Modulating Electrochemical and Optical Properties of Oligothiophenes via Subtle Changes in Donnor ‐ Acceptor Sequence

Abstract This study explores the synthesis and electronic properties of oligothiophenes derived from the 3‐hexyloxy‐4‐cyanothiophene building block. By exploiting the differential reactivity of thiophene's α‐positions, regioisomeric derivatives were synthesized with varying donor–acceptor sequences. These derivatives displayed distinct optical and electrochemical characteristics based on the relative positions of cyano acceptor and hexyloxy donor groups. Spectroscopic, computational, and electrochemical analyses revealed that substituent placement critically affects electronic properties, such as HOMO‐LUMO levels and band gaps. The introduction of alkoxy groups at external β‐sites promoted coupling reactions upon oxidation, leading to polymerization or dimerization. Conversely, cyano groups at these positions stabilized radical cations and dications, suppressing further reactions. These findings offer insights into designing conjugated systems with tunable properties, emphasizing the importance of substituent positioning for optimizing performance.