Bridging effects

The situation is different if electronic interaction between vicinal substituents is involved. Maciel and co-workers, for example, found large deviations from SCS additivity in 1,2-substituted ethanes if the substituents -I or -C CH are involved the deviations could be accounted for by the high polarizability of the two groups (311,312). Steric, electronic, and hydrogen-bridging effects are... 

Mangenot, S., Raspaud, E., Tribet, C., Belloni, L., and Livolant, F. (2002) Interactions between isolated nucleosome core particles A tail-bridging effect Eur. Phys. J. E 7, 221-231. 

The bridge effect was scrutinized in the range of diferrocenyl derivatives, especially of those that are applicable in catalysis and material science (Atkinson et al. 2004). One-electron oxidation of these derivatives also proceeds easily, reversibly, and gives rise to cation-radicals (ferrocenium ions). In contrast to the cation-radical of ferrocenylacrylonitrile, the hole transfers through conjugated systems were proven for the bis(ferrocenyl)acetylene cation-radical (Masuda and Shimizu 2006), the bis(ferrocenyl) ethylene cation-radical (Delgado-Pena et al. 1983), and the cation-radical of bis(fulvaleneiron) (LeVanda et al. 1976). These structures are presented in Scheme 1.30. 

Air-entrained pastes possess a higher viscosity than pastes with little or no air content, mainly because of the bridging effect of cement particles by air bubbles increasing the structure of the system. 

Shinkai et al.111-151 synthesized a series of azobis(benzocrown ethers) called butterfly crown ethers , of which compounds 9 and 10 are examples. Their photoresponsive molecular motion resembles that of a flying butterfly. It was found that the proportion of their Z forms at the photostationary state increases remarkably with increasing concentration of Rb+ and Cs+, which interact with two crown rings in a 1 2 sandwich fashion. This is clearly due to the bridge effect of the metal cations with the two crowns, results that support the view that the Z forms make an intramolecular 1 2 complex with these metal cations. As expected, the Z forms extracted alkali metal cations with large ion radii more efficiently than did the corresponding E forms. In particular, the photoirradiation effect on 9 is quite remarkable for example, ( )-9 (n= 2) extracts Na+ 5.6 times more efficiently than (Z)-9 (n= 2), whereas (Z)-9(n= 2) extracts K+ 42.5 times more efficiently than ( )-9(n= 2). l ... 

The dispersion of SiC-coated MWCNTs increases the microhardness and fracture toughness of SiC. The SiC coating on MWCNTs at 1150°C is effective in improving the weak adhesion between MWCNTs and the SiC matrix. SiC-coated MWCNT/SiC composites show elastic behavior due to the crack-bridging effect of MWCNTs. 

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