Photoexcited state of the organic electron acceptor TCNQ molecular anion in the condensed state

The first and second excited states of 7,7,8,8-tetracyanoquinodimethane (TCNQ) anions in acetonitrile were studied employing femtosecond time-resolved photoluminescence and transient absorption spectroscopy. It was found that the second excited state, which is a superexcited state, undergoes ultrafast decay due to spontaneous electron emission with a time constant of 0.16 ps. The rationale for the fast electron emission in acetonitrile is discussed in terms of the interactions with the surrounding polar solvent molecules.