Coronene cation

Arenium ion energies (AAH ion - neutral) and changes in carbon charges [Aq = (ion) - q (neutral)] for protonation of 90 and 91 were probed by the AMI method. The singlet oxidation dication of 90 was also calculated. The charge delocalization modes in the PAH arenium ions were discussed and compared. The AMI studies indicated that benzo[<3]coronene cations were less delocalized than benzo[g/z/]perylene ions. Benzannelation (91 92) severely limited the conjugation path in the carboca-tions despite the fact that coronene 92 was still planar. Further benzannelation (92 90) had a minimal effect on the charge delocalization mode. 

The LA process may be carried out in the presence of gaseous molecules or near a stream of gas (60) (e.g., oxygen) producing cluster anions such as GdvO( or ammonia producing complex cations such as Cr(NH3)J, where x = 2-15 (61). Metal complexes may also be obtained by LA (e.g., LA of an iron rod produces Fe+), but when the rod is coated with C60 and coronene, ions such as [C60Fe(coronene)]+ are produced (62). 

The coronene radical anion has been obtained in a half-sandwich contact ion pair 84, (Fig. 54) with the [K(TMEDA)(THF)2] cation.136 The metal interacts with one of the outer rings of the hydrocarbon [K-C 318.5(4) to 345.5(4) and 313.3(4) to 354.8(4) pm in two crystallographically independent molecules]. There is almost no distortion of the anion compared with the neutral molecule, suggesting that the electron is well delocalized. UHF-... 

In addition to naphthalene, the triplet states of coronene, tri-phenylene, and 1,3,5-triphenylbenzene have been studied by this technique (van der Waals and de Groot, 1959, 1960). Hyperfine structure has been observed, and is presumably governed by the same principles as for aromatic cations and anions. The spin-spin splittings have been discussed theoretically (Gouterman, 1959 Gouterman and Moffitt, 1959 Hameka, 1959). 

An interesting aspect of this problem is that posed by the Jahn-Teller effect in the benzene anion. These ions, together with the cations and anions of coronene (Bolton and Carrington, 1961c de Boer and Weissman, 1958), have spectra consisting of unusually broad lines which are very hard to saturate. Theoretical studies (McConnell, 1961 McConnell and McLachlan, 1961) suggest that the broadening is a result of spin-orbit interaction but the relaxation is linked to the dynamic Jahn-Teller effect. 

Fig. 11. Mass spectra showing the progression towards complete dehydrogenation of the coronene radical cation as a function of increasing lamp power [138]...

Fig. 3.7 ESR spectra observed at room temperature for 1,1,1,3.3,3-hexafluoropropen-2-ol (HFP) solution containing ca 5 mmol dm coronene (C) and thallium trifluoroacetate (TIIII). (a) Spectrum attributed to the monomer radical cation, (C) from a solution containing -10 mmol dm TIIII Simulated spectmm calculated with an isotropic H-hfs of 0.156 mT (12 H) and a peak-peak line width (ABpp) of 0.035 mT (b) Spectrum attributed to a mixture of (C) and the dimeric radical, (Ci), from a solution containing -2 mmoi dm TIIII Simulated spectrum calculated with the concentration ratio [(C) ] [ (C)2 ] = 20 1. The line shape of (C2) was calculated with an isotropic H-hfs of 0.0766 mT (12 H) and ABpp of 0.(X)9 mT. The satellite lines denoted by an asterisk, flanking the sharp (Ca) features, are attributed to the trimeric cation, (C3) (c) Spectrum attributed to a mixture of (C2) and (Cs) formed in a solution containing < 1 mmol dm TIIII. The figure is reproduced from [K. Komaguchi et al. Spectrochim. Acta A 63, 76 (2(X)6)] with permission from Elsevier...

As in the case of pyrones, the contribution to carbon basicity of n-cation interactions in model aromatic systems was investigated by carrying out ab initio calculations [64], The energies for benzene-HjO pyrene-benzene-HjO", and coronene-H30+ interactions were considered in an attempt to understand the basicity contributions of the basal plane. These theoretical results did support the experimental data concerning the ability of basal planes to contribute to carbon basicity and suggested that n-cation interactions may play an important role in the surface chemistry of carbon materials. 

The so-called superbenzene, coronene, was used as a substrate by Pozniak and Dunbar (1997) in an FTICR-MS study of the formation kinetics of monomer and dimer association complexes with Sc and Y, together with several other main-group and transition metal cations. The formation of coronene adducts was also observed for RO" " and R(OH)2 ions, for both Sc and Y, with rates similar to the attachment rates for the corresponding bare metal ions the same ions were produced by the reaction of R(coronene) with background oxygen/water. In a different approach, Duncan and coworkers used covaporization of Nd oxide and pyrene in a laser plasma source with time-of-flight mass spectrometry (TOF-MS) detection to produce NdO(pyrene) " ions, with =1, 2 (Ayers et al., 2004). 

Thanks to the versatility of the Raman spectroscopy, nanoparticles AgNP(25) were used also to detect other policyclic aromatic pollutants (PAHs), like benzo [cjphenanthrene, triphenylene, and coronene [67]. In this case, selectivity is not as important as in other sensors, because the pollutant molecule can be in principle identified by its Raman spectrum. The affinity constants and the limits of detection of PAHs were also determined. In 2012, Coleman and co-workers developed a method to determine the critical micellar concentration (CMC) of cationic surfactants exploiting the SPB of a series of sulfonato calix [njarene-capped AgNPs [68]. The nanoparticles were synthesized by reducing AgNOs with sodium borohydride in aqueous solution in the presence of the sulfonate calix[n]arene derivatives 24, 26 and 27 (see Fig. 35.15) and characterized by TEM, DLS and UV-visible spectroscopy. Suspensions of the... 

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