Case Studies Electronic Absorption Spectrum of Phenyl Radical

3 Case Studies Electronic Absorption Spectrum of Phenyl Radical 

The electronic absorption spectmm of phenyl radical is an interesting example where computational approaches can be compared to the experimental spectrum assigned to the above-mentioned radical on the basis of the strict correlation of intensity evolution in simultaneously measured IR and UV-vis spectra, for which several independent precursors gave consistent results. 

In general, the accuracy of a simulated spectrum depends on the quality of the description of both the initial and the final electronic states of the transition. This is obviously related to the proper choice of a well-suited computational model a reliable description of equilibrium structures, harmonic frequencies, normal modes, and electronic transition energy is necessary. In the study of the A Bj Aj electronic transition of phenyl radical the structural and vibrational properties have been obtained with the B3LYP/TDB3LYP//N07D model, designed for computational studies of free radicals. Unconstrained geometry optimizations lead to planar 

FIGURE 6.9 Phenyl radical, atom numbering scheme and plot of the electron density difference between the and X Ai electronic states. The regions that have lost electron density as a result of the transition are shown in bright yellow, and the darker blue regions gained electron density. 

TABLE 6.18 Geometry Structure of Phenyl Radical in the Ground Aj and First 

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