the first time their direct and efficient optical resolution using chiral HPLC techniques. By means of this method, pentacoordinate silicon compounds exhibiting high Si-inversion have been obtained as single enantiomers. A rationalisation of the enantiomerisation pathways has been also carried out using DFT calculations.

The effects of alpha irradiation on the optical reflectivity of composite polymers

This paper reports an increase in the optical reflectivity of two kinds of copolymers used in contact lenses, with different proportions of silicon and fluorine derivatives, when irradiated with 4.1 MeV alpha particles from an 241Am source. The fiber-optic reflectance technique showed that the lens with a higher proportion of silicon and fluorine content and a lower proportion of methyl-methacrylate is more susceptible to alpha radiation. X-Ray photoelectron spectroscopy and Raman spectroscopy have revealed the formation of silicon oxide and carbide species as a result of chain scission and recombination in the 20 μm thick irradiated regions of lens materials. It is presumed that the high (260 eV/nm) linear energy transfer of alpha particles in polymers creates trapped gas “Bubbles”, and the observed increase in the optical reflectivity with increased irradiation time is explained on the basis of diffuse reflectance caused by the scattering of light from the hard surfaces of these “Bubbles”.

Transition-Metal-Catalyzed Stereo- and Regioselective Hydrosilylation of Unsymmetrical Alkynes

AbstractAlkyne hydrosilylation is one of the most efficient methods for the synthesis of alkenyl silicon derivatives and has been a hot topic of research for decades. This short review summarizes the progress in transition-metal-catalyzed stereo- and regioselective hydrosilylation of unsymmetrical alkynes. Topics are discussed based on different types of alkynes and the selectivities.1 Introduction2 Terminal Alkyne Hydrosilylation2.1 β-E Selectivity2.2 β-Z Selectivity2.3 α-selectivity3 Internal Alkyne Hydrosilylation3.1 Aryl–Alkyl Acetylenes3.2 Alkyl–Alkyl Acetylenes3.3 Internal Alkynes with Polarized Substituents4 Summary and Outlook

A Parisian Vision of the Chemistry of Hypercoordinated Silicon Derivatives.

Less than ten years of acquaintance with hypercoordinated silicon derivatives in our lab is described in this account. Martin's spirosilane derivatives open new opportunities as ligands and as agents for the activation of small molecules and bis-catecholato silicates have proven to be exquisite radical precursors in photoredox conditions for broad synthetic applications.

Wetting layer and size effects on the nonlinear optical properties of semi oblate and prolate Si0.7Ge0.3/Si quantum dots

Semi oblate and semi prolate are among the most probable self-organized nanostructures shapes. The optoelectronic properties of such nanostructures are not just manipulated with the height and lateral size but also with the wetting layer element. The practical interest of derivatives of germanium and silicon has a great important role in optoelectronic devices. This study is a contribution to the analysis of linear and nonlinear optical properties of Si0.7Ge0.3/Si. In the framework of the effective mass approximation, we solve numerically the Schrödinger equation relative to one particle confined in Si0.7Ge0.3/Si semi prolate and semi oblate quantum dots by using the finite element method and by taking into consideration the effect of the wetting layer. The energy spectrum of the lowest states and the dipolar matrix for the fourth allowed transitions are determined and discussed. We also calculate the detailed optical properties, including absorption coefficients, refractive index changes, second and third harmonic generation as a function of the quantum dot sizes. We found that with the change in the size of prolate and oblate quantum dots, there is a shift in the resonance peaks for the absorption coefficient and refractive index. It is due to the modification in the energy levels with changing size. The study proves a redshift in the second harmonic generation and third harmonic generation coefficients with an increase in the height/radius of the oblate/prolate quantum dot, respectively. We also demonstrated the variation of wavefunction inside the quantum dot with the change in wetting layer thickness.

Bonding Relationship between Silicon and Germanium with Group 13 and Heavier Elements of Groups 14–16

The topic of heavier main group compounds possessing multiple bonds is the subject of momentous interest in modern organometallic chemistry. Importantly, there is an excitement involving the discovery of unprecedented compounds with unique bonding modes. The research in this area is still expanding, particularly the reactivity aspects of these compounds. This article aims to describe the overall developments reported on the stable derivatives of silicon and germanium involved in multiple bond formation with other group 13, and heavier groups 14, 15, and 16 elements. The synthetic strategies, structural features, and their reactivity towards different nucleophiles, unsaturated organic substrates, and in small molecule activation are discussed. Further, their physical and chemical properties are described based on their spectroscopic and theoretical studies.