Self-Assembled Tin-Based Bridged Hybrid Materials

Molecular Cage Assembly by Sn-O-Sn Bridging of Di-, Tri- and Tetranuclear Organotin Tectons: Extending the Spacing in Double Ladder Structures

Hydrolysis reactions of di- and trinuclear organotin halides yielded large novel cage compounds containing Sn-O-Sn bridges. The molecular structures of two octanuclear tetraorganodistannoxanes showing double-ladder motifs, viz., [{Me3 SiCH2 (Cl)SnCH2 YCH2 Sn(OH)CH2 SiMe3 }2 (μ-O)2 ]2 [1, Y=p-(Me)2 SiC6 H4 -C6 H4 Si(Me)2 ] and [{Me3 SiCH2 (I)SnCH2 YCH2 Sn(OH)CH2 SiMe3 }2 (μ-O)2 ]2 ⋅0.48 I2 [2⋅0.48 I2 , Y=p-(Me)2 SiC6 H4 -C6 H4 Si(Me)2 ], and the hexanuclear cage-compound 1,3,6-C6 H3 (p-C6 H4 Si(Me)2 CH2 Sn(R)2 OSn(R)2 CH2 Si(Me)2 C6 H4 -p)3 C6 H3 -1,3,6 (3, R=CH2 SiMe3 ) are reported. Of these, the co-crystal 2⋅0.48 I2 exhibits the largest spacing of 16.7 Å reported to date for distannoxane-based double ladders. DFT calculations for the hexanuclear cage and a related octanuclear congener accompany the experimental work.

Molecular Tectonics with Di- and Trinuclear Organotin Compounds

Di- and trinuclear organotin(IV) complexes, in which the metal atoms are separated by large aromatic connectors, are useful building blocks for self-assembly. This is demonstrated by the preparation of [1+1], [2+2], and [2+3] macrocyclic and cage-type structures in combination with organic aromatic dicarboxylates. The linkage of the metal atoms by organic binders and the option of varying the number of reactive M-X sites generate versatile building blocks enabling molecular tectonics instead of the node-based strategy generally employed in metallo-supramolecular self-assembly.

Hybrid organotin and tin oxide-based thin films processed from alkynylorganotins: synthesis, characterization, and gas sensing properties

Hydrolysis-condensation of bis(triprop-1-ynylstannyl)butylene led to nanostructured bridged polystannoxane films yielding tin dioxide thin layers upon UV-treatment or annealing in air. According to Fourier transform infrared (FTIR) spectroscopy, contact angle measurements, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and scanning electron microscopy (SEM) data, the films were composed of a network of aggregated "pseudo-particles", as calcination at 600 °C is required to form cassiterite nanocrystalline SnO2 particles. In the presence of reductive gases such as H2 and CO, these films gave rise to highly sensitive, reversible, and reproducible responses. The best selectivity toward H2 was reached at 150 °C with the hybrid thin films that do not show any response to CO at 20-200 °C. On the other hand, the SnO2 films prepared at 600 °C are more sensitive to H2 than to CO with best operating temperature in the 300-350 °C range. This organometallic approach provides an entirely new class of gas-sensing materials based on a class II organic-inorganic hybrid layer, along with a new way to include organic functionality in gas sensing metal oxides.

Nanoscaled tin dioxide films processed from organotin-based hybrid materials: an organometallic route toward metal oxide gas sensors

Nanocrystalline tin dioxide (SnO(2)) ultra-thin films were obtained employing a straightforward solution-based route that involves the calcination of bridged polystannoxane films processed by the sol-gel process from bis(triprop-1-ynylstannyl)alkylene and -arylene precursors. These films have been thoroughly characterized by FTIR, contact angle measurements, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force (AFM) and scanning electron (SEM) microscopies. Annealing at a high temperature gave 30-35 nm thick cassiterite SnO(2) films with a mean crystallite size ranging from 4 to 7 nm depending on the nature of the organic linker in the distannylated compound used as a precursor. In the presence of H(2) and CO gases, these layers led to highly sensitive, reversible and reproducible responses. The sensing properties were discussed in regard to the crystallinity and porosity of the sensing body that can be tuned by the nature of the precursor employed. Organometallic chemistry combined with the sol-gel process therefore offers new possibilities toward metal oxide nanostructures for the reproducible and sensitive detection of combustible and toxic gases.

Tin(IV) oxide coatings from hybrid organotin/polymer nanoparticles

Tin dioxide coatings are widely applied in glasses and ceramics to improve not only optical, but also mechanical properties. In this work, we report a new method to prepare SnO(2) coatings from aqueous dispersions of polymer/organotin hybrid nanoparticles. Various liquid organotin compounds were encapsulated in polymeric nanoparticles synthesized by miniemulsion polymerization. Large amounts of tetrabutyltin and bis(tributyltin) could be successfully incorporated in cross-linked and noncross-linked polystyrene nanoparticles that served as sacrificial templates for the formation of tin oxide coatings after etching with oxygen plasma or calcination. Cross-linked polystyrene particles containing bis(tributyltin)--selected for having a high boiling point--were found to be especially suited for the oxide coating formation. The content of metal in the particles was up to 12 wt %, and estimations by thermogravimetrical indicated that at least 96% of the total organotin compound was converted to SnO(2). The resulting coatings were mainly identified as tetragonal SnO(2) (cassiterite) by X-ray diffraction, although a coexistence of this phase with orthorhombic SnO(2) was observed for samples prepared with bis(tributyltin).

Linear or cross-shaped di(cyclopentadienyltitanium) compounds with aryl or heteroaryl spacers

The preparation of hexamethylated and hexabenzylated arylene or heteroarylene bridged dinuclear di(cyclopentadienyltitanium) compounds from the reaction of the corresponding hexachlorides with methyllithium or benzylmagnesium chloride is described. The spacers between the cyclopentadienyl rings consist of one, two or three phenylene groups, a dioctyloxyphenylene group or a 2,2'-bithienylene group. The corresponding hexachlorides and hexaisopropoxides have also been prepared.

Precursors for the Formation of Tin(IV) Oxide and Related Materials

Molecular precursors for the formation of tin oxide and related materials by chemical vapour deposition or sol-gel routes are reviewed.

Sn(3) and Sn(10) sulfonate-oxide-hydroxide clusters with two different sulfonate binding modes

A tin sulfonate-oxide-hydroxide tetracation with two different sulfonate bindings, an electrostatic and a monohapto covalent one, and a tin sulfonate-oxide-hydroxide monocation with two other kinds of sulfonate bindings, an electrostatic and a dihapto bridging one are described here.

Particle growth of hybrid materials followed by dynamic light scattering

The hydrolysis of distannylated compounds in which the tin atoms are linked by an organic spacer has been studied under microemulsion conditions using dynamic light scattering and infrared spectroscopy. The experiments provided evidence that the growth of hybrid material particles occurs in the aqueous phase, outside the organic phase of the microemulsion. The growth rates of the particles were found to be strongly dependent on the nature of the spacers, a polymethylene chain inducing the fastest process. This different behavior was explained by a slower condensation process rather than a slower hydrolysis. The high surface areas measured for the hybrid materials could be explained by a possible coating of the hybrid particles by surfactant molecules, thus preventing either their growth or their aggregation.

A doubly folded spacer in a self-assembled hybrid material

The hydrolysis of a bridged alpha,omega-bis(trialkynylstannylated) compound leads to a hybrid material ordered by self-assembly where the spacer forms two six-membered [1,2]oxastanninane rings by intramolecular coordination.