Efficient collection of excitation energy from a linear-shaped weakly interacted perylenetetracarboxylic diimides array.

A series of novel light-harvesting compounds (namely PO-PN, PO-PO-PN and PO-PO-PO-PN) were synthesized with a linear-shaped phenoxy group-substituted perylenetetracarboxylic diimide (PO) oligomer as donor and a pyrrolidinyl group-substituted perylenetetracarboxylic diimide (PN) as acceptor. The photophysical properties of these linear-shaped compounds are investigated by steady state electronic absorption, fluorescence spectra and lifetime measurements. The ground state interactions between the neighbor PO subunits within these three compounds are weak. No matter which PO subunit is excited in these linear molecules, the excitation energy is finally collected by the PN subunit. The excitation energy can transfer as long as 47 Å without any decrease in efficiency. The energy transfer rate constants determined by femtosecond transient absorption experiments are fast and close to that of the energy transfer from B800 to B850 in LH II of natural photosynthesis.