9 research outputs found
Orbital Mechanism of the Specific Effect of a Polar Solvent in Optical Absorption Spectra
Application of polar solvent effects in absorption spectra for determination of lowest electron-excited states of phthalide
The Lowest Triplet of Tetracyanoquinodimethane via UV–vis Absorption Spectroscopy with Br-Containing Solvents
This
study was undertaken to find the previously unknown lowest
triplet of the isolated molecule of tetracyanoquinodimethane (TCNQ),
which is a widely used organic semiconductor. The problem is topical
because the triplet excitation of this compound is involved in some
processes which occur in electronic devices incorporating TCNQ and
its derivatives, and information on the TCNQ triplet is needed for
better understanding of these processes. The lowest triplet of TCNQ
was obtained at 1.96 eV using UV–vis absorption spectroscopy
with Br-containing solvents. Production of the triplet band with sufficient
intensity in the spectra was provided by the capacity of the Br atom
to augment the triplet excitation and through using a 100 mm cuvette.
The assignment of the corresponding spectral band to the triplet transition
was made by observation that this band appeared only in the spectra
recorded in Br-containing solvents but not in spectra recorded in
other solvents. Additional support for the triplet assignment came
from the overall UV–vis absorption spectra of TCNQ recorded
in various solvents, using a 10 mm cuvette, in the 1.38–6.5
eV energy range. Singlet transitions of the neutral TCNQ<sup>o</sup> molecule and doublet transitions of the TCNQ<sup>ÂŻ</sup> negative
ion were identified in these overall spectra and were assigned with
TD B3LYP/6-31G calculations. Determination of the lowest triplet of
TCNQ attained in this work may be useful for theoretical studies and
practical applications of this important compound
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