We report a monometallic dysprosium complex, [Dy(O Bu) (py) ][BPh ] (5), that shows the largest effective energy barrier to magnetic relaxation of U =1815(1) K. The massive magnetic anisotropy is due to bis-trans-disposed tert-butoxide ligands with weak equatorial pyridine donors, approaching proposed schemes for high-temperature single-molecule magnets (SMMs). The blocking temperature, T , is 14 K, defined by zero-field-cooled magnetization experiments, and is the largest for any monometallic complex and equal with the current record for [Tb N {N(SiMe ) } (THF) ].

A reversible single-crystal-to-single-crystal transformation is used to dramatically change the relaxation behavior of a single-ion magnet. The coordination geometry of the Dy III site of a [Zn-Dy-Zn] complex changes from pentagonal-bipyramid (quasi-D 5h ) to octahedron (quasi-O h ), inducing an energy barrier change from 305 cm À1 (439 K) to a negligible value, respectively. Ab initio calculations reveal that the ideal D 5h -Dy III is of perfect axiality with a substantial energy barrier in accordance with the experimental result.

Single-molecule magnets (SMMs) could potentially store binary information in future ultra-high-density information storage devices. The current challenge to improve performance is understanding and preventing memory loss via molecular vibrations. In this work, we synthesize an improved SMM over a previous design and use a computational approach to probe how molecular vibrations contribute to memory loss.

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 J T pathway in the star lattice is weaker than the inter-triangular J D 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. [7][8][9] including the desired magnetically frustrated star lattice. This star lattice can be described in vertex notation as 3.12 2 (see Scheme S1 in the Supporting Information), a lattice that is a uniform, three-connected twodimensional net with large voids.[10] Three-connected node subunits that prefer to bond in a planar fashion, such as the basic cationic iron(III) carboxylate cluster [Fe 3 [11] where L may be water, methanol, or pyridine, must be used to avoid three-dimensional connections. These carboxylate clusters are good potential building blocks because they are easily prepared, prefer planar bonding, and the R groups and L ligands can easily be varied. [12] The cationic [Fe 3 + moiety has previously served as a six-or three-connected node (see Scheme S2 in the Supporting Information) to form either three- [12a-e] or zero-dimensional [12f] porous frameworks depending upon the nature of the carboxylate, which may be either fully or partially substituted by dicarboxylates; the L ligands are usually retained as terminal ligands. Although no example is known to date, it should be possible to substitute the L ligands located in the triangular [Fe 3

The magnetocaloric effect of orthorhombic Gd(OH)CO3 has been experimentally studied, which exhibits −ΔSm up to 66.4 J kg−1 K−1 (355 mJ cm−3 K−1) for ΔH = 7 T and T = 1.8 K.