Dispersion interactions,electronic absorption spectra of anthracenes in polar glassy media at 77–300 K,and the change in polarizability upon excitation

The effect of dispersion interactions on the electronic spectra of organic compounds is analyzed within second-order perturbation theory. A formula is obtained which makes is possible to determine the change in the polarizability of the molecules upon excitation, Δα_eg, using data on the effect of the bulk polarizability P_n of the solvent on the position of the electronic spectrum. It is shown that when the solutions are cooled, the long-wavelength shift of the absorption spectra for the studied anthracenes in alcohols is mainly due to dispersion interactions and is caused by an increase in P_n. The possibility of using the new formula for Δα_eg is demonstrated for anthracenes as an example. It is found that for anthracene, 1-chloroanthracene, 9,10-dichloroanthracene, 9,10-dibromoanthracene, 9,10-diiodoanthracene Δα_eg is 16.5, 16.9, 17.2, 18.6, and 20.2 ų respectively. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 2, pp. 162–168, March–April, 2007.