Structure, optical and electro-physical properties of tetramerized anion-radical salt (N-Xy-Qn)(TCNQ)2

• Published in: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Molecular and biomolecular spectroscopy, 2022-04, Vol.270, p.120822, Article 120822
• Main Authors: Barszcz, Bolesław, Starodub, Tetiana N., Mizera, Adam, Świetlik, Roman, Rytel, Karol, Iaroshenko, Viktor O., Starodub, Vladimir A.
• Format: Article
• Language: English
• Subjects: Charge transfer; Conductivity; EMV; Infrared; Raman; TCNQ; Tetramerization
• ISSN: 1386-1425
• DOI: 10.1016/j.saa.2021.120822

[Display omitted] •TCNQ molecules in (N-Xy-Qn)(TCNQ)2 salt are organized in tetramerized stacks.•Charge disproportionation in TCNQ stacks is observed (−0.83 e vs −0.33 e).•Tetramerization and EMV coupling complicates the vibrational spectra.•The room temperature conductivity equals 2.6 mS cm−1. The (N-Xy-Qn)(TCNQ)2 anion-radical salt characterized by tetramerized stacks of the TCNQ acceptor molecules has been synthesized and characterized using vibrational spectroscopy and electrical resistivity measurements. The bond lengths analysis based on the crystal structure data, indicates that the TCNQ molecules are non-uniformly charged with −0.83 e localized on the inner B molecules and −0.33 e on the outer A molecules within ABBA tetramers. Both infrared and Raman spectra of (N-Xy-Qn)(TCNQ)2 are dominated by vibrational modes of TCNQ and display splitting related to the tetramerized structure. Many of these features are affected by the strong electron-molecular vibration (EMV) coupling. Other charge-sensitive modes allowed estimation of charge localized on TCNQ, with the results that confirm the charges estimated on basis of the crystal data. Electrical measurements revealed the low-conducting behavior with room temperature conductivity value of 2.6 mS cm−1 and temperature dependence of resistivity that can be explained within the band conduction model. The calculated activation energies range from 0.169 eV to 0.187 eV, depending on the crystallographic direction and thermal history of the sample.