Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published June 4, 1998 | public
Journal Article

Solvation Ultrafast Dynamics of Reactions. 14. Molecular Dynamics and ab Initio Studies of Charge-Transfer Reactions of Iodine in Benzene Clusters


Previous experiments have been carried out in this laboratory to investigate the dynamics of iodine−benzene charge-transfer reactions. Both 1:1 solute−solvent complexes and 1:n clusters were studied on the femtosecond time scale with kinetic energy time-of-flight mass spectrometry (Cheng, P. Y.; Zhong, D.; Zewail, A. H. J. Chem. Phys. 1996, 105, 6216). Here, we report theoretical studies of the structure and dynamics of iodine−benzene clusters with direct comparison to experimental findings. In particular, ab initio calculations confirm that iodine binds to benzene near-axially with an energy of 3.5 kcal/mol (MP2/6-311G^(**)), which is consistent with the experimental time scale of the reaction and with the angular and kinetic energy distributions of product fragments. Experimental observations have shown that the dynamics of iodine dissociation under cluster solvation is described by two caging time scales. Using Monte Carlo and molecular dynamics simulations, we find that this effect arises from a fundamental asymmetry in the structure of 1:n iodine−benzene clusters. The benzenes tend to form mouth-shaped structures around the iodine, causing one of the iodine atoms to be more strongly solvated than the other. The dynamics therefore reflect two types of solvation forces, free and bound, in a homogeneous structure, rather than a distribution of structures. The two distinct time scales, femtosecond and picosecond, are a result of caging dynamics in the solvent structure. In this way, caging dynamics may be used as a probe of structural features of solvation.

Additional Information

© 1998 American Chemical Society. Received: December 18, 1997; In Final Form: January 26, 1998. Publication Date (Web): April 17, 1998. This work was supported by the National Science Foundation. J. Su wishes to thank the SURF program and T. Tombrello of the Ph 11 course at Caltech for summer fellowships. We also thank V. McKoy, W. Goddard, K. Kuwata, P. Cheng, S. Baskin, and E. Diau for their help and suggestions. We thank Dongping Zhong and the referees for their thorough reading of the manuscript and for their useful comments.

Additional details

August 19, 2023
October 20, 2023