Chaki N, Muramatsu S, Iida Y, Kenjo S, Inokuchi Y, Iimori T, Ebata T. Laser Spectroscopy and Lifetime Measurements of the S
1 State of Tetracyanoquinodimethane (TCNQ) in a Cold Gas-Phase Free-Jet.
Chemphyschem 2019;
20:996-1000. [PMID:
30865359 DOI:
10.1002/cphc.201900214]
[Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Indexed: 11/05/2022]
Abstract
The S1 electronic state of 7,7,8,8-Tetracyanoquinodimethane (TCNQ) has been investigated by laser induced fluorescence (LIF), dispersed fluorescence (DF) spectroscopy, and lifetime measurements under jet-cooled conditions in the gas-phase. The LIF spectrum showed a weak origin band at 412.13 nm (24262 cm-1 ) with prominent progression and combination bands involving vibrations of 327, 1098, and 2430 cm-1 . In addition, very strong bands appeared at ∼363.6 nm (3300 cm-1 above the origin). Both the LIF and DF spectra indicate considerable geometric change in the S1 state. The fluorescence lifetime of S1 at zero-point level was obtained to be 220 ns. This lifetime is 40 times longer than the radiative lifetime estimated from the S1 -S0 oscillator strength. Furthermore, the lifetimes of the vibronic bands exhibited drastic energy dependence, indicating a strong mixing with the triplet (T1 ) or intramolecular charge-transfer (CT) state. This study is thought to disclose intrinsic nature of TCNQ, which has been well known as a component of organic semiconductors and a versatile p-type dopant.
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