2- -benzimidazole ligands

Monomeric complexes have been formed with the bis(benzimidazolylmethyl) sulfide ligands to give tetrahedral N2S2 coordinated zinc in combination with thiolates.125 The benzimidazole ligand (9) shown has also been used to form polynuclear complexes with zinc and benzylthiolates.126... 

A trimeric species was formed with one equivalent of a bis(benzimidazole) ligand in the presence of benzylthiolates (59) (Figure 10). Zinc-zinc distances were in the range 3.069-3.958(2) A.126 Other zinc-thiolate trinuclear compounds include Zn3(CH2SiMe3)3(SC6H2iPr3)3 and Zn3(o-phen)2(toluene-3,4-dithiolate)3 but have little structural similarity.81,525... 

The application of ESR to the ribonucleotide reductase system indicates that the catalytic intermediate is a Co(I)-species. The appearance of Cob(Il)alamin is probably caused by partial oxidation of the Co(I)-species. In the enzyme bound Co(II)-species the benzimidazole ligand is coordinated, and the corrin ring is bound so tightly that the enzyme produces a unique highly resolved ESR spectrum. 

Numerous other examples of reactions of this type have been described and a particularly dramatic example of a product derived from oxygen atom transfer to a co-ordinated ligand is seen in the reaction of the benzimidazole ligand 9.16 with dioxygen in the presence of a copper(i) catalysts. The isolated product of the reaction is the copper(n) complex of the benzimidazole-3-carboxylic acid, 9.17. 

The new substituted tridentate ligands L5c-e are synthesized in six steps using a Krohnke reaction for the construction of the 4-substituted central pyridine ring.25 Novel polymeric benzimidazole ligands as an extended system of H2L7 and H2Lllb are also available.2, 27... 

DESIGN OF IMIDAZOLE/BENZIMIDAZOLE LIGANDS 1.8.3.1 Modular Approach... 

CHEMICAL FUNCTIONS OF COORDINATION COMPOUNDS WITH IMIDAZOLE/BENZIMIDAZOLE LIGANDS... 

Other approaches to self-assembling receptors have been reported in recent years. A self-assembling, trimeric palladium complex based on the bis(benzimidazole) ligand (17) was designed by Williams and coworkers [4]. The complex contains a hydrophobic cavity that in the X-ray structure has included a molecule of acetonitrile. In a different context, Schepartz and McDevitt [70] have used the chelation of nickel(n) by A,7V -bis(salicylaldehy-de)ethylenediamine (salen) derivatives to control the position of K -binding glyme chains, and it has been shown that these self-assembled ionophores influence alkali metal transport across liquid membranes [71]. Also, Shinkai and coworkers [72] and Schneider and Ruf [73] have used metal chelation to induce an allosteric effect on binding at a second site. 

The binuclear iron(III) complex [Fe2(HPTP)(p-OH)(N03)2](C104)2 (1) with HPTP = A W,7W,-tetrakis(2-pyridyl methyl)-2-hydroxy-1,3-diamino-propane [5], reacts with H2O2 to yield a blue species [6], The crystal structure of (1) and its interaction with montmorillonites (MMT) has been reported [7]. The occlusion of [Fe2(HPTP)(p-OH)] complexes in new families of hexagonal mesoporous materials such as MCM-41 and HMS will be described elsewhere [8], Related HPTB complexes, with benzimidazole instead of pyridine, have their tripodal N atoms tmns to strong basic peroxo-ligands, the benzimidazole ligands perpendicular to the Fc203 plane and tmns to each other on every iron [9]. 

Figure 4 Linear coordination of Cu by bis-benzimidazol ligands generates a [Cu2L2] macrocycle. ...

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