INFRARED NEAR-ISOTROPY IN A MIXED STACK ORGANIC CONDUCTOR - OMTSF-NI(DMIT)2

From transport measurements the mixed stack organic conductor OMTSF-Ni (DMIT)2 (OMTSF: bis-tetramethylene-TSF, Ni(DMIT)2: (4,5-dimercapto-1,3 -dithiole-2-thione)nickel) is known to possess near isotropy in the cr ystallographic a-c plane, where there are indeed a large number of clo se interstack contacts in different directions. A study is presented o f the polarized infrared reflectance spectra for various directions in the a-c plane. Only weak polarization dependence is found in the enti re frequency range. The spectra display a broad, asymmetric CT band at 2,600 cm-1 as well as a number of distinct electron-molecular vibrati on features. One of the spectra is discussed within a simple model for the coupling between charge transfer processes and intramolecular vib rations.