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Molecules (Basel, Switzerland) Jan 2021A number of mono- and dioligosilanylated silocanes were prepared. Compounds included silocanes with 1-methyl-1-tris(trimethylsilyl)silyl,...
A number of mono- and dioligosilanylated silocanes were prepared. Compounds included silocanes with 1-methyl-1-tris(trimethylsilyl)silyl, 1,1-bis[tris(trimethylsilyl)silyl], and 1,1-bis[tris(trimethylsilyl)germyl] substitution pattern as well as two examples where the silocane silicon atom is part of a cyclosilane or oxacyclosilane ring. The mono-tris(trimethylsilyl)silylated compound could be converted to the respective silocanylbis(trimethylsilyl)silanides by reaction with KOBu and in similar reactions the cyclosilanes were transformed to oligosilane-1,3-diides. However, the reaction of the 1,1-bis[tris(trimethylsilyl)silylated] silocane with two equivalents of KOBu leads to the replacement of one tris(trimethylsilyl)silyl unit with a -butoxy substituent followed by silanide formation via KOBu attack at one of the SiMe units of remaining tris(trimethylsilyl)silyl group. For none of the silylated silocanes, signs of hypercoordinative interaction between the nitrogen and silicon silocane atoms were detected either in the solid state. by single crystal XRD analysis, nor in solution by Si-NMR spectroscopy. This was further confirmed by cyclic voltammetry and a DFT study, which demonstrated that the N-Si distance in silocanes is not only dependent on the energy of a potential N-Si interaction, but also on steric factors and through-space interactions of the neighboring groups at Si and N, imposing the orientation of the p(N) orbital relative to the N-Si-X axis.
Topics: Organosilicon Compounds; Silanes; Silicon
PubMed: 33466467
DOI: 10.3390/molecules26010244 -
Molecules (Basel, Switzerland) Mar 2021In this study, new biodegradable and biocompatible amphiphilic polymers were obtained by modifying the peripheral hydroxyl groups of branched polyethers and polyesters...
In this study, new biodegradable and biocompatible amphiphilic polymers were obtained by modifying the peripheral hydroxyl groups of branched polyethers and polyesters with organosilicon substituents. The structures of the synthesized polymers were confirmed by NMR and GPC. Organosilicon moieties of the polymers were formed by silatranes and trimethylsilyl blocks and displayed hydrophilic and hydrophobic properties, respectively. The effect of the ratio of hydrophilic to hydrophobic organosilicon structures on the surface activity and biological activity of macromolecules was studied, together with the effect on these activities of the macromolecules' molecular weight and chemical structure. In particular, the critical micelle concentrations were determined, the effect of the structure of the polymers on their wetting with aqueous solutions on glass and parafilm was described, and the aggregation stability of emulsions was studied. Finally, the effect of the polymer structures on their antifungal activity and seed germination stimulation was examined.
Topics: Antifungal Agents; Ascomycota; Biocompatible Materials; Bridged Bicyclo Compounds, Heterocyclic; Micelles; Molecular Structure; Organosilicon Compounds; Polyesters
PubMed: 33810558
DOI: 10.3390/molecules26071893 -
Environmental Science & Technology Nov 2022Volatile methyl siloxanes (VMS) are ubiquitous in indoor environments due to their use in personal care products. This paper builds on previous work identifying sources...
Volatile methyl siloxanes (VMS) are ubiquitous in indoor environments due to their use in personal care products. This paper builds on previous work identifying sources of VMS by synthesizing time-resolved proton-transfer reaction time-of-flight mass spectrometer VMS concentration measurements from four multiweek indoor air campaigns to elucidate emission sources and removal processes. Temporal patterns of VMS emissions display both continuous and episodic behavior, with the relative importance varying among species. We find that the cyclic siloxane D5 is consistently the most abundant VMS species, mainly attributable to personal care product use. Two other cyclic siloxanes, D3 and D4, are emitted from oven and personal care product use, with continuous sources also apparent. Two linear siloxanes, L4 and L5, are also emitted from personal care product use, with apparent additional continuous sources. We report measurements for three other organosilicon compounds found in personal care products. The primary air removal pathway of the species examined in this paper is ventilation to the outdoors, which has implications for atmospheric chemistry. The net removal rate is slower for linear siloxanes, which persist for days indoors after episodic release events. This work highlights the diversity in sources of organosilicon species and their persistence indoors.
Topics: Siloxanes; Environmental Monitoring; Organosilicon Compounds; Ventilation
PubMed: 36327170
DOI: 10.1021/acs.est.2c05438 -
Molecules (Basel, Switzerland) Apr 2017The purification of endohedral metallofullerenes by high performance liquid chromatography is very time-consuming and expensive. A number of rapid and inexpensive... (Review)
Review
The purification of endohedral metallofullerenes by high performance liquid chromatography is very time-consuming and expensive. A number of rapid and inexpensive non-chromatographic methods have thus been developed for large-scale purification of metallofullerenes. In this review, we summarize recent advances in non-chromatographic purification methods of metallofullerenes. Lewis acid-based complexation is one of the most efficient and powerful methods for separation of metallofullerenes from empty fullerenes. The first oxidation potential of metallofullerenes is a critical factor that affects the separation efficiency of the Lewis acid-based method. Supramolecular methods are effective for separation of fullerenes and metallofullerenes that are different in size and shape. Chemical/electrochemical reduction and exohedral functionalization are also utilized to separate and purify metallofullerenes on a large scale.
