| Abstract
| - Molecular photonic wires, which absorb light and undergo excited-state energy transfer, are ofinterest as biomimetic models for photosynthetic light-harvesting systems and as molecular deviceswith potential applications in materials chemistry. We describe the stepwise synthesis of fourmolecular photonic wires. Each wire consists of an input unit, transmission element, and outputunit. The input unit consists of a boron-dipyrrin dye or a perylene-monoimide dye (linked either atthe N-imide or the C9 position); the transmission element consists of one or three zinc porphyrinsaffording short or long wires, respectively; and the output unit consists of a free base (Fb) porphyrin.The components in the arrays are joined in a linear architecture via diarylethyne linkers (anethynylphenyl linker is attached to the C9-linked perylene). The wires have been examined bystatic absorption, static fluorescence, and time-resolved absorption spectroscopy. Each wire (withthe exception of the C9-linked perylene wire) exhibits a visible absorption spectrum that is thesum of the spectra of the component parts, indicating the relatively weak electronic coupling betweenthe components. Excitation of each wire at the wavelength where the input unit absorbspreferentially (typically 480−520 nm) results in emission almost exclusively from the Fb porphyrin.The static emission and time-resolved data indicate that the overall rate constants and quantumefficiencies for end-to-end (i.e., input to output) energy transfer are as follows: perylene-(N-imide)-linked short wire, (33 ps)-1 and >99%; perylene-(C9)-linked short wire, (26 ps)-1 and >99%; boron-dipyrrin-based long wire, (190 ps)-1 and 81%; perylene-(N-imide)-linked long wire, (175 ps)-1 and86%. Collectively, the studies provide valuable insight into the singlet−singlet excited-state energy-transfer properties in weakly coupled molecular photonic wires.
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