Electrosynthesis as an old and rich discipline can be easily controlled to achieve high levels of selectivity as a promising green methodology for organic chemistry. It can fulfill several important criteria that are needed to develop environmentally compatible processes. Using electric current as reagent, it can be used to replace toxic or dangerous oxidizing or reducing reagents. The total energy consumption can be reduced and unstable and hazardous reagents can be generated in situ. The thermodynamics and kinetics at solid-liquid interface can be accelerated by controlling potentials and current intensities, while the electrochemistry can simplify the purification and post-treatment processes. We particularly focus on electrochemical synthesis of novel organic electric materials. Special emphasis of our philosophy is that how to understand the polymer synthesis from electrochemical approaches. The most recent information about current research activities of our group can be found in the group's publications, but a brief introduction to each example of recent projects is provided below.
Keywords: Electrochemical Synthesis, Sequence-Controlled Polymerization, Controlled Electropolymerization, Precise Electropolymerization, Iterative Synthesis, Metallopolymer, Conducting Polymer, Polymer Brush, Optoelectronic Materials
(1) Controlled Electropolymerization
Electropolymerization is one of the most important methodologies to synthesize and develop conducting polymers. The complexity of the polymerization mechanism, ion doping processes and structural defects are considered to be symbiotic and unavoidable, making the stagnant state and huge band gap with advanced interdisciplinary research fields and important applications in the last three decades. We have provided a point of view into controlled electropolymerization by regioselective activation reactions of monomers, where self-dimerizations instead of self-electropolymerizations were utilized. The resulting dimers play a role in the connections between functional building blocks to form functional polymers on demand.
Fig. 1 Redox dimerizations of electroactive units as the connections between building blocks for controlled electropolymerizations of functional polymers. R are functional building blocks, and M are metal cores of complexes.
Current Opinion in Electrochemistry 2022, 33, 100952 (invited review)
We have first provided the effect of oxidative strength on N-alkylcarbazolyl reactions (Fig. 2). By utilizing this controllable reaction, we have developed the junction-controlled topological polymerization (Fig. 3), which is both chemical and electrochemical radicals initiated step polymerization for synthesis and process of functional polymers.
Fig. 2 Topology-controlled oxidations of carbazoles
Chem. Eur. J. 2019, 25, 1142–1151. (invited review, cover page)
Fig. 3 Junction-controlled topological polymerization
Angew. Chem. Int. Ed. 57, 4936 (2018). (hot paper)
(2) Electrochemical Iterative Synthesis (Precise Synthesis)
We have presented the electrochemical iterative synthesis of a monomer A-B through individual A–A or B–B coupling driven by electrochemical switching of positive and negative bias on a self-assembled A or B electrode.
Fig. 4 Electrochemical iterative synthesis guided by self-assembled monolayer
Angew. Chem. Int. Ed. 2018, 57, 16698–16702.
(3) Sequence-Controlled Electropolymerization
Single rich-stimuli-responsive organometallic polymers are considered to be the candidate for ultrahigh information storage and anti-counterfeiting security. However, their controllable synthesis has been an unsolved challenge. We have reported the rapidly sequence-controlled electrosynthesis of organometallic polymers with the exquisite insertion of multiple and distinct monomers.
Fig. 4 Rapidly sequence-controlled electrosynthesis
Nature Communications 2020, 11, 2530.
(4) Crystalline Monolayer of Metallopolymers
Long-range ordered nanoarchitecture of polymers is hampered by kinetic and statistical restrictions during polymer synthesis and manipulation. We have reported the monolayer nanoarchitecture of long-range crystalline metallopolymers via kinetically accelerated and statistically allowed iterative growth, guided by a self- assembled monolayer with monitoring and defect-repair abilities.
Fig. 5 Monolayer nanoarchitecture of crystalline metallopolymers by electrochemical iterative growth
Cell Reports Physical Science 2022, 3, 100852.