The Polarography of Quinoxaline¹

Voltammetry study of quinoxaline in aqueous electrolytes

“…By rounding each entry for n in Table 3, the nearest integer value is always n = 2, providing strong evidence that the quinoxaline redox processes incorporated two electron transfers. This result is in agreement with previous literature which reported two electron transfer behavior in aqueous electrolytes [29][30][31][32][33], although only recent work by Aleksi c et al quantitates the process [32]. Thus, on this basis, we conclude that quinoxaline exhibits a two-electron transfer process during redox reactions, leading to a theoretical capacity of 410 mAh g À1 .…”

“…11, which implies that the quinoxaline redox mechanism involved H + . Similar results of pH dependent redox potentials for quinoxaline derivatives were observed in buffered aqueous experiments [29,32,33] and in a study of quinoxaline voltammetry in DMF / water-mixed acidic media [45].…”

“…First consider the unstable redox behavior in acidic electrolytes. Prior studies hypothesized that under acidic conditions, quinoxaline undergoes a coupled 2 e À / 2H + electrochemical reaction where quinoxaline reduces to 1,4-dihydroquinoxaline [29][30][31][32]. Prior work also noted that 1,4-dihydroquinoxaline can undergo a H + catalyzed chemical reaction to produce 1,4-dihydroquinalin-1-ium, followed by an additional electrochemical reaction to an unagreed upon quinoxaline derivative [30][31][32].…”

“…Aqueous quinoxaline was recently applied as a redox active compound in a solar-rechargeable RFB device, however, exploration of quinoxaline electrochemical behavior was not the focus of that study [28]. Finally, several studies investigated quinoxaline electrochemical behavior in acidic and near-neutral electrolytes with a focus on determining kinetic rate parameters and related organic chemistry [29][30][31][32][33].…”

Electrochemical behavior of conjugated quinoxaline derivatives

“…The reduction of quinoxalines in aprotic media produces the radical species [11][12][13][14], and is different from that in protic media [15][16][17][18][19][20][21][22]. For this reason, 98% H 2 SO 4 was used to adjust the solution pH and to act as the proton source of the electrochemical reaction.…”