Topics: Chromatography, High Pressure Liquid; Fullerenes; Lewis Acids; Organosilicon Compounds; Oxidation-Reduction; Photochemical Processes
PubMed: 28468241
DOI: 10.3390/molecules22050718 -
Toxicology Letters Oct 2017Octamethylcyclotetrasiloxane (D) is a volatile cyclic siloxane used primarily as a monomer or intermediate in the production of some silicon-based polymers widely used... (Review)
Review
Octamethylcyclotetrasiloxane (D) is a volatile cyclic siloxane used primarily as a monomer or intermediate in the production of some silicon-based polymers widely used in industrial and consumer applications and may be present as a residual impurity in a variety of consumer products. A robust toxicological data set exists for D Treatment-related results from a chronic inhalation study conducted in rats are limited to mild effects on the respiratory tract, increases in liver weight, increases in the incidence of uterine endometrial epithelial hyperplasia, and a dose-related trend in the incidence of endometrial adenomas. The observed increases in liver weight appear to be related to the induction of hepatic metabolizing enzymes, similar to those that are induced in the presence of phenobarbital. D is not mutagenic or genotoxic in standard in vitro and in vivo tests; therefore, the benign uterine tumors observed likely occur by a non-genotoxic mechanism. Results from mechanistic studies suggest that D has very weak estrogenic and antiestrogenic activity, as well as dopamine agonist-like activity. In rats, D exposure delays ovulation and hypothesized to prolong exposure of the uterine endometrium to endogenous estrogen. Though this mode of action may play a role in the development of benign uterine tumors in the rat, it is considered unlikely to occur in the human due to the marked differences in cycle regulatory mechanisms. Reproductive effects were observed following D exposure in female rats. These effects appear to be related to a delay of the luteinizing hormone (LH) surge, which fails to induce complete ovulation in the rat. However, based on differences in ovulatory control in rats and humans, it appears these effects may be species-specific with no risk or relevance to human health. Results from pharmacokinetic studies indicate that dermal absorption of D is limited, due to its high volatility and, if absorbed via dermal, oral or inhalation exposure, the majority of D is rapidly cleared from the body, indicating bioaccumulation is unlikely.
Topics: Animals; Environmental Pollutants; Humans; Molecular Structure; Siloxanes
PubMed: 28645863
DOI: 10.1016/j.toxlet.2017.06.007 -
Molecules (Basel, Switzerland) Feb 2021Intrinsic hydrophobicity is the reason for efficient bacterial settlement and biofilm growth on silicone materials. Those unwelcomed phenomena may play an important role...
Intrinsic hydrophobicity is the reason for efficient bacterial settlement and biofilm growth on silicone materials. Those unwelcomed phenomena may play an important role in pathogen transmission. We have proposed an approach towards the development of new anti-biofilm strategies that resulted in novel antimicrobial hydrophobic silicones. Those functionalized polysiloxanes grafted with side 2-(carboxymethylthioethyl)-, 2-(-propylamidomethylthioethyl)- and 2-(mercaptoethylamidomethylthioethyl)- groups showed a wide range of antimicrobial properties towards selected strains of bacteria (reference strains , and water-borne isolates , ), fungi () and algae (), which makes them valuable antibacterial and antibiofilm agents. Tested microorganisms showed various levels of biofilm formation, but particularly effective antibiofilm activity was demonstrated for bacterial isolate with high adhesion abilities. In the case of modified surfaces, the relative coefficient of adhesion for this strain was 18 times lower in comparison to the control glass sample.
Topics: Anti-Infective Agents; Cell Adhesion; Hydrophobic and Hydrophilic Interactions; Siloxanes
PubMed: 33557279
DOI: 10.3390/molecules26040814 -
Molecules (Basel, Switzerland) Apr 2020Multidrug resistance (MDR) that occurs in cancer cells constitutes one of the major reasons for chemotherapy failure. The main molecular mechanism of MDR is...
Multidrug resistance (MDR) that occurs in cancer cells constitutes one of the major reasons for chemotherapy failure. The main molecular mechanism of MDR is overexpression of protein transporters from the ATP-binding cassette (ABC) superfamily, such as ABCB1 (multidrug resistance protein 1 (MDR1), P-glycoprotein). At the expense of ATP hydrolysis, ABCB1 pumps a diverse range of substrates (including anticancer drugs) out of the cell, thereby reducing their intracellular concentration. In the present study, the ability of two patented disiloxanes (SILA-409 and SILA-421) to reverse drug resistance in human colon adenocarcinoma cell lines LoVo and LoVo/Dx was investigated. It was demonstrated that both compounds in concentrations of 0.5-1 µM strongly increased the sensitivity of LoVo/Dx cells to doxorubicin. By means of an accumulation test in which rhodamine 123 was used as an ABCB1 substrate analogue, both organosilicon compounds were also shown to inhibit ABCB1 transport activity. The intracellular accumulation of doxorubicin was also increased, and more drug entered the cellular nuclei of resistant cells in the presence of the studied compounds. In conclusion, both SILA-409 and SILA-421 were demonstrated to be effective MDR reversal agents in resistant human colon cancer cells.
