Influence of an External Electric Field on the Charge Transfer State of the TCNE-trans-Stilbene Molecular Complex

An experimental investigation of the effect of an external electric field on the absorption spectrum of the tetracyanoethylene-trans-stilbene molecular complex in cyclohexane solution yielded values of 1.1±0.1 D for the ground state electric dipole moment and 10.5±0.9 D for the change of the electric dipole moment upon transition to the charge transfer excited state. The ground state electric dipole moment determined by the electro-optic effect is in agreement with the value of 1.4±0.5 D obtained from the dielectric constant measurements made on solutions of the complex. The directions of the transition moment, the ground state electric dipole moment, and the excited state electric dipole moments were found to be parallel. These results give a 5% ionic character for the ground state of the complex and 76% ionic character of the excited state. These results are consistent with the theory of Mulliken.