Chelating unit

Fig. 6. (a) (b) Replacement of a peptide-bound l-hydroxy-2-pyridinone unit by a catechol unit on a tris(ammoethyl)aniine (tren) cap. (c) A tren-capped hexadentate ligand with two 3-hydroxy-2-pyridinone (3,2-hopo) and one terephthalamide (tarn) chelating units. 

Recently, the same ai,p3 target has been addressed with lipidic nanoparticles containing a huge number of Gd-chelated units (94,400 Gd/particle characterized by ri = 19.1 s mM (per Gd) = 1,800,000 per particle). One of the lipidic components is covalently bound to the ot p3 - integrin peptidomimetic antagonist (168). 

Tetrakis(picolyl)propane-l,3-diamine and its butane-1,4-diamine analogue each contain two terdentate chelating units and can thus provide the groups L on both iron atoms, giving further bridging (see also Section 5.4.S.4.3 below). ... 

The marine siderophore aquachelin has two hydroxamate and one —CH(0 )C02 chelating units. Photolysis of its ironQII) complex results in dechelation of the hydroxycarboxylate moiety and reduction to iron(II). ... 

Figure 14.14 Two different macrocycles containing a diimine chelating unit. The use of a dpp fragment as chelate, in macrocycle 8, leads to pronounced steric hinderance once a metal center is coordinated. On the other hand, hy using a dphiiq chelate, a sterically nonhindering macrocycle 9 is obtained.

ECL investigations of dinuclear or polynuclear Ru(II) complexes have been recently performed with hope for developing more efficient electrochemiluminescent materials. Centrally or peripherally functionalized dendrimers with active RuL32 + chelate units can produce higher (up to four to five times) ECL intensities as compared to their monomeric RuL32 + precursors alone. It was also found that the ECL intensities of metallodendrimers become larger as the multiplicity of the involved Ru(II) units increases. Similar observations have been reported for binuclear Ru(II) complexes with weak interaction between both metallic centers.84-88 These results indicate that further studies in such direction may result in design of still more efficient ECL systems based on Ru(II) luminophores. 

The N,P,0-ligand depicted in 338 in the N,P-chelate unit follows from L(x 4-cod)Pd(Cl)MeJ (04JCS(D)3251). With silver tetrafluoroborate in acetonitrile/methylene chloride, cationic 339 follows, which under carbon monoxide is transformed to acetylated 340. The product of interaction of ligand 341 with [(T)3-C3H5)Pd(Cl)]2 is an efficient catalyst of asymmetric allylic substitutions (04JOC5060). 

In 2003, we first used self-assembled zinc(II) terpyridine polymers in the fabrication of PLEDs.22 We synthesized a series of monomers containing two terpyridine as chelating units, which are at opposite ends and separated by a spacer group (R) (Fig. 5). The self-assembled zinc(II) coordination polymers were easily prepared by the addition of Zn(OAc)2 into solution of monomers. The product yields were up to 80%, and the inherent viscosities of the polymers were in the range of 0.48 to 1.21 dL/g, as determined using an Ubbelohde viscometer in NMP at 30 0.1 °C. 

The capping of both termini of three tridentate chelating units with covalent tripods provides highly rigid macrobicyclic receptors (i.e., cryptands), which are ideally suited for investigating variations of crystal-field parameters within isostructural series. Platas et al. (1999) have iso-... 

An important place among chelating ligands belongs to N,0-donors (Sec. 2.2.5.3) which, similarly to discussed above with N,N-donor ligand systems, allow us to create programmed metal-cycles of different size (Sec. 2.2.5.3 414, 418, 422, 424, 427, 428, 432, 433, 436, 438, 445, 446-449). To obtain metal chelates with four-member chelate unit, the interaction of, for example, 2-hydroxy derivatives of azines and metal salts is used (3.45) [52] ... 

A comparison of data on the ICC structures of types 592, 907 910 allows us to conclude that the linkage of an additional chelate unit is the main factor determining the possibility of participation of the N atom of the heterocyclic substituent in the coordination. As expected, the four-member coordination unit (pyridine) has low stability, while the five-member (quinoline) forms stable metal-cycles. 

Their capacity to form chelating units having different oxidation states explains a variety of formed coordination compounds [133-136], A series of novel preparative synthetic methods of o-semiquinolate (SQ) and catecholate complexes of transition (Mn, Re, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Ti, Hg), nontransition, and rare-earth metals in various oxidation states and ligand environments has been developed... 

Members of a second prominent group of mechanism-based inhibitors contain a peptide isostere, an element mimicking an intermediate formed during amide bond cleavage. Inhibitors of metalloproteases often contain a metal-chelating unit such as hydroxamate or phosphonic acids, which act as a bidentate ligand. 

Lehn120) has also reported the synthesis of a lateral macrobicyclic molecule, 193, where a macrocyclic unit is bridged by a chelating unit which contains a... 

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