Absorption spectra, resonance Raman spectra and depolarization ratios, fluorescence spectra and emission polarizations, and simulations of the resonance Raman excitation profiles and absorption spectra are reported for a donor-acceptor substituted distyrylbenzene (DADSB) and two covalent "dimers" formed by joining two DADSB chains at their center phenyl ring through a paracyclophane moiety. Semiempirical and density-functional theory calculations of the ground-state geometries and ZINDO calculations of the electronic excitations are also reported. Both the spectroscopic results and the electronic structure calculations agree that the electronic states of these "dimers" are not adequately described by excitonic coupling between the nominally degenerate electronic transitions localized on each DADSB moiety. The resonance Raman spectra of both dimers are essentially identical but show additional lines and intensity differences relative to the monomer. The excitation profiles of all three molecules exhibit interference effects between the Raman amplitudes for the first two strongly allowed electronic transitions. All three molecules exhibit Raman depolarization ratios of 1/3 throughout the lowest-energy absorption band, but the fluorescence of both dimers immobilized in polymer matrixes is considerably depolarized relative to that of the monomer. This suggests that the electronic excitation, initially delocalized over both conjugated chains of the dimers, may become localized on a single chain as geometric relaxation and solvent reorganization occur.