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 I 2 and trifluoroacetic acid (TFA). Specifically, we show that 1) electron transfer occurs from 1 to give I 3 - upon the addition of I 2 , 2) proton-coupled electron transfer (PCET) from 1 to give H 3 2 •2+ and H 3 2 + upon the addition of TFA to a dichloromethane mixture of 1 and 2 , and 3) that further, stepwise treatment of 1 and 2 with I 2 and TFA promotes electron transport from 1 to give first I 3 - and then H 3 2 •2+ and H 3 2 + . The present findings are substantiated through UV-vis-NIR, 1 H 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.