Phenazine Phen

Phenazine (Phen). In aprotic solvents (DMF) this tricyclic aromatic heterocycle ex ts two one-electron reductions that are 

These H-atom transfer cycles closely resemble those of 3-methyl-lumiflavin and riboflavin, and may represent the redox mechanisms of flavin/hydroflavin/ dihydroflavin proteins in biology. 

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The primary process for the oxidation by O2 - of dihydrophenazine and dihydro-lumiflavin must be analogous to that for PhNHNHPh (Scheme 7-14) to give the anion radicals of phenazine (Phen ) and lumiflavin (Fl ). These in turn react with O2 to give O2 - plus phenazine and lumiflavin, respectively the process is analogous to that for the anion radical of azobenzene (PhN NPh), The oxidation potentials (Ep,a) for PhN NPh, Phen - and Fl - in Me2SO are -1.1 V versus NHE, -0.9 V, and -0.6 V, respectively. Each value is sufficiently negative to reduce O2 to O2 - (-0.5 V versus NHE in Me2SO). Hence, the (O2 )-induced auto-oxidation of PhNHNHPh also is thermodynamically feasible for dihydrophenazine and dihydro-lumiflavin and does occur for these two model substrates of reduced flavoproteins (Table 7-3). Such an auto-oxidation reaction sequence may be relevant to the fractional yield of 02 - from the flavin-mediated activation of 02 ° and the auto-oxidation of xanthine [catalyzed by xanthine oxidase (XO), a flavoprotein]. ... 

A photocatalytic system using phenazine (Phen, 28) as a photosensitizer instead of 15 has been reported. A solution containing 28, 26, and TEA was irradiated using > 290-nm light under a CO2 atmosphere to produce HCOOH selectively ( HCOOH = 0.07) [45]. Since the oxidation potential of Phen produced by photochemical electron transfer is —1.18 V vs SCE, Phen can reduce Co to Co ( p (Co ) = -0.69 V) but cannot reduce Co to Co ( p (Co " ) = -1.9 V). Time-resolved spectroscopy and pulse radiolysis studies showed that Phen was... 

The DNA binding of [cp Ir(dppz)(Aa)]"+, dppz = dipyrido[3,2-a 2, 3 -c]phenazine, Aa = S-coor-dinated amino acid or peptide, has been investigated by UV-vis spectroscopy, 2D-NOESY, and gel electrophoresis. The complexes intercalate into DNA adjacent to T2 from the major groove. The X-ray structural data for [cp IrCl(dppz)](CF3S03)4 and [ cp Ir(9-EtG)(Phen)](CF3S03)2, where GH = guanine, are reported.423... 

The preparation and structure of [Ru(phen)2(l,5,6,10-tetraazaphenanthrene)]Cl2 have been reported NMR spectroscopic data provide insight into the hydrophilic properties of the complex. The bpy-containing complexes [Ru(bpy)2(92)] + and [ Ru(bpy)2 2(M 92)] ((92) = dipyrido(2,3-a 2, 3"-/z)phenazine) were described earlier in the chapter.The analogous [Ru(phen)2(92)] and [ Ru(phen)2 2(M 92)]" have also been prepared and characterized, as has [ (phen)2Ru(/i-92) 3Ru] +. The electronic spectra exhibit intense MLCT bands in the visible region the electrochemical properties of the complexes have been investigated and for [ (phen)2Ru(/i-92) 3Ru], two sets of reduction waves centered on ligand (92) are separated by those assigned to phen reductions. ... 

Dynamic quenching of the MLCT excited state of [Ru(phen)2(dppz)] " " by H" " transfer in MeCN solution occurs for proton donors with pAa values in the range 4.7-15.7. Comparisons of the quenching have been made in the presence and absence of DNA. " The addition of Cu " " to DNA-bound [Ru(bpy)2L] " " (L is the phenazine derivative (167)) leads to luminescence quenching. This is explained in terms of complexation of Cu " " with the vacant coordination site of L in [Ru(bpy)2L] " ". Formation of the [Ru(bpy)2L] " "/Cu " " complex in the presence of DNA is proposed to place one metal center in the major groove and one in the minor groove. " ... 

Onfelt, B., Lincoln, P., Norden, B., Enantioselective DNA threading dynamics by phenazine-linked [Ru(phen)2dppz]2+ dimers. J. Am. Chem. Soc. 2001, 123, 3630-3637. 

Balzani et al. (70) employed a strategy focusing on complexes as metals and as ligands (71,72), for developing a number of interesting supramolecular systems. Ditopic polypyridyl ligands, for example, 2,3- and 2,5-dipyridylpyrazine (2,3-dpp and 2,5-dpp), 2,2 -biquinoline (biq), tetrapyrido[3,2-fl 2, 3 -c 3",2"-/z 2", 3 "-/]-phenazine (73,74) (tppz), and 2,3,5,6-tetrakis(2-pyridyl)pyrazine (75-77) (tpypz), in combination with monotopic ligands (e.g., bpy and phen) were utilized in the preparation of a number of homo- and heteropolynuclear complexes of well-defined structures (Fig. 2). 

The intercalation of several Os complexes such as [Os (Phen)2(dppz)] + dppz = dypyiido[3,2-a 2, 3 -c]phenazine and charge transfer through the DNA base stack has been reviewed. Os complexes have also been tethered... 

A resonance Raman study has been reported for MLCT and intraligand (IL) transition states of Ru(phen)2(qdppz)2+, where qdppz = naphtha[2,3-a]dipy-rido[3,2-/z 2,3 -/]phenazine-5,18-dione.242 IR bands due to vBH of the hydri-dotrispyrazol-l-ylborate (Tp) in Ru(K2-Tpphcl)(CO)2 lie in the range 2445-2476 cm-1.243... 

As with pyrazines (Section 6.2.7.1), phenazines, the dibenzo derivatives of pyrazine, can also be prepared from the reaction of diamines and dicarbonyl compounds. Chattopadhyaya and co-workers utilized this method to build phenazine systems in the synthesis of [Ru(phen)2dppz] 228, which were used for structure elucidation of nucleic acids without radioactive probes <01JACS3551>. The phenazine component of [Ru(phen)2dppz] was prepared by condensation of 226 and 3,4-diaminobenzoic acid. Diketone complex 226 was prepared by two consecutive ligand displacements from RuQs. 

ECL approach, several pathogens were detected and a good specificity of single point mutations for hepatitis disease was accomplished by DAPI intercalated Ru(bpy)3 + ECL. In addition, some ruthenium complex can also be used as ECL-switch molecule with high affinity, such as [Ru(bpy)2dppz] +(dppz = dipyrido[3,2-a 20,30-c]phenazine) ° and Ru(phen)3. ... 

H N,0, AthyI-bU-[3-ozy-1.2-banzo-phen azinyl.(4)]-amin oder [3-Ozy>1.2-benzo-phenazinyI-(4)]-[4-9thylamiilo-1.2-benzo. phenazin l-(3)]-Sther 85, 438. 

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