Multispin superatoms: seven-nuclear rhenium clusters with unusual magnetic properties

Obtaining nanosized, solution-processable molecules and ions with switchable magnetic moments is crucial for the development of storage devices. In this work, two seven-nuclear rhenium cluster complexes Cs₇[{Re₃S₄(CN)₉}{Re₄S₄}(CN)₉]·10H₂O (1) and K₇[{Re₃Se₄(CN)₉}{Re₄Se₄}(CN)₉]·15H₂O (2) were prepared and comprehensively characterized. The obtained clusters with an even number of cluster valence electrons (CVE) are found to consist of triangular and tetrahedral fragments strongly bonded together by bridging inner ligands and constitute a new structural type. Magnetochemical analysis of complexes has revealed the presence of non-magnetic singlet (M_S = 0) and magnetic doublet (M_S = ±1) states with a temperature-dependent population. These states, according to DFT calculations, may originate from the zero-field splitted S = 1 ground state, which is quite surprising given that clusters with an even number of CVE usually possess low-spin states (S = 0) due to the delocalized nature of the frontier molecular orbitals (MOs) and the effective removal of MO degeneracy by Jahn–Teller spatial distortion of the clusters. We have also succeeded in controlling one-electron oxidation of the clusters, which results in an odd number of CVE and drives the compound into a conventional paramagnetic S = 1/2 state.