In situ FT-IR spectroelectrochemical study of the reduction of 1,4-dinitrobenzene in room-temperature ionic liquids

• In ionic liquid, CV of 1,4-dinitrobenzene shows only one redox wave and undergoes two-step one-electron process.
• Ion-pairing forms between the electrochemical products of 1,4-dinitrobenzene and cation in ionic liquid.
• The interaction of hydrogen-bonding is much stronger than the interaction of ion-pairing.

The electrochemical reduction of 1,4-dinitrobenzene (PNB) in ionic liquid (BMIMPF6 and HMIMPF6) has been studied by cyclic voltammetry (CV) and IR spectroelectrochemistry. In ionic liquid, only one couple of redox peak is observed, but the results obtained from IR spectroelectrochemistry support the existence of intermediate (PNB−) in ionic liquid, hence it is reduced in two-step one-electron transfer. The results obtained in mixed media (CH3CN with ionic liquids) suggest that the electrochemical products (radical anion PNB− and dianion PNB2 −) can form strong ion-pairing with the cation of ionic liquid, and the interaction between the electrochemical products and BMIM+ is much stronger than HMIM+. In proton donors mixed media (ionic liquid with ethanol), the interaction of hydrogen-bonding between the electrochemical products and ethanol is much stronger than the interaction of ion-pairing between the electrochemical products and the cation of ionic liquid.