Redox patterns

In conclusion, the electrochemical data offer a fingerprint of the chemical and topological structure of these dendrimers. Furthermore, the knowledge of the electrochemical properties of the mononuclear components and the synthetic control of the supramolecular structure allow the design of dendrimers with predetermined redox patterns. 

V. Balzani, S. Campagna, G. Denti, A Juris, S. Serroni, M. Venturi, Designing Dendrimers Based on Transition-Metal Complexes. Light-harvesting Properties and Predetermined Redox Patterns , Acc Chem Res. 1998, 31, 26-34. 

As the energy of the excited states and the redox levels of each metal-polypyridine unit depend on metal and ligands in a predictable way, the simultaneous presence of different metals in a dendritic structures gives rise to intramolecular energy transfer processes as well to different redox patterns with multielectron processes. In particular, the tetranuclear [Os(2,3-dpp)3 (2,3-dpp)Ru(bpy)2 3]8+ (OsRu3) shown in Fig. 5.3 has been designed to achieve an efficient antenna effect. This species can also be considered a first-generation mixed-metal dendrimers.31... 

Figure 6.16 Redox patterns (differential pulse voltammetric peaks) for decanuclear den-drimers 22-24.61b 63 Peak Fc indicates the oxidation of ferrocene as an internal standard. The symbols used to represent the dendrimers are those displayed in Fig. 6.15.

Because of the presence of several redox-active units, the cyclic voltammogram of this rotaxane shows a complex redox pattern. However, the comparison to the electrochemical behavior of its molecular components and suitable model compounds (Fig. 13.29) enables to obtain useful information not only on its coconforma-tional features, but also, and most importantly, on its machine-like operation. 

Nonetheless, equilibrium considerations can greatly aid attempts to understand in a general way the redox patterns observed or anticipated in natural waters. In all circumstances equilibrium calculations provide boundary conditions toward which the systems must be proceeding, however slowly. Moreover, partial equilibria (those involving some but not all redox couples) are approximated frequently, even though total equilibrium is not approached. In some instances active poising of particular redox couples allows one to predict significant oxidation-reduction levels or to estimate properties and reactions from computed redox levels. 

C.O. Schmakel, K.S.V. Santhanam and P.J. Elving, Nicotinamide adenine dinucleotide (NAD+) and related compounds. Electrochemical redox pattern and allied chemical behavior, J. Am. Chem. Soc., 97(18) (1975) 5083-5092. 

Balzani V, Campagna S, Denti G, Juris A, Serroni S, Venturi M. Designing dendrimers based on transition-metal complexes. Light-harvesting properties and predetermined redox patterns. Acc Chem Res 1998 31 26-34. 

Experimentally observed redox patterns can be compared with those calculated by quantum-chemical techniques for a particular localization [5, 212], This approach is especially useful for assignment of ligand-localized reductions in heteroleptic complexes. 

Electron-transfer Properties of Ground-state Polypyridine Complexes 823 5.3.2 Redox Patterns... 

Typical polypyridine complexes of second- or third-row d transition metals are characterized by metal-localized oxidation and a series of predominantly polypyridine-localized one-electron reductions. Their redox patterns are schematically shown in Figure 1. 

Figure 1. Redox patterns of a free polypyridine ligand and typical mono-, bis- and tris-polypyridine complexes [4, 8, 9, 212], is the orbital energy, Ua and are pair interaction energies between electrons placed on the same and different polypyridine ligands, respectively, t/g. Kg, and Gg are solvation energy terms. In the first approximation, interaction and solvation terms are assumed to be independent of the number of electrons, that is to be constant along the redox series. In reality, they show small changes. Interaction energies are positive and solvation terms are negative. Hence, solvation diminishes the redox potential differences. Dashed lines show the origin of reduction doublets and triplets in bis- and tris-polypyridine complexes, respectively.

Redox patterns of first-row transition metal polypyridine complexes are very much... 

Os-based units is followed by one-electron oxidation of the core Ru-based unit. Interestingly, the redox pattern can be easily reversed. Removal of the six acidic protons changes the oxidation potential of the metal ions and the oxidation pattern becomes 1-3 the core Ru unit is oxidized first, followed by oxidation of the Os units at more positive potential. 

Smedley P. L. and Edmunds W. M. (2002) Redox patterns and trace-element behavior in the East Midlands Triassic Sandstone Aquifer, UK. Ground Water 40, 44-58. 

Equilibrium considerations can greatly aid attempts to understand in a general way the redox patterns observed or anticipated in natural waters. In all circumstances equilibrium calculations provide boundary conditions toward which the system must be proceeding. Moreover, partial equilibria (those in-... 

Natural waters are often in a highly dynamic state with regard to oxidation-reduction rather than in or near equilibrium. Most oxidation-reduction reactions have a tendency to be much slower than acid-base reactions, especially in the absence of suitable biochemical catalysis. Nonetheless, equilibrium diagrams can greatly aid attempts to understand the possible redox patterns in natural waters and in water technological systems. 

SnIv. These metalloporphyrins are extremely acid-stable and produce a normal electronic spectrum [Snlv OEP (OAc)2 576 (19,100) 538 (19,100) 411 (403,000)] [Parnemann (139)]. The electrochemical redox pattern probably does not involve a SnIV Sn11 reduction. It follows that the porphyrin ligand is reduced, not the SnIV central ion [Fuhrhop (74)]. 

The simplicity of the redox patterns produced by metal ions in the porphyrin cavity also renders superfluous the various models for porphyrins which, being usually not very rigid and unsymmetrical macrocycles, tend to complicate rather than clarify the situation [Tang (172), Tokel (174)]. 

Santhanam KSV, Elving PJ (1974) Redox pattern for purine and 6-substituted purines in nonaqueous media. Free radical behavior. J Am Chem Soc 96(6) 1653-1660. doi 10.1021/ ja00813a002... 

An interesting aspect of the reactivity of the [Ire(CO)is]congeners is deducible from Figure 5, which compares the redox pattern of [Ire(CO)is]in the... 

Figure 6 shows the redox patterns exhibited by the two octahedral clusters [Feirs(CO)is]and [Feirs(CO)le]", respectively. ... 

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