Energy Transfer, Excited-State Deactivation, and Exciplex Formation in Artificial Caroteno-Phthalocyanine Light-Harvesting Antennas

• DOI: 10.1021/jp071010q
• Publication Date: 2007-05-16T11:01:18Z
• Authors: Rudi Berera; Ivo H. M. van Sto...; Gerdenis Kodis; Amy E. Keirstead; Smitha Pillai; Christian Herrero; Rodrigo E. Palacios; Mikas Vengris; Rienk van Grondelle; Devens Gust; Thomas A. Moore; Ana L. Moore; John T. M. Kennis
• Keywords: Excimer

We present results from transient absorption spectroscopy on a series of artificial light-harvesting dyads made up zinc phthalocyanine (Pc) covalently linked to carotenoids with 9, 10, or 11 conjugated carbon−carbon double bonds, referred as 1, 2, and 3, respectively. assessed the energy transfer excited-state deactivation pathways following excitation strongly allowed carotenoid S2 state function conjugation length. The rapidly relaxes S* S1 states. In all systems we detected new pathway within manifold in which acts an intermediate → internal conversion sub-picosecond time scale. dyad novel type collective carotenoid−Pc electronic is observed that may correspond excited state(s)−Pc Q exciplex. exciplex only upon direct nonfluorescent. two singlet states, S1, contribute singlet−singlet Pc, making process very efficient (>90%) while for 2 3 channel precluded capable transferring Pc. latter systems, lifetime first Pc dramatically shortened compared 9 double-bond model indicating strong quencher energy.