Experimental determination of conjugation lengths in long polyene chains

Since the low energy absorption spectrum of a linear polyene is dominated by the strongly allowed 1 1Ag→1 1Bu transition (S0 to S2), it can be reconstructed for any chain length if the 0–0 band excitation energy, the band profile, and intensity are known. From this premise, this paper uses information developed in high resolution experiments on well-defined linear polyenes to extract the distribution of effective conjugation lengths from absorption spectra of solutions of long linear polyenes. These distributions are found to be dominated by short conjugation lengths.