Abstract
| - We present the synthesis and characterization of new light-harvesting arrays containing two, four,or eight perylene-monoimide accessory pigments attached to a zinc porphyrin. Each perylene issubstituted with one or three 4-tert-butylphenoxy substituents. A 4,3‘- or 4,2‘-diarylethyne linkerjoins the perylene N-imide position and the porphyrin meso-position, affording divergent orconvergent architectures, respectively. The architectures are designed to provide high solubility inorganic media and facile perylene-to-porphyrin energy transfer, while avoiding charge-transferquenching of the excited porphyrin product. For the array containing four perylenes per porphyrinin both nonpolar (toluene) and polar (benzonitrile) media and for the array containing eight perylenesper porphyrin in toluene, the photoexcited perylene-monoimide dye (PMI*) decays rapidly (∼3.5ps) and predominantly (≥90%) by energy transfer to the zinc porphyrin to form the excited zincporphyrin (Zn*), which has excited-state characteristics (lifetime, fluorescence yield) comparable(within ∼10%) to those of the isolated chromophore. For the array containing eight perylenes inbenzonitrile, PMI* decays ∼80% by energy transfer (forming Zn*) and ∼20% by hole transfer(forming PMI- Zn+); Zn* subsequently decays ∼20% by electron transfer (also forming PMI- Zn+)and ∼80% by the normal routes open to the porphyrin monomer (intersystem crossing, internalconversion, fluorescence). In addition to rapid and efficient perylene-to-porphyrin energy transfer,the broad blue-green to yellow absorption of the perylene dyes complements the blue absorption ofthe porphyrin, resulting in excellent light harvesting across a significant spectral region. Collectively,the work described herein identifies multiperylene−porphyrin arrays that exhibit suitablephotochemical properties for use as motifs in larger light-harvesting systems.
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