Azulene ionization potential

The free valence number therefore provides a good guide to reactivity in alternant hydrocarbons unfortunately this approach cannot easily be extended to compounds of other types. It can be used only when the contribution to 6E due to changes in the qt is the same for different aromatic systems and this is so only if coulomb integrals a, are the same for all the atoms present. Equation (33) shows that this is not so for molecules containing heteroatoms the ionization potential Wt is different for different atoms. Equation (33) shows that non-alternant hydrocarbons such as azulene must also be excluded here the... 

Buenker min CLGTO as naphthalene and azulene. FSGO gives poor first ionization potential... 

As more experimental values of both electron affinities and ionization potentials were measured, this relationship was tested. For the alternate aromatic hydrocarbons the EN is approximately 4.02 eV, as opposed to the work function of graphite that is 4.39 eV. The EN for the smaller aromatic hydrocarbons is 4.1 eV. The EN for hydrocarbons with hve-membered rings, 4.4 eV, and Cwork function of graphite. Table 4.4 gives the Ea, IP, and EN values for several hydrocarbons. From a larger set of data the EN is not constant. If the values for styrene, fluoranthene, naphthalene, styrene, and azulene are not included, then EN = 4.02 0.02 eV can be used to calculate either the Ea or IP. The calculated Ea are compared to the ECD values in Table 4.4 [10]. 

Another example that illustrates the effect of the overlap density i/z/i/zy upon the magnitude of A /y involves two conjugated hydrocarbons. Listed in Table 8.1 are the experimental values of the first ionization potential (IP), the electron affinity (EA), the first singlet excitation energy (E Eq), and the first triplet excitation energy (Ex - Eg) for azulene 8.7 and anthracene 8.8. For simplicity of notation, the... 

TABLE 8.1. The Ionization Potentials, Electron Affinities, and Excitation Energies of Azulene and Anthracene... 

Non-alternant hydrocarbons do not appear to fit easily into the linear relation with the singlet separation (Fig. 1). Also, they do not fit on the line of log k2 versus ionization potential. For example, the ionization potential of azulene is similar to that of anthracene but the rate of protonation of the former is four orders of magnitude slower (see Table I), which is in line with the large difference between their respective AEg g values. The same considerations hold also for iluSranthene and acenaphthylene. Because of sparse experimental data the apparent fit of these latter compounds with the line in Fig. 1 should be treated cautiously. These findings indicate... 

The TCT method of obtaining relative molecular electron affinities and gas phase acidities has a demonstrated precision of 0.05 to 0.10 eV in the midrange of values from 0.5 eV to 3.0 eV. At the extremes the precision is less, 0.2 eV. Most of the TCT Ea are ground-state electron affinities. The exceptions are the HPMS electron affinities determined for azulene, anthracene, QJv, and CS2, and the ICR value for fluoroanil. The TCT method has been applied to more than 200 molecules. About 30 have been determined by the HPMS and ICR methods and many have been confirmed by the ECD method. Many have also been confirmed by the half-wave reduction potential method and/or solution charge transfer complex spectra. These will be discussed in Chapter 10. The colli-sional ionization method of measuring relative electron affinities can produce inverted orders of intensities and give excited-state Ea rather than ground-state Ea. 

Fewer than 300 Ea for organic molecules have been determined in the gas phase. The majority of the Ea have been determined by the ECD and/or TCT methods. The direct capture magnetron, AMB, photon, and collisional ionization methods have produced fewer than 40 values. Only the Ea of p-benzoquinone, nitrobenzene, nitromethane, azulene, tetracene, and perylene have been determined by three or more methods. Excited-state Ea have been obtained by each of these methods. Half-wave reduction potentials have determined the electron affinities of 50 aromatic hydrocarbons. The electron affinities of another 50 organic compounds have been determined from half-wave reduction potentials and the energies of charge transfer complexes. It is a manageable task to evaluate these 300 to 400 Ea. 

---