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. ExBox(4+), 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 ExBox(4+) using a combination of transient absorption and femtosecond stimulated Raman spectroscopy (FSRS). Upon photoexcitation of ExBox(4+), 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 ExBox(2+) was obtained.
Department of Chemistry, Northwestern University (USA).
Scott M
SM
Dyar
Jonathan C
JC
Barnes
Michal
M
Juríček
J Fraser
JF
Stoddart
Dick T
DT
Co
Ryan M
RM
Young
Michael R
MR
Wasielewski
ExBox; cyclophanes; electron transfer; femtochemistry; photochemistry