Laser Spectroscopy and Lifetime Measurements of the S₁ State of Tetracyanoquinodimethane (TCNQ) in a Cold Gas‐Phase Free‐Jet

Abstract

The front cover artwork is provided by the groups of Prof. Takayuki Ebata, Prof. Yoshiya Inokuchi at Hiroshima University, and Prof. Toshifumi Iimori at Muroran Institute of Technology. The image shows the first laser spectroscopic study of jet‐cooled TCNQ in the gas‐phase, which is compared with the absorption and emission in solution. Read the full text of the Communication at 10.1002/cphc.201900214.

New aspect of photophysics of 7,7,8,8-tetracyanoquinodimethane and its solvated complexes: intra- vs. inter-molecular charge-transfer

“…In order to gain an insight of the excited state dynamics of TCNQ monomer, we focus on uorescence decay proles. We previously mentioned that the proles of most of the vibronic bands exhibit double exponential decay, 20 which is consistent in the present study (Fig. S3 †).…”

“…The overall spectral feature well reproduced the previous report in which an OPO laser with low resolution ($7 cm À1 ) was used. 20 The use of the dye laser resulted in the stronger intensities of low energy vibronic bands (<$26 000 cm À1 ), compared to those measured by OPO laser, as shown in Fig. S1 (ESI †).…”

“…The HB spectra exhibited almost the same spectral pattern regardless of the monitoring vibronic bands, indicating that main bands observed in the LIF spectrum belong to a single species; these bands are certainly assigned to a TCNQ monomer, as supported by vibrationally-resolved dispersed uorescence spectroscopy with the help of DFT calculations in our previous study. 20 It should be noted that the dip intensities at low wavenumber region (<25 300 cm À1 ) are weak or sometimes missing. This is due to insufficient pumping efficiency due to low resolution of OPO laser, as described above (Fig.…”

“…The experimental apparatus used in this study consists of (1) supersonic jet source with heating nozzle and (2) LIF spectrometer, whose details are described elsewhere. 20,21 Briey, in (1), a sample housing which contained TCNQ powder, attached at the head of a pulse valve, was heated to $210 C. The gaseous mixture of sample vapor and He carrier gas ($6 atm) was expanded into the vacuum chamber through a 1 mm aperture of the valve, generating a supersonic free jet. For the generation of micro-solvated complexes, the vapor of the solvent (acetonitrile (À25 C) or benzene (10 C)) was seeded to the He carrier gas.…”

“…The powder sample of TCNQ (purity: >98.0%) was purchased from Tokyo Chemical Industry and used without purication; we actually compared the obtained LIF excitation spectra of aspurchased samples with those of recrystallized ones, 20 where no signicant difference was discerned. The purity of TCNQ was examined by 1 H NMR measurements (Camcor, Varian Mercury-300) before and aer the LIF measurement to conrm no decomposition upon the heating of the sample.…”