DFT Study of a Series of Nicotinic Acid Benzylidenehydrazide Derivatives: Structure, Stability and Reactivity

Hydrazones especially nicotinic acid benzylidenehydrazide derivatives constitute an important class of compounds that has received much interest in recent years, due to their diverse biological characteristics, such as antimicrobial, anticonvulsant, analgesic, anti-inflammatory, antiplatelet, antituberculous and antitumor activities. These compounds have donor sites such as N and O which have non-bonding doublets which allow them to coordinate with metal ions. For this purpose, ten hydrazones structures were optimized in the DFT method, using the B3LYP functional, with the basis 6-31G** for all atoms, in the gas phase using the Gaussian 09 program. The structural, energetic (energies, EHOMO-LUMO gaps), electronic (dipolar moments, atomic charges) parameters were determined. A study of the stability of the ligands was carried out based on the relative energies to study the chemical reactivity of the optimized structures, we calculated the global reactivity parameters (ionization potential, electronic affinity, electronic chemical potential, absolute hardness, overall softness and overall electrophilicity). The results obtained show that All the systems considered are stabilized by two types of electronic effect. Either; an inductive attractor effect, with a coexistence of mesomeric effects. Analysis of chemical hardness values indicates that the most stable isomers found are the hardest, with larger HOMO/LUMO gaps, and therefore less reactive. As a result, charge transfer will be predominant. The most nucleophilic systems are also determined based on the calculation of the eletrophicity and nucleophilicity indices.