Anion functional group

Ion bridging is a specific type of Coulombic interaction involving the simultaneous binding of polyvalent cations (e.g., Ca, Fe, Cu ) to two different anionic functional groups on biopolymer molecules. This type of ionic interaction is commonly involved in associative self-assembly of biopolymers. As a consequence it is also an important contributory factor in the flocculation (via bridging or depletion) of colloidal particles or emulsion droplets in aqueous media containing adsorbed or non-adsorbed biopolymers (Dickinson and McClements, 1995). 

Like other aieas of spectioscopy, visible spectrometry has a wide range of applications. Included are most of the elements, many anions, functional groups, and innumerable compounds. 

Among the NHC ligands with N-substituents containing centers of chirality, polydentate ligands that combine the NHC unit with an anionic functional group have been developed recently. They thus combine two complementary ligating anchor units, which avoids the rotation of the chiral substituents around the C - N axis. Arnold and coworkers reported the synthesis of the... 

The first group 1 carbene complex with an N-bound anionic functional group was reported in 2004.12 An alkylamino carbene is readily deprotonated using //-butyl lithium to afford 4 (Fig. 3). The solid state structure comprises a discrete dimer via bridging amido groups. Although there is severe distortion of the lithium-NCN bond (147.9° compared to the closer to linear 161.8° in 3), the lithium-NHC bond distance of 2.124(4) A is still short, suggesting that the interaction is predominantly ionic. 

Figure 4.41. Schematic representations of the hydrogen bonds made by the anionic functional groups in the diastereomeric salts of a) carboxylates, (b) sulfonates, (c) O-alkylphosphonates, and (d) O-alkylphosphonothioates. The dotted lines represent hydrogen bonds.

Numerous squalamine analogs have been prepared and examined for biological activity (Figure 9.1). The squalamine structure has been varied through the length of the polyamine chain [41-44] the nature of the anionic functional group [41] the position of the polyamine [43-45], sulfate [45,46], and free hydroxyl [41,43,44,47] on the steroid scaffold the stereochemistry and substitution at C-3, C-7, and C-24 [41-44] the length of the steroid side chain [41,45,46] and the unsaturation of the steroid [43,44]. 

N-Heterocyclic Carbenes with Anionic Functional Groups... 

In contrast, reversed-phase sorbents have non-polar functional groups, e.g. octadecyl, octyl and methyl, and conversely are more likely to retain non-polar compounds, e.g. polycyclic aromatic hydrocarbons. Ion-exchange sorbents have either cationic or anionic functional groups and when in the ionized form attract compounds of the opposite charge. A cation-exchange phase, such as benzene-sulfonic acid, will extract analytes with positive charges (e.g. phenoxyacid herbicides) and vice versa. A summary of the commercially available silica-bonded sorbents is given in Table 8.1. 

Due to the presence of the ionic P4VP-Re-complex block on the film surface, nanoparticles decorated with anionic functional groups can be deposited on the copolymer film surface by electrostatic attraction. The copolymer film was immersed into a solution of cadmium sulfide nanoparticles (diameter = 10 nm), functionalized with carboxylate groups on the particle surface. The attachment of cadmium sulfide nanoparticles on the film surface was confirmed by X-ray photoelectron spectroscopy (XPS). In addition, particles deposited on the cylindrical blocks in the copolymer film surface were also observed in AFM image (Figure 5.12). This approach has potential in fabricating nanoparticle-polymer composites on patterned surface. 

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