Naphthalene energy bands

Predict the effect of aza substitution on the first absorption bands of naphthalene (quinoline and isoquinoline energy, band intensity). [No shift, increased intensity of the 1La band, cf. Figure 4.27]... 

Fig. 8.38 shows the energy bands F (k) for electrons and holes for five different directions of the k vector in the naphthalene crystal and also the densities of state (DOS) in the conduction band and the valence band. Here, a, b, and c are the crystal axes and di = (1/2,1/2, 0) and A2 = (-1/2,1/2, 0) are the directions along the near neighbours in the (a - b) plane, which are degenerate in the monocUnic crystals naphthalene and anthracene, but not in the triclinic crystals tetracene and pentacene. The dispersion along the c direction is smaller than within the (a - b) plane, which is due to the smaller intermolecular interactions between the (a - b) planes compared to those within the (a-b) planes. Similarly, the mobilities are also higher in the (a-b) plane than between the (a-b) planes (see below). 

Conformationally rigid cis-2,3-dihydroindan-l-ones have been prepared " and intramolecular energy transfer in these systems has been studied. For (395), for example, irradiation in the Lj, band and the n-n transition showed neither fluores-ence from naphthalene nor phosphoresence from indanone, but only phosphoresence from naphthalene. Energy-transfer and energy-wasting processes are discussed in relation to the configurations of the molecules. 

For some aromatic hydrocarbons such as naphthalene, anthracene and pery-lene, the absorption and fluorescence spectra exhibit vibrational bands. The energy spacing between the vibrational levels and the Franck-Condon factors (see Chapter 2) that determine the relative intensities of the vibronic bands are similar in So and Si so that the emission spectrum often appears to be symmetrical to the absorption spectrum ( mirror image rule), as illustrated in Figure B3.1. 

Fig. 5 Bottom 2PA spectrum for linearly polarized light (intensity in arbitrary units) and (top) polarization ratio of naphthalene in ethanol. 0-0 is the origin of the band (I), the La band (II) is not visible, and the numbers III-VI identify transitions to higher electronic states. The abscissa, representing the total excitation energy, is in units of cm". Reproduced with permission from [46]. 1981, Elsevier...

Since Forster s original work, a large number of aromatic compounds, including benzene, naphthalene, and anthracene, have been found to have concentration-dependent fluorescence spectra under some conditions. Most of these excimers are not as stable a.s the pyrene prototype, and require lower temperatures or higher concentrations to be observed.29 Some crystals also exhibit excimer emission. Crystalline pyrene, for example, has only a single structureless fluorescence band of the same energy as its excimer emission in solution.30... 

The spectrum of naphthalene is shown above. Its broad bands reflect the absorption of energy by the extended pi-electron system. 

Fig. 7. Mulliken plots for CTcomplexes of hexamethylbenzene (HMB), octamethylbiphenylene (OMB), and naphthalene (NAP) with various acceptors. Points on the ordinate at °ox — °red = 0 represent the band energies of the charge-resonance (CR) complexes between these donors and their cation radicals. Data from ref. [49],...

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