electron regions electron geometry chart

Nitroxides, including TEMPO, are crucial in controlled radical polymerization reactions 13, 14, 15, 16 and are often used in magnetic resonance hyperpolarization methods, such as dynamic nuclear polarization, to enhance the intensity of NMR signals 17, 18, 19. The size and amphiphilic character of these can be easily adjusted by changing the structural unit in the 4-position of the piperidine ring, allowing for the use of a wide range of structurally diverse spin probes for several applications 12. ) radicals, like 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and its derivatives, are highly suitable for studying macromolecular systems, particularly nanoscale inhomogeneities in polymers, due to their ability to probe different regions based on size and polarity 10, 11.Additionally, nitroxide radicals serve as building blocks for organic magnetic materials, propagating ferromagnetic interactions within supramolecular assemblies 8, 9.Īmphiphilic nitroxide (NO Nitroxides play vital roles in the nervous system 6 and serve various functions in the immune system to counteract infectious and autoimmune diseases 7. Nitroxides are stable organic free radicals with an N–O group containing an unpaired electron 1, and they have diverse applications in chemistry, biology, and biochemistry 1, 2, 3, 4, 5.

This indicates stronger hydrogen bonding interactions between the N–O group and water molecules. The AIM analysis reveals that the N–O…H interaction in H 2O complexes has the most favorable hydrogen bond energy computed at bond critical points (3, − 1), and the planar configurations of TEMPO derivatives exhibit the highest E HB values. The studied DFT method calculations show that O-protonation is more stable than N-protonation, with an energy difference of 16.64–20.77 kcal/mol (22.80–25.68 kcal/mol) at the B3LYP (M06-2X) method. The proton affinity and gas-phase basicity of the studied compounds were computed at T = 298 K for O-protonation and N-protonation, respectively. This work also considers electron density, atomic charges, and energetic and thermodynamic properties of the studied NO radicals, and their relative stability. The study reveals that the stability of TEMPO derivatives is mainly influenced by LP(e) → σ ∗ electronic delocalization effects, with the highest stabilization observed on the oxygen atom of the nitroxide moiety. NO 2-substituted TEMPO displays high reactivity, less stability, and softer properties. Intermolecular interactions are analyzed using natural bond orbital (NBO) and atoms in molecules (AIM) techniques. The study investigates the molecular structure of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and its derivatives in the gas phase using B3LYP and M06-2X functional methods.

Electron regions electron geometry chart