Long-range electron transfer in zinc-phthalocyanine-oligo(phenylene-ethynylene)-based donor-bridge-acceptor dyads.
In the context of long-range electron transfer for solar energy conversion, we present the synthesis, photophysical, and computational characterization of two new zinc(II) phthalocyanine oligophenylene-ethynylene based donor-bride-acceptor dyads: ZnPc-OPE-AuP(+) and ZnPc-OPE-C(60). A gold(III) porphyrin and a fullerene has been used as electron accepting moieties, and the results have been compared to a previously reported dyad with a tin(IV) dichloride porphyrin as the electron acceptor (Fortage et al. Chem. Commun. 2007, 4629). The results for ZnPc-OPE-AuP(+) indicate a remarkably strong electronic coupling over a distance of more than 3 nm. The electronic coupling is manifested in both the absorption spectrum and an ultrafast rate for photoinduced electron transfer (k(PET) = 1.0 × 10(12) s(-1)). The charge-shifted state in ZnPc-OPE-AuP(+) recombines with a relatively low rate (k(BET) = 1.0 × 10(9) s(-1)). In contrast, the rate for charge transfer in the other dyad, ZnPc-OPE-C(60), is relatively slow (k(PET) = 1.1 × 10(9) s(-1)), while the recombination is very fast (k(BET) ≈ 5 × 10(10) s(-1)). TD-DFT calculations support the hypothesis that the long-lived charge-shifted state of ZnPc-OPE-AuP(+) is due to relaxation of the reduced gold porphyrin from a porphyrin ring based reduction to a gold centered reduction. This is in contrast to the faster recombination in the tin(IV) porphyrin based system (k(BET) = 1.2 × 10(10) s(-1)), where the excess electron is instead delocalized over the porphyrin ring.
Physical Chemistry, Department of Chemistry-Ångström, Uppsala University, Box 523, 751 20 Uppsala, Sweden.
Erik
E
Göransson
Julien
J
Boixel
Jérôme
J
Fortage
Denis
D
Jacquemin
Hans-Christian
HC
Becker
Errol
E
Blart
Leif
L
Hammarström
Fabrice
F
Odobel
D004579:Electron Transport; D004583:Electrons; D037741:Fullerenes / Q000737:chemistry; D007211:Indoles / Q000737:chemistry*; D054833:Isoindoles; D008958:Models, Molecular; D050607:Organogold Compounds / Q000737:chemistry; D009942:Organometallic Compounds / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D011166:Porphyrins / Q000737:chemistry; D013057:Spectrum Analysis; D017967:Zinc Compounds
D037741:Fullerenes; D007211:Indoles; D054833:Isoindoles; D050607:Organogold Compounds; D009942:Organometallic Compounds; D011108:Polymers; D011166:Porphyrins; D017967:Zinc Compounds; C473966:poly(phenylene ethynylene); C052159:Zn(II)-phthalocyanine