Gold complexes 2,2 -bipyridyl

The cationic dinuclear oxo-gold(m) complexes of substituted bipyridyls react with olefins to give the stable coordination compounds shown in Scheme 79. The reactions are often incomplete, produce many byproducts, and give low yields of the olefin complexes/... 

Both the cyanide, [Au(CN)2] , and fulminate, [Au(CNO)2] , ions contain linear gold(I) centres.387,388 A report that KAu(CN)2(2,2 -bipyridyl) contains square planar gold(I) has been disproved the bipy ligand is not coordinated to gold and the complex contains linear [Au(CN)2J ions. 390 AuCN is polymeric with a linear (—Au—CN—) Au— chain structure.391... 

Other aqueous preparative methods include aerial oxidation of an alkaline solution of CoS04 and NaCNO to give the fulminatocobaltate(III) anion [Co(CNO)6]3-, reduction of ruthenate(VI) by excess of fulminate to give [Ru(CNO)6]4, and displacement of 2,2 -bipyridyl or 1,10-phenan-throline from nickel(II) or cobalt(III) complexes to give [Ni(CNO)4]2 or [Co(CNO)6]3. Liquid ammonia may replace water as solvent [Ni(NH3) ]2+ and [Co(NH3)6]3+, for example, react with sodium fulminate in this solvent to form [Ni(CNO)4]2 and [Co(CNO)6]3. In all these reactions fulminate behaves very like cyanide with [AuClJ-, however, reduction to form the gold(I) complex [Au(CNO)2] takes place and no gold(III) complex can be isolated. 

A fluorescent cationic tetranuclear gold(I) rectangle, [(/v-Ph2PAnPPh2)Au2 (//-4,4,-bpy)2Au2(/i.-Ph2PAnr,Ph2)]X4 (X = PF6, NO3), was assembled using 9,10-bis(diphenylphosphino)anthracene and 4,4/-bipyridyl [124]. The molecular rectangle has a cavity of 7.921(3) x 16.76(3) A as reflected from its crystal structure, and its complexation behavior towards various aromatic molecules at the cavity was demonstrated. 

Marcon G, Carotti S, Coronnello M, Messori L, Mini E, Orioli P, Mazzei T, Cinellu MA, Minghetti G (2002) Gold(III) complexes with bipyridyl ligands solution chemistry, cytotoxicity, and DNA binding properties. J Med Chem 45 1672-1677... 

A series of gold(III) complexes with bipyridyl ligands have been shown to be cytotoxic [71]. The compounds [Au(bipyc-H)(OH)]PF6 (Aubipyc) (bipyc = 6-(l, l-dimethylbenzyl)-2,2 -bipyridine) and [Au(bipy)(OH)2]PF6 (Aubipy) (bipy = bipyridine) (Fig. 12) were particularly active [72], the former being an organo-gold(III) complex [73]. 

As discussed before in the case of nucleic acids the authors have also considered the incidence of the interfacial conformation of the hemoproteins on the appearance of the SERRS signals from the chromophores. Although under their Raman conditions no protein vibration can be observed, the possibility of heme loss or protein denatura-tion are envisaged to explain a direct interaction of the heme chromophores with the electrode surface in the case of the adsorl Mb. extensive denaturation of Cytc at the electrode appears unlikely to the authors on the basis of the close correspondence of the surface and solution spectra. Furthermore, the sluggish electron transfer kinetics measured by cyclic voltammetry in the case of Cytc is also an argument in favour of some structural hindrance for the accessibility to the heme chromophore in the adsorbed state of Cytc. This electrochemical aspect of the behaviour of Cytc has very recently incited Cotton et al. and Tanigushi et al. to modify the silver and gold electrode surface in order to accelerate the electron transfer. The authors show that in the presence of 4,4-bipyridine bis (4-pyridyl)disulfide and purine an enhancement of the quasi-reversible redox process is possible. The SERRS spectroscopy has also permitted the characterization of the surface of the modified silver electrode. It has teen thus shown, that in presence of both pyridine derivates the direct adsorption of the heme chromophore is not detected while in presence of purine a coadsorption of Cytc and purine occurs In the case of the Ag-bipyridyl modified electrode the cyclicvoltammetric and SERRS data indicate that the bipyridyl forms an Ag(I) complex on Ag electrodes with the appropriate redox potential to mediate electron transfer between the electrode and cytochrome c. 

Functionalization of nanorods with polyelectrolytes has been carried out by layer-by-layer deposition (92). First, CTAB-coated nanorods are prepared. Since these nanorods are positively charged, they can adsorb cationic and anionic poly electrolytes. Functionalization of nanorods with dyes is possible a fluorescent dye, 4-chloro-7-nitrobenzofurazan has been functionalized on the surface of Ti02 nanorods (93). Functionalization with a photoactive molecule such as ruthenium(II) tris(bipyridine) is also possible (94). A thiol derivative of the bipyridyl complex (Ru(bpy)3+-Cs-SH) in dodecane thiol is used for the functionalization of gold nanorods. Functionalization of block magnetic nanorods is very useful (95), for example, in the separation of proteins. Consider a triblock nanorod consisting of only two metals, Ni and Au. If the Au blocks are functionalized with a thiol (e.g. 11-amino-1 undecane thiol) followed by covalent attachment of nitrostreptavidin, then one can... 

A number of recent papers report a dramatic increase in luminescence of diheptyl-bipyridyl-diol [45], organic dyes, and other species in the presence of silver [33,56-59], gold [60], and copper [61] NPs (plasmons) compared with the luminescence of the same complex without plasmons. The absorption coefficient of the NPs is six orders of magnitude higher than that of organic molecules. These papers provide a promising approach to increase the efficiency of LSCs. 

Electrochemical indication makes use either of redox labels, which are bound chemically to DNA strands, or of redox active intercalators . The latter are flat molecules able to intercalate the windings of DNA helix. It has been shown, that the well known, commercially available fluorescence quenching agent dabcyl (p-methyl red) is useful also for hybridisation detection with heated electrodes [51]. It was found that osmium tetroxide in different forms is a most powerful redox label for hybridisation detection, especially at heated electrodes [42, 52-55]. OSO4 has been used as bipyridyl complex and also botmd to a heated gold electrode surface via thiol bridges. 

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