Tuning the Rates of Long‐Range Charge Transfer across Phenylene Wires

Abstract

Walking a tight wire: Phototriggered charge transfer across a tetra‐p‐dimethoxybenzene bridge is three orders of magnitude faster than that across a structurally similar tetra‐p‐xylene spacer, despite equal reaction driving forces in both cases (see picture). This result is interpreted in terms of markedly different donor–bridge energy gaps.magnified image

Fluoride binding to an organoboron wire controls photoinduced electron transfer

“…1a , 2g , 4g , 30 An alternative and equally valid view (discussed in more detail below) is that the barrier height associated with the tunneling process depends crucially on the redox potentials of the bridging units. 1a , 2g , 31 As noted in the introduction, F – binding to organoboron units strongly affects their HOMO/LUMO energies due to disruption of p π –π* conjugation between the boron atom and the π-system to which it is attached. 7b , f , s Moreover, and perhaps even more importantly, the resulting organofluoroborate species is anionic, and consequently the LUMO is energetically raised compared to the organoboron unit before F – addition.…”

Electron transfer within 1,3‐dinitrobenzene radical anions: electron hopping or superexchange?

“…Decreasing the reduction potential of the bridge in anionic MV compounds lowers the energy gap between the SOMO of the donor (the reduced nitro group in this case) and the LUMO of the bridge. The enhancement of electronic coupling by lowering the energy gap to the bridge is a well‐known effect in MV chemistry …”

Stereoretention in styrene heterodimerisation promoted by one-electron oxidants

“…86,87 Nevertheless, ET barriers on the order of 1-3 kcal mol À1 have been observed experimentally. [88][89][90] This suggests that this product-forming SET step is not overall rate-limiting. The reverse of this elementary step, oxidation of the cyclic products by the anethole radical cation, has an estimated (MH) barrier of about 14 kcal mol À1 .…”