Naphthalene anion radical

For example, naphthalene radical anion L -I with counterion (Li, ). 

This type of polarization appears to be general in such systems and it has been proposed that it arises because of T i-S mixing. An interesting and important addif ional observation comes from a study of the reaction of isopropyl chloride with sodium naphthalene in a field of 60 G. Net emission in the products is predicted for T i-S mixing and multiplet polarization for Tq-S mixing. Since no multiplet polarization can be detected, it would seem that Tq-S mixing is suppressed in this system (Garst et al., 1971). Presumably, the naphthalene radical anion... 

An interesting initiator is the naphthalene radical-anion formed by electron-transfer from sodium to naphthalene... 

The naphthalene radical-anion transfers an electron to a monomer such as styrene to form the styryl radical-anion which dimerizes to a dianion... 

In complex organic molecules calculations of the geometry of excited states and hence predictions of chemiluminescent reactions are very difficult however, as is well known, in polycyclic aromatic hydrocarbons there are relatively small differences in the configurations of the ground state and the excited state. Moreover, the chemiluminescence produced by the reaction of aromatic hydrocarbon radical anions and radical cations is due to simple one-electron transfer reactions, especially in cases where both radical ions are derived from the same aromatic hydrocarbon, as in the reaction between 9.10-diphenyl anthracene radical cation and anion. More complex are radical ion chemiluminescence reactions involving radical ions of different parent compounds, such as the couple naphthalene radical anion/Wurster s blue (see Section VIII. B.). 

The importance of radical ions and electron-transfer reactions has been pointed out in the preceding sections (see also p. 128). Thus, in linear hydrazide chemiluminescence (p. 103) or acridine aldehyde or ketone chemiluminescence, the excitation steps consist in an electron transfer from a donor of appropriate reduction potential to an acceptor in such a way that the electron first occupies the lowest antibonding orbital, as in the reaction of 9-anthranoyl peroxide 96 with naphthalene radical anion 97 142> ... 

Szwarc and coworker have studied the interesting and useful polymerizations initiated by aromatic radical-anions such as sodium naphthalene [Szwarc, 1968, 1974, 1983]. Initiation proceeds by the prior formation of the active initiator, the naphthalene radical-anion (XVIII)... 

Other methods that use 55 anions as precursor for the synthesis of fullerene-derivatives usually involve chemical formation of the anion. Alkylation of 55 has been accomplished, e.g. by reduction with propanethiol and potassium carbonate in DMF [91,92], sodium methanethiolate in acetonitrile [93], the naphthalene radical anion in benzonitrile[94], potassium naphthalide [95] or simply with zinc [96]. 

The delocalization of the conduction electron onto the side chains would be expected if the pendant groups were replaced with more electrophilic substituents than the phenyl group. However, this is not the case. Figure 22 shows the absorption spectrum of poly-(methylnaphthylsilane) radical anion. The absorption spectrum is very similar to that of the naphthalene radical anion, which implies that the unpaired electron is localized on the pendant group. Increase of the electron affinity of pendant groups does not necessarily cause the delocalization. 

Figure 22 Comparison of the electronic absorption spectra of poly(methylnaphthylsilane) and naphthalene radical anions at 77 K in 7-irradiated MTHF matrices.

Figure 1. Visible and 11V spectra of (A) naphthalene radical anion (NRA) (THF, 25°C) (B) naphthalene dianion (OD values shifted upward by 0.2 unit) (C) naphthalene dianion after neutral naphthalene addition (OD values shifted upward by 1 unit the NRA concentration is the same in A and ).

The metalation of naphthalene 8-substituted by both an ethyl group or polyisoprene chain (PIP) is completely similar as established by the titration of the carbanions formed and the UV analysis of the reaction medium (21, 22, 25). Accordingly the naphthalene radical anion, naphthalene dianion and its further isomerization by hydrogen transfer sure successively observed and the final stage of the metalation can be represented by the following structure ... 

