Transition metal ion complexes

There are three types of electron transfers, firstly the generation of an electron electrochemically, by y-irradiation, or by photolytic dissociation, secondly the transfer of an electron from an inorganic or organic compound, referred to as a nucleophilic homolytic leaving group (Zollinger, 1973 a), and thirdly a transfer from a transition metal or transition metal ion complex. In this section we will discuss the fundamental aspects of these three types. In the following sections and in Chapter 10, specific examples and synthetic applications will be summarized. 

The determination of structural properties of dimeric transition metal ion complexes from e.p.r. spectra. T. D. Smith and J. R. Pilbrow, Coord. Chem. Rev., 1974, 13,173-278 (186). 

Extremely high ion exchange affinities are however sometimes observed for alkali metals (e.g. Cs) and transition metal ion complexes in clay minerals and zeolites. The objective of this paper is to give an account of the factors which are involved in these high selectivity phenomena. The discussion will be focussed mostly on montmorillonites and faujasites as representatives of the phyllosilicate and tectosilicate groups. 

Rurack K, RadegliaR (2000) Transition metal ion complexes of 2,2 -bipyridyl-3,3 -diol and 2,2 -bipyridyl-3-ol spectroscopic properties and solvent-dependent binding modes. Eur J Inorg Chem 2271-2282... 

The above discussion was based on the results of molecular dynamics simulations on unsaturated or conjugated hydrocarbons. Although the general features can be extended to molecular structures of more general types, in practice it is appropriate to consider the specific form of the electron orbitals involved. For instance, d d transitions in transition metal ion complexes involve orbitals mainly localized on the metal ion that, in the crystal field... 

Abraham SA, McKenzie C, Masin D, et al. In vitro and in vivo characterization of doxorubicin and vincristine coencapsulated within liposomes through use of transition metal ion complexation and pH gradient loading. Clin Cancer Res 2004 10 728. 

E. Other transition metal ions complexes and proteins 158... 

E. Other Transition Metal Ions Complexes and Proteins... 

At present, the correlation contains one transition metal complex, Cu(Hfacac)2. The results on this complex are very interesting and somewhat unusual for a transition metal system in that enthalpies have been obtained in a poorly solvating solvent with nonionic donors (52), instead of the t5 ical stability constant study on a metal cation in some highly polar solvent. Data from this latter type of investigation have many practical uses, but are impossible to interpret and understand. The transition metal ion complex we have studied can be incorporated into the E and C scheme using the same base parameters that are used to correlate the enthalpies of formation of all the other Lewis acid-base adducts in the scheme. 

Fritz G, Heizmann CW, Kroneck PM. 1998. Probing the structure of the human Ca2+- and Zn2+-binding protein S100A3 spectroscopic investigations of its transition metal ion complexes, and three-dimensional structural model. Biochim Biophys Acta 1448(2) 264-276. 

Gas-Phase Photodissociation of Transition Metal Ion Complexes and Clusters... 

Nord6n, B. Lincoln, P. Akerman, B. Tuite, E. DNA Interactions with Substitution-Inert Transition Metal Ion Complexes, Nord6n, B. Lincoln, R Akerman, B. Tuite, E. eds. Marcel Dekker, Inc. New York, 1996 vol. 33, p. 177. 

Fig. 2.8. Factors controlling the production of free radicals in cells and tissues (Rice-Gvans, 1990a). Free radicals may be generated in cells and tissues through increased radical input mediated by the disruption of internal processes or by external influences, or as a consequence of decreased protective capacity. Increased radical input may arise through excessive leukocyte activation, disrupted mitochondrial electron transport or altered arachidonic acid metabolism. Delocalization or redistribution of transition metal ion complexes may also induce oxidative stress, for example, microbleeding in the brain, in the eye, in the rheumatoid joint. In addition, reduced activities or levels of protectant enzymes, destruction or suppressed production of nucleotide coenzymes, reduced levels of antioxidants, abnormal glutathione metabolism, or leakage of antioxidants through damaged membranes, can all contribute to oxidative stress.