Topics: ATP Binding Cassette Transporter, Subfamily B; Cell Line, Tumor; Cell Proliferation; Cell Survival; Colonic Neoplasms; Doxorubicin; Drug Resistance, Neoplasm; Drug Synergism; Gene Expression Regulation, Neoplastic; Humans; Piperazines; Siloxanes
PubMed: 32260260
DOI: 10.3390/molecules25071654 -
Journal of Controlled Release :... Dec 2015Nanoparticle anticancer drug delivery enhances therapeutic efficacies and reduces side effects by improving pharmacokinetics and biodistributions of the drug payloads in... (Review)
Review
Nanoparticle anticancer drug delivery enhances therapeutic efficacies and reduces side effects by improving pharmacokinetics and biodistributions of the drug payloads in animal models. Despite promising preclinical efficacy results, monotherapy nanomedicines have failed to produce enhanced response rates over conventional chemotherapy in human clinical trials. The discrepancy between preclinical data and clinical outcomes is believed to result from the less pronounced enhanced permeability and retention (EPR) effect in and the heterogeneity of human tumors as well as the intrinsic/acquired drug resistance to monotherapy over the treatment course. To address these issues, recent efforts have been devoted to developing nanocarriers that can efficiently deliver multiple therapeutics with controlled release properties and increased tumor deposition. In ideal scenarios, the drug or therapeutic modality combinations have different mechanisms of action to afford synergistic effects. In this review, we summarize recent progress in designing hybrid nanoparticles for the co-delivery of combination therapies, including multiple chemotherapeutics, chemotherapeutics and biologics, chemotherapeutics and photodynamic therapy, and chemotherapeutics and radiotherapy. The in vitro and in vivo anticancer effects are also discussed.
Topics: Animals; Antineoplastic Agents; Drug Combinations; Drug Delivery Systems; Ferric Compounds; Gold; Humans; Nanoparticles; Neoplasms; Organometallic Compounds; Organosilicon Compounds; Polymers
PubMed: 26387745
DOI: 10.1016/j.jconrel.2015.09.029 -
Reactions of Dihaloboranes with Electron-Rich 1,4-Bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadienes.Molecules (Basel, Switzerland) Jun 2020The reactions of electron-rich organosilicon compounds 1,4-bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene (),...
The reactions of electron-rich organosilicon compounds 1,4-bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene (), 2,3,5,6-tetramethyl-1,4-bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene (), and 1,1'-bis(trimethylsilyl)-1,1'-dihydro-4,4'-bipyridine () with -amino and -aryl dihaloboranes afforded a series of novel B=N-bond-containing compounds - and . The B=N rotational barriers of (>71.56 kJ/mol), (58.79 kJ/mol), and (58.65 kJ/mol) were determined by variable-temperature H-NMR spectroscopy, thus reflecting different degrees of B=N double bond character in the corresponding compounds. In addition, ring external olefin isomers were obtained by a reaction between and DurBBr. All obtained B=N-containing products were characterized by multinuclear NMR spectroscopy. Compounds , , , , and were also characterized by single-crystal X-ray diffraction analysis.
Topics: Crystallography, X-Ray; Cyclohexenes; Electrons; Heterocyclic Compounds; Magnetic Resonance Spectroscopy; Models, Molecular; Organosilicon Compounds; Temperature
PubMed: 32580464
DOI: 10.3390/molecules25122875 -
Molecules (Basel, Switzerland) Dec 2020Divalent silicon species, the so-called silylenes, represent attractive organosilicon building blocks. Isolable stable silylenes remain scarce, and in most hitherto...
Divalent silicon species, the so-called silylenes, represent attractive organosilicon building blocks. Isolable stable silylenes remain scarce, and in most hitherto reported examples, the silicon center is stabilized by electron-donating substituents (e.g., heteroatoms such as nitrogen), which results in electronic perturbation. In order to avoid such electronic perturbation, we have been interested in the chemistry of reactive silylenes with carbon-based substituents such as ferrocenyl groups. Due to the presence of a divalent silicon center and the redox-active transition metal iron, ferrocenylsilylenes can be expected to exhibit interesting redox behavior. Herein, we report the design and synthesis of a bis(ferrocenyl)silirane as a precursor for a bis(ferrocenyl)silylene, which could potentially be used as a building block for redox-active organosilicon compounds. It was found that the isolated bis(ferrocenyl)siliranes could be a bottleable precursor for the bis(ferrocenyl)silylene under mild conditions.
Topics: Chemistry Techniques, Synthetic; Electrons; Humans; Metallocenes; Organosilicon Compounds; Oxidation-Reduction; Silicon
PubMed: 33327589
DOI: 10.3390/molecules25245917