Binding of Butadiene Molecules Mediated by Ni Atom and Ni+ Ion

Silicon-doped graphene: an effective and metal-free catalyst for NO reduction to N2O?

Density functional theory (DFT) calculations were performed on the NO reduction on the silicon (Si)-doped graphene. The results showed that monomeric NO dissociation is subject to a high barrier and large endothermicity and thus is unlikely to occur. In contrast, it was found that NO can easily be converted into N2O through a dimer mechanism. In this process, a two-step mechanism was identified: (i) the coupling of two NO molecules into a (NO)2 dimer, followed by (ii) the dissociation of (NO)2 dimer into N2O + O(ad). In the energetically most favorable pathway, the trans-(NO)2 dimer was shown to be a necessary intermediate with a total energy barrier of 0.464 eV. The catalytic reactivity of Si-doped graphene to NO reduction was interpreted on the basis of the projected density of states and charge transfer.

Ultrafast Energy Transfer and Strong Dynamic Non-Condon Effect on Ligand Field Transitions by Coherent Phonon in γ-Fe2O3 Nanocrystals

Relaxation dynamics of an optically excited ligand field state and strong modulation of oscillator strengths of ligand field transitions by coherent acoustic phonon in gamma-Fe(2)O(3) nanocrystals were investigated through transient absorption measurements. A near-infrared pump beam prepared the lowest excited ligand field state of Fe(3+) ions preferentially on the tetrahedral coordination site. A time-delayed visible probe beam monitored the dynamics of various ligand field transitions and modification of their oscillator strengths by a coherent lattice motion. Transient absorption data exhibited dynamic features of a few distinct time scales, 100 fs, 1 ps, and 17-100 ps, as well as intense oscillatory features resulting from a coherent acoustic phonon. The initial decay of the induced absorption in 100 fs has been attributed to the exchange interaction-mediated energy transfer from the tetrahedral to octahedral Fe(3+) sites. The dynamics of slower time scales were assigned to the vibrational and electronic relaxations. Excitation of the ligand field state created a coherent acoustic phonon resulting in unusually intense modulation of the transient absorption signal despite its predominantly local nature and relatively small vibronic coupling. Excitation of each Fe(3+) ion in the nanocrystal was estimated to modulate up to 60% of its contribution to the total absorption intensity of the nanocrystal. The intense modulation of the absorption has been attributed to the strongly modulated oscillator strength of the ligand field transitions rather than oscillating Frank-Condon overlap. Dynamic modification of the metal-ligand orbital overlap and exchange interaction between the neighboring metal ions are the main factors responsible for the modulation of the oscillator strength.

Thermochemistry, bonding, and reactivity of Ni+ and Ni2+ in the gas phase

In this review, we present a general overview on the studies carried out on Ni(+-)- and Ni(2+)-containing systems in the gas phase since 1996. We have focused our attention in the determination of binding energies in parallel with an analysis of the structure and bonding of the complexes formed by the interaction of Ni(+) with one ligand, or in clusters where this metal ion binds several identical or different ligands. Solvation of Ni(2+) by different ligands is also discussed, together with the theoretical information available of doubly charged Ni-containing species. The final section of this review is devoted to an analysis of the gas-phase uni- and bimolecular reactivity of Ni(+) and Ni(2+) complexes.