Using a similar approach, Evans and co-workers obtained values of hsi = -1.50, kcsi = 0.55, 8 = 0.15 for a series of trimethylsilyl-substituted naphthalene radical anions based on a Q value of -26.1 49). For phenyltrimethylsilylacetylene radical anion, the values of the heteroatom parameters that gave the best fit of the Huckel calculated spin densities with experimental values, using a Q value of 28, were hs, = -1.3, and kCSi = 0.65 when a 8 value of 0.1 was assumed. A resulting C—Si 7r-bond order of about 0.3 is obtained 43). 

Electron transfer from polycyclic aromatic radical anions in polar solvents can also initiate propagation.120 168 169173 One of the early and best understood systems is naphthalene-sodium, a green solution of stable, solvated naphthalene radical anion.176 177 The electron transfer from the radical anion to the monomer yields a new radical anion [Eq. (13.33)]. The dominant reaction of the latter is its head-to-head dimerization to the stabile dimeric dicarbanion [Eq. (13.34)], which is the driving force for the electron transfer even when electron affinity of the monomer is less than that of the polycyclic molecule. Propagation proceeds at both ends of the chain ... 

Figure 29.6 Spectrum of the naphthalene radical anion and a reconstruction of the spectrum.

Cyclic methylpolysilanes very readily undergo rearrangement reaction. By refluxing pure decamethylcyclopentasilane in THF in the presence of naphthalene radical anions, 10% of the cyclic hexamer is formed after 1 h. 

Naphthalene Naphthalene radical anion Naphthalenated electron... 

These results indicate that the naphthalene radical anion is not stable to the solvent tetrahydrofuran at room temperature on a time scale of 100 hours. Decomposition pathways are alkali metal dependent. Sodium and potassium naphthalene attack THF through a proton abstraction, cycloreversion mechanism, as previously described by Bates for the butyllithium/THF system (27). Lithium naphthalenide attacks the THF not only by the Bates mechanism but also by a nucleophilic ring opening, as is implicit in earlier high temperature work on lithium naphthalenide in THF (28) and in work on the attack of THF by tritylmagnesium bromide (29). The two smaller alkali metals, lithium and sodium, leave behind a... 

A radical anion of an aromatic hydrocarbon was implicated as early as 1866, when Berthelot obtained a black dipotassium salt from naphthalene and potassium [41]. This reaction must have proceeded via the naphthalene radical anion as a more or less fleeting intermediate. Again, Schlenk and co-workers captured the essence of such an intermediate. In the case of anthracene they noticed the existence of two different species, a purple dianion and a blue transient species with a banded spectrum [42]. They identified this intermediate as a monosodium addition product which contains trivalent carbon . Further details were revealed only with the advent of electron paramagnetic resonance spectroscopy. 

A scheme of this variant of electron transfer from the naphthalene radical anion was first proposed by Morton et al. to describe the initiation of octamethylcyclotetrasiloxane polymerization [191], Initiation according to scheme (47) is rapid with oxirane and slow with octamethylcyclotetrasiloxane. 

Many aromatic compounds can undergo one-electron reduction by alkali metals, such as Na and Li. For example, the reaction of naphthalene with sodium in an aprotic solvent gives the naphthalene radical anion - sodium ion salt. 

A more remarkable elongation of the CS lifetime was attained by complex formation of yttrium triflate [Y(OTf)3] with the CS state in photoinduced ET of a ferrocene-anthraquinone (Ec AQ) dyad (53). Photoexcitation of the AQ moiety in Ec AQ in deaerated PhCN with femtosecond (150 fs width) laser light results in appearance of the absorption bands 420 and 600 run at 500 fs, as shown in Eig. 14(a) (53). The absorption bands 420 and 600 nm, which are assigned to AQ by comparison with the absorption spectrum of AQ produced by the chemical reduction of AQ with naphthalene radical anion (53). The decay process obeys first-order kinetics with the lifetime of 12 ps [Eig. um. 

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