Steric and Electronic Control of the Spin State in Three-Fold Symmetric, Four-Coordinate Iron(II) Complexes

The three-fold symmetric, four-coordinate iron­(II) phosphoraminimato complexes PhB­(MesIm)₃Fe–NPRR′R″ (PRR′R″ = PMePh₂, PMe₂Ph, PMe₃, and PⁿPr₃) undergo a thermally induced <i>S</i> = 0 to <i>S</i> = 2 spin-crossover in fluid solution. Smaller phosphoraminimato ligands stabilize the low-spin state, and an excellent correlation is observed between the characteristic temperature of the spin-crossover (<i>T</i>_1/2) and the Tolman cone angle (θ). Complexes with <i>para</i>-substituted triaryl phosphoraminimato ligands (<i>p</i>-XC₆H₄)₃PN^– (X = H, Me and OMe) also undergo spin-crossover in solution. These isosteric phosphoraminimato ligands reveal that the low-spin state is stabilized by more strongly donating ligands. This control over the spin state provides important insights for modulating the magnetic properties of four-coordinate iron­(II) complexes

Coherent Manipulation of a Molecular Ln-Based Nuclear Qudit Coupled to an Electron Qubit

We demonstrate that the [Yb­(trensal)] molecule is a prototypical coupled electronic qubit–nuclear qudit system. The combination of noise-resilient nuclear degrees of freedom and large reduction of nutation time induced by electron–nuclear mixing enables coherent manipulation of this qudit by radio frequency pulses. Moreover, the multilevel structure of the qudit is exploited to encode and operate a qubit with embedded basic quantum error correction

Large Orbital Magnetic Moment Measured in the [TpFe^III(CN)₃]⁻ Precursor of Photomagnetic Molecular Prussian Blue Analogues

Photomagnetism in three-dimensional Co/Fe Prussian blue analogues is a complex phenomenon, whose detailed mechanism is not yet fully understood. Recently, researchers have been able to prepare molecular fragments of these networks using a building block synthetic approach from mononuclear precursors. The main objective in this strategy is to isolate the smallest units that show an intramolecular electron transfer to have a better understanding of the electronic processes. A prior requirement to the development of this kind of system is to understand to what extent electronic and magnetic properties are inherited from the corresponding precursors. In this work, we investigate the electronic and magnetic properties of the <b>FeTp</b> precursor (N­(C₄H₉)₄)­[TpFe^III(CN)₃], (Tp being tris-pyrazolyl borate) of a recently reported binuclear cyanido-bridged Fe/Co complex. X-ray absorption spectroscopy and X-ray magnetic circular dichroism measurements at the Fe <i>L</i>_2,3 edges (2p → 3d) supported by ligand field multiplet calculations have allowed to determine the spin and orbit magnetic moments. Inaccuracy of the spin sum rule in the case of low-spin Fe^III ion was demonstrated. An exceptionally large value of the orbital magnetic moment is found (0.9 μ_B at <i>T</i> = 2 K and <i>B</i> = 6.5 T) that is likely to play an important role in the magnetic and photomagnetic properties of molecular Fe/Co Prussian blue analogues