Localized molecular orbitals for excited states of polyenals, polyendials, and polyenones

The work is focused on the generation of localized molecular orbitals for excited states. A recently developed a priori method based in a CAS-SCF-type algorithm is applied. The method generates directly localized orbitals and can be applied to multireference wavefunctions. A detailed description of the performance of the method as well as the locality of the MOs for the example of the singlet n-->pi* (CO) excited state is given. It is in general possible to obtain local orbitals for the doubly occupied and virtual valence orbitals. The partial delocalization of the pi* (CO) orbital is discussed, as is the effect of the use of different CAS spaces. The systems under study are polyenals, polyendials, and polyenones where the pi* (CO) orbital interacts with the rest of the pi system. (C) 2003 Wiley Periodicals, Inc.