Table 2 Typical experimental magnetic moments of first-row transition metal-ion complexes compared with theoretical predictions...

Quenching of Ru(bipy)32+ by the organic cations trans-1,2-bis(N-methYl-4-pyridyl)ethylene and l,l -dimethy 1-4,4 -bipyridine (paraquat ) and by the transition metal ion complexes Fe(H20)g and Ru(NH3) 3+ occurs at near diffusion controlled rates (241). In all four cases flash studies indicated that electron transfer is a principal component of the quenching mechanism. Selective excitation of Ru(bipy)3 in the presence of these quenchers (Qqx produced the oxidized ruthenium complex, Ru(bipy)33+, and the reduced quencher, Qj-gd quenching... 

Electronic transitions in octahedral and square planar transition metal complexes disobey rules (2) and (3). Consider the promotion of a 3d1 electron from a t2g to an eg orbital in a complex of octahedral symmetry. The parity (g -o- g) remains the same during the excitation of the electron from one 3d orbital to another. Such transitions are, therefore, formally forbidden. For various reasons including molecular vibration, however, the above rules can be relaxed and the transitions become partially allowed. Because they are formally forbidden, d d transitions are weak. This is reflected in the small molar absorp-tivities, s (1-500 M-1 cm-1) associated with many transition metal ion complexes. 

Norden, B., Lincoln, P., Akerman, B., Tuite, E., DNA interactions with substitution-inert transition metal ion complexes, Met. Ions Biol. Syst. 1996, 33, 177-252. 

Transition metal ions complexes may be entrapped into zeolitic cavities. Moreover a desired complex may be directly synthesized into the zeolite cavities. For instance Rh(lII) ions in Y-zeolite are converted by CO into a Rh(l) dicarbonyl complex at 2100 and 2040 cm as evidenced by IR and XPS techniques (IbV. Rh.(CO)., Rh,(C0).2 potentially active catalysts... 

The decomposition rate constant kd for pure benzoyl peroxide in styrene polymerizations is 1.33x10" s at 90°C, while that for the benzoyl peroxide-N,N-diethylaniline redox system is 1.25x10" L/mol-s at 60°C and 2.29x10" L/mol-s at 30°C [15]. The redox system thus has a much larger decomposition rate. Peroxide decomposition is also accelerated in the presence of transition metal ion complexes such as copper (II) acetylacetonate and ammonium salts [17,18]. 

Photoreactions that involve transition metal ions, complexes or compounds can usually be classified as (photo)redox (simultaneous oxidation and reduction) processes. A representative non-photoassisted catalytic system is Fenton s reagent that produces HO radicals on reaction of ferrous ions (Fe2 +) and hydrogen peroxide (Scheme 6.287a). Its photochemical counterpart is the photo-Fenton process,1527 in which ferric (Fe3 + ) complexes in aqueous solutions (absorbing over 300 nm) are reduced to ferrous ions (Scheme 6.287b). 

In the case of transition metal ion complexation, on the other hand, bi-denate and/or chelate complex formation in addition to monodentate complex formation have been revealed. The complexation modes of the transition metal ions, such as Cu2+, Cd2+, and Pb2+, depend on the degree of PAA... 

VVTith the exception of molecules in the gas phase at low pressures, the properties of any species are mediated to some degree by the environment. In particular, the photophysical processes within a transition metal ion complex are often markedly dependent on the surroundings in which the complex is embedded. Interest in transition metal ion photophysics has been high not only for the intrinsic importance e.g., phosphors and lasers) but also because photochemistry and photophysics are intimately interrelated. It is this connection between photochemistry and photophysics that will be emphasized in this discussion. 

The bonding of polypyrazolylborates to metal is determined primarily by the number of pyrazolyl groups attached to boron. Dipyrazolylborates are necessarily bidentate, and they form with divalent transition metal ions complexes, 1, that are similar to -diketonates but that are always monomeric for steric reasons. The major difference between dipyrazolylborates and -diketonates is that the R2B(pz)2M ring is not planar but is puckered in the boat form as in Structure 2. This results in asym-... 

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