Determination of Atomic Structures and Relative Stabilities of Diadduct Regioisomers of C₂₀X₂ (X = H, F, Cl, Br, and OH) by the Hybrid Density-Functional B3LYP Method

摘要

We have studied the relative stability and atomic structures of five C20X2 regioisomers obtained as diadducts of a C20 cage (X = H, F, Cl, Br, and OH). All the regioisomers are geometric isomers, i.e., they differ in their spatial arrangement. Full-geometry optimizations of the regioisomers have been performed using the hybrid density-functional (B3LYP/6-31G(d, p)) method. Our results suggest that the cis-1 regioisomer (the 1,2- diadduct) is the most stable and that the second most stable is the trans-2 (1,13-diadduct) regioisomer, implying that the long-range interaction between the two adducts and the resonance effect are more pronounced than the diadduct-induced strain in the C20 cage. The HOMO and LUMO characteristics of each regioisomer with the same symmetry of structural regioisomers except C20(OH)2 are topologically same. This suggests that by using an entirely different set of characteristic chemical reactions for each regioisomer, we can distinguish between the five regioisomers for each C20 diadduct derivative.