Chlorates and perchlorates as potential high-energy materials: chlorate- and perchlorate-substituted methanes

The structures and properties of thirty-three of the thirty-four possible chlorato-Cl-, chlorato-O- and perchlorato-derivatives of methane have been computed using the range-separated hybrid generalized gradient approximation density functional method ωB97X-D with the 6-311+G(2d,p) basis set. These results indicate that the chlorato-O-substituent confers more stability to a molecule than does the chlorato-Cl-substituent; the perchlorato-substituent is approximately intermediate in this regard when decomposition energies are calculated. The C-Cl bond lengths in the chlorato-Cl-substituents generally elongate and the C-O distances in the chlorato-O- and perchlorato-substituents tend to shorten as the number of chlorate/perchlorate substituents increases. In addition, as the C-O bond shortens, the CO-Cl bond lengthens. The calculated Mulliken and Löwdin bond orders for these bonds exhibit the opposite of the trends exhibited by the bond lengths, as expected: As the bond lengthens, the bond order decreases, and vice versa. The single molecule that could not be optimized as a stable methane derivative, (chlorato-Cl-)tris(chlorato-O-)methane, rearranged during all optimization attempts to an isomer of the neutral Cl₂O₅ molecule and a hitherto unknown molecule, bis(chlorato-O-)carbonyl, (O₂ClO)₂C=O.