Molecular-scale periodicity

Since the discovery of this first benzene-bridged mesoporous hybrid material with crystal-like pore walls, the series of organosilica precursors that give PMOs exhibiting molecular-scale periodicity was considerably extended. Kapoor et al. demonstrated with the formation of PMO products from the precursor 1,3 -bis(triethox-ysilyl)benzene (10) that a crystal-like organization of the organic bridges within the pore walls is not restricted to linear-substituted precursors.264... 

Of special significance in the development of PMO materials was the synthesis of porous materials with crystalline order of the bridged silsesquioxane inside the framework walls, initially achieved through the use of tt-tt interactions between 1,4-phenylene-bridged silsesquioxane precursors.33 Molecular scale periodicity in... 

Q. Yang, M. P. Kapoor, and S. Inagaki, Sulfuric acid-functionalized mesoporous benzene -silica with a molecular scale periodicity in the walls, /. Am. Chem. Soc. 124, 9694-9695 (2002). 

This resolution limit seems to contradict the numerous AFM images that have been reported, in which atomic or molecular-scale periodicities are observed. The atomic or molecular-scale contrast is actually due to the periodic forces felt by the tip as it moves over the surface of the periodic lattice of the sample, generating what is tantamount to a Moire pattern of the convolved forces between the macroscopic tip and periodic lattice of the sample. Fortunately, molecularly smooth films with sufficiently large domains, such as those described herein, allow attainment of molecular-scale contrast. But it must be emphasized that molecular-scale contrast is not identical to molecular-scale resolution. 

BTEB to produce the first PMO system with a hierarchically ordered structure including meso- and molecular-scale periodicity. The as-prepared... 

Mizoshita et al. [132] used BTENph under basic hydrolytic conditions to synthesize a 2,6-naphthylene-bridged PMO exhibiting unique fluorescence behavior that reflected molecular-scale periodicity in the framework (0.98 nm). 

Bion, N., Ferreira, P., Valente, A., Gonqalves, I.S., and Rocha, J. (2003) Ordered benzene-silica hybrids with molecular-scale periodicity in the walls... 

Sulfuric acid-functionalized mesoporous benzene-silica with a molecular-scale periodicity in the walls. /. 

Inagaki S, Guan S, Fukushima Y, Ohsuna T, Terasaki O (1999) Self-assembly of biphenylene-bridged hybrid mesoporous solid with molecular-scale periodicity in the pore walls. J Am Chem Soc 121 9611-9614... 

Lourenco et al. (2013) reported N-alkylation reaction of amine functionalized phenylene moieties in crystal-like mesoporous silica. A potassium iodide catalyzed method commonly used for the selective N-monoalkylation of aniline, was adapted and optimized to the N-monoalkylation reactions of the amine functionalized periodic mesoporous phenylene-silica (NH2-PMO) under microwave irradiation with conservation of the ordered mesostructure and the crystal-like molecular scale periodicity of the material. This functionalization opens a path for the preparation of new materials with different amino-alkyl groups specially designed for a desired application. 

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