Solvatochromic comparison water

To estimate how many dye molecules fit into the dendritic micelles, UV-titra-tion experiments have been employed. In comparison with the spectra of a pure pinacyanol chloride solution in water, the peaks of the absorption maxima of the dye in the presence of the dendrimer are shifted bathochromically due to solvatochromic effects, which indicates the incorporation of the dye within the branches of the dendrimer. At dye-to-dendrimer molar ratios higher than 4 1, in addition to the bathochromic shifts, hypsochromically shifted peaks start to appear, indicating that the dendrimer is not incorporating further dyes. We interpret this as an incorporation of up to four dyes within the branches of the dendrimer. This observation correlates with the calculated available space within the dendrimer, obtained from the molecular simulations. Further studies of the interactions of the dyes within the dendritic micelle are in progress. 

Buhvestov U, Rived F, Rafols C, Bosch E, Roses M (1998) Solute-solvent and solvent-solvent interactions in binary solvent mixtures. Part 7. Comparison of the enhancement of water structure in alcohol-water mixtures measurement by solvatochromic indicators. J Phys Org Chem 11 185-192... 

By nature ILs are polar compounds, a property that is easily studied with solvatochromic compounds such as Reichardt s dye [4]. On the normalized polarity scale ( ) from 0.0 (tetramethylsilane, TMS) to 1.0 (water), most ILs can be foimd around 0.6-0.7. By comparison, for ethanol is 0.654 [4]. In general, the polarity is largely controlled by the nature of the cahon, whereas the ability of the ILs to parhcipate in hydrogen bonding seems to depend on the anion. On the other hand, the miscibility of ILs with water seems unpredictable. A well-known example is [BMIMjjBFJ which is water-miscible, while [BMIM][PFj] is not. Regarding biocatalysis, it has been pointed out that even trace amoimts of ionic impurihes can significantly affect the properties of the IL as well as the activity of added enzyme. 

This donor number scale is widely referenced in relation to thermodynamic properties, as well as electron-transfer kinetics and photochemical properties. It has been criticized because of the neglect of solvent effects and side reactions that contribute to and because a one-parameter scale can never be entirely adequate. Ambiguities can arise for solvents which have more than one donor site, such as the formamide and sulfoxide derivatives. Recent measurements with BFj as the acid have provided some points of comparison and criticism for the original donor numbers. Recently, Linert et al. have used the solvatochromic shifts of a Cu(II) complex to define donor numbers for anions in dichloromethane. They also have suggested how these values can be converted for use in other solvents through a correlation with the acceptor number of the solvent. Linert et al. have reviewed the area and provided an extensive compilation of donor numbers from calorimetric and solvatochromic shift measurements. Some anion donor numbers in dichloromethane are included in Table 3.4, and the values for anions in water are 21 kcal moH smaller than those given. 

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