Real-time observation of interfragment vibration and charge transfer within the TCNQF4 dimer

The organic electron acceptors, 7,7,8,8-tetracyanoquinodimethane (TCNQ) and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (TCNQF(4)); are widely used to synthesize multivalent charge-transfer complexes. Their corresponding radical anion complexes have specific electronic, optical, and magnetic characters that have attracted attention in the field of materials development. In the present work,, we have performed time-resolved absorption spectroscopy of the (Na+)(2)(TCNQE(4)(center dot-))(2) radical anion complex to elucidate the reaction dynamics ([TCNQF(4)(center dot-)](2) -> TCNQF(4) + TCNQF(4)(2-)). A visible sub-10 fs laser pulse was used to observe the ultrafast dynamics of the charge transfer and real-time change of the molecular structure during the reaction. Unlike our previous work on the (Na+)(2)(TCNQ(.-))(2) radical anion complex, the interfragment vibrational mode was clearly observed for (Na+)(2)(TCNQP(4)(center dot-))(2). The difference in the intermolecular interaction is considered to reflect the difference in the pi-pi interaction and/or the difference in the flexibility of the molecular plane predicted by theoretical calculations. (C) 2017 Elsevier B.V. All rights reserved.