Alumosilicates molecular

Microporous inorganic materials dominated historically by the 2eohtes and alumosilicates, and the great variety of more recent nonoxide and coordination framework materials should also be mentioned here (171—174) but not discussed in detail. This type of molecular recognition is usually known as molecular sieving. 

In 1992, researchers of the Mobil Oil Company introduced a new concept in the synthesis of mesoporous materials. They used supramolecular arrays of surfactant molecules as templating agents in order to obtain mesostructured silicates or alumosilicates which retain after calcination an ordered arrangement of pores with diameters between 2 and 10 nm and a narrow pore size distribution comparable to that of zeolites. These materials called M41S phases give access to the regime of the mesopores which is very interesting for different kinds of new size selective applications, e.g., molecular sieves, catalysis and nanocomposites [1]. 

Similar spectra of molecular cation radicals have been obtained earlier in the author s laboratory for diphenylamine, iV-methyldiphenyl-amine, N, iV -dimethyl-p-phenylenediamine (77a) and also for benzidine (27), when adsorbed from their vapors on the natural alumosilicate, bentonite. However, in these instances the degassing and vacuum treatment of the adsorbent could not be pushed so far, as for silica-alumina. Therefore doubt might arise whether the coloration should not be ascribed to traces of active oxygen (cf. Section V, G). 

As the hydrogen atoms in (Ph2Si0)8[Al(0)0H]4 are quite acidic, an obvious step was to replace them by electropositive elements such as lithium, potassium or divalent tin and thus to create molecular alumosilicates. The reactions can easily be performed with reactants like butyllithium, phenyllithium, lithium amide, potassium tert-butoxide, tin di(fert-butoxide), bis(hexamethyldisilazyl)-... 

Table 27.1. Selection of molecular alumosilicates obtained by hydrogen-substitution from (Ph2Si0)8[Al(0)0H]4 ...

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