Quinolones and fluoroquinolones are heterocyclic compounds with important antibacterial properties, and they have been extensively used in medicinal chemistry to treat diverse bacterial infections. However, their clinical applications have been limited by several factors. On one side, there is an increasing number of resistant bacterial strains. On the other side, some of these heterocyclic compounds have shown several adverse effects such as photocarcinogenic cutaneous reactions, with the development of skin tumors. These adverse properties have motivated a large number of studies on the photophysical, photochemical and phototoxic properties of these compounds. In this review, several important chemical aspects about quinolones and fluoroquinolones are discussed. In the first sections, their basic structure is presented, along with some important physicochemical properties. In the next sections, their photochemical and photophysical processes are discussed. Upon photolysis in aqueous neutral conditions, these heterocyclic compounds generate several highly reactive intermediates that could initiate diverse reactions with molecules. In a biological environment, quinolones and fluoroquinolones are known to associate with biomolecules and generate complexes. Within these complexes, photophysical and photochemical processes generate intermediates, accelerating diverse reactions between biomolecules and these heterocyclic compounds. For several decades, diverse fluoroquinolones have been prepared for the treatment of a variety of bacterial infections. However, their prescription has been restricted due to the associated severe side effects. In the last decade, new derivatives have been developed and are already in use. Their introduction into actual practice extends the number of antibiotics and provides new options for difficult-to-treat infections. Thus, for new pharmaceutical compounds to be used in medicinal practice, it is important to investigate their biological activity, as well as other biological properties and adverse effects, such as phototoxicity.

Introduction: Organic azides are valuable precursors of 1,2,3-triazoles, a class of heter-ocyclic compounds with broad biological relevance and diverse applications as functional materi-als. The understanding of the electronic effects of substituents on azide reactivity is crucial for optimizing copper(I)-catalyzed azide–alkyne cycloaddition processes. Methods: A series of 1,2,3-triazoles were synthesized via copper(I)-catalyzed azide–alkyne cy-cloaddition employing microwave radiation as an alternative energy source. Computational studies were performed using Molecular Electrostatic Potential maps and the dual descriptor at the B3LYP/6-311G(d,p) level of theory to analyze the electronic structure of the aromatic azides em-ployed as precursors of 1,2,3-triazoles. Results: Compounds 3a and 3e-g were obtained in moderate to good yields (72-78 %), whereas strongly electron-withdrawing substituents avoided the formation of products 3b-d. The computa-tional analysis revealed differences in the distribution charge on the azide group. Discussion: The absence of products 3b-d is attributed to the presence of strong electron-withdraw-ing substituents. According to the dual descriptor, the formation of the metallacycle between azide and alkyne is favored when N and N exhibit predominantly electrophilic and nucleophilic char-acters, respectively, which promotes the mesomeric effect of the azide. Conclusion: The molecular electrostatic potential maps and dual descriptor revealed that for the evaluated compounds, electron-withdrawing substituents modify the distribution of the electronic density on the azide group. The phenylazides with enhanced positive character at Nβ and higher electron density at Nγ showed better reactivity toward triazole formation. The integration of exper-imental and computational approaches provides insights into the electronic effects in azide reactiv-ity and supports the design of 1,2,3-triazole compounds.