Excitonic and charge transfer states in oligomeric 9,10-anthrylene chains

The dimer (9,9'-bianthryl), trimer, and tetramer of anthracene, linked in the 9,10-position and equipped with solubility-increasing alkyl substituents, were investigated by steady state and time-resolved fluorescence spectroscopy and by transient absorption. In polar solvents, charge separation occurs with dipole moments increasing with chain length. The ease of charge separation depends on the energetic competition of the charge transfer (CT) and the lowest excitonic state. It is especially favorable for the tetramer in which the CT state was observed even in a 77 K frozen alcoholic matrix.