Unexpected and frustrating transformations of double-decker silsesquioxanes

This paper outlines an unexpected type of intramolecular transformation of DDSQ during hydrolytic condensation and surprising catalytic reactivity in silylative coupling.

Silsesquioxane cages as fluoride sensors

Pyrene functionalized silsesquioxane cages (PySQ) not only provide significant fluorescence from pyrene-pyrene excimers with a very large Stokes shift (Δλ = 143 nm, 69 930 cm^-1) in DMSO but also exhibit fluoride capture results coincidentally with a π-π* fluorescence enhancement. On the other hand, PySQ-F^- in THF significantly exhibits π-π* fluorescence quenching and a color change can be observed with the naked eye from light yellow to deep orange by forming a charge-transfer (CT) complex among the pyrenyl rings. Moreover, PySQ selectively captures F^- with a response time of <2 min and with a very low detection limit (1.61 ppb), while ¹⁹F NMR is used to confirm encapsulation of F^- with Δδ = 19 ppm.

POSS-Appended Diphenylalanine: Self-Cleaning, Pollution-Protective, and Fire-Retardant Hybrid Molecular Material

Ordered self-assemblies of hybrid molecules have potential as protective umbrellas against environmental pollution and corrosion. This article describes the design and fabrication of a new self-cleaning hybrid molecular material containing polyhedral oligomeric silsesquioxane (POSS) and diphenylalanine as hydrophobic and pollution-protective coating. The colorless organic-inorganic hybrid materials, in which the diphenylalanine motif controls the self-assembly, exhibit unique water resistance property and enhance mechanical strength of paper 1.5-fold. The hybrid building blocks self-assemble in antiparallel sheet manner through noncovalent interactions to form a supramolecular layerlike surface with enhanced roughness. The hybrid material is soluble in organic solvents at room temperature that makes it easy to coat on paper, wood, or metal surfaces. The coating is effective against rusting, corrosion, environmental pollution, and bacterial attack. The coating has been used as fire retardant and enhances fire safety. The sustainable molecular material is promising for the packaging industry and metal industry and artifact preservation.

First cage-like pentanuclear Co(ii)-silsesquioxane

A new pentanuclear “cylinder”-like cobalt(ii) phenylsilsesquioxane [(PhSiO_1.5)₁₀(CoO)₅(NaOH)] exhibits a slow relaxation of the magnetization and a high catalytic activity and stereoselectivity in the oxidation of alkanes and alcohols.

D 5h [PhSiO1.5]10 synthesis via F− catalyzed rearrangement of [PhSiO1.5]n. An experimental/computational analysis of likely reaction pathways

Fluoride catalyzed rearrangement of PhSiO_1.5 favoring [PhSiO_1.5]₁₀.

Synthesis of aromatic functionalized cage-rearranged silsesquioxanes (T8, T10, and T12) via nucleophilic substitution reactions

Organic-inorganic hybrid nano-building blocks of aromatic nitro-, aldehyde-, and bromo-functionalized polyhedral oligomeric silsesquioxanes were easily prepared through nucleophilic substitutions, starting from the reactions between octakis(3-chloropropyl)octasilsesquioxane and phenoxide derivatives. These phenoxide anions not only supply the substitution functions to a silsesquioxane cage, but can also induce a cage-rearrangement leading to the formation of octa-, deca-, and dodecahedral silsesquioxane cages.

Novel organic–inorganic hybrids based on T8 and T10 silsesquioxanes: synthesis, cage-rearrangement and properties

A simple approach for the synthesis of well-defined macromolecules based on isolated amino- and amido-functionalized octa T₈ and deca T₁₀ silsesquioxanes is presented. Here we show how the reorganization of the siloxane cage-like core (cage rearrangement) can be performed.

Synthesis and reactivity of nitrogen nucleophiles-induced cage-rearrangement silsesquioxanes

Novel phthalimide and o-sulfobenzimide-functionalized silsesquioxanes were successfully synthesized via nucleophilic substitution reactions from octakis(3-chloropropyl)octasilsesquioxane. Surprisingly, the formation of deca- and dodecasilsesquioxanes cages was discovered during substitution with phthalimide, but only octasilsesquioxane maintained a cage in the o-sulfobenzimide substitution reaction. Moreover, we report the electronic effect of nitrogen nucleophiles to promote cage-rearrangement of inorganic silsesquioxane core for the first time. Structures of products were confirmed by (1)H, (13)C, and (29)Si NMR spectroscopy, ESI-MS analysis, and single-crystal X-ray diffraction.

A new, higher yielding synthetic route towards dodecaphenyl cage silsesquioxanes: synthesis and mechanistic insights

Cage dodecaphenylsilsesquioxane (T12-Phenyl) was synthesized in a one batch, mildly basic aqueous solution under room temperature conditions using a trialkoxysilane precursor. Significant improvements in synthetic yield (>95%) were observed compared with previous reports. Kinetic studies of the hydrolysis of phenyltrimethoxysilane were conducted and the condensation was monitored by (29)Si NMR which revealed the presence of a transient, intermediary T1 species as the pathway to dodecaphenylsilsesquioxane spherulites, and the tendency for T12 structures over T8, T10, and other substructures was explained through MM2 simulations.