Cobalt complexes phenanthroline

Using the tri-iodide/iodide redox couple and the sensitizers (22) and (56), several groups have reported up to 8-10% solar cell efficiency where the potential mismatch between the sensitizer and the redox couple is around 0.5 V vs. SCE. If one develops a suitable redox couple that decreases the potential difference between the sensitizer and the redox couple, then the cell efficiency could increase by 30%, i.e., from the present value of 10% up to 13%. Towards this goal, Oskam et al. have employed pseudohalogens in place of the triiodide/iodide redox couples, where the equilibrium potential is 0.43 V more positive than that of the iodide/iodide redox couple.17 Yamada and co-workers have used cobalt tris-phenanthroline complexes as electron relays (based on the CoII/m couple) in dye-sensitized solar cells.95... 

As an active initiator for a co-polymerization, acyl-cobalt complexes also work well. As demonstrated by Alper and Lee, an equimolar mixture of Go2(GO)s, benzyl bromide (BnBr), and dihydro-1,10-phenanthroline 17, possibly generating BnGOGo(GO)4 under the reaction conditions, co-polymerized PO or 1,2-butene oxide with GO, and the... 

Okada, T. et al., A comparative study of organic cobalt complex catalysts for oxygen reduction in polymer electrolyte fuel cells, J. Inorg. Organometal. Polym., 9,199,1999. Bron, M. et al., EXAFS, XPS and electrochemical studies on oxygen reduction catalysts obtained by heat treatment of iron phenanthroline complexes supported on high surface area carbon black, J. Electroanal. Chem., 535, 113, 2002. 

For the investigation of interaction mechanism of some compounds as metal coordination complexes with DNA, Bard et al. [76] reported comprehensive electrochemical studies using cobalt/ferrum phenanthroline or cobalt/ferrum bipyridine. In that paper, they evaluated limiting shifts and binding constants of mediator compounds by cyclic voltammetry in the absence and presence of DNA in solution phase experiments. As a result of their report, they found those forms (oxidized or reduced form) of mediator compounds which bind to the DNA molecule with a high affinity. 

Scheme 6 Iron and cobalt complexes bearing 1,10-phenanthroline derivatives...

For the approach detailed above to be successful, the metal binding domain must form robust complexes, yet retain synthetic flexibility. Although substituted phenanthroline and bipyridine easily form self-assembled receptors (12), the substitution stability of terpyridine (Fig. 2) makes this ligand more suited for the creation of libraries. The choice of metal also permits some flexibility in library creation. Iron complexes form easily through the addition of ammonium iron(II) sulfate hexahydrate, but can be cleaved by the addition of chelating guests (11,13), Cobalt complexes are also easily formed using cobalt(II)... 

Hawecker et a/.141 used Re(bpy)(CO)3X (X = Cl, Br) complexes as photosensitizers and succeeded in improving markedly the efficiency of CO formation using a system similar to that described above, where DMF was used as a solvent and 2,9-dimethyl- 1,10-phenanthroline was added, as a ligand for the cobalt ion, to a solution containing Ru(bpy)3+, Co2+, and triethanolamine. 

It has long been known that, when bound to cobalt(II), the pyridine-based chelate ligands 2,2 -bipyridine (bipy), 1,10-phenanthroline (phen), and 2,2 6, 2"-terpyridine (terpy) form complexes that react with dioxygen in aqueous solution (32-34). The mixed-ligand complexes [Co(terpy)(bipy)]2+ and [Co(terpy)(phen)]2+ can act as oxygen carriers in aqueous solutions at pH values as low as 3.0 (34b), and the superoxo species thus formed are apparently dinuclear. In addition, the dinuclear bipyridine complex [(bipy)2Coin(/ 2-0 )(/ 2-02 )CoIn(bipy)2 ]3+ has been shown to catalyze the oxidation of 2,6-di-ter -butylphenol to the feri-butyl-substituted diphenoquinone and quinone (35). 

A much milder route to 5-nitro-1,10-phenanthroline involves nitration of the tris-phenanthroline complex of cobalt(III) which is readily nitrated in concentrated sulfuric acid at 80°. The free 5-nitro-l,10-phenanthroline can be isolated in 70% yield from the nitrated complex.276... 

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