Chemically Mediated Artificial Electron Transport Chain

Electron transport chains (ETCs) are ubiquitous in nearly
all living
systems. Replicating the complexity and control inherent in these
multicomponent systems using ensembles of small molecules opens up
promising avenues for molecular therapeutics, catalyst design, and
the development of innovative energy conversion and storage systems.
Here, we present a noncovalent, multistep artificial electron transport
chains comprising cyclo[8]­pyrrole (1), a meso-aryl hexaphyrin(1.0.1.0.1.0) (naphthorosarin 2), and
the small molecules I2 and trifluoroacetic acid (TFA).
Specifically, we show that 1) electron transfer occurs from 1 to give I3– upon the addition
of I2, 2) proton-coupled electron transfer (PCET) from 1 to give H32•2+ and H32+ upon the addition of
TFA to a dichloromethane mixture of 1 and 2, and 3) that further, stepwise treatment of 1 and 2 with I2 and TFA promotes electron transport from 1 to give first I3– and then H32•2+ and H32+. The present findings are substantiated through
UV-vis-NIR, 1H NMR, electron paramagnetic resonance (EPR)
spectroscopic analyses, cyclic voltammetry studies, and DFT calculations.
Single-crystal structure analyses were used to characterize compounds
in varying redox states.