Electron Transfer and Multi‐Electron Accumulation in ExBox4+

Molecules capable of accepting and storing multiple electrons are crucial components of artificial photosynthetic systems designed to drive catalysts, such as those used to reduce protons to hydrogen. ExBox⁴⁺, a boxlike cyclophane comprising two π‐electron‐poor extended viologen units tethered at both ends by two p‐xylylene linkers, has been shown previously to accept an electron through space from a photoexcited guest. Herein is an investigation of an alternate, through‐bond intramolecular electron‐transfer pathway involving ExBox⁴⁺ using a combination of transient absorption and femtosecond stimulated Raman spectroscopy (FSRS). Upon photoexcitation of ExBox⁴⁺, an electron is transferred from one of the p‐xylylene linkers to one of the extended viologen units in ca. 240 ps and recombines in ca. 4 ns. A crystal structure of the doubly reduced species ExBox²⁺ was obtained.