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The preparation of new geometrically spin-frustrated magnetic materials [1] that approximate theoretical models [1, 2] is a challenge. Although the Mermin–Wagner theorem [3] indicates that long-range magnetic order can exist in two dimensions at zero Kelvin, order can be destroyed either by quantum fluctuations or geometric frustration even at this temperature. Theoretical studies indicate that the ground state of a spin-1/2 Heisenberg antiferromagnet is most likely to be semiclassically ordered.[4] However, the interplay of geometric frustration and quantum fluctuations has been found to give rise to a paramagnetic ground state without semi-classical long-range order in two types of lattice. The first of these lattices is the famous KagomØ lattice (T8) and the second is the so-called “star” lattice (T9; Scheme 1), which may serve as a new example of a quantum paramagnet.[4, 5] The triangles are corner-sharing in the KagomØ lattice whereas they are separated by a bridge in the star lattice, which means that their next-nearest-neighbor exchange interactions are different.[4, 5] The magnetic J exchange pathways in the KagomØ lattice are all equivalent, whereas the intra-triangular JT pathway in the star lattice is weaker than the inter-triangular JD pathway. In contrast to the rapid development of KagomØ-type antiferromagetic lattices [6, 7] and related, geometrically spin-frustrated lattices,[8] there appears to date to be no report of a compound with a genuine star lattice.

Triangular clusters with superexchange pathways, such as the widely employed M3 (μ3-O) clusters, where M may be FeIII, FeII, CoII, NiII, CuII, VIII, or CrIII, can be used to generate …