Naphthalene electrochemically oxidized

While such a device has yet to be constructed, Debreczeny and co-workers have synthesized and studied a linear D-A, -A2 triad suitable for implementation in such a device.11641 In this system, compound 6, a 4-aminonaphthalene monoimide (AN I) electron donor is excited selectively with 400 nm laser pulses. Electron transfer from the excited state of ANI to Ai, naphthalene-1,8 4,5-diimide (NI), occurs across a 2,5-dimethylphenyl bridge with x = 420 ps and a quantum yield of 0.95. The dynamics of charge separation and recombination in these systems have been well characterized.11651 Spontaneous charge shift to A2, pyromellitimide (PI), is thermodynamically uphill and does not occur. The mechanism for switching makes use of the large absorption cross-section of the NI- anion radical at 480 nm, (e = 28,300). A second laser pulse at 480 nm can selectively excite this chromophore and provide the necessary energy to move the electron from NI- to PI. These systems do not rely on electrochemical oxidation-reduction reactions at an electrode. Thus, switching occurs on a subpicosecond time scale. 

The electrochemical oxidation at BDD as final treatment in a combined two-step biological/electrochemical process was investigated by Panizza et al. (2006) for the removal of naphthalene sulfonates contained in infiltration water of an industrial site. Mono and disulfonate naphthalenes were easily removed in the biological step, whereas bio-refractory compounds with complex molecules were oxidised by electrolysis at BDD anodes. With this combination the energy demand was significantly lowered with respect to mat required in a single electrochemical step. 

When benzenoid organic hydrocarbons such as naphthalene (60), fluoranthene (116), perylene (112) or pyrene (117) are subjected to electrochemical oxidation at a platinum electrode in the presence of supporting electrolytes in solvents such as methylene chloride or acetonitrile, one frequently observes the deposition of crystals on the electrode [310]. When denoting the substrate as A and the supporting electrolyte as MX there are two nucleophilic species competing for the radical cation A", i.e., the neutral molecule A and the closed-shell counteranion X , and it is, indeed, the equilibrium constant of the... 

This scheme explains the loss of substrate selectivity in nitration with nitronium salts and the high position selectivity which is determined by the spin density distribution in the radical cation (see above) and by the relative stability of the formed a-complexes. In favour of this scheme naphthalene is electrochemically oxidized in CH3CN with NO2 at a lower oxidation potential than that of NOj but sufficient to fonn the radical cation of naphthalene 1- and 2-nitronaphthalenes are formed in the same ratio (9 1) as from nitration by HNO3 and H SO in CH3CN. Later, however, the formation of nitronaphthalenes was shown to be mainly, if not completely, due to the nitration of naphthalene by catalyzed by the acid... 

Radicals may also result from chemical or electrochemical oxidation or reduction of stable molecules. Single-electron transfer processes initially generate radical cations (for oxidation) or radical anions (for reduction), which may then fragment to radicals and ions. For example, Sargent and coworkers determined that in 1,2-dimethoxyethane solutions the radical anion of naphthalene (sodium naph-thalenide, Na" " Ar ) transferred an electron to propyl iodide. Subsequent loss of... 

Panizza M, Zolezzi M, Nicolella C (2006) Biological and electrochemical oxidation of naphthalene sulfonates in a contaminated site leachate. J Chem Technol Biotechnol 81 225-232... 

Tautomeric trifluoromethyl-substituted spirocyclic quinazolines 693 and 694 were formed when p-benzoquinone imines 692 (synthesized by electrochemical oxidation of the corresponding p-anisidine derivatives 691) were heated in DMSO at 120 °C (Scheme 145) [409], The reaction was affected by solvent (DMSO giving the highest yields) and nature of the substituents in 692, In the case of naphthalene derivatives (e.g. 695), thecyclization gave single tautomers (e.g. 696). A synchronous mechanism was proposed for this transformation. 

A third important reaction of aromatic radical-cations is carbon-carbon bond formation with a further aromatic substrate. This reaction is limited to the oxidation in acetonitrile of substrates with electrondonating substituents. Radical-cations from benzene, naphthalene and anthracene form a-complexes but do not form a a-bonded reaction intermediate. Tlie dimerization reaction has been investigated both by pulse-radiolysis [22] in water and by electrochemical methods [27] in acetoni-... 

Benzene, naphthalene and anthracene afford quinones by oxidation in aqueous based media and these processes are technically important. Electrochemical oxida-... 

Electron transfer to and from the exocyclic double bond of diphenylmethylenes 94c306 and 96c307 has been effected by electrochemical techniques. In each case reduction gives a stable anion radical while oxidation leads to a quasistable cation radical that can be further oxidized to a very short-lived dication. The spectroelectrochemical results306,307 show that naphthalene 96c" is more stable than the benzenoid 94" as excitation requires... 

Also, HPLC methods with electrochemical or fluorescent detection are used (H19, M3). In proteins, dityrosine can be estimated by immunochemical methods employing dityrosine-specific antibodies (K5). Measurements of o,o -dityrosine and o-tyrosine levels in rat urine express dityrosine contents in skeletal muscle proteins, and have been proposed as the noninvasive oxidative stress test in vivo. One should be aware, however, that A-formylkynurenine, also formed in protein oxidation, has similar fluorescence properties as dityrosine (excitation 325 nm, emission at 400-450 nm) (G29). Also, oxidation of mellitin when excited at 325 nm produces an increase in fluorescence at 400—450 nm, despite the fact that mellitin does not contain tyrosine. Oxidation of noncontaining Trp residues ribonuclease A and bovine pancreatic trypsin inhibitor with "OH produces loss of tyrosine residues with no increase in fluorescence at 410 nm (S51). There are also methods measuring the increased hydrophobicity of oxidized proteins. Assays are carried out measuring protein binding of a fluorescent probe, 8-anilino-l-naphthalene-sulfonic acid (ANS). Increase in probe binding reflects increased surface hydrophobicity (C7). 

Copolymers containing alternating l,4-bis(phenylethenyl)benzene, l,4-bis(phenylethenyl)-2,5-dimethoxybenzene or l,5-bis(phenylethenyl)naphthalene chromophores, and dibenzo-24-crown-8 spacers within the polymer backbone, best represented by 87, showed blue light emission in solution, and tunable photoluminescence and electroluminescence depending on the structure of the chromophore. Blends of these copolymers with a small amount of poly(ethylene oxide), and lithium salt as active layers, form efficient light-emitting electrochemical cells <2003JMC800>. 

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