In the visible region of the spectrum the PPC films with small concentrations of CPDs 1-3 have one absorption band due to the π-π* transition polarized along the long axis of the chromophore of the dye (Fig. ). It has the universal form with a vibrational maximum at the short-wave edge typical of organic dyes . Its intensity decreases regularly in the series of CPDs 1-3 as a result of weakening of the vibronic interactions with increase in the length of the polymethine chain .