Magnetic Bistability in an Organic Radical-Based Charge Transfer Cocrystal

We report herein an organic charge transfer cocrystal complex, consisting of a stable radical TPVr and an electron acceptor TCNQF 4, as a rare sort of all-organic-based magnetic bistable materials with a thermally activated magnetic hysteresis loop over the temperature range from 170 to 260 K. Detailed X-ray crystallographic studies and theoretical calculations revealed that while a π-associated radical anion dimer was formed upon an integer charge transfer process from TPVr to the TCNQF 4 molecules within the cocrystal lattice, the resulting TCNQF 4 ·– π-dimers were found to exhibit varied intradimer π-stacking distances and singly occupied molecular orbital overlaps at different temperatures, thus yielding two different singlet states with distinct singlet–triplet gaps above and below the loop, which eventually contributed to the thermally excited molecular magnetic bistability.