Electron Accumulative Molecules

With the goal to produce molecules
with high electron accepting
capacity and low reorganization energy upon gaining one or more electrons,
a synthesis procedure leading to the formation of a B–N­(aromatic)
bond in a cluster has been developed. The research was focused on
the development of a molecular structure able to accept and release
a specific number of electrons without decomposing or change in its
structural arrangement. The synthetic procedure consists of a parallel
decomposition reaction to generate a reactive electrophile and a synthesis
reaction to generate the B–N­(aromatic) bond. This procedure
has paved the way to produce the metallacarboranylviologen [M­(C2B9H11)­(C2B9H10)-NC5H4-C5H4N-M′(C2B9H11)­(C2B9H10)] (M = M′ = Co, Fe and M = Co and M′ = Fe)
and semi­(metallacarboranyl)­viologen [3,3′-M­(8-(NC5H4-C5H4N-1,2-C2B9H10)­(1′,2′-C2B9H11)] (M = Co, Fe) electron cumulative molecules. These
molecules are able to accept up to five electrons and to donate one
in single electron steps at accessible potentials and in a reversible
way. By targeted synthesis and corresponding electrochemical tests
each electron transfer (ET) step has been assigned to specific fragments
of the molecules. The molecules have been carefully characterized,
and the electronic communication between both metal centers (when
this situation applies) has been definitely observed through the coplanarity
of both pyridine fragments. The structural characteristics of these
molecules imply a low reorganization energy that is a necessary requirement
for low energy ET processes. This makes them electronically comparable
to fullerenes, but on their side, they have a wide range of possible
solvents. The ET from one molecule to another has been clearly demonstrated
as well as their self-organizing capacity. We consider that these
molecules, thanks to their easy synthesis, ET, self-organizing capacity,
wide range of solubility, and easy processability, can find important
application in any area where ET is paramount.