Electric Field Effect on Condensed-Phase Molecular Systems. IV. Conformational Change of 1,2-Dichloroethane in a Frozen Molecular Solid

摘要

In this work, we studied the effect of an externally applied electric field on the conformation and orientation of 1,2-dichloroethane (DCE) in a frozen molecular solid. An electric field in the order of 10(8) V m(-1) was applied across the sample by means of interfacial charging of Cs+ ions. Reflection absorption infrared spectroscopy (RAIRS) was used to monitor the gauche/trans conversion and reorientation of the DCE molecules due to an electrostatic interaction with the field. trans-DCE molecules were converted to gauche conformers via internal C-C rotation with the conversion efficiency of 24% at the field strength of 1.5 x 10(8) V m(-1) and temperature 75 K. gauche-DCE molecules were reoriented along the field at an average tilt angle of 36 degrees under the same conditions. These field-induced molecular changes were prohibited at 8 K and visible above 50 K. Therefore, both electrostatic and thermal energies are required to induce molecular transformations in the metastable solid by overcoming the activation barrier. This study suggests the possibility of controlling molecular conformation and orientation of condensed molecular solids by applying an external electric field whose magnitude is comparable to that of the intermolecular electric fields.