EXCITON COUPLED CIRCULAR DICHROISM OF INTRAMOLECULARLY INTERACTING BIS-PORPHYRIN CHROMOPHORES IN PEPTIDE CONJUGATES:DISTANCE AND ORIENTATION EFFECTS

摘要

When two chromophores are chirally oriented and close enough to one another in space, their excited states couple and become non-degenerate. This phenomenon, termed exciton coupling, produces a typical, bisignate, CD curve. The intensity of the CD couplet is dependent on the molar extinction coefficient and the distance between the interacting chromophoric moieties, while the sign is governed by the angle between the effective electron transition moments. In particular, exciton coupling over a long distance can be observed only with strongly absorbing chromophores, e. g. porphyrin derivatives, characterized by their extremely intense and sharp Soret band near 415 nm .