An [Fe^III₃₄] Molecular Metal Oxide

Abstract

The dissolution of anhydrous iron bromide in a mixture of pyridine and acetonitrile, in the presence of an organic amine, results in the formation of an [Fe34] metal oxide molecule, structurally characterised by alternate layers of tetrahedral and octahedral FeIII ions connected by oxide and hydroxide ions. The outer shell of the complex is capped by a combination of pyridine molecules and bromide ions. Magnetic data, measured at temperatures as low as 0.4 K and fields up to 35 T, reveal competing antiferromagnetic exchange interactions; DFT calculations showing that the magnitudes of the coupling constants are highly dependent on both the Fe‐O‐Fe angles and Fe−O distances. The simplicity of the synthetic methodology, and the structural similarity between [Fe34], bulk iron oxides, previous FeIII–oxo cages, and polyoxometalates (POMs), hints that much larger molecular FeIII oxides can be made.

Atomically Precise Lanthanide‐Iron‐Oxo Clusters Featuring the ϵ‐Keggin Ion

“…[27] The magnetic susceptibility curveso f Gd 12 Fe 33 and Gd 16 Fe 29 show almostt he same tendency.W ith decreasing temperature, the c M T valuesg radually decreased to 114.63 and 125.46 cm 3 Kmol À1 at 120 Ka nd then rapidlyi ncrease to the maximum values of 413.56 and 523.00 cm 3 Kmol À1 at 3K for Gd 12 Fe 33 and Gd 16 Fe 29 ,r espectively.T he c M T values slightly decrease to 366.05 and 438.12 cm 3 Kmol À1 at 2K,r espectively. [28] The resultsr evealed that the substitution of metal sites resultsi nd ifferent magnetic coupling behaviour between Gd and Y-based compounds. For Y 16 Fe 29 ,t he c M T decreases rapidlyt ot he minimum value of 9.52 cm 3 Kmol À1 2Kdue to the strong antiferromagnetic interaction between the iron ions.…”

“…As shown in Figure 4, two Y 3 + ions (Y1) and two Fe 3 + ions (Fe1) in Y 12 Fe 33 (Figure 4b)a re exchanged by two Fe 3 + ions (Fe1')a nd two Gd 3 + ions (Gd1')i nGd 12 Fe 33 (Figure 4d), respectively.T he positiono f the lanthanide ions and iron ions are exchanged due to the different radii between the Y 3 + (0.0893 nm) and Gd 3 + (0.0938 nm) ions under the same reaction conditions. Meanwhile,t he four Fe 3 + ion (Fe1) 28 ] 25À that features the same metal ions arrangement as that reported prior for {Fe 17 }( Figure S8 d). [3] Furthermore, the neutral chelate [Fe(TEOA)]u nit formed by the Fe 3 + ion and deprotonated triethanolamine in 1-4 is invariable and cannotb er eplacedb yl anthanide ions.…”

“…It was accomplished by use of Bi 3 + to stabilizet he hydrolytically reactive cluster. [14] Employing ligands trans-4-Hydroxyl-l-proline (Hyp) and triethanolamine (TEOA-H 3 ), we isolated [Y 12 Fe 33 (TEOA) 12 (Hyp) 6 -(m 3 -OH) 20 (m 4 -O) 28 While TEOA hasb een used extensively in isolating iron-oxo clusters, [15] prolineh as been more scarcely exploited in this role. [10] Both processes involved deliberate removal of the capping bismuth.…”

“…In contrast, in the previously described a-Fe 13 , [9] hydroxyls occupy the m 2 -bridging sites within the edge-sharing trimers of the Keggini on, and oxos link the trimers by corner-sharing. This clusteru nit is then protected and stabilized by six organic Hyp ligandsa nd twelve coordinated water molecules, producing the cationic cluster unit [Y 12 Fe 33 (TEOA) 12 (Hyp) 6 (m 3 -OH) 20 (m 4 -O) 28 (H 2 O) 12 ] 23 + .F rom the structural profile, it may be speculated that Y 12 Fe 33 has ap rocess of growing from insidet oo utside. This clusteru nit is then protected and stabilized by six organic Hyp ligandsa nd twelve coordinated water molecules, producing the cationic cluster unit [Y 12 Fe 33 (TEOA) 12 (Hyp) 6 (m 3 -OH) 20 (m 4 -O) 28 (H 2 O) 12 ] 23 + .F rom the structural profile, it may be speculated that Y 12 Fe 33 has ap rocess of growing from insidet oo utside.…”

“…The four currently reported isostructural lanthanide-iron-oxo clusters are fully formulated [Y 12 Fe 33 (TEOA) 12 (Hyp) 6 (m 3 -OH) 20 (m 4 -O) 28 (H 2 O) 12 ](ClO 4 ) 23 ·50 H 2 O (1, Y 12 Fe 33 ), [Gd 12 Fe 33 (TEOA) 12 (Hyp) 6 (m 3 -OH) 20 (m 4 -O) 32 (H 2 O) 12 ]-(ClO 4 ) 15 ·50 H 2 O( 2, Gd 12 Fe 33 )a nd [Ln 16 Fe 29 (TEOA) 12 (Hyp) 6 (m 3 -OH) 24 (m 4 -O) 28 (H 2 O) 16 ](ClO 4 ) 16 (NO 3 ) 3 ·n H 2 O( Ln = Yf or 3, Y 16 Fe 29 , n = 37 and Ln = Gd for 4, Gd 16 Fe 29 n = 25;H yp = trans-4-Hydroxyl-l-proline and TEOA = triethanolamine). Devising strategies for synthesis and isolation of these molecular forms remains ac hallenge.…”