Electron transfer induced dissociation of chloro-cyano-benzene radical anion: driving chemical reactions via charge restraints

We introduce a new quantum mechanics/mol. mechanics based method to drive electron transfer reactions. Our approach uses the dynamically restrained electrostatic potential derived charges of the quantum atoms as a reaction coordinate, and allows an estn. of the free energy barrier of the electron transfer process. Moreover, it provides an accurate description of the electronic structure changes and of the nuclear reorganization assocd. with the reaction. We use the method to describe the electron-transfer induced dissocn. of the m-chloro-cyano-benzene radical anion in aq. soln. The reaction is triggered by solvent reorganization by a change in the coordination water shell around the cyano nitrogen atom. At the onset of the reaction, charge-spin segregation is obsd. The neg. charge is transferred to the leaving Cl, while the spin d. localizes on the non-satd. carbon atom of the benzene ring. The calcd. free energy barrier of dissocn. is in good quant. agreement with the exptl. data. [on SciFinder (R)]