Modern magnetic materials have the potential to be break through materials for magnetic data storage, quantum computers, or magnetic refrigerants. Over the past 20 years, work in the field has moved from using only transition metals to the incorporation of lanthanide ions to form mixed 3d-4f complexes. The first reported Mn-4f SMM was a metallacrown-based DyIII6MnIII4MnIV2 compound. Since this initially reported metallacrown-based SMM, metallacrowns (MCs) have shown great promise as a tool to study the impact of modifying individual structural parameters, such as lanthanide ion choice, metal ion count, and overall molecular shape, have on magnetic behavior. Here, we report the magnetic properties of two distinct families of MCs that demonstrate the versatility of the MC-architecture. One family represents the classic mixed 3d-4f approach yielding metal stoichiometries of LnIII4MnIII4 and LnIII6MnIII2MnIV2. Probing the impact of Ln ion choice and metal stoichiometry, it was found that in either stoichiometry, only the DyIII-containing compounds showed frequency-dependent out-of-phase ac susceptibility behavior, a hallmark of the energy barrier present in SMMs. Another family of MCs present the unique opportunity to modify individual structural components in a family of DyIII-containing 12-MCMn(III)N(shi)-4 complexes. It was found that in a family of DyX4M 12-MCMn(III)N(shi)-4 (X = acetate, benzoate, salicylate, trimethylacetate, M = KI or NaI) that the identity of the bridging ligand X impacted only the out-of-phase susceptibility of the compounds. This seems to indicate that for DyX4M 12-MCMn(III)N(shi)-4 that the identity of the bridging ligand X, in particular the pKa of X, correlates with the onset of SMM-like behavior. Comparing the two families reveal that the DyX4M 12-MCMn(III)N(shi)-4 provides similar out-of-phase magnetic behaviors to the larger LnxMny compounds, but with fewer metal ions and with additional perturbations through ligand pKa control.

Controlling single-molecule magnetic behavior of two families of metallacrowns by modifying lanthanide choice or structural components

253rd National Meeting (2017)

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