Chelating bases

While 52 stands for simple base-stabilized complexes 148), 53 is an example of a chelated base-stabilized stannylene coordinated with a transition metal149). 54 144) and 55 150) illustrate that the aggregation state of the stannylene remains unchanged in the complexes. 

SCHEME 3.47 Chemical structure of a boron chelate-based green dopant. 

Compound 113 (O-TRENSOX) is a promising water-soluble iron chelator based on 3 hydroxyquinoline sub-units (548) which forms... 

A new method for radiolabeling glutathione-containing liposomes with using a different chelator based on SNS/S pattern complexes has been recently reported (21). One particular chelator, A,A-bis(2-mercaptoethyl)-A, A diethyl-ethylenediamine (BMEDA), was shown to efficiently label the liposomes. 

In addition, such chelators, based on the hydroxamic acid bidentate ligand, may diminish the toxic effect of Reactive Oxygen Species (ROS), such as hydroxyl and superoxide radicals, by generating relatively stable nitroxyl radicals. ... 

There is a considerable difference in the antimalarial action of desferrioxamine B (DFO) and the hydrophobic chelators based on ferrichrome analogs. While the former is limited to mature forms in the life cycle of P. falciparum (trophozoites and schizonts), the latter effects to a greater extent early developing stages (ring). Therefore, studies explored... 

Most interestingly, reaction of 393 with nitrones gave a 2-(di-alkenyl)-substituted oxazoline 402. A chelation-based transition state model was proposed to rationalize this unusual cis selectivity. " The 2-(trans-alkenyl)-substituted oxazoline can be obtained using the analogous des-chloro lithiated 2-aIkyloxazo-line. " ... 

The earliest known dioxygen complex contained [(NH3)10Co2O2]4+, first described by Werner and Myelius in 1893.94 A surge of interest in dioxygen complexes arose after the Co11 chelate of bis(salicylaldehyde)ethylenediimine was shown to take up oxygen reversibly by Tsumaki in 1938.95 It is only recently, however, that the existence of mononuclear superoxo complexes has been established and structural studies performed upon them. A vast array of Co chelates based on Schiff bases such as (4) and (5) have been synthesized. 

Selective esterification at OH-2 was also observed in the formation of tosyl derivatives.106 Esterification of metal chelates based on the known affinity of carbohydrates for metal cation species107 also afforded variations in the regio-isomeric distribution, with the 3- or 3 -esters as major compounds108 or in the degree of substitution.109... 

The application of such techniques to high-molecular weight compound chemistry is complicated by problems involved in the synthesis of the corresponding macroligands. Among the examples which are few in number is the production of binuclear Co (II) and Ni(II) chelates based on PE-g-poly (iV-salicyloylacryl-amide) [15, 22d] ... 

Fig. 1. Two ribbon representations of the crystal structure of the DNA decamer d(CCTCG -CTCTC/GAGAG CGAGG) containing a unique cisplatin interstrand cross-link at d(GpC)-d(GpC) site (asterisks indicate the chelated bases in the adduct). A front view (A) allows to see the structure with the lesion in the minor groove. A side view (B) shows the chicane of the backbone with the helix-sense reversal. Ptn atom, yellow ammine groups, navy blue sugars, pink guanines, navy blue adenines, red thymines, yellow cytosines, hght blue phosphodiester backbone, green.

Adherent, conformal LPD ceramic film either crystalline (Method 2) or amorphous (Method 1) can be obtained on polyimides. This is in contrast to silanol-bearing surfaces (good for Method 1 only) or sulfonated surfaces (good for Method 2 only). The fact that the polyimides accommodate both titania preparations may be due to the partial hydrolysis of the polymer surface under oxide deposition conditions. This provides a mix of carboxylic acid and amide sites that anchor the titania by a combination of coulombic and chelation-based effects.22 An important lesson of this work is that the interaction of the polymer surface with the deposition solution may create oxide film anchoring sites. This does not negate activating the polymer surface. It recognizes that the polymer surface can react further under the deposition conditions. 

In 5-carboxylmethyluridine [CXMURD] (Fig. 17.8 c) there is an interesting chelation of the ribosyl hydroxyl groups by the uracil N-H, and a comparable chelated base-sugar association is observed in 5-methoxy-uridine [MXURID01] (Fig. 17.8d). 

Frecht [2] prepared Generation-0 polyhydroxyl dendrimeric monomers, (I), for use as diagnostic agents in metal chelate-based contrast materials. 

An interaction of metal ions with phosphates usually leads to stabilization of polynucleotide secondary and tertiary stmctures, depending on the metal ions and their concentrations, whereas base binding or chelating base and phosphate by the same metal ion may result in destabilization, conformational change, or denaturation of the polynucleotide structures (see also Sections 3.3.1 and 3.3.2). However, phosphate-specific binding can also induce significant conformational changes in DNA structure. The mechanisms of the latter structural interconversions are... 

Song, B., Wang, G.L., and Yuan, J.L. (2005) A new europium chelate-based phosphorescence probe specific for singlet oxygen. Chemical Communications, 3553—3555. 

Only possible for some covalent and metal chelate-based processes Phase partitioning of monomers complicates system... 

H. Hoyer. Chem. Ber. 89, 146-50 (1956). IR chelation, base strengths compared of halogens, carbonyls, nitros, etc. 

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