MO CALCULATIONS ON THE ABSORPTION-SPECTRA OF ORGANIC DIMERS - THE INTERACTION ENERGY BETWEEN DIPOLE-MOMENTS OF ELECTRONIC-TRANSITIONS IN MONOMERS AND THE SHAPE OF ABSORPTION-BANDS

The interaction energy between dipole moments of electronic transitions in the monomers and the shape of absorption bands of organic dimers are calculated by the CNDO/S-CI method. It is found that the through-space resonance interaction between rr orbitals of the monomers has a strong effect on the shifts and widths of absorption bands of diners with the structure of H-aggregates. A large intermediate region of structures is found between structures corresponding to H- and J-aggregates. In the intermediate region, the interaction energy between the dipole moments of electronic transition in the monomers is small, and the dimer has a broad unshifted spectral band similar to that of the monomers. The large size of the intermediate region is due to a violation of the point-dipole approximation.