Substituent effect on the properties of pyridine-N-oxides

Abstract

Quantum chemical calculations using DFT (B3LYP and PBE0) and MP2 approximations with ccpVTZ basis sets have been performed for 10 N-oxides with different substituents. The influence of the substituent nature on the geometry and redox properties of the compound, as well as on the parameters of the semipolar N ? O bond, has been analyzed. The presence of strong electron-withdrawing substituents on the pyridine ring results in increase in the electron affinity value and, consequently, in the enhancement of the antifungal activity of the compound. The compounds with the electron-donating substituents have greater complexation ability. The main conclusions based on the calculation results are in good agreement with the available experimental data.

The molecular structure of 4-methylpyridine-N-oxide: Gas-phase electron diffraction and quantum chemical calculations

“…[14,15] and in this work. The parameters obtained in our research is in a good agreement with the theoretical results (therein and [18]) and, also, with the parameters for non-substituted N-oxide in contrast to the values recommended by Chiang J. F. et al [15]. Furthermore, the parameters of free molecules of PyO [14] and 4-Me-PyO obtained in this work are in a good agreement with the crystal structures [34,35].…”

“…One can conclude that in this case the nucleophilic properties of the molecule increase. Furthermore, as it has been mentioned previously [18] the introduction of electron-donating substituents to the heterocyclic ring of N-oxides results in increasing ability for complex formation. Our experimental and calculated data (Tables 3, 6 and 7) reveal the incorrectness of the authors of [15] in their conclusion about more single NeO bond character in 4-MePyO.…”

“…the interactions between p(CeC) and p*(CeC) and between p(CeC) and p*(CeN). The nature of semipolar NeO bond was explained in detail [18]. The largest second order interaction energies (E 2 ) in both molecules correspond to the LP3(O) interaction with the antibonding p*(NeC) NBO ( Fig.…”

“…The crystal structures of PyO, 4-NO 2 PyO and 4-MePyO have been studied by X-ray crystallography [16,17]. The quantum chemical study of the substituent effect on the properties of pyridine-N-oxides has been performed for ten compounds with different substituents [18]. The comparative analysis of structural data obtained by different methods suggests that the molecular parameters of N-oxides obtained by GED [15] look rather strange.…”

Strategic Approach on N‐Oxides in Gold Catalysis – A Case Study

“…It is evident, therefore, that the reaction behavior is independent of the usage of isolated or in situ generated gold(I) complexes. In a first set of experiments differently substituted pyridine derivatives bearing one or more electronwithdrawing substituents were converted ( Table 2; entries 1-10, [13][14][15][16][17][18][19]. Unexceptionally, a significantly increased catalytic activity was obtained compared to the gold(I) complexes of the unsubstituted pyridine ( Table 2; entry 23) and quinoline ( Table 2; entry 22).…”