Ruthenium tris-bipyridine, fluorescence

Fluorescent redox switches based on compounds with electron acceptors and fluorophores have been also reported. For instance, by making use of the quinone/ hydroquinone redox couple a redox-responsive fluorescence switch can be established with molecule 19 containing a ruthenium tris(bpy) (bpy = 2,2 -bipyridine) complex.29 Within molecule 19, the excited state of the ruthenium center, that is, the triplet metal-to-ligand charge transfer (MLCT) state, is effectively quenched by electron transfer to the quinone group. When the quinone is reduced to the hydroquinone either chemically or electrochemically, luminescence is emitted from the ruthenium center in molecule 19. Similarly, molecule 20, a ruthenium (II) complex withhydroquinone-functionalized 2,2 6, 2"-terpyridine (tpy) and (4 -phenylethynyl-2,2 6, 2"- terpyridine) as ligands, also works as a redox fluorescence switch.30... 

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... 

Bhasikuttan, A. C. Suzuki, M. Nakashima, S. Okada, T. Ultrafast fluorescence detection in tris(2,2 - bipyridine)ruthenium(II) complex in solution relaxation dynamics involving higher excited states. J. Am. Chem. Soc. 2002, 124, 8398-8405. 

The interactions of various cationic species with polyacids, such as polyCmethacrylic acid), PMA and polyCacrylic acid), PAA have been studied. In particular, the effect of polyacid conformation on the interaction is discussed in detail, and also the nature of the aggregation of PMA and cationic surfactants al)tyltrimethylammonium bromide, C TAB. The effect of the intermediate conformation states of PMA around pH 4-6 is noted, where the photophysical properties of cationic probes bound to PMA dramatically change, effects such as a large enhancement of the fluorescence intensity of Auramine 0, Au 0 at pH 4.5, a blue shift of the luminescence spectra of tris(2,2 -bipyridine)ruthenium(II) complex, Ru(bpy)3 at pH 5, and a great increase of the excimer yield of 1-pyrenebutyltrimethyl ammonium bromide, C PN at pH 6. 

A method based on fluorescence quenching that did not depend on the nature of the transition was used to determine the micelle size of the hexyl copolymer (24). The basic idea underlying this method is that, in a solution containing luminescent probe and quencher molecules, both solubilized in an excess of micelles, the quenching will be inversely related to the number of micelles, because the more micelles there are, the smaller is the chance of both a probe and a quencher molecule inhabiting the same micelle (25-27). The hexyl copolymer used in our study had a degree of polymerization of 1700. The fluorescent probe was tris(2,2 -bipyridine)ruthenium(II) ion [Ru(bpy)3 ], the quencher was 9-methylanthracene (9-MeA), and the solvent was an aqueous 0.1 M LiCl solution. The fluorescence experiments were supplemented with solubilization experiments from these, the distribution of the 9-MeA between the polymer molecules and the solvent molecules, as well as the extent to which the polymer was in micellar form, could be simultaneously determined. The results indicated that the micelles inside the domain of a macromolecule encompassed approximately 24 repeat units, and that this micelle size was independent of the polymer concentration, of the probe concentration, and the extent to which the polymer was micellized. 

Matsui K., Momose F. Luminescence properties of tris(2,2 -bipyridine)ruthenium(II) in sol-gel systems of Si02. Chem. Mater. 1997 9 2588-2591 Matsui K., Nozawa K. Molecular probing for the microenvironment ofphotonics materials prepared by the sol-gel process. Bull. Chem. Soc. Jpn. 1997 70 2331-2335 Matsui K., Yamamoto T., Goto T., Nozawa K., Bessho K. Fluorescence and infrared spectra of phenyl-modified silica gels prepared by the sol-gel process. J. Chem. Soc. Jpn. 1998 489-494 Matsui K., Nozawa K., Yoshida T. Phosphorescence of benzophenone in sol-gel silica. Bull. Chem. Soc. Jpn. 1999 72 591-596... 

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