| Abstract: | For the examples of aromatic and antiaromatic five-membered heterocycles, the static electronic polarizabilities and hyperpolarizabilities are determined in the ground and first singlet- and triplet-excited electronic states. The theoretical calculations are carried out in the SOS formalism and the correlation effects are taken into account using all mono- and biexcited configuration in the PPP approximation. It is shown that the singlet excitation of the molecules for the antiaromatic case is connected to an significant decrease of both polarizabilities and hyperpolarizabilities. Their values are discussed in terms of the index of average bond-order alternation for the ground and excited states and the localization of the electronic transitions in the molecules. © 1993 John Wiley & Sons, Inc. |
