Low-frequency spectra of the hexamethylbenzene/tetracyanoethylene electron donor-acceptor complexes in solution studied by terahertz time-domain spectroscopy.
We have measured the frequency dependent extinction coefficients and refractive indices of electron donor-acceptor (EDA) complexes consisting of hexamethylbenzene (HMB; electron donor) and tetracyanoethylene (TCNE; electron acceptor) in the low-frequency region by terahertz time-domain spectroscopy (THz-TDS). A mixture of the 1:1 (DA) and 2:1 (D2A) EDA complexes exist in carbon tetrachloride solution, and we successfully obtained the spectral components of the 1:1 and 2:1 EDA complexes separately by analyzing the concentration dependence of the THz spectra. The 1:1 and 2:1 complexes show quite different THz spectra of the extinction coefficient, reflecting unique features of dynamics, fluctuations and intermolecular interactions of these complexes. Polarization-selective THz-TDS on the crystalline DA complex shows two peaks at 53 and 70 cm(-1) in the spectral component perpendicular to the crystal axis. On the other hand, the crystalline D2A complex exhibits peaks at 42 and 50 cm(-1) in the perpendicular spectral component. We compare the obtained spectra of the crystalline complex and the results of molecular orbital calculations at the HF/6-31G(d) level of theory to discuss the intermolecular vibrational modes of the complexes.
Molecular Photoscience Research Center, Kobe University, Nada, Kobe, 657-8501, Japan.
Kohji
K
Yamamoto
Md Humayun
MH
Kabir
Michitoshi
M
Hayashi
Keisuke
K
Tominaga
D000388:Air; D001555:Benzene Derivatives / Q000737:chemistry*; D002251:Carbon Tetrachloride / Q000737:chemistry; D002627:Chemistry, Physical / Q000379:methods*; D003460:Crystallization; D004583:Electrons; D005030:Ethylenes / Q000737:chemistry*; D007700:Kinetics; D008956:Models, Chemical; D008968:Molecular Conformation; D009570:Nitriles / Q000737:chemistry*; D012997:Solvents; D055068:Terahertz Spectroscopy / Q000379:methods*; D014867:Water / Q000737:chemistry
D001555:Benzene Derivatives; D005030:Ethylenes; D009570:Nitriles; D012997:Solvents; D014867:Water; C003393:tetracyanoethylene; D002251:Carbon Tetrachloride; C091695:hexamethylbenzene