Synthesis of Bulk High Spin Density Organic Solids Derived from Triplet Donor Molecule HMT

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Abstract
We describe a synthetic approach to the preparation of bulk high spin density organic solids as a probe to organic ferromagnets utilizing an external doping process to achieve a molecular sequence of alternate donors and acceptors in different spin states for, in principle, the ground state ferrimagnets. We found that the introduction of arsenic pentafluoride into molecular crystals of (HMT)2-TCNQF4 disintegrates the long range order of crystal without rearranging the molecular stacking sequence of HMT and TCNQF4. The previously reported magnetic data were summarized. The observed bulk spin in doped (HMT)2-TCNQF4 increases with the amount of doping to a maximum of 1.6 spins ½ per complex, when HMT molecules reach monocationic state. It then decreases slowly to 1.3 spins ½ per complex as most of HMT being oxidized to dicationic state. In highly doped samples with dicationic HMT molecules, the comparison of field dependence of magnetization for (HMT)2-TCNQF4 at 1.4K with theoretical calculations from the Brillouin functions for magnetization suggests up to 50% of the magnetization at low temperatures arising from S = 1 spin triplets. The static magnetic data of partially doped sample with monocationic HMT agree with the molecularly isolated donor pair model. The interpretation of magnetic data on highly doped samples involves a physical molecular spin separation of triplet dicationic HMT spins into a disordered matrix by arsenic fluorides.