David Y. Son

Silyl-substituted thioether ligands and their Ag(I) complexes.

Silyl-substituted thioether ligands were prepared that differed in the identity and number of ligating groups attached to silicon and the nature of the alkyl groups on silicon. The ligand syntheses involved deprotonation of a thioether with n-butyllithium followed by reaction with the appropriate chlorosilane. Yields were 45-75% after purification. The majority of the ligands reacted with silver(I) triflate to give stable crystalline products in high yields that could be characterized by single-crystal X-ray crystallography. Depending on the ligand, the structures of the products ranged from discrete complexes to infinite polymeric structures. Apparent argentophilic interactions were commonly observed in the solid-state structures of the complexes (Ag-Ag = 2.909-3.196 A).

Hydrosilylation reactions of bis(dimethylsily)acetylenes: A potential route to novel σ- and π-conjugated polymers

Abstract Chloroplatinic acid catalyzes hydrosilylation reactions between bis(dimethylsilyl)acetylenes and simple aromatic monoethynyl compounds, yielding styrenic derivatives. Reactions of the bis(dimethylsilyl)acetylenes with aromatic diethynyl compounds yield conjugated short chain oligomers.

Versatile dendrimer-derived nanocrystal microreactors towards fluorescence colloidal photonic crystals

The ability to finely bind colloidal photonic crystals with nanocrystals (NCs) is critical in many applications ranging from light-emitting devices to flexible displays and biological labels. Herein, the use of carbosilane–thioether generation 2 vinyl-terminated (G2-Vi) dendrimers facilitates zero dimensional (0D) and two dimensional (2D) microreactors with high-uptake NCs, allowing them to generate fluorescent colloidal photonic crystals. Dendrimer-functionalized microspheres were prepared by seeded copolymerization from micrometer-sized polystyrene (PS) seed particles and G2-Vi dendrimers. As an independent 0D microreactor, such dendrimer-functionalized microsphere latices bearing abundant thioether anchor sites can capture guest metal ion components, followed by the introduction of chalcogenides, and hence the in situ generation of higher-uptake NCs was realized. Furthermore, the as-obtained NC–latex hybrids from 0D microreactors were directly self-assembled into large-scale ordered colloidal arrays with uniform fluorescence. Additionally, compact assemblies from the Cd2+-loaded dendrimer-functionalized microspheres were constructed and were employed as a large-scale 2D reactor. An on-demand fluorescence pattern was freely and quickly displayed via a reaction-induce-response process by screen stencil oriented printing.

Thiol-ene chemistry of vinylsilanes

The thiol-ene addition reaction is a clean, effective method for the introduction of the thioether functionality into unsaturated compounds. Though widely used in organic, polymer and materials chemistry, the application of the thiol-ene reaction in organosilicon chemistry has been relatively minimal. The literature discussed here emphasizes the synthetic utility of thiol-ene reactions of vinylsilanes by highlighting the following areas: (1) the tolerance of various vinylsilane derivatives, (2) the reactivity of various substituents on the vinylsilane moiety, (3) the simplicity of reaction conditions, and (4) the versatility of reaction products as intermediates.

Simplified preparations of trialkylsilyl- and bis(trialkylsilyl) dihalomethanes via the deprotonation of dihalomethanes

Abstract Simple, high-yield routes to trialkylsilyl- and bis(trialkylsilyI)dihalomethanes are described. These compounds are prepared by the deprotonation of dibromomethane or dichloromethane by lithium diisopropylamide in the presence of a chlorosilane. The reactions are carried out at temperatures below −70°C in THF/hexane solvent mixtures. After aqueous workup, the air- and water-stable products are isolated by either distillation or crystallization. Further reactions on these compounds are possible, as illustrated by one example.

Irradiation- and thermoinduced synthesis of Ag nanoparticles within amphiphilic carbosilane-thioether dendrimers

We report on the preparation of new amphiphilic carbosilane-thioether dendrimers by thiol-ene chemistry and their application in the in situ formation of silver nanoparticles (AgNPs) with unusual versatility in approach. In the presence of the dendrimers, AgNPs can be prepared in either water or organic solvents, and by simply using UV irradiation or heat in the reduction step without the need for a chemical reducing agent. Monodisperse size-tunable AgNPs possessing a simple cubic crystal structure were characterized by TEM, SAED, XRD, and other techniques. Susceptibility examination of E. coli indicated strong antibacterial activity of the AgNPs in aqueous solution.

Silylated amino-triazines: new ligands with potential multi-coordination modes

Abstract Melamine (1a), 2,4-diamino-6-phenyl-1,3,5-triazine (1b), and 2,4-diamino-6-methyl-triazine (1c) react with chlorotrimethylsilane and triethylamine in refluxing acetonitrile to give the corresponding monosilylated products 2a–c in good yields. Conversion of 2a–c to the lithium silylamides with n-BuLi occurs readily, as evidenced by a subsequent reaction with chlorodimethylsilane. The silylamides show promise as chelating ligands with the possibility of multi-coordination bonding modes.

Synthesis of an organosilicon hyperbranched oligomer containing alkenyl and silyl hydride groups

A new organosilicon hyperbranched oligomer has been prepared that contains both double bonds and silyl hydride groups. The monomer is prepared via the hydrosilylation of propargyl chloride with methyldichlorosilane in the presence of a platinum catalyst. The product is a mixture resulting from both α- and β-addition. Treatment of the monomer mixture with magnesium results in the formation of a hyperbranched oligomer, which is then treated with LiAlH4. Control of monomer addition speed to the magnesium is critical in order to keep head-head coupling low. The resulting oligomer is air- and water-stable, and has an average degree of polymerization of 8. This material gives a char yield of 24% but after crosslinking with platinum catalyst, the char yield increases to 69%.

Degradable, silyl ether thiol–ene networks

A system of multifunctional silyl ether containing alkene and thiol monomers are synthesized and polymerized into uniform degradable networks with widely tunable thermomechanical properties. The glass transition temperature of the hydrolytically unstable networks can be controlled between −60 °C and 40 °C. Near total degradation is observed and the rate of degradation is controlled to occur between hours and months. Dynamic mechanical analysis, mass loss, uniaxial compression testing, multinuclear NMR spectroscopy, and gas chromatography-mass spectrometry are utilized to characterize the degradation of these networks. Importantly, this system of materials allows for rapid hydrolytic degradation that is not preceded by swelling. These degradable polymers are demonstrated to be compatible with microfabrication techniques, namely photolithography. As a demonstration, partially biodegradable cortical electrodes were fabricated and electrochemically characterized on silyl ether substrates.

Synthesis of N,N′‐bis(2‐Thiazolinyl)‐, N,N′‐bis(2‐Thiazolyl)‐, and N,N′‐bis(2‐Pyrimidinyl)‐Benzene Dicarboxamides

Abstract New heteroaromatic benzene dicarboxamides have been synthesized in moderate to good yields by the reactions of 2‐aminothiazoline, 2‐aminothiazole, and 2‐aminopyrimidine with phthaloyl dichloride, isophthaloyl dichloride, and terephthaloyl dichloride in the presence of an organic base. The amides are sparingly soluble in common organic solvents but dissolve readily in dimethyl sulfoxide. Reactions of 2‐aminothiazoline and 2‐aminopyrimidine with phthaloyl dichloride yield a tricyclic compound and an imide, respectively, instead of the expected products.