6- -2,2 -bipyridine rhenium complexes

In 1986, Breikss and Abruna reported electrochemical and mechanistic studies on a close analogue of the rhenium complex, (Dmbpy)Re[CO]3Cl, where Dmbpy = 4,4 dimethyl 2,2 bipyridine. The cyclic voltammogram of the complex at platinum in CH3CN/tetrabutylammonium perchlorate is shown in Figure 3.56 for simplicity we will consider only the electrochemistry taking place above c. —2.3V vs. SCE. 

A few other interesting molecular architectures exhibiting uncharacteristic electrochemical behavior have been constructed on the basis of the methanofullerene building block. These include two methanofullerene-substituted bipyridine ligands complexed to rhenium and ruthenium ((35) and (36) in Fig. 17), which were prepared as possible candidates for photoinduced electron transfer processes [138]. In addition, three fullerene crown ether conjugates ((38), (39), and (40) in Fig. 18) have... 

In the case of the rhenium(I) bipyridine tricarbonyl complexes with a phosphorous ligand such as 3a in Table I, both the MLCT absorption and the emission bands are blue shifted because of the stronger LF induced by the phosphorous ligand. This causes the lifetime of the MLCT excited state to be longer. The photophysical parameters of some t5rpical Re(I) complexes are smnmarized in Table I (5,26). 

The substituents on the bipyridine ligand are also of importance (65). The complex 3c, which has electron-withdrawing CF3 groups, shows only low C02-reducing abilities ( co = 0.005). However, the introduction of electron-donating MeO groups did not influence the photocatalytic ability of the rhenium complex 3j. 

Although the structure of the CO2 adduct, which is an important intermediate in the photocatalysis of the rhenium complexes, has not yet been confirmed, several proposals have been made. As candidates, a C02-bridged binuclear complex (CO)3(dmb)Re—CO2—Re(dmb)(CO)3 (16, dmb = 4,4 -dimethyl-2,2 -bipyridine) and a rhenium carboxylate complex Re(bpy) (COlsCCOOH) (17) were synthesized. 

The 6-substituted cyano bipyridine has been generated in 95% yield from bipyridine A-oxide by reaction with trimethylsilylcyanide and dimethylcarbamylchloride.76 This is an improvement on an earlier method that generated 6-cyano bipyridine from the A-oxide in 62% yield using potassium cyanide and benzoyl chloride.77 This ligand has been used in electrochemical studies of rhenium complexes with sterically hindered bipyridine derivatives, as well as a precursor in the synthesis of 6-carbothioamide-bpy, which showed antitumor activity against P-388 lymphocytic leukemia in mice.77... 

Low-valent rhenium complexes with Tp and bpy (bpy = bipyridine) ligands that do not include CO in the coordination sphere have been synthesized. Complexes of the type TpRe(bpy)Y (Y = Cl or cyclopentene bpy = 2,2 -bipyridyl) are derived from [TpRe bpy)Cl][OTf with the accompanying one or two electron reduction by Zn/Hg or Na/Hg amalgam, respectively (Scheme 60). " TpRe(bpy)(f/ -cyclopentene) is a potent 7i-base as evidenced by the II/I oxidation potential of —0.66 V versus NHE, 0.89 V more cathodic than TpRe(CO)(PMe3)( -cyclohexene). 

FOjSjC.oH, 2,2 -Bi-13-dithiolo[4>b]-[l,4]dithiinylidene fluorosulfiite, 26 393 F3HO2P, Phosphorodifluoridic acid, rhenium complex, 26 83 F2N303PReC 3H9, Rhenium, (2,2 -bipyridine)tricarbonyl(phosphorodi-fluoridato)-, 26 83... 

The enhancement of the luminescence properties of the rhenium(I) complexes has also been demonstrated by Belser and coworkers with a bis(anthracene)-functionalized bipyridine ligand (Figure 11). This rhenium complex did not show any MLCT phosphorescence as the emissive excited state was effectively quenched by the anthracene moieties. With the disruption of tt-conjugation through the reversible photoinduced [4-1-4] cycloaddition of the anthracene moieties, the lowest lying excited state of the cycUzed dimer could not quench the MLCT emission, leading to the enhancement of the luminescence properties. 

Other systems for electrochemical CO2 reduction utilize transition metal complexes of nitrogen-containing (nickel and cobalt) macrocycles (including porphyrins and phthalocyanines) and (ruthenium, cobalt, and rhenium) complexes of 2,2 -bipyridine. ... 

M. Gottschaldt, D. Koth, D. Muller, I. Klette, S. Rau, H. Gorls, B. Schafer, R. P. Baum, and S. Yano, Synthesis and structure of novel sugar-substituted bipyridine complexes of rhenium and 99m-technetium, Chem. Eur. 13 (2007) 10273-10280. 

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