Alkyl Chain spacer

A remarkable application of phosphines by Grey and coworkers for acid site characterization is the use of diphosphines with alkyl chain spacers of different length between the phosphine moieties. Based on careful NMR analysis and appropriate loading levels with diphosphines, the Al distribution can be determined [223, 224], The idea behind this tool is that the phosphine groups will be proto-nated, when they are close to an acid site in the zeolite structure. Protonation of both phosphine groups in one probe molecule will only occur, when the distance between the two acid sites is compatible with the molecular dimension of the diphosphine. 

Stable monolayers of S-D amphiphilic dyads with a single alkyl chain spacer containing a naphthalene and a ferrocene moiety... 

The transfer of the stable monolayers onto substrate plates and the comparison of the photoinduced electron transfer rates between S-D dyads with a rigid and a single alkyl chain spacer is now under investigation. 

Fig. 1 An ideal self-assembled monolayer of alkanethiolates supported on a gold surface. The terminal groups are amenable to synthesis, providing a means to immobilize and present ligands from the surface the alkyl chain spacer promotes tight, regular packing, and the gold-sulfur interface stabilizes surface atoms and alkane chains during packing...

Synthesis of the phenolic bromide building block 40 was similar to the that of previously reported monomer 48 but the alkyl chain spacer unit was shortened in an attempt to increase the nematic mesophase isotropization temperature. 50 Construction of the related building blocks 41 and 42 followed similar pathways the latter were prepared to create hyperbranched macromolecules with a broader mesophase. 50 ... 

Saturated alkyl chain spacers have been used to separate the phenanthroline subunits in the bridging ligands (49a)148 and (49b).149... 

Organically modified silica gel finds a number of applications as stationary phases in chromatography or as anchors for transition metal complexes used as inunobilized catalysts. The metal complexes are attached to the silica gel by coordinating them with phosphine (PR2-), mercapto (-SH) or other groups, which are linked to the support over an alkyl chain ( spacer ) [1-3]. To understand the mechanism of catalysis by supported metal complexes it is necessary to know more about the coordination of the silica-supported catalyst on the surface and the influence of the spacer length on the catalytic activity [4]. 

The side chain LC polymer via conventional route is made by polymerizing two acrylate/methacrylate monomers in which one has free hydroxyl side group (5-8%) linked via long alkyl chain and the other has LC moiety linked via alkyl chain spacer. This hydroxyl is later crosslinked by using diisocyanates such as, hexamethylene diisocyanate etc. to get LC elastomer (Figure 8.20) [53]. 

Fig. 4 Proton NMR spectrum of the model compound 9DDA9 deuterated on the alkyl chain (spacer), 9DDA9-d2o, in the nematic phase at 89-5 C, on cooling. (S) represents the main contribution of the spacer to the proton spectrum, which has disappeared as a consequence of deuteration (a small contribution, S, remains due to incomplete deuteration). (For further details see Section 3.2.)...

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