Antoni K. Wisor

All-valence-electron and transition density matrix calculations of the electronic spectra of [2.2]paracyclophanequinones

The combined CNDO/S and transition density matrix methods reproduced well the UV-VIS spectra of the intramolecular charge-transfer complexes of double- and triple-layered [2.2]paracyclophanequinones in which benzene and p-benzoquinone represent the donor and acceptor layers: DA, DDA and DAD. Calculations pointed to the already known experimental bathochromic shifts of the longest wavelength absorption band for the DA→DDA→DAD transformations. The electronic transitions corresponding to this band are for DA and DDA the CT transitions of the π→π* type; however, for DAD the band represents the n→π* transition localized on the acceptor ring.

Electronic structure of multilayered and multistepped cyclophanes

Abstract The electronic structure of multilayered, MLP, and multistepped, MSP, cyclophanes containing 2–5 layers and 2–4 steps, respectively, was investigated using the PPP CI-1 method with application of the supermolecule approximation and consideration of σ-π polarization and σ-π orbital interactions between the bridges and the rings. The electronic excitations were evaluated as a combination of exciton resonance (ER%) and charge resonance (CR%) both based on the localization of excitation numbers on given molecular fragments. The transition ascribed to the new (when compared with 2L) long wavelength absorption band in 3L localized on the inner ring was influenced by the deformation and substituent effects, but transannular interactions were predominant, CR% = 53. These interactions increased with the attachment of every new benzene ring. The transfer from the inner ring (s) to the outer rings prevailed over the opposite trend. CR% values were 15–20% greater for MLP than MSP, pointing to the differences in transannular interactions.