No abstract

The rhombus structure of small aluminum‐oxygen clusters anions, A12Ox− (x=2−5), were constructed using high‐accuracy quantum chemical calculations. Of the presented DFT‐D methods, M05‐2X, M06‐2X, and ωB97X‐D functionals are comparable to MP2 level to perform well for determination of the properties of the anionic clusters. The rhombus‐type Al2O2− cluster has a desired D2h cyclic structural view. The most favored Al2O3− isomer is evolved from the D2h cyclic Al2O2− structure generated by adding the third O atom to the Al atom. The Al2O4− with rhombus structure probably has two coexist low‐lying isomers, one symmetric D2h and the other C2v “twisted pair”, and stability of the former is in preference over that of the latter. The most probable Al2O5− structure would be made by replacing a terminal O atom of the symmetric D2h A12O4− with an O2 unit. Consequently, structures of the most stable anionic clusters possess a rhombus character. Moreover, our findings also suggest that the more oxygen atoms the anionic cluster has, the more stable the structure is, and the stronger the H2O effect is. Beyond that, for the identified cluster anion with same degree of oxidation the symmetric structure becomes more stable with respect to the asymmetric analog, however, the H2O effect on the asymmetric geometry turns out to be predominant, in comparison with the symmetric case.

In the present work, the considered hydrogen abstraction (HAT) reactions of CCl3H molecule driven by three different small anions MO − (M = Be, B, and Al) have been investigated using electronic structure calculations. While full geometry optimizations were operated to locate all of the relevant stationary points using the DFT-BHandHLYP/aug-cc-pVTZ level, the potential-energy profiles were constructed using the coupled-cluster theory with extrapolation to complete basis set CCSD(T)/CBS. Our theoretical findings suggest that the most favored pathway determined for the HAT reactions mainly stems from the MO − type, namely, for facilitating the HAT pathway the B atom is predicted to be an inherent key in the BO − -reaction whereas it becomes O atom in both BeO − -and AlO − -reactions. Of the three favored pathways obtained here, the activations of the CCl3H in the presence of both BeO − and AlO − anions are significantly efficient, in which the energy barrier for the cleavage of the C-H bond with the assistance of BeO − was to be relatively low. Again, through the transition state theory the rate constants at 298-1000 K are also evaluated for the most favored HAT reactions studied here, indicating the lower the temperature, the faster the BO − chemical reaction.