The special case of robust complexes

The curariform action of some robust chelates was discovered by Beccari 

For more on platinum-containing anti-cancer agents, see Roberts and Pera (1983). 

Spirogermanium 11.50), a newly introduced robust complex, seems useful in treating tumours of the colon and ovary. It is one of the few carcinolytic agents that do not attack the bone-marrow (myelosuppression). Large doses show toxic effects on the central nervous system (Slavik etal., 1982). 

The starting-point for these considerations must be the hard fact that the majority of chelating agents have no biological action. For example, very few of the metal-binding agents commonly used in analytical work are antibacterial (Albert, etal., 1947 Schraufstatter, 1950). 

Very small changes in a molecule can produce large changes in partition coefficients. Thus, the insertion of an extra ring-nitrogen into oxine to give 3-aza-oxine (8-hydroxyquinazoline) makes the molecule much more hydrophilic and it lowers the oil/water partition coefficient from 67 to 5 (see Table 11.9). The addition of a side-chain of only three carbon atoms (the propyl-group) restores the partition coefficient. 

In aqueous solution, the complexes of most metal cations exist in dynamic equilibrium with their components. If we disturb this equilibrium, another one is instantly formed. It is quite otherwise with robust complexes which persist for hours (or even days) under conditions favourable to their decomposition any biological properties that they may have are strikingly different from those of their components. Robust complexes are formed where metal ions have 3,4 (low spin), 5, or 6 d electrons provided that formation of the complex involves large values of ligand-field stabilization energy. Metals most prone to form robust complexes are the transition metals platinum, iridium, osmium, palladium, rhodium, ruthenium, also (but not so frequently) nickel, cobalt, and iron. The halide and, particularly, the cyanide anions most readily form robust complexes with these transi- 

11 Fundamental considerations in designing new chelating agents. Promising avenues of application 

No chelating agent can be expected to be active, in a biological environ- 

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The admissible region for closed-loop eigenvalues is denoted as F, a system is called F-stable if all its eigenvalues are located in this region and an imcertain system is called robustly F-stable if all eigenvalues for all operating conditions are contained in F. The definition of F-stability permits arbitrary regions in the complex 5 -plane and does not imderlie any restrictions. It also includes the special cases of the left half-plane for Hurwitz stability and the unit circle for Schur stability. 

The approximate statistical distribution of unidentate ligands on TV sites is a special case of the hypothesis of step-wise complex formation that all the intermediate complexes ML occur in mixtures with 0 < /Tpreparatively separate) and imperfect (labile, equilibrating in solution) complexes. The latter suggestion is similar to the influence of Aristotle s principle of the excluded middle on a housewife when she declares that a given compound either is toxic or not. Though most of the reactions of iridium(III) are slower than the reactions of carbon compounds in organic chemistry, there is little doubt... 

The reliable, robust classification of diseases or disease states via biomedical spectroscopy requires special methodology that can handle complex data. In most cases, such data defy simple analyses that assume the presence of easily identified features ( markers ) in the data set. In particular, the methodology must be able to handle data sets that contain relatively few spectra (in the 50s) but many attributes (data points) per spectrum (in the 1000s) ideally, it should also provide some measure of the degree of confidence in a given diagnosis. 

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