Dimer formation upon deprotonation: synthesis and structure of a m-terphenyl substituted (R,S)-dilithium disiloxanolate disilanol.

The synthesis and structural characterization of the first dilithium salt of a tetrahydroxydisiloxane, [DmpSi(OH)OLi]2O (6), is described (Dmp = 2,6-dimesitylphenyl). The solid state structure reveals the presence of a dimeric motif where two disiloxane units are linked by coordinating lithium atoms which differs from those found for the sodium and potassium analogs. The arrangement imposed by the cluster formation leads to diastereomeric silicon atoms exhibiting (R,S) configuration in the solid state. In addition, the intermediates of the reaction, monolithiated and dilithiated silanetriol could be identified by means of high-resolution mass spectrometry and the formation of 6 is discussed. Moreover, the fully protonated tetrahydroxydisiloxane, [DmpSi(OH)2]2O has been obtained as well and its solid state structures with varying hydrogen bond acceptors have been surveyed.

Silanol-based surfactants: synthetic access and properties of an innovative class of environmentally benign detergents.

Herein, environmentally friendly surfactants based on new silanols as substitutes for the isoelectronic phosphonates were explored. Surface tensions of aqueous solutions are significantly reduced, particularly with those silanols that feature a high ratio of organic moiety to silanol. Besides their use as surfactants, their potential as coating agents for hydrophilic oxide surfaces was investigated for the example of glass substrates. In the solid-state sheet structures with silanol, double layers are present, in which the sheet spacing varies with the alkyl-chain length.

Silanetriols as Powerful Starting Materials for Selective Condensation to Bulky POSS Cages.

Controlled condensation reactions of tertiary silanetriols CH3(CH2) n (CH3)2CSi(OH)3 (1b-f; n = 1-5) in the presence of trifluoroacetic acid and the hydrolysis of CH3(CH2)6(CH3)2CSiCl3 (3) lead to the selective formation of the corresponding disiloxane tetrols [CH3(CH2) n (CH3)2CSi(OH)2]2O (2b-g; n = 1-6) in good yields. The TBAF-driven condensation reactions of the silanetriols CH3(CH2) n (CH3)2CSi(OH)3 (1a-c; n = 0-2) as well as of the disiloxane-1,1,3,3-tetrol 2d (n = 3) yield in the selective formation of the first T8 cages bearing tertiary carbon substituents, CH3(CH2) n (CH3)2C (4a-d; n = 0-3), which was not possible via the condensation of their alkoxysilane counterparts so far. The resulting compounds 2b-g and 4a-d have been characterized by multinuclear NMR, MS, and single-crystal X-ray diffraction.

A 32 vertex polyhedron via supramolecular assembly of silanedithiolate silanolate units.

A high yield synthesis of the first silanedithiolate silanolate is reported which spontaneously assembles forming an inorganic rugby ball shaped 32 vertex polyhedral cluster stabilized by sterically demanding 2,6-dimesitylphenyl substituents and two LiCl units.

Silanetriols as in vitro inhibitors for AChE.

Three stable silanetriols with increasing steric protection of the silicon atom have been tested for inhibition of acetylcholinesterase (AChE). For all tested silanetriols we found reversible inhibition of the AChE activity at a 100 µM concentration. The highest inhibition rate was found for the sterically least hindered cyclohexylsilanetriol with 45% inhibition relative to galanthamine hydrobromide for which an IC(50) value of 121 ± 3 µM was determined as well. The cytotoxicity of the silanetriols used was found to be negligible at concentrations relevant for inhibition.

Surface modifications using a water-stable silanetriol in neutral aqueous media.

Surface modifications of glass slides employing the sterically hindered tert-butyl substituted silanetriol are described. To the best of our knowledge, this is the first time that a stable silanetriol has been directly used for this purpose. So far unprecedented, this process runs under neutral aqueous conditions and in the absence of organic solvents, which makes coating protocols accessible to acid-sensitive substrates. The layer thickness and surface topography are investigated by the Sarfus technique, by X-ray reflectivity, and by atomic force microscopy (AFM). These techniques yield values of 0.8±0.1 (XRR) and 0.6±0.2 nm (Sarfus) for layer thickness and 0.33 nm for root mean square roughness (AFM). The modified surfaces have hydrophobic and oleophilic character and contact angles (CA) between 60° (formamide, CH2I2) and 90° (water) are obtained. The thin coatings allow a structuring by UV/ozone treatment in order to get hydrophilic and hydrophobic compartments on the surfaces. For all coatings, surface free energies are calculated using different models. To determine the isoelectric points (IEP) of the modified surfaces, we performed zeta-potential measurements. Correlations between zeta potentials and hydrophilicity of the surfaces are shown.

Electrochemistry and spectroscopy of organometallic terpyridine nickel complexes.

Organonickel complexes [(R'terpy)Ni(aryl)]X (R'terpy = derivatives of 2,2';6',2''-terpyridine; aryl = 2,6-dimethylphenyl = Xyl or 2,4,6-trimethylphenyl = Mes; X = Br or PF(6)) have been investigated by multiple electrochemical methods as well as combined electrochemical/spectroscopic techniques (spectroelectrochemistry). Reversible electrochemical reduction fills successively pi* orbitals in the terpy ligand. Some of the occurring species were characterized spectroscopically (EPR and UV/vis/NIR spectroelectrochemistry). The presumably nickel-centered oxidation occurs irreversibly.