Synthesis of Compounds 1-3

The synthesis of 1-3 is straightforward, and the compounds were recovered in varying yields. All reactions are modified versions of the published work on the unsubstituted benzoate Fe₆Ln₃ compounds (Kühne et al., 2016). The elemental analysis was performed on dried polycrystalline samples. Due to the volatility of the methanol molecules within the crystal lattice, the elemental analysis was fitted using water molecules in the crystal lattice replacing the methanol molecules. The IR spectra of 2 and 3 are shown in Figure S21, and highlight the structural similarities of the clusters, including the carboxylate C-O stretching bands [~1,540 cm⁻¹ (antisymmetric) and ~1,410 cm⁻¹ (symmetric)] and the oxime bands (C=N ~1,590 cm⁻¹). No differences resulting from a monodentate 4-bromobenzoate in 3 are found in the IR spectra. PXRD patterns of 2 and 3 were recorded on dried samples (Figure S23), highlighting the presence of the main peaks in the correct positions. The relative intensities of the peaks show some differences with the predicted pattern likely caused by the loss of solvent. However, despite this the extracted unit cell parameters are in good agreement with the single crystal data.

Compound 1: [Fe₆Dy₃(μ-OMe)₉(vanox)₆(F-benz)₆]^.12MeOH^.H₂O: H₂vanox (0.4 mmol; 0.066 g) and NaOMe (1.0 mmol; 0.054 g) were dissolved in 10 ml MeOH and were added to a solution of FeCl2.4H₂O (0.2 mmol; 0.040 g), Dy(NO₃)3.6H₂O (0.2 mmol; 0.092 g) and 4-fluorobenzoic acid (0.4 mmol; 0.056 g) in 10 ml MeOH. The dark red, almost black, solution was stirred for 10 min at room temperature, and left to stand for crystallization without filtration. After 1 week, 1 crystallized as dark red-black blocks suitable for single crystal X-ray analysis.

Yield of [Fe₆Dy₃(μ-OMe)₉(vanox)₆(F-benz)₆]^.12MeOH^. H₂O: 55 mg (50% related to Fe)

Elemental analysis for [C₉₉H₉₃Fe₆Dy₃N₆O₃₉F₆]^.10.6H₂O (%): calculated: C: 38.13, H: 3.69; N: 2.69; found: C: 38.11; H: 3.67; N: 2.71.

IR (KBr):/cm⁻¹ = 3,441 (m), 2,822 (w), 1,606 (s), 1,591 (s), 1,543 (s), 1,508 (w), 1,459 (s), 1,439 (m), 1,410 (s), 1,354 (w), 1,269 (m), 1,239 (w), 1,221 (m), 1,153 (m), 1,094 (w), 1,056 (s), 965 (m), 856 (m), 783 (m), 764 (m), 737 (w), 691 (w), 657 (m), 618 (m), 555 (w), 500 (w), 461 (m).

Compound 2: [Fe₆Dy₃(μ-OMe)₉(vanox)₆(Cl-benz)₆]^. 13MeOH: H₂vanox (0.4 mmol; 0.066 g) and NaOMe (1.5 mmol; 0.081 g) were dissolved in 10 ml MeOH and were added to a solution of FeCl2.4H₂O (0.2 mmol; 0.040 g), Dy(NO₃)3.6H₂O (0.2 mmol; 0.092 g) and 4-chlorobenzoic acid (0.4 mmol; 0.063 g) in 10 ml MeOH. The dark red, almost black, solution was stirred for 10 min at room temperature, and left to stand for crystallization without filtration. After 1 week, 2 crystallized as dark red-black blocks suitable for single crystal X-ray analysis.

Yield of [Fe₆Dy₃(μ-OMe)₉(vanox)₆(Cl-benz)₆]^.13MeOH: 51 mg (44% related to Fe)

Elemental analysis for [C₉₉H₉₃Fe₆Dy₃N₆O₃₉Cl₆]^.4.6MeOH^. 5.9H₂O (%): calculated: C: 37.94, H: 3.78; N: 2.56; found: C: 37.73; H: 3.57; N: 2.35.

IR (KBr):/cm⁻¹ = 3,439 (m), 2,991 (w), 2,927 (m), 2,821 (m), 1,592 (s), 1,537 (s), 1,459 (s), 1,407 (s), 1,268 (s), 1,221 (s), 1,171 (m), 1,093 (s), 1,056 (s), 964 (s), 853 (m), 776 (m), 737 (m), 656 (s), 584 (w), 540 (m), 458 (m).

Compound 3: [Fe₆Dy₃(μ-OMe)₉(vanox)₆(Br-benz)₆ (MeOH)]^.9MeOH: H₂vanox (0.4 mmol; 0.066 g) and NaOMe (1.5 mmol; 0.081 g) were dissolved in 10 ml MeOH and were added to a solution of FeCl2.4H₂O (0.2 mmol; 0.040 g), Dy(NO₃)3.6H₂O (0.2 mmol; 0.092 g), and 4-bromobenzoic acid (0.4 mmol; 0.080 g) in 10 ml MeOH and 5 ml CH₂Cl₂. The dark red, almost black, solution was stirred for 10 min at room temperature, then filtered and left to stand for crystallization. After 2 weeks, 3 crystallized as dark red-black blocks suitable for single crystal X-ray analysis.

Yield of [Fe₆Dy₃(μ-OMe)₉(vanox)₆(Br-benz)₆(MeOH)]^. 9MeOH: 43 mg (36% related to Fe)

Elemental analysis for [C₁₀₀H₉₇Fe₆Dy₃N₆O₄₀Br₆]^.0.9 MeOH^.13.2H₂O (%): calculated: C: 33.74, H: 3.56; N: 2.34; found: C: 33.52; H: 3.79; N: 2.57.

IR (KBr):/cm⁻¹ = 3,437 (m), 2,943 (w), 2,822 (w), 1,588 (s), 1,537 (s), 1,459 (s), 1,438 (w), 1,406 (s), 1,356 (w), 1,270 (m), 1,222 (m), 1,171 (m), 1,057 (s), 1,013 (m), 966 (m), 854 (m), 771 (s), 736 (m), 657 (m), 572 (w), 504 (m), 460 (m).