Benzimidazole-derived metal complexe

Acceptably stable metal complexes also may be prepared, such as the cobalt-cthy-Icnediamine product 156. The reaction on benzimidazole derivatives affording seven-membered rings (158) confirms the tendency to produce cycles larger than the pentaatomic ones, as a molecule containing two fused fivc-membered rings would in principle be expected from this type of substrate (see also the derivatives 130,131,140, 149 described above). 

Besides porphyrin derivatives, several other boronated DNA-binding molecules, such as alkylating agents, intercalators, minor-groove binders, polyamines, and metal complexes have been reported. Some examples of such molecules are shown in Figure 10.15, and include derivatives of aziridines (61), acridines (62), phenanthridines (63), Pt(ll) complexes (64, 65), trimethoxyindoles (66), carboranylpolyamines, di- and tri-benzimidazoles, and dequalinium derivatives (67). "... 

Several F NMR studies have been reported on ligand exchange reactions of metal complexes (i.e. the Al(Ttfac)3-Al(bzac)3 system) and also on relative polarity and reactivity of N-H, N-Hg and N-Au bonds in intermolecular exchange reactions of fluorine-containing ligands (for example, 2-(4-fluoro-phenyl) benzimidazole) and their PhHg and Ph3PAu derivatives. 

Figure 7.4 shows the structures of typical electron transport organic semiconductors. Alq3, which can act both as an electron conductor and green emitter, was used by Tang in his first OLEDs and is still in use today. Besides metal complexes electron deficient heterocycles are frequently used as electron transport materials. The triazine derivative TPT [14, 15], the oxadiazole PBD and its spiro analogue spiro-PBD [16, 17] and the benzimidazole TPBI serve as typical examples. 2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) has a very low HOMO level and is often used as a hole blocking layer. 

Stabilization of a metal-substituted derivative of a minor tautomeric form of the Ugand was reported for the complexes of mixed benzothiazo-line-benzimidazole (388 —> 389) (71ZOB1370 98POL381) and benzothia-zoline-pyridine ligands (390 —> 391/392) (Scheme 144) (77JA7704). 

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. 

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