Vibronic Intramolecular Resonant Energy Transfer along More than 5 nm: Synthesis of Dyads for a Re-Examination of the Distance Function of FRET.

Dyads of chromophores with orthogonal transition moments and sequences of aliphatic cage-structures as spacers were prepared where resonance energy transfer (FRET) proceeded in contrast to Förster's theory even until 58 Å. The distance dependence of the efficiency was re-examined by means of various functions; the commonly used R -6 dependence gave acceptable results, but a slightly larger exponent was more useful for practical applications.