Unusual solvation through both p-orbital lobes of a carbene carbon

As a result of a configurational space search done to explain the experimental evidence of transient specific solvation of singlet fluorocarbene amide with tetrahydrofuran, we found that the most stable structures consist in a group in which each oxygen of two tetrahydrofuran molecules act as electron donor to its respective empty p-orbital lobe of the carbene carbon atom, located at each side of the carbene molecular plane. This kind of species, which to our knowledge has not been reported before, explains very well the particular experimental characteristics observed for the transient solvation of this system. We postulate that the simultaneous interaction to both p-orbital lobes seems to confer a special stability to the solvation complexes, because this situation moves away the systems from the proximity of the corresponding transition states for the ylide products. Additionally, we present an analysis of other solvation complexes and a study of the nature of the involved interactions

Spin-Orbit Coupling Effects in AumPtn Clusters (m + n = 4)

A study of AumPtn(m + n = 4) clusters with and without spin–orbit (SO) coupling using scalar relativistic (SR) and two component methods with the ZORA Hamiltonian was carried out. We employed the PW91 functional in conjunction with the all-electron TZ2P basis set. This paper offers a detailed analysis of the SO effects on the cluster geometries, on the LUMO–HOMO gap, on the charge distribution, and on the relative energies for each relativistic method. In general, SO coupling led to an energetic rearrangement of the species, to changes in geometries and structural preferences, to changes in the structural identity of the global minimum for the Au3Pt, AuPt3 and Pt4 cases, and to a reduction of relative energies among the clusters, an effect that appears stronger as the amount of Pt increases

Theoretical design of stable hydride clusters: isoelectronic transformation in the EnAl4−nH7+n − series

Indexación: Web of Science; Scopus.New stable hydrogen-rich metallic hydrides are designed by systematic transformations of the stable known Al4H7 − species, carried out by successive isoelectronic substitutions of one aluminum atom by one E-H unit at a time (where E = Be, Mg, Ca, Sr and Ba atoms). Searches on the potential energy surfaces (PESs) of EAl3H8 −, E2Al2H9 −, E3AlH10 − and E4H11 − systems indicate that structural analogues of Al4H7 − become higher energy isomers as the number of E-H units increases. The electronic descriptors: Vertical Electron Affinity (VEA), Vertical Ionization Potential (VIP) and the HOMO-LUMO gap, suggest that the systems composed of EAl3H8 −, E2Al2H9 −, E3AlH10 −, with E = Be and Mg, would be the most stable clusters. Additionally, for a practical application, we found that the Be-H and Mg-H substitutions increase the hydrogen weight percentage (wt%) in the clusters, compared with the isoelectronic analogue Al4H7 −. The good capacity of beryllium and magnesium to stabilize the extra hydrogen atoms is supported by the increment of the bridge-like E-H-Al, 3center-2electron chemical bonds. Finally, explorations on the PESs of the neutral species (using Na+ as counterion) indicate that the NaBe2Al2H9, NaBe3AlH10 and NaMg3AlH10 minimum-energy structures retain the original geometric shapes of the anionic systems. This analysis supports the potential use of these species as building blocks for cluster-assembled hydrides in the gas phase.http://pubs.rsc.org/en/Content/ArticleLanding/2017/RA/C7RA01422H#!divAbstrac

Selective Catalytic Activation of Acetylene by a Neutral Gold Cluster of Experimentally Known Gas-Phase Geometry

The electronic and structural details for the acetylene selective catalytic activation by one of the few small gold clusters whose experimental gas-phase initial geometry in neutral charge state is known, the gold heptamer, are investigated. Doing an exhaustive search of the acetylene–gold heptamer ZORA scalar relativistic PW91/TZ2P configurational space, we determine the main, secondary, and also the unimportant structures relative to the catalytic activation. We found that the leading mechanism of activation consists in the tendency to the disappearance of one of the acetylene π bonds at the expense of the formation of C–Au strong interactions, by the predominant dative interaction of s/d-like gold heptamer molecular orbitals toward a π* orbital of acetylene. This results in adducts having very diminished energy barriers toward processes such as, for example, the selective hydrogenation reaction to ethylene. This activation would occur with a considerable change of the participant species geometries and, with the formation of a frontier single occupied molecular orbital, very localized at carbon atoms region