The perovskite manganites AMnO3 and their doped analogues A1–xBxMnO3 (A and B = main group and lanthanide metals) are a fascinating family of magnetic oxides exhibiting a rich variety of properties. They are thus under intense investigation along multiple fronts, one of which is how their structural and physical properties are modified at the nanoscale. Here we show that the molecular compound [Ce3Mn8O8(O2CPh)18(HO2CPh)2] (CeIII 2CeIVMnIII 8; hereafter Ce3Mn8) bears a striking structural resemblance to the repeating unit seen in the perovskite manganites. Further, magnetic studies have established that Ce3Mn8 exhibits both the combination of pairwise MnIII 2 ferromagnetic and antiferromagnetic exchange interactions, and the resultant spin vector alignments that are found within the 3-D C-type antiferromagnetic perovskites. First-principles theoretical calculations reveal not only the expected nearest-neighbor MnIII 2 exchange couplings via superexchange pathways through bridging ligands but also an unusual, direct MnIII–CeIV–MnIII metal-to-metal channel involving the CeIV f orbitals.

The ability to design quantum systems that decouple from environmental noise sources is highly desirable for development of quantum technologies with optimal coherence. The chemical tunability of electronic states in magnetic molecules combined with advanced electron spin resonance techniques provides excellent opportunities to address this problem. Indeed, so-called clock transitions have been shown to protect molecular spin qubits from magnetic noise, giving rise to significantly enhanced coherence. Here we conduct a spectroscopic and computational investigation of this physics, focusing on the role of the nuclear bath. Away from the clock transition, linear coupling to the nuclear degrees of freedom causes a modulation and decay of electronic coherence, as quantified via electron spin echo signals generated experimentally and in silico. Meanwhile, the effective hyperfine interaction vanishes at the clock transition, resulting in electron-nuclear decoupling and an absence of quantum information leakage to the nuclear bath, providing opportunities to characterize other decoherence sources.

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Designing single-molecule magnets (SMMs) for potential applications in quantum computing and high-density data storage requires tuning their magnetic properties, especially the strength of the magnetic interaction. These properties can be characterized by first-principles calculations based on density functional theory (DFT). In this work, we study the experimentally synthesized Co(II) dimer (Co 2 (C 5 NH 5 ) 4 (μ-PO 2 (CH 2 C 6 H 5 ) 2 ) 3 ) SMM with the goal to control the exchange energy, ΔE J , between the Co atoms through tuning of the capping ligands. The experimentally synthesized Co(II) dimer molecule has a very small ΔE J < 1 meV. We assemble a DFT data set of 1081 ligand substitutions for the Co(II) dimer. The ligand exchange provides a broad range of exchange energies, ΔE J , from +50 to −200 meV, with 80% of the ligands yielding a small ΔE J < 10 meV. We identify descriptors for the classification and regression of ΔE J using gradient boosting machine learning models. We compare one-hot encoded, structure-based, and chemical descriptors consisting of the HOMO/LUMO energies of the individual ligands and the maximum electronegativity difference and bond order for the ligand atom connecting to Co. We observe a similar overall performance with the chemical descriptors outperforming the other descriptors. We show that the exchange coupling, ΔE J , is correlated to the difference in the average bridging angle between the ferromagnetic and antiferromagnetic states, similar to the Goodenough−Kanamori rules.