On the spectral properties of the family of complex TCNQ salts with substituted pyrazines

The group of six TCNQ salts with N-methyl derivatives of pyrazine, bearing up to four methyl groups in various pyrazine sites, was selected for the spectral studies. The influence of the spatial structure of the donors on the charge distribution on the acceptor as well as spectral features of adequate TCNQ salts were deduced. The stretching vibrations of the CC bonds (mode ν4) were used for the evaluation of the charge density on the TCNQ− anions but the stretching vibrations of the CN bonds (mode ν2) indicate a diversity of the neighborhood of TCNQ species. It was shown that for the salts containing nonequivalent TCNQ anions the band ν2 is splitted; each component of the multiplet seen in the IR and Raman spectra represents various environment of the anion. On the other hand the splitted mode ν4 indicates an existence of TCNQ− anions differently charged. Thus, it was shown that the spectral methods are suitable for indicating nonequivalence of the TCNQ in their salts.