CH-ti interactions

On the other hand, it was found that the 4-methoxybenzyl (Z,Z)- and (E,E)-muconates (7 and 8, respectively) alternately stack in a column by a CH/ti interaction between the methoxy hydrogens and the n electrons of the phenyl... 

The 71-electrons of aromatic rings can interact with charged species, yielding strong cation-71 interactions dominated by electrostatic and polarization effects. Interactions with CH units is also possible. For CH-ti interactions in both alkyl-and aryl-based model systems, dispersion effects dominate the interaction, but the electrostatics term is also relevant for aryl CH-ti interactions. ... 

The characteristic of a hydrogen bond resides in its attractive nature and orientation dependence. This is shown in Fig. 1 for CH/ti interactions as a typical example. Notice that the directionality and H/n-plane distance correlate and depend on the strength of the proton... 

The number of papers reporting the role of CH/ti interaction is rapidly increasing. Only recent key papers are cited here. Chloroform interacts favorably with an arene n-oloud of fullerene complexes of calixarenes " and cyclotriveratrylene. Evidence for the role of CH/ti interaction in self-assembly was presented.The significance in molecular capsules " " and lattice- and cavity-inclusion type clathrates is well documented. 

Illustrated in Fig. 3 is an example. Notice that the nonpolar CH/ti interactions dominate over the ordinary hydrogen bonds. 

By analyzing 19 adenine-cofactor specific enzymes, Chakrabarti and Samanta found CH/ti interactions to play... 

Nishio. M. Hirota. M. Umezawa, U. The CH/ti Interaction. Evidence, Nature, and Consequences Wiley-VCH New Uork. 1998. 

CH/ti interaction as an important factor in the crystal 72. packing and in determining the structure of elathrates. J. 

Polydimethylsiloxane polymers have also been used for CNT coating via non-covalent CH-ti interactions. " " ... 

Otherwise, a similar upshift of 10-15 cm" was observed in the Raman spectra of poly(butadiene)-MWNT composites [67], The CH-ti interactions observed between nanotube and polymer are stronger than that of the n-n interactions observed between nanotube bundles, resulting in a restriction of the C-C bond vibrations and a corresponding upshift of the Raman signal. A 17 cm" upshift in G-band Raman signal of MWNTs embedded in melt-blended polyethylene-MWNT composites and the evolution of a shoulder to this peak were attributed to compressive forces exerted on the MWNTs by polyethylene chains following intercalation into MWNT bundles. So, the proposed compression-induced effect on MWNT Raman G-band position appears to be consistent with the results obtained for rrP3HT-MWNT composites. 

Nishio M, Hirota M, Umezawa Y (1998) The CH/ti interaction, evidence, nature, and consequences. Wiley-VCH, New York... 

For compoimds 16, this conformation is in slow exchange (AG = 70-88 kJ/mol at 328K in CDCI3) with the 1,2,3-alternate conformation, the latter being less stable (AG° = 2-7 kJ/mol). ° Therefore it is possible to conclude that three important factors stabilize the flattened cone structure, viz. (i) the self-inclusion of the methoxy groups in the apolar cavity driven by CH-ti interactions, (ii) the presence of three bulky groups in 2,4,6 positions at the lower rim, and (iii) the presence of the ter/-butyl groups at the upper... 

Only 38 exhibits a selective response toward three analytes capable of CH-ti interactions, while for the other ones the responses are comparable or even lower to those of the polymer coatings, where no host-guest interactions are present. Therefore the dimensions of the preorganized cavity do not constitute a determinant factor for sensor selectivity, which depends on the presence of a 71-basic cavity, easily attainable from the gaseous analyte. 

It was postulated that the increased stabilisation imparted to complexes with the longer-chained saccharides could be derived from secondary effects such as advantageous hydrophobic interactions with the extended aromatic 7i-system or from CH-ti interactions. 

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