From Neutral Aniline to Aniline Trication: A Computational and Experimental Study

We report density functional theory computations and photoionization mass spectrometry measurements of aniline and its positively charged ions. The geometrical structures and properties of the neutral and singly, doubly, and triply positively charged aniline are computed using density functional theory with the generalized gradient approximation. At each charge, there are multiple isomers closely spaced in total energy. Whereas the lowest energy states of both neutral and cation have the same topology C₆H₅-NH₂, the dication and trication have the C₅NH₅-CH₂ topology with the nitrogen atom in the meta- and para-positions, respectively. We compute the dissociation pathways of all four charge states to NH or NH⁺ and NH₂ or NH₂⁺, depending on the initial charge of the aniline precursor. Dissociation leading to the formation of NH (from the neutral and cation) and NH⁺ (from the dication and trication) proceeds through multiple transition states. On the contrary, the dissociation of NH₂ (from the neutral and cation) and NH₂⁺ (from the dication and trication) is found to proceed without an activation energy barrier. The trication was found to be stable toward abstraction on NH⁺ and NH₂⁺ by 0.96 and 0.18 eV, respectively, whereas the proton affinity of the trication is substantially higher, 1.98 eV. The mass spectra of aniline were recorded with 1300 nm, 20 fs pulses over the peak intensity range of 1 × 10¹³ to 3 × 10¹⁴ W cm^-2. The analysis of the mass spectra suggests high stability of both dication and trication to fragmentation. The formation of the fragment NH⁺ and NH₂⁺ ions is found to proceed via Coulomb explosion.

Effect of hydrogenation on the structure and magnetic properties of an iron oxide cluster

Hydrogenation of an iron oxide particle influences the geometrical topology and total magnetic moment and invokes different superexchange mechanisms.

A comparative study of small 3d-metal oxide (FeO)n, (CoO)n, and (NiO)n clusters

Geometrical and electronic structures of the 3d-metal oxide clusters (FeO)_n, (CoO)_n, and (NiO)_n are computed using density functional theory with the generalized gradient approximation in the range of 1 ≤ n ≤ 10.