Extension ladders - synthesis and characterisation of new spacer-bridged tetraorganodistannoxanes

Preliminary results are described on the synthesis and characterization of novel spacer-bridged tetraorganodistannoxanes, {[[R(Cl)Sn]₂(CH₂)₂]O}₄ (n = 5 – 8, 10, 12; R = CH₂SiMe₃) containing particularly long organic spacers. In the solid state, these compounds reveal typical double-ladder structures with eight tin atoms per molecule, whereas in solution a partial and reversible rearrangement takes place to form tetraorganodistannoxanes, {[[R(Cl)Sn]₂(CH₂)_n]O}₂ (n = 5 – 8, 10, 12; R = CH₂SiMe₃), having four tin atoms per molecule.

A spacer-linked molecular diorganotin oxide

The synthesis and molecular structure are reported of the first example of a diorganotin oxide, {p-[R(O)SnCH₂SiMe₂]₂C₆H₄}₃ (3) (R = (Me₃Si)₂CH), in which two six-membered Sn₃O₃ units are linked by three -CH₂Si(Me)₂C₆H₄Si(Me)₂CH₂- spacers.

Hydrolysis of dinuclear spacer-bridged diorganotin(IV) triflates. A novel cationic double ladder with supramolecular association

A series of oligomethylene-bridged diorganotin triflates R(OTf)₂Sn(CH₂)_nSn(OTf)₂R (R = CH₂SiMe₃; n = 3, 4, 8, 10) were synthesized by reaction of triflic acid with the precursor oxides R(O)Sn(CH₂)_nSn(O)R. On the basis of ¹¹⁹Sn NMR (in acetonitrile) the triflates appear to be the simple six-coordinated ionic species [(MeCN)₄(RSn(CH₂)_nSnR)(MeCN)₄]²⁺. These triflates readily undergo hydrolysis to give products, the identity of which depends on the length of the oligomethylene bridge. For n = 3 (5), the solid-state structure shows association of two dimeric units, which results in a tetracationic double ladder. Extensive hydrogen bonding gives rise to a supramolecular association. Solution ¹¹⁹Sn NMR and ES MS suggest some dissociation of 5 into dimers containing four tin atoms and possibly monomers containing two tin atoms. A rudimentary solid-state structure for n = 4 (6) indicates a linear polymer based on dimeric (four tin atoms) units. The structure of 6 also features extensive hydrogen bonding, this time effectively giving rise to alternating layers of cations and anions.

The first spacer-bridged tetraorganodistannoxanes with a mixed double ladder structure

The reaction of Me₃SiCH₂Cl₂Sn(CH₂)₃SnCl₂Ph (6) with (tBu₂SnO)₃ gave a statistical mixture of the corresponding tetraorganodistannoxanes whereas the reaction of the spacer-bridged ditin tetrachlorides RCl₂Sn(CH₂)₄SnCl₂R (3, R = Me₃CCH₂; 4, R = Me₂CHCH₂; 10, R = Me₃SiCH₂) with the polymeric spacer-bridged ditin oxides [R(O)Sn(CH₂)₄Sn(O)R]_n (7, R = Me₂CHCH₂; 8, R = Me₃CCH₂; 11, R = Me₃SiCH₂) provided the mixed double ladder compounds {[R(Cl)Sn(CH₂)₄Sn(Cl)R][R(Cl)Sn(CH₂)₄Sn(Cl)R']O₂}₂ (9, R = Me₃CCH₂, R' = Me₂CHCH₂; 12, R = Me₃CCH₂, R' = Me₃SiCH₂) in almost quantitative yield. In solution, 9 and 12 are in equilibrium with their corresponding dimers, as was evidenced by ¹¹⁹Sn NMR spectroscopy, molecular mass determination, and electrospray mass spectrometry. The molecular structures of 9 and 12 were established by single crystal X-ray diffraction.

π-Selective stationary phases: (I) Influence of the spacer chain length of phenyl type phases on the aromatic and methylene selectivity of aromatic compounds in reversed phase high performance liquid chromatography

Phenyl type stationary phases of increasing spacer chain length (phenyl, methyl phenyl, ethyl phenyl, propyl phenyl and butyl phenyl, with 0–4 carbon atoms in the spacer chain, respectively) were synthesised and packed in house to determine the impact that the spacer chain length has on the retention process. Two trends in the aromatic selectivity, q_aromatic, were observed, depending on whether the number of carbon atoms in the spacer chain is even or odd. Linear log k′ vs ϕ plots were obtained for each stationary phase and the S coefficient was determined from the gradient of these plots. For the phenyl type phases, the S vs n_c plots of the retention factors of linear polycyclic aromatic hydrocarbons vs the number of rings exhibit a distinct discontinuity that between 3 and 4 rings, which increases with increasing spacer chain length for even phases but decreases for odd phases. Accordingly, we suggest that the retention factors depend differently on the number of carbon atoms in the spacer chain depending on whether this number is even or odd and that this effect is caused by different orientations of the aromatic ring relative to the silica surface.

Evolution of moisture management behavior of high-wicking 3D warp knitted spacer fabrics

Moisture management behavior is a vital factor in evaluating thermal and physiological comfort of functional textiles. This research work studies functional 3 dimensional (3D) warp knitted spacer fabrics containing high-wicking materials characterized by their profiled cross section. These spacer fabrics can be used for protective vest to absorb a user’s sweat, to reduce the humidity and improve user’s thermal comfort. For this reason, different 3D warp knitted spacer fabrics were produced with functional fiber yarns in the back layer of the fabric (close to the body) and polyester in the front and middle layers (outer surface). Comfort properties such as air and water vapor permeability and wicking and other moisture management properties (MMP) of different fabric samples were measured. It is demonstrated that by using profiled fibers such as Coolmax fiber, moisture management properties of spacer fabrics can be improved, enabling them to be use as a snug-fitting shirt worn under protective vests with improved comfort.

Decolorization and mineralization of an azo reactive dye using loaded nano-photocatalysts on spacer fabric: kinetic study and operational factors

In this study, the photocatalytic decolorization and mineralization of Remazol Black B (RBB), an azo reactive dye, in aqueous solutions was investigated using UV/H2O2/ZnO, UV/H2O2/TiO2 and UV/H2O2/ZnO:TiO2 systems. ZnO and TiO2 nanoparticles were loaded on 3-dimensional polyethylene terephthalate fabrics (spacer fabrics). Morphology of the spacer fabrics and the presence of the nanoparticles were studied by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), respectively. Furthermore, the effects of key operational parameters on the efficiency of the decolorization were investigated. These parameters included initial pH value, initial hydrogen peroxide concentration, initial dye concentration, the loaded nanoparticle ratio and the presence of anions (sulfate, chloride and bicarbonate). Zero-, first- and second-order reaction kinetics were evaluated. Complete decolorization and high efficient mineralization with 90% total organic carbon (TOC) reduction were achieved at 120min treatment in the case of ZnO:TiO2 under optimum condition. The results proved that the novel heterogeneous photocatalytic process is capable of decolorizing and mineralizing azo reactive dyes in textile wastewater.