Triplet States of Cyanine Dye Dimers

The results of investigations of the properties of cyanine dye dimers in the triplet state are presented. The formation of dimers is demonstrated as two absorption bands of differing intensities, which are due to splitting of the S*-level of monomers as a result of their resonance interaction. The cyanine dye dimers are characterized by a relatively high quantum yield of the intersystem crossing. In the triplet-triplet absorption spectra two bands appear, where the long-wavelength band is assigned to a charge transfer state. The cyanine dye dimers in the triplet state are involved in the energy and electron transfer and can act as the photosensitizes of redox reactions.