Microsecond dynamics of molecular negative ions formed by low-energy electron attachment to fluorinated tetracyanoquinodimethane

Low-energy (0-15 eV) electron interactions with gas-phase 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) molecules are studied under single collision conditions using dissociative electron attachment (DEA) spectroscopy. The experimental findings are supported by density functional theory calculations of the virtual orbital energies and energetics of the dissociative decays. Long-lived molecular negative ions F4-TCNQ– are detected in a wide electron energy range (0-3 eV) with electron detachment times in the range of milliseconds. Although plenty of decay channels are observed, their intensities are found to be very small (two to four orders of magnitude relative to the F4-TCNQ– signal). These findings prove that the structure of this strong electron-accepting molecule bearing an excess electron is robust in its electronic ground state, even when highly (up to 6 eV) vibrationally excited. As many as nine metastable fragment anions formed slowly (in the 16-23 µs range) are found in the negative ion mass spectrum of F4-TCNQ, as never observed before in compounds possessing high electron-accepting ability. The present results shed some light on microsecond dynamics of isolated F4-TCNQ molecules under conditions of excess negative charge, which are important for understanding the functionality of nanoscale devices containing this molecule as a structural element

Electron attachment spectroscopy as a tool to study internal rotations in isolated negative ions

Electron-driven processes in the triclosan molecule are studied under gas-phase conditions using dissociative electron attachment (DEA) spectroscopy with the support of density functional theory calculations. Several decay channels of the short-lived (less than 17 \ub5s) molecular anion of triclosan are associated with excitation of internal rotations of the phenyl rings around the C\u2013O bonds. This leads to production of a dioxin anion, by elimination of a neutral HCl molecule, or negatively charged hypochlorous acid and dibenzofuran as neutral counterpart. These decays are accompanied by cleavage and formation of several covalent bonds and appear on the microsecond timescale, as confirmed by detection of metastable anions. On the basis of the present and earlier findings, DEA spectroscopy demonstrates to be a suitable technique for studying internal rotations in negative ions, although quite different from the experimental techniques \u2013 microwave and Raman spectroscopies \u2013 usually employed to study internal rotations in neutral molecules

Dissociative electron attachment to 3-benzelidenephthalide and phenolphthalein molecules.

Electron attachment to the 3-benzelidenephthalide and phenolphthalein molecules and decay channels of their molecular anions were investigated by means of Dissociative Electron Attachment (DEA) spectroscopy and Electron Transmission Spectroscopy (ETS). Interpretations of these experimental data were supported with UV-spectroscopy and DFT calculations. The average electron detachment times for the long-lived molecular anions of 3-benzelidenephthalide and phenolphthalein were measured to be 150 microseconds at 120 \ub0C and 560 microseconds\uf06dat 190 \ub0C, respectively. The long-lived molecular anions of phenolphthalein are ascribed to an isomer formed by ring opening. The present results suggest that, oppositely to phenolphthalein, polymeric materials based on 3-benzylidenephthalide cannot be switched to a high conductive state due to different mechanisms of stabilization of their long-lived molecular anions