Anilines, charge transfer

The well-known photopolymerization of acrylic monomers usually involves a charge transfer system with carbonyl compound as an acceptor and aliphatic tertiary amine, triethylamine (TEA), as a donor. Instead of tertiary amine such as TEA or DMT, Li et al. [89] investigated the photopolymerization of AN in the presence of benzophenone (BP) and aniline (A) or N-methylaniline (NMA) and found that the BP-A or BP-NMA system will give a higher rate of polymerization than that of the well-known system BP-TEA. Still, we know that secondary aromatic amine would be deprotonated of the H-atom mostly on the N-atom so we proposed the mechanism as follows ... 

Many anodic oxidations involve an ECE pathway. For example, the neurotransmitter epinephrine can be oxidized to its quinone, which proceeds via cyclization to leukoadrenochrome. The latter can rapidly undergo electron transfer to form adrenochrome (5). The electrochemical oxidation of aniline is another classical example of an ECE pathway (6). The cation radical thus formed rapidly undergoes a dimerization reaction to yield an easily oxidized p-aminodiphenylamine product. Another example (of industrial relevance) is the reductive coupling of activated olefins to yield a radical anion, which reacts with the parent olefin to give a reducible dimer (7). If the chemical step is very fast (in comparison to the electron-transfer process), the system will behave as an EE mechanism (of two successive charge-transfer steps). Table 2-1 summarizes common electrochemical mechanisms involving coupled chemical reactions. Powerful cyclic voltammetric computational simulators, exploring the behavior of virtually any user-specific mechanism, have... 

Bosch LI, Mahon MF, James TD (2004) The B-N bond controls the balance between locally excited (LE) and twisted internal charge transfer (TICT) states observed for aniline based fluorescent saccharide sensors. Tetrahedron Lett 45(13) 2859-2862... 

The nitrosonium cation can serve effectively either as an oxidant or as an electrophile towards different aromatic substrates. Thus the electron-rich polynuclear arenes suffer electron transfer with NO+BF to afford stable arene cation radicals (Bandlish and Shine, 1977 Musker et al., 1978). Other activated aromatic compounds such as phenols, anilines and indoles undergo nuclear substitution with nitrosonium species that are usually generated in situ from the treatment of nitrites with acid. It is less well known, but nonetheless experimentally established (Hunziker et al., 1971 Brownstein et al., 1984), that NO+ forms intensely coloured charge-transfer complexes with a wide variety of common arenes (30). For example, benzene, toluene,... 

Intramolecular charge transfer in p-anthracene-(CH2)3-p-Ar,Af-dimethylaniline (61) has been observed174 in non-polar solvents. Measurements of fluorescence-decay (by the picosecond laser method) allow some conclusions about charge-transfer dynamics in solution internal rotation is required to reach a favourable geometry for the formation of intramolecular charge-transfer between the donor (aniline) and the acceptor (anthracene). 

In fac-(bpy)Re(I) (CO)3-A (where bpy is 2,2 -bipyridine and A is an aromatic amine), the d-7t(Re)—>jr (bpy) MLCT fluorescent excited state is strongly quenched via intramolecular aniline-Re charge transfer leading to a nonfluorescent LLCT state. By incorporating the donor amino group belonging to the A moiety into a crown-macrocycle, Schanze and Mac Queen(137) have provided a new luminescent cation sensor whose quantum yield of fluorescence raises from 0.0017 (without cation) to... 

Torrance obtained a sample that showed ferromagnetic properties with a high Curie temperature by a reaction of 1,3,5-triaminobenzene with iodine under rather drastic conditions (Torrance et al., 1987). A charge-transfer complex of iodine with an aniline-black-type polymer [32], a heteroatom-containing analogue to [14 ] (Johannsen et al., 1989), may have been... 

It is assumed that an excited state charge transfer complex is formed between the nitroaromatic in its first triplet state and the respective substrate. Internal proton transfer is immediately followed by hberation of carbon dioxide. Finally hydrolysis of the hemiacetal Ar —X—CH2OH (X = NH or S) leads to 2-chloro-aniline or thiophenol, respectively. In the decarboxylation of a-phenylthio-acetic acid, some methyl-phenylsulfide is also formed. (7t,7r )-nitroaromatics are more reactive than nitro compounds with lowest (n,7t )-triplets iso). 

Figure 3.20 Charge transfer in the HOMO-LUMO transitions of (a) nitrobenzene and (b) aniline...

TNT forms charge-transfer, or 7r, complexes with polycyclic aromatic hydrocarbons, aromatic amines, and aromatic nitro compds a number of these are listed below in Table 2. The complexes with three amines (diphenylamine, diethyl-aniline, p-anisidine) have characteristic colors this forms the basis for a rapid and convenient thin-layer chromatographic analytical procedure (Ref 34) for the identification of very small amounts of TNT. (For a discussion of the many color reactions of TNT, and of composite expls containing it, see Vol 3, C405-L ff)... 

Talamoni and coworkers17 found that in methanol, allylamine has no influence on the yield of 0-Ps. Other amines, such as w-propylamine and triethylamine, increase the yield of the o-Ps. The authors ascribe this difference to the higher ionization potential of allylamine, making positive charge transfer from the solvent ions (the holes) ineffective. The ionization potential of allylamine (9.6 V) is considerably higher than that of other amines (w-propylamine 8.8 eV, triethylamine 7.8 eV, aniline 7.7 eV). They found a correlation between the ionization potentials and the enhancement factors. In water, allylamine also enhances the formation of 0-Ps, due to the much higher ionization potential of water, 12.6 eV (while the value for methanol is only 10.8 eV). 

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