AIM studies on SSHX → HSSX (X = F, Cl, Br, I) reaction

The reactions of SSHX to HSSX (X = F, Cl, Br and I) have been studied at the MP2/6-311++G(2df,pd)//B3LYP/6-311++G(2df,pd) level. The SSH and SSX ring structure transition region (STR) and respective structure transition state (STS) have been studied in the framework of the “Atoms in Molecules” theory. The following conclusions are drawn: (a) For the SSH and SSX ring structures, according to the sequence of X = F, Cl, Br and I, the STR becomes broader and the STS appears later. (b) For the H atom transfer pathway and X atom transfer pathway, the lower the energy barrier is, the broader the ring STR (SSH ring STR or SSX ring STR) is and the later the STS appears.