On the intramolecular vibrational energy redistribution dynamics of aromatic complexes: A comparative study on C6H6–C6H5Cl, C6H6–C6H3Cl3, C6H6–C6Cl6 and C6H6–C6H5F, C6H6–C6H3F3, C6H6–C6F6

Abstract

Chemical dynamics Simulation studies on benzene dimer (Bz2) and benzene–hexachlorobenzene (Bz–HCB) as performed in the past suggest that the coupling between the monomeric (intramolecular) vibrational modes and modes generated due to the association of two monomers (intermolecular) has to be neither strong nor weak for a fast dissociation of the complex. To find the optimum coupling, four complexes are taken into consideration in this work, namely, benzene–monofluorobenzene, benzene–monochlorobenzene, benzene–trifluorobenzene (Bz–TFB), and benzene–trichlorobenzene. Bz–TFB has the highest rate of dissociation among all seven complexes, including Bz2, Bz–HCB, and Bz–HFB (HFB stands for hexafluorobenzene). The set of vibrational frequencies of Bz–TFB is mainly the reason for this fast dissociation. The mass of chlorine in Bz–HCB is optimized to match its vibrational frequencies similar to those of Bz–TFB, and the dissociation of Bz–HCB becomes faster. The power spectrum of Bz–TFB, Bz–HCB, and Bz–HCB with the modified mass of chlorine is also computed to understand the extent of the said coupling in these complexes.