Binding of chlorides

SURYVANSHI, A. K., SCANTLEBURY, J. D. LYON, S. B. 1995. The binding of chloride ions by sulphate resistant portland cement. Cement and Concrete Research, 25, 581-592. 

This type of receptor is represented by compounds 16a,b bearing ruthenium ) bipyridine moieties. Both calixarenes [18] exhibit 1 1 binding of chloride and bromide anions (DMSO-d6), and they are especially suitable for the complexation of H2POj (X16a=2.8-104 M-1 K16b=5.2 103 M"1). On the other hand, if we compare these results with those for similar non-calixarene receptors, where the bipyridine unit is substituted by alkyl, aryl or ethylene glycol substituents, the introduction of calixarene does not bring any substantially new features into the complexation abilities of these derivatives. As shown by X-ray analysis, the anion is encapsulated within the cavity formed by amidic functions with the contributions of CH...anion interactions from the bipyridine unit. 

The viscometric curves of the polyzwitterion form are not symmetrical, e.g., the increment in the reduced viscosity is significantly lower on the acidic side in contrast to the basic region. The reason is either the formation of hydrogen bonds between carboxylate ions and H+ of the type COO H" "- "OOC that reduce the hydrodynamic volume of the polybetaines, or the specific binding of chloride ions to the protonated amine groups. 

Proton NMR titrations in DMSO-de at 298 K were conducted in order to determine the stability constants of receptors 12a, 12b and 12c with a range of anions, added as their tetrabutylammonium salts. The strongest association constants were obtained for the 20-membered macrocycle 12b with the most significant increase in affinity between the macrocycles being observed in the binding of chloride. Enlargement from the 18-membered macrocycle... 

The penetration or addition of chloride-bearing salts changes the chemical composition of the pore solution, depending also on the type of salt (i. e. sodium chloride or calcium chloride). This is due to chemical or physical binding of chloride and hydroxyl ions for instance, sodium chloride increases the OH concentration (and thus the pH), while calcium chloride decreases the pH [9]. 

J. F. Lopez, E. Viqueira, C. Andrade, Transport and binding of chlorides through non-saturated concrete after an initial limited chloride supply ,... 

Considerable work has gone into differentiating between bound and free chlorides. As only the free chlorides contribute to corrosion that is ideally what we want to know. However, the binding of chlorides is a reversible and dynamic reaction, so attempts to remove and measure free chlorides will release bound chlorides. A further complication is that carbonation breaks down chloroaluminates thus freeing chlorides which proceed as a wave ahead of the carbonation front. 

Jensen, H.U., and Pratt, P.L. (1989) The binding of chloride ions in pozzolanic products fly ash cement blends. Advances in Cement Research 2,121-129. 

Inclusion of a carbazole lluorophore, as in the complex derived from ligand 129, can create a fluorescent sensor, whereby the binding of chloride results in charge transfer from the chloride to a Ru-pyridyl-centered orbital which quenches the fluorescence emission. 

The binding of chloride was also investigated by UV/vis titration of 54-56 with tetrabutylannnonium chloride in... 

A report from Flood employed the concept of hydrophobic collapse to enable the binding of chloride to an aryl-triazole foldamer, 21 (Figure 9.18), with high stabilities (B2 lO M ) in 50 50 water acetonitrile. The authors found that a [2 + 1] (host chloride) double helical complex was formed in acetonitrile and that its stability increased dramatically when the water content increased from 0 to 50%. 

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