Giving a Second Life to Curphey's Reagent

Thomas J. Curphey (1934-2024) made seminal contributions to sulfur chemistry with the development of a highly efficient thionation system based on phosphorus pentasulfide (P₄S₁₀) and hexamethyldisiloxane (HMDSO), now widely recognized as Curphey's reagent (CR). This reagent offers a practical, selective, and user-friendly alternative to Lawesson's reagent (LR) for the conversion of carbonyl compounds into their thiocarbonyl counterparts. In this work, we explore the application of CR in the synthesis of multithionated perylenediimide (PDI) derivatives as important n-type organic semiconductors with growing interest in photophysical and biomedical fields. Under optimized conditions, CR enables the selective formation of tri- and tetrathionated PDIs with significantly improved yields compared to LR, which typically favors lower degrees of thionation. Structural variations at the bay and imide positions reveal the role of electronic and steric effects in controlling the extent of thionation. These findings underscore the versatility of Curphey's reagent as a powerful tool for tuning the electronic properties of PDI scaffolds, highlighting its potential for the development of advanced materials for organic electronics and phototherapy. This study not only honors Professor Curphey's original insight but also revives interest in a potent yet underexploited reagent in contemporary organic synthesis.