TY - JOUR AU - Duvanel, Guillaume AU - Grilj, Jakob AU - Vauthey, Eric TI - Ultrafast Long-Distance Excitation Energy Transport in Donor-Bridge-Acceptor Systems PY - 2013 JF - The Journal of Physical Chemistry A JA - The J. Phys. Chem. A SN - 1089-5639 VL - 117 IS - 5 SP - 918 EP - 928 L1 - http://pubs.acs.org/doi/pdf/10.1021/jp311540x L2 - http://pubs.acs.org/doi/full/10.1021/jp311540x L3 - http://pubs.acs.org/doi/abs/10.1021/jp311540x L4 - http://www.unige.ch/sciences/chifi/publis/pics/double/ref01335.png M3 - 10.1021/jp311540x UR - http://dx.doi.org/10.1021/jp311540x N2 - The excited-state dynamics of two energy donor–bridge–acceptor (D–B–A) systems consisting of a zinc tetraphenylporphyrin (ZnP) and a free base tetraphenylporphyrin (FbP) bridged by oligo-p-phenyleneethynylene units with different substituents has been investigated using ultrafast spectroscopy. These systems differ by the location of the lowest singlet excited state of the bridge, just above or below the S2 porphyrin states. In the first case, Soret band excitation of the porphyrins is followed by internal conversion to the local S1 state of both molecules and by a S1 energy transfer from the ZnP to the FbP end on the 10 ns time scale, as expected for a center-to-center distance of about 4.7 nm. On the other hand, if the bridge is excited, the energy is efficiently transferred within 1 ps to both porphyrin ends. Selective bridge excitation is not possible with the second system, because of the overlap of the absorption bands. However, the time-resolved spectroscopic data suggest a reversible conversion between the D*(S2)–B–A and D–B*(S1)–A states as well as a transition from the D–B*(S1)–A to the D–B–A* states on the picosecond time scale. This implies that the local S2energy of the ZnP end can be transported stepwise to the FbP end, i.e., over about 4.7 nm, within 1 ps with an efficiency of more than 0.2. ID - 1335 ER -