Roles of allene-group in an intramolecular charge transfer character of a short fucoxanthin homolog as revealed by femtosecond pump-probe spectroscopy

Ultrafast excited state dynamics of the short fucoxanthin homolog with four conjugated double bonds and its allene-modified analog in various solvents have been studied by femtosecond pump-probe spectroscopy. The results clarified that the short fucoxanthin homolog exhibits a strong intramolecular charge transfer character in an excited manifold even in a nonpolar solvent. Then, the data show that a modification of the allene-group induced the lifetime shortening of the lowest singlet state of the short fucoxanthin homolog. This implies that the allene-group enhances the ICT character of the short fucoxanthin homolog.