Electrochemical Behavior of Pyridinium and N-Methyl Pyridinium Cations in Aqueous Electrolytes for CO Reduction.

The electrochemical reduction of aqueous pyridinium and N-methyl pyridinium ions is investigated in the absence and presence of CO and electrolysis reaction products on glassy carbon, Au, and Pt electrodes are studied. Unlike pyridinium, N-methyl pyridinium is not electroactive at the Pt electrode. The electrochemical reduction of the two pyridine derivatives was found to be irreversible on glassy carbon.

Formation and reactivity of 3-diazopyridinium cations and influence on their reductive electrografting on glassy carbon.

The in situ generation of 3-diazonium cations from 3-aminopyridine and their subsequent stability under experimental conditions used for electrografting of pyridine groups were investigated by spectroscopy and electrochemistry. UV spectroscopy revealed the rapid kinetics for the reaction of 3-aminopyridine with sodium nitrite in HCl to form the 3-diazopyridinium cation with a second-order rate constant of 550 ± 20 L mol(-1) s(-1) at 22 °C. UV spectroscopy showed that the 3-diazopyridinium ion was relatively unstable and its transformation into 3-hydroxypyridine was proven by (1)H NMR.