An extensive vibrational assignment of TTF and TTF-d4 is achieved, improving the previously reported one through the use of polarized infrared spectra of single crystals of the monoclinic form. Infrared spectra of the monoclinic and triclinic forms are compared and the different crystal field effects discussed. Powder Raman and infrared spectra of (TTF)Br1.0 and (TTF-d4)Br1.0, Raman depolarization ratios and infrared spectra of (TTF)ClO4 and (TTF-d4)ClO4 solutions are reported. The assignment of the ag, b1u, b2u, and b3u fundamental modes of (TTF)+ and (TTF-d4)+ radicals allows the identification of most of the relevant frequency shifts following the ionization of the TTF structure. The possible use of the ionization shifts for the study of the electronic charge distribution in the conducting TTF systems is considered. The parallel investigation of the concentration effects on the visible and infrared absorption spectra of TTF+ in solution let us to identify anomalous infrared absorptions associated with the formation of (TTF+)2 dimer. They are attributable to an intensity borrowing from the charge transfer band due to the electron–molecular vibration (e–mv) interaction and their identification opens the way to an experimental evaluation of the e–mv coupling constants of TTF.

The results of an extensive vibrational analysis of tetramethyltetrathiafulvalene (TMTTF) and tetramethyltetraselenafulvalene (TMTSF) and of their radical cations are presented. The polarized infrared absorption spectra of oriented crystalline samples of neutral TMTTF and TMTSF (4000–80 cm−1) are reported and compared with powder and solution spectra. The polarization data are used as a basis for the symmetry assignment of the infrared active fundamental modes. Powder and solution Raman spectra are presented and discussed considering the values of the depolarization ratios measured for some bands. Raman and infrared spectra of powder and solution samples of the (1:1) bromide and perchlorate salts of TMTTF and TMTSF are reported. Vibronic infrared absorptions originated by the coupling of the unpaired electrons to totally symmetric modes are identified and compared with those previously reported for unsubstituted tetrathiafulvalene (TTF) radical systems. The assignment of the normal modes of the radical cations is based on the measured Raman depolarization ratios and on the correlation with the neutral molecules and with neutral and ionized TTF. The results of a normal coordinate calculation using a modified valence force field for TMTTF, TMTSF, and their radical cations are presented and the calculated shape of the normal modes of the neutral molecules are reported. The frequency changes following ionization observed for the present case of TMTTF and TMTSF and previously reported for TTF are compared and discussed

Vapor-solvent shift of the lowest frequency vibration of p-benzoquinone and toluquinone and the consequences for the vibrational and electronic spectral assignmentsThe vibrational assignment of the fundamental modes of 2,3,5,6-tetrachloro-and 2,3,5,6-tetrabromo-pbenzoquinone (chloranil and bromanil, respectively) radical anions is reported and compared with that of the neutral molecules. For this purpose the single crystal Raman and infrared spectra of bromanil are also given and interpreted. The absence of the vibronic effects present in the infrared spectra of some free radical salts is demonstrated, and the vibrational spectra of the potassium salts of both radical ions are shown to be interpretable in terms of substantially unperturbed molecular structures even in the case of crystalline samples. The vibrational assignments and their normal coordinate analysis allow one to obtain most of the relevant information on the frequency shifts proceeding from the addition of an extra electron to the perhalo-p -benzoquinone structure.

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The CS2 bands which lie near 2100 Å have been photographed in absorption with a high-dispersion spectrograph and a partial analysis has been made of the band system. Though a number of features remain unexplained, strong evidence has been obtained that in the upper state (a 1B2 state) the molecule is nonlinear with an S–C–S bond angle of 153° and a C–S bond distance of 1.66 Å.