). There is good agreement between measured and calculated magnetization values, and those expected for free M(III) ions Ce(III) (4f 1 2 F5/2), Nd(III) (4f I9/2) and U(III) (4f I9/2). However, low magnetic susceptibility values were observed for several different batches of 1-Pr; at 300 K the discrepancy between the experimental data presented and the expected value for a Pr(III) ion (4f 2 3 H4) and the CASSCF-SO predicted value (see below) is ca. 0.3 cm 3 mol -1 K, which may warrant future investigation. A gradual decrease in χT with temperature was observed for all 1-M, due to thermal depopulation of excited crystal field states, with a sharper drop in χT < ca. 30 K attributed to poor thermal equilibration of the sample at lower temperatures. Magnetic saturation (Msat) was not reached at 2 K for 1-Ce or 1-Pr in fields up to 7 T, but this was effectively reached for 1-Nd and 1-U under the same conditions, with 2 K and 4 K magnetization vs. field traces in good agreement with those calculated for 1-Ce, 1-Nd and 1-U. Both 1-Nd and 1-U exhibit similar butterfly-shaped hysteresis loops at 2 K (see Supporting Information Figure ). EPR Spectroscopy. The electronic structures of the Kramers ion complexes 1-Ce, 1-Nd and 1-U were probed further by continuous wave X-band (ca. 9.4 GHz) EPR spectroscopy, with spectra modelled using EasySpin. The easy-axis powder EPR spectrum for 1-Ce at 7 K (Table , see Supporting Information Figure ) is best modelled as an effective S = ½ with g1 = 2.445 and g2 = 0.786 which are clearly observed, whilst g3 ~ 0.57 is broadened into the baseline. An easy-axis powder EPR spectrum was also observed for 1-Nd at 5 K, where hyperfine coupling to I = 7/2 143 Nd (12.2%) and 145 Nd (8.3%) nuclei could be modelled for the sharp low-field feature (g1 = 6.26, A1 = 1,860 MHz) and a broad absorption at high field to account for g2 (0.36), g3 was not observed (< 0.4; Table , Figure ). A frozen solution EPR spectrum of 1-Nd in 2-Me-THF at 7 K reveals a sharp easy-axis component, consistent with the powder EPR spectrum, in addition to a broad rhombic signal spanning 115 -850 mT with a peak centered at g1 ~ 4.8, a broad derivative-like feature at g2 ~ 2.1 and no resolved g3 feature (broadened into g2 or < 0.4; Table , Figure ). The broad rhombic signal, which deviates significantly from the solid-state data, could arise from Nd(THF)n (n = 0 or 1) and/or a range of intermediate geometries; this assertion is supported by the significant change in the g-values of the ground Kramers doublet when THF ligands are removed, see below (see Supporting Information Table ). The powder EPR spectrum of 1-U is dominated by a broad feature from 100 -600 mT that shows two lower-field features at g ~ 6.6 and 5.4 and contains a sharp organic radical signal at g = 2.0023 (Table , see Supporting Information Figure ). This spectrum suggests the presence of multiple species from sample decomposition with allowed EPR transitions. [La{Si(SiMe3)3}3(THF)n] (n = 0 or 1) using the Amsterdam Density Functional (ADF) suite version 2017 with standard convergence criteria, in order to probe their electronic structures (see Experimental Section for details). The model for 1-La used the metrical parameters observed by single crystal XRD with geometry-optimized H-atom positions, whilst in the absence of crystallographic metrical data the atomic positions of models of La(THF)1 and La(THF)0 desolvated analogues were fully geometry-optimized (see Supporting Information Tables S6-S8 for atomic coordinates of geometry-optimized structures). We calculated the δSi chemical shifts of both the metal-bound Si atoms and the SiMe3 groups for 1-La, La(THF)1 and La(THF)0 using BP86, PBE0, SAOP and B3LYP functionals, with a range of hybrid density functionals for the latter incorporating between 10 and 50% of the exact exchange energy from Hartree-Fock (HF) theory. Whilst PBE0 has been used often to calculate NMR chemical shifts, and SAOP often provides good correlation with experimental data despite being less computationally demanding, we find that B3LYP with 40% HF exchange energy (B3LYPHF40) gives the best agreement for the complexes investigated herein, noting that in our hands B3LYPHF20-40 calculations have well-reproduced experimental f-element-bound C, N, and 31 P chemical shift parameters. Here we report mean values of calculated δSi chemical shifts for metal-bound Si atoms and weighted averages for those within SiMe3 groups from all hypersilanide ligands to account for dynamic averaging (Table ; see Supporting Information Tables S9-S14 for results from other functionals). However, we note that for 1-La, La(THF)1