Absorption Spectra of Organic Dyes Containing Two Chromophores

The Review begins with consideration of the absorption spectra of dyes whose molecules contain non-conjugated (isolated) chromophores. The major portion of the Review, however, is devoted to the spectra of dyes having two conjugated chromophores. According to the view adopted until recently the interaction of conjugated chromophores is apparent in a displacement of the absorption band to longer wavelengths and in an increase in its intensity. The Reviewer and his coworkers have recently established that this view is valid only for the particular case of conjugated chromophores which absorb similar light quanta and lie on the same straight line.
If the light quanta absorbed by the conjugated chromophores are very different, the chromophores do not interact. If the conjugated chromophores are at an angle, their absorption bands do not merge into a single band: on the contrary, they either split or move apart. The intensities of the two new bands are then determined by the angle between the interacting chromophores.
The spectra of bis-dyes which illustrate these principles are examined, and an elementary theory is given for the interaction of conjugated chromophores.
A list of 61 references is included.