FT-IR spectroelectrochemical study of the reduction of 1,4-dinitrobenzene on Au electrode: Hydrogen bonding and protonation in proton donor mixed media

The electrochemical behavior of 1,4-dinitrobenzene (1,4-PNB) on the Au electrode was investigated by cyclic voltammetry (CV), in situ FT-IR spectroelectrochemistry, cyclic voltabsorptometry (CVA) and derivative cyclic voltabsorptometry (DCVA) techniques. In aprotic media, 1,4-dinitrobenzene is reversibly reduced in two-step one-electron transfer. A series of IR absorption bands at 1056, 1210, 1341, 1356, 1464 and 1549 cm−1, tracing to PNB; PNB− and PNB2− are observed. In the presence of proton donors mixed media, with increasing concentrations of proton donors, hydrogen-bonding and protonation process are found successively. The values of combining proton donors with per PNB2− to form hydrogen-bonding are estimated by using electrochemical parameters. The result of forming aromatic nitroso compound is supported by tracing the change of IR absorption bands at 1149 and 1587 cm−1 at high concentration of proton donors. Based on CVA and DCVA techniques, it is clearly distinguished that the mechanisms of electrochemical reduction of PNB are elaborated in different systems.

► 1,4-Dinitrobenzene electrochemical reduction on the Au electrode is explored. ► Radical anion (PNB−) is found both in aprotic media and in proton donors mixed media. ► The H-bonding forming between PNB−, PNB2− and proton donors in low donors concentration. ► The protonation of PNB2− occurs in high concentration proton donor mixed media.