Paired Electrosynthesisat Interdigitated MicrobandArray Electrodes without Intentionally Added Electrolyte: C–CCoupling of Dicyanobenzenes with Methanol

The formation of substituted benzyl alcohols from dicyanobenzenes and methanol (C–C coupling) is demonstrated as a model system for paired electrosynthesis and investigated at interdigitated microband array electrodes in a microreactor with/without intentionally added supporting electrolyte. A Pt–Pt microband array with 5 μm bands separated by 5 μm gaps is employed in a dimethyl sulfoxide (DMSO) solvent. Yields are optimized to approximately 50% at the point of 100% conversion. The mechanism is investigated by employing isotope labeling (CD₃OD, CH₃OD, <i>d</i>₆-DMSO, ¹³CH₃OH). The methylene group (¹²C or ¹³C) is obtained with H₂, D₂, and DH substitution patterns, and a hypothesis for a corresponding mechanism is discussed aided with density functional theory (DFT) calculations. Implications for sustainable electrosynthesis at paired microband electrodes are discussed.