Phenalenyl anion

The orbital coefficients for the MO of energy a for the phenalenyl system described in Fig. 9.7 are as shown below. Predict the general appearance of the NMR spectra of the anion and cation derived from phenalene. 

Allyl (27, 60, 119-125) and benzyl (26, 27, 60, 121, 125-133) radicals have been studied intensively. Other theoretical studies have concerned pentadienyl (60,124), triphenylmethyl-type radicals (27), odd polyenes and odd a,w-diphenylpolyenes (60), radicals of the benzyl and phenalenyl types (60), cyclohexadienyl and a-hydronaphthyl (134), radical ions of nonalternant hydrocarbons (11, 135), radical anions derived from nitroso- and nitrobenzene, benzonitrile, and four polycyanobenzenes (10), anilino and phenoxyl radicals (130), tetramethyl-p-phenylenediamine radical cation (56), tetracyanoquinodi-methane radical anion (62), perfluoro-2,l,3-benzoselenadiazole radical anion (136), 0-protonated neutral aromatic ketyl radicals (137), benzene cation (138), benzene anion (139-141), paracyclophane radical anion (141), sulfur-containing conjugated radicals (142), nitrogen-containing violenes (143), and p-semi-quinones (17, 144, 145). Some representative results are presented in Figure 12. 

A simple model which correlates the HOMO and LUMO of cycl-[3,3,3]azine with the degenerate nonbonding orbitals of [12]annulene accounts for the ESR spectra of the radical cations and anions of 2a and some derivatives. This model also predicts the almost identical rc-spin population observed for the 2a-cation and the isoelectronic phenalenyl... 

Perimidine is one of the few azines in which the lone pair of a pyrrole-like nitrogen participates in the 7t-system of the molecule. Perimidine is therefore a 14-7t electron system, isoelectronic with the phenalenyl anion. An important consequence of this interaction is a transfer of electron density from the heterocyclic ring into the naphthalene moiety. Therefore perimidine exhibits simultaneously the characteristics of both 7r-deficient and 7t-excessive systems <87H(26)I029>. 

Bowl-shaped carbocations (33) were obtained by alkylation of the parent corannulene. ° The cations were obtained as stable salts and characterized by X-ray analysis. Phenalenyl cations (e.g. (34)) were obtained as air-stable BPh4 salts. Observations made in a selective synthesis of l,2-di(organo)fullerenes led to a mechanism whereby a cationic fullerene intermediate is generated by Cu(ll) oxidation of a fullerene radical (or anion). ... 

The pK for conversion of phenalene to its anion is 19. The cation is estimated to have a pXr+ of about 0-2." Several methods for generating the phenalenyl cation have been developed." ... 

The phenalenyl radical 4 represents the most fundamental and widely explored member in this family. Unlike typical stable neutral radicals such as TEMPO and a-nitronylnitroxide derivatives with a spin-localized nature, 4 is characterized by a planar, rigid structure with the spin spread over the whole molecular skeleton (Fig. 3). The resonance structures of 4 show that the spin density is predominantly at its oc positions, while the spin at the peripheral positions (jS positions) is much smaller, which can be explained by the spin polarization effect. In addition, 4 exhibits a high amphoteric redox ability with thermodynamically stable cation, neutral radical and anion species. All of these features of 4 lead to new insights in the field of physical chemistry. 

Nakasuji K, Yamaguchi M, Murata I, Yamaguchi K, Fueno T, Ohya-Nishiguchi H, Sugano T, Kinoshita M (1989) Synthesis and characterization of phenalenyl cations, radicals, and anions having donor and acceptor substituents three redox states of modified odd alternant systems. 

The for conversion of phenalene to its anion is 19. The cation is estimated to have a plphenalenyl cation have been developed. Because the center carbon is part of the conjugated system, the Huckel rule, which applies only to monocyclic conjugated systems, caimot be applied to just the peripheral conjugation. The nature of the phenalenyl system is considered further in Problem 12 at the end of this chapter. 

Semiempirical calculations and NMR spectroscopy have revealed the polarization of phenalenyl anions induced by charge-attracting capabilities of trimethylsilyl and cyano substituents. ... 

The cyclization also yields an aromatic phenalenyl anion moiety. This was demonstrated by the high-field shift of carbon atoms C8, C9, and ClOa (and their symmetrically equivalent atoms) and hydrogen atoms H8 and H9, which are part of the periphery of phenalene. This conclusion was supported by the similarity between the carbon chemical shifts of the phenalene moiety of 44b and 48b and those of the 2-methylphenalenyl anion 50 [128]. 

It was suggested that the formation of the new cr-bond allows the system to avoid anti-aromaticity by separating the two charges, as well as releasing some of the strain in the pyrene moiety by producing a three membered ring and leaving behind a relatively flat aromatic phenalenyl anion. 

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