In this paper we reinterpret the magnetic-susceptibility data and present and discuss specificheat data on MEM-(TCNQ)2 in terms of a spin-Peierls transition theory. We find that the data can be described reasonably well by a mean-field spin-Peierls transition theory which suggests that at low temperatures the TCNQ chain should be tetramerized. The magnetic susceptibility above the transition temperature is shown. to behave like a one-dimensiona) Heisenberg antiferromagnet. The consequences of this behavior on the relative magnitude of the on-site Coulomb interaction are discussed.

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The electronic absorption and emission spectra of TCNQ and its mono-and divalent anions were measured. An SCMO CI calculation in the PPP approximation was performed with one set of parameters for the three species yielding good agreement with experiment. The energy of the disproportionation reaction 2TCNQ -→ TCNQ 0 + TCNQ 2-was estimated at 3.5 eV.

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Molecular complexes of the aromatic hydrocarbons pyrene and perylene with iodine were found to have an electronic conductivity 10 to 12 orders of magnitude higher than that of the constituent compounds. The specific resistivities measured were 75 and 8 ohm-cm, respectively. The materials behaved like semiconductors and plots of log σ vs 1/T gave activation energies of 0.14 ev and 0.019 ev. No Hall effect could be found, but an upper limit for the mobility of μ≤.01 cm2v—1 sec—1 could be set. Single crystals of the perylene-iodine complex were obtained. The preparation and identification of the complexes are discussed and the results of a phase study on the system of pyrene and iodine are reported.