Silver complexes benzimidazoles

By treating benzimidazole-phosphamethin-cyanines 8a with methanolic silver tetrafluoro-borate solutions, Greif isolated colorless, crystalline silver complexes. Their absorption bands lie at shorter wavelengths. The extinction coefficients are httle changed. Here, too, a clear dependence of the position of the absorption maxima on the nature of the N-alkyl substituents can be observed (Table 3). 

Imidazolines are also formed in silver cyanide-catalyzed cyclization of alkyl isocyanides with aliphatic diamines (Scheme 103).169 This simple synthesis can be applied in a general way with difunctional nucleophiles and has been used to prepare benzimidazoles, oxazoles, thiazoles, and oxazines.169 It is suggested that transient carbene complexes are formed in these reactions (cf. 87 in Scheme 103) but further work is required to ascertain the mechanism and scope of these processes. 

A large number of imidazole (4) and benzimidazole (5) silver(I) complexes have been prepared.64 Early reports predicted that the site of complex formation of the imidazole molecule would be the pyridine nitrogen rather than the pyrrole nitrogen. However, the crystal structure of bis(imidazole)silver nitrate showed that the two pyrrole nitrogens were bound in almost linear arrangement (Ag—N 212.0, 213.2 pm, N—Ag—N, 1720).65... 

Oxidation (with such reagents as iron(III) chloride, potassium dichromate, silver oxide or nitrous acid) of 4,7-, 6,7-, and 5,6-dihydroxy-, and 5,6-dimethoxy-benzimidazoles gives the corresponding quinones. A 5-methyl group is oxidized by permanganate to carboxy (74CRV279). In the presence of copper(II)-piperidine or -dimethylamine complexes oxygen... 

In the case of biocides giving antibacterial property to the textile material based on nano silver, nano zinc, triclosan, tin organic compounds, benzimidazole derivatives, etc. the limit of detection is 1 ppm for individual substances. The testing method for them is quite complex, requiring derivatization of the same with acetic anhydride, and analysis on capillary GLC with electron capture detection. These antibacterial agents... 

Huckaba AJ, Hollis TK, Howell TO, Valle HU, Wu Y. Synthesis and characterization of a 1,3-phenylene-bridged N-alkyl bis(benzimidazole) CCC-NHC pincer ligand precursor homobimetaUic silver and rhodium complexes and the catalytic hydrosilylation of phenylacetylene. Organometallics. 2013 32 63-69. 

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