Fullerene-like boron nitride cages BxNy (x + y = 28): stabilities and electronic properties from density functional theory computation.

Computations based on density functional theory (DFT) were performed to get insights into the structural stability, electronic, and magnetic properties of fullerene-like boron nitride cages (f-like BNCs) for different BxNy chemical stoichiometry (x + y = 28). The results reveal at least metastable nanostructures for anionic charge (Q = -1) and doublet state (M = 2); furthermore, a magnetic moment of 1.0 bohr magneton is associated with them. These systems, in general, have high chemical stability due to their large values of cohesion energy, and the structural stability was corroborated by means of vibrational calculations. According to quantum descriptors, they exhibit high polarity (except to B27N and B28 systems), low average chemical reactivity and average work function, and electronic behavior like semiconductors. Therefore, the properties of these systems are improved compared to the B28 system, and thus the nonstoichiometry fullerenes can be used for more applications than the pristine one.

Interactions of B12N12 fullerenes on graphene and boron nitride nanosheets: A DFT study.

In the search of nanomaterials to be used in drug delivery applications, Density Functional Theory calculations were implemented to study the interaction between graphene (G) and hexagonal boron nitride nanosheet (hBNN) with octahedral B12N12 fullerenes. These B12N12 fullerenes were considered in two cases: pristine and the modified one with boron-boron, nitrogen-nitrogen (tetragon) and boron-boron-boron (hexagon) homo-nuclear bonds. The whole systems were analyzed in the gas and aqueous phases. The results reveal for all these systems that the interaction is in the range of physisorption (Eads = from -0.03 to -0.37 eV) for both phases, limiting its functions as a vehicle. However, for the nano-composite: B12N12 fullerene modified and hBNNs, the values of average chemical reactivity and HOMO-LUMO gap decreased whereas the polarity was improved, thereby this combination of quantum descriptors lead them to be considered as potential vehicle for drug delivery.

Theoretical analysis of C-F bond cleavage mediated by cob[I]alamin-based structures.

In the present work, C-F bond cleavage mediated by the super-reduced form of cobalamin (i.e., CoICbl) was theoretically studied at the ONIOM(BP86/6-311++G(d,p):PM6) + SMD level of theory. Dispersion effects were introduced by employing Grimme's empirical dispersion at the ONIOM(BP86-D/6-311++G(d,p):PM6) + SMD level. In the first stage of the study, cobalamin was characterized in terms of the coordination number of the central cobalt atom. The ONIOM(BP86/6-311++G(d,p):PM6) results showed that the base-off form of the system is slightly more stable than its base-on counterpart (ΔE = E base-off - E base-on ~ -2 kcal/mol). The inclusion of dispersive forces in the description of the system stabilizes the base-on form, which becomes as stable as its base-off counterpart. Moreover, in the latter case, the energy barrier separating both structures was found to be negligible, with a computed value of 1.02 kcal/mol. In the second stage of the work, the reaction CoICbl + CH3F → MeCbl + F- was studied considering the base-off and the base-on forms of CoICbl. The reaction that occurs in the presence of the base-on form of CoICbl was found to be kinetically more favorable (ΔE ≠ = 13.7 kcal/mol) than that occurring in the presence of the base-off form (ΔE ≠ = 41.2 kcal/mol). Further reaction-force analyses of the processes showed that the energy barrier to C-F bond cleavage arises largely due to structural rearrangements when the reaction occurs on the base-on form of the CoICbl complex, but is mainly due to electronic rearrangements when the reaction takes place on the base-off form of the complex. The latter behavior emerges from differences in the synchronicity of the bond strengthening/weakening processes along the reaction path; the base-on mode of CoICbl is able to decrease the synchronicity of the chemical events. This work gives new molecular-level insights into the role of Cbl-based systems in the cleavage of C-F bonds. These insights have potential implications for research into processes for degrading fluorine-containing pollutants.