Ion-Metal Interactions

This reaction is one example of several possible radical transition-metal ion interactions. The significance of this and similar reactions is that radicals are destroyed and are no longer available for initiation of useful radical reactions. Consequentiy, the optimum use levels of transition metals are very low. Although the hydroperoxide decomposes quickly when excess transition metal is employed, the efficiency of radical generation is poor. 

Silica Polymei Metal Ion Interactions in Solution. The reaction of metal ions with polymeric sihcate species in solution may be viewed as an ion-exchange process. Consequently, it might be expected that sihcate species acting as ligands would exhibit a range of reactivities toward cations in solution (59). Sihca gel forms complexes with multivalent metal ions in a manner that indicates a correlation between the ligand properties of the surface Si-OH groups and metal ion hydrolysis (60,61). For Cu +, Fe +, Cd +, and Pb +,... 

Attempts have been made to categorize the interactions between metal ions and ligands. Whereas all metal ions interact more strongly with fluoride than with chloride in the gas phase, in aqueous solution a number of exceptions occur. Metal ions that have the normal (class a) aqueous solution stabiUty order of F Cl > Br > I also have N P > As > Sb and 0 S > Se > Te donor stabiUty order (13). The inverse (class b) aqueous solution stabiUty... 

There are cationic, anionic, and non-ionic micelles. Divalent metal ions having positive charges are highly hydrophilic and cannot be incorporated into cationic micelles. Anionic micelles tend to form water insoluble salts with divalent metal ions. Interactions of non-ionic micelles with divalent metal ions appear to be small. Thus incorporation of a divalent metal ion into a micelle to form a catalytic center... 

Sites and thermodynamic quantities associated with proton and metal ion interaction with ribonucleic acid, deoxyribonucleic acid and their constituent bases, nucleosides and nucleotides. R. M. Izatt, J. J. Christensen and J. H. Rytting, Chem. Rev., 1971, 71, 439-481 (229). 

Metal ion interactions with nucleic acids and nucleic acid derivatives. L. G. Marzilli, Prog. Inorg. 

It is now almost 50 years since the structure of DNA was elucidated by Watson and Crick (1) (Fig. 1). Since then the double helix has become an icon for modern scientific achievement. With the rapid growth of molecular biology and the consequent success of the human genome project (2) we are now firmly in a post-genomic era. However, in spite of, or perhaps because of this, efforts to understand fundamental aspects of metal-ion interactions with DNA continue to be vigorously pursued. 

A red shift of the absorption band in the visible spectrum is also recorded after the anthocyanin-metal ion interaction. In such a configuration, metallic ions compete with protons and the flavonoids adopt the quinonoidal form (Figure 9.3). 

Fig. 2.7. Characteristic rate constants (s 1) for substitution of inner-sphere H20 of various aqua ions. Note The substitution rates of water in complexes ML(H20)m will also depend on the symmetry of the complex (adapted from Frey, C.M. and Stuehr, J. (1974). Kinetics of metal ion interactions with nucleotides and base free phosphates in H. Sigel (ed.), Metal ions in biological systems (Vol. 1). Marcel Dekker, New York, p. 69).

In aqueous solutions, metal ions interact with and are bound to H20 molecules. Thus, in such solutions, Ni2+ should more accurately be represented as the aquo-metal ion [Ni(H20)6]2+. Aquometal ions tend to be acidic, and have a tendency to hydrolyze ... 

SN)X can act as an efficient barrier electrode in ZnS junctions, increasing the quantum efficiency of the blue emission by a factor of 100 over gold.14 It can also be used to increase the efficiency of GaAs solar cells by up to 35%. Metal ions interact more strongly with a poly(sulfur nitride) surface than with other metal electrodes. This property has stimulated investigations of possible applications of (SN)X as an electrode material. 

Transition-metal hydrides, 13 626 Transition-metal impurities causes of color, 7 326t, 328-331 Transition-metal ion interactions,... 

T.G. Spiro, Nucleic Acid-Metal Ion Interactions (John Wiley Sons, New York, 1980). 

In the simplest case in which the trivalent Fe-57 ions are completely incorporated into the cooperative antiferromagnetic system of the bulk substrate, the Fe-57 ions are expected to align parallel or antiparallel to the magnetic ions of the substrate in a similar manner as the ferric ions of the substrate. When the trivalent Fe-57 ions are on the surface, however, their magnetization is considered to be reduced to some extent due to reduction in the number of neighboring magnetic metal ions interacting with them. 

The structure of the adsorbed ion coordination shell is determined by the competition between the water-ion and the metal-ion interactions, and by the constraints imposed on the water by the metal surface. This structure can be characterized by water-ion radial distribution functions and water-ion orientational probability distribution functions. Much is known about this structure from X-ray and neutron scattering measurements performed in bulk solutions, and these are generally in agreement with computer simulations. The goal of molecular dynamics simulations of ions at the metal/water interface has been to examine to what degree the structure of the ion solvation shell is modified at the interface. 

An electron spin can relax by coupling with a neighboring electron spin. Therefore, when a paramagnetic metal ion interacts with a second paramagnetic metal ion, the electron relaxation rates of the two metal ions may be dramatically affected. If Si and S2 are the two spins coupled by a scalar interaction, new spin levels will be established due to the interaction, with total S varying in unitary steps from Si — S2I to Si + S2. The energies of these spin levels are given by )... 

The most important point is that this procedure provides a reliable and effective way for dealing with metal ion interactions with nucleotides. By maintaining the free magnesium ion at a single fixed concentration, the experimenter avoids any chance of uncontrolled variation in the [MgATp2-]/[ATP -j ratio. 

In addition to enthalpic contributions, the entropy effects accompanying protein-metal ion interactions are substantial. These effects manifest themselves in the desolvation of the metal ion and its binding site. However, as the metal ion binds to a protein, the entropy gain of solvent release may be offset to some degree by the reduction of the conformational entropy of the polypeptide chain as it becomes more firmly bound... 

As for carboxylate-hydrogen bond donor interactions, carboxylate-metal ion interactions are expected to be most favorable with syn stereochemistry. In a survey of the Cambridge Structural Database, Carrell et al. (1988) presented a stereochemical analysis of carboxylate—metal ion interactions which supports this expectation (Scheme 1). These investigators found that the syn-oriented lone electron pair of the carboxylate... 

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