Proton-coupled electron transfer (PCET) reactions occur in many reactions of global importance, including H2 evolution, among other applications. Surprisingly, knowledge gaps remain in our fundamental understanding of PCET and CPET reactions. In recent studies graphitic electrode systems that are modified by o-phenylenediamines have been singled out as an ideal platform for studying single-site CPET. Although this CPET experimental platform has been established, synthetic access to 4,5-o- phenylenediamines remains limited. Herein we discuss three distinct synthetic strategies aimed toward developing a modular synthetic route to symmetrical and asymmetrical 4,5-o-phenylenediamines. We demonstrate the utility of 4,5-o-dinitrobenzenes as relatively stable precursors to 4,5-o- phenylenediamines and a modular route to make 4,5-o-phenylenediamines in just 2-4 steps from commercial material.

The earth faces a pressing environmental challenge with the annual pollution of millions of tons of plastic waste. This issue is exacerbated by the inherent characteristics of plastics, including their high thermal stability and low biodegradability. In response, the scientific community has dedicated significant efforts to combat plastic pollution and develop environmentally sustainable soft materials. A promising approach is the creation of soft materials that can be efficiently recycled within a closed-loop system, thereby minimizing their chemical impact on the environment. This study introduces polyacylhydrazones as a novel class of soft materials with the potential for closed-loop recycling. Closed-loop polymers are sought after as sustainable materials of the future. Dynamic covalent polymers have the potential to act as closed-loop materials because of their reversible linkages. However, very few materials currently exist. Polyacylhydrazones have been explored as dynamic covalent polymers with multiple uses. Herein we demonstrate the first study that shows their potential as closed-loop materials. We show novel synthetic techniques that produce hydrophobic polyacylhydrazones with unique length and morphology under kinetic control. We demonstrate preliminary potential applications. Finally, we show the facile decom-position of a benzylic hydrazone bond down to monomeric units and extraction-based separation, without the need for chromatography. This work advances our understanding of these innovative materials and validates benzylic polyacylhydrazones as “closed-loop” materials for a more sustainable future.