Synthesis and tunability of highly electron-accepting, N-benzylated "phosphaviologens".
We report a structure-property study on phosphoryl-bridged viologen analogues with a remarkably low reduction threshold. Utilizing different benzyl groups for N-quaternization, we were able to confirm the p-benzyl substituent effect on the electronic tunability of the system while maintaining the characteristic chromic response of viologens with two fully reversible one-electron reductions. Due to the considerably increased electron-acceptor properties of the phosphoryl-bridged bipyridine precursor, N-benzylation was found to be very challenging and required the development of new synthetic strategies toward the target viologen species. This study also introduces a new and convenient way for the anion exchange of viologen systems by utilizing methyl triflate. Finally, the practical utility of the new species was verified in simplified proof-of-concept electrochromic devices.
Department of Chemistry and Centre for Advanced Solar Materials, University of Calgary , 2500 University Drive Northwest, Calgary, Alberta T2N 1N4, Canada.
Monika
M
Stolar
Javier
J
Borau-Garcia
Mark
M
Toonen
Thomas
T
Baumgartner