## 4 Conclusions  
In this work, the electrooxidation ability of nine pyridones was evaluated using CV and SWV in BR aqueous buffer solutions on a GC electrode. The electrochemical experiments showed that the structural requirement for electrochemical activity was the presence of a hydroxyl group in position 6 of the pyridine ring. UV-Vis spectra of pyridine (**9**) containing a pyridinium substituent in position 3 indicated specific pH-dependent structures, wherein the protonated form (positively charged) was dominant in an acidic medium, while with an increase in pH value, the ratio of the deprotonated (zwitter-ionic) form increased. DFT calculations revealed that in the solution, the most stable protonated form belonged to the structure with a proton present in position 5 of the pyridine ring, while in an alkaline medium only one deprotonated form existed. CV experiments showed that the electrochemical activity of pyridine **9** was highly affected by solution pH value. In an acidic medium, CV peaks were ascribed to the oxidation of the most stable protonated form, while in an alkaline medium, peaks originated from the oxidation of the deprotonated form. It is suggested that the deprotonated form was more electrochemically active than the protonated one. The experiments revealed that the electrooxidation of pyridine **9** was a two-electron and one-proton process. SWV also indicated that the investigated molecules were more electrochemically active in an alkaline medium, evidenced by higher current values as well as peak potential shifts  
Figure 7: Distribution maps of the spin density obtained for the radicals formed in protonated form **A** and deprotonated form **D** of compounds **5–9**. towards less positive values with respect to voltammograms in an acidic medium. This was in accordance with DFT calculations suggesting that the radicals of deprotonated forms were more stable. Although groups in position 3 of the pyridone ring did not directly participate in the electrooxidation process, they indirectly stabilized the formed radicals through their electron-accepting ability. The highest current values obtained for 3-amido-substituted pyridone in an acidic medium are ascribed to the lower capability of the amido group to withdraw electrons, wherein radicals were more easily formed when compared to 3-cyano (5, 6 and 7) and 3-pyridinium (9) analogues. On the other hand, the positive charge in molecule 9 makes radical formation more challenging, as reflected in the highest potential value. This work will furnish the essentials of their structure-property relationship and enable a general understanding of properties affected by the nature of these compounds, thus ensuring their application across diverse domains, such as drug development, materials engineering and catalyst design. The work in this study highlights the use of SWV and CV complemented by DFT calculations in order to define the structural fragments of 2-pyridone derivatives responsible for their electrochemical activity, representing a comprehensive framework for the characterization of the electrochemical attributes of heterocyclic compounds, namely compounds incorporating 2-pyridone fragments. This work not only advances their fundamental understanding but also enables their application across diverse domains such as drug development, materials engineering and catalyst design through tailored molecular modifications based on a profound grasp of their electronic structure-property relationship. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app131810276/s1](https://www.mdpi.com/article/10.3390/app131810276/s1)]([https://www.mdpi.com/article/10.3390/app131810276/s1](https://www.mdpi.com/article/10.3390/app131810276/s1)): Figure S1: CVs of \(5\times 10^{-4}\) M 5-8 in BR buffer at v = 50 mV s\({}^{-1}\); Figure S2: A putative mechanism of the electrooxidation of compound 9.