Hydrophobic metal complexes

INTERACTION OF HYDROPHOBIC METAL COMPLEXES AND ORGANOMETALLIC COMPOUNDS WITH BIOLOGICAL INTERPHASES... 

In 1988, Schiffrin s group [4] claimed that the use of lutetium biphthalocyanine (LuPc2) complex more hydrophobic than Fc enabled observation and investigation of a true , or heterogeneous, ET across the 0/W interface. A series of subsequent papers reported ET systems by other hydrophobic metal complexes including tin diphthalo-cyanine [5], iron and ruthenium metalloporphyrin complexes with pyridine [6] and Fc derivatives [7]. These experimental studies then stimulated theoretical studies on the ET kinetics [8-12]. 

Ideally, to ensure the complete removal of the metal ions from the aqueous phase, the complexant and the metal complex should remain in the hydrophobic phase. Thus, the challenges for separations include the identification of extractants that quantitatively partition into the IL phase and can still readily complex target metal ions, and also the identification of conditions under which specific metal ion species can be selectively extracted from aqueous streams containing inorganic complexing ions. 

Upon formation of a metal chelate or complex, the next rate-limiting step in delivering iron to the cell is the diffusion of iron complexes through the. soil in response to diffusion gradients. In the vicinity of plant roots, metal chelates and complexes may also move by bulk flow in the transpiration stream as water moves from the soil into the plant. However, depending on their charge characteristics and hydrophobicity, metal chelators and complexes can become adsorbed to clay and organic matter, which may then decrease their mobility and bioavail-... 

It has already been mentioned that metal complexes with confined binding pockets often display unusual chemical reactivities (see Section II). Thus, complexes of substituted hydrotris (pyrazolyl)borates, in which the substituents serve to from a hydrophobic binding pocket, have already been shown to exhibit enhanced chemical reactivity when compared with their unmodified analogs (282,283). Likewise, cyclodextrin and calixarene-based metallocavitands have been used as catalysts for selective organic transformations, and even as catalysts for reactions that... 

On the other hand, the presence of hydrophobic complexes is a prerequisite for partitioning and diffusion of metals into the lipid bilayer. In the following paragraphs, various types of metal complexes will be discussed, which are relevant to the interactions of metals in aquatic systems. The role of these various types of metal complexes with respect to interactions at the biological interphases will be systematically examined. 

Partitioning of metal complexes into the lipid bilayer of membranes is only significant for hydrophobic species. FA and HA, and their metal complexes, are not expected to enter to a significant extent into the lipid bilayer, due to their large molecular size. Uptake of hydrophobic metal species by diffusion across... 

The rate of metal complex formation is often modified (usually enhanced) by the presence of a charged interface in the aqueous phase. This may be provided by ionic micelles, e. g., SDS, microemulsions or polyelectrolytes. jjjg reactions of Ni + and Co with hydrophobic ligands pan, pap and pad 14-16 are popular ones for examining effects, since they are well characterized in the bulk water. The simple model (4.126)... 

The influence of DNA on the photo-electron transfer process between a variety of donor-acceptor couples has been examined during the last ten years. For all the systems studied, the metal complex interacts with the DNA and plays the role of electron acceptor or donor in the hydrophobic DNA microenvironment, whereas the other partner of the process, i.e. the reducing or oxidising agent in the ground state, is localised either on the DNA double helix, or does not interact with the nucleic acid and remains in the aqueous phase. Thus three... 

A large adduct formation constant increases the hydrophobicity of the metal complex and thus the distribution ratio of the metal. This is commonly referred to as a synergistic effect. Figure 4.2 illustrates the extraction of the U02(TTA)2 complex from 0.01 M HNO3 into cyclohexane. Because the linear O-U-0 group is believed to have five to seven coordination sites, where only... 

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