Tuning the Condensation Degree of {Fe^III_n} Oxo Clusters via Ligand Metathesis, Temperature, and Solvents

Abstract

Trinuclear μ-oxo-centered iron(III) isobutyrate clusters readily react with polyalcohol organic ligands under one-pot synthesis conditions. Depending on the ligand, solvent, and temperature, a range of hexa-, dodeca-, and doicosanuclear iron(III) oxo-hydroxo condensation products, isolated as (mdeaH)[FeO(thme)Cl]·0.5(MeCN)·0.5(HO) (1), [FeO(OH)(teda)(N)(MeO)]N(NO)(MeO)·2.5(HO) (2), [FeO(teda)Cl]·6(CHCl) (3), [FeO(OH)(OCCHMe)(bdea)(EtO)(HO)]·2(EtOH)·5(MeCN)·6(HO) (4), and [FeO(OH)(OCCHMe)(mdea)(EtO)(HO)](NO)·EtOH·HO (5), where tedaH = N, N, N', N'-tetrakis(2-hydroxyethyl)ethylenediamine; thmeH = 1,1,1-tris(hydroxymethyl)ethane; mdeaH = N-methyldiethanolamine; and bdeaH = N-butyldiethanolamine. Complete carboxylate metathesis in the {Fe} precursor complexes by thme or teda and the agglomeration of the formed species under solvothermal conditions afforded carboxylate-free {Fe} product (1) in MeCN/CHCl or {Fe} complexes (2 and 3) in MeOH/EtOH and CHCl/thf, respectively (thf = tetrahydrofuran). Single-crystal X-ray diffraction analyses revealed that 1 contains a [FeO(thme)Cl] cluster anion with a Lindqvist-type {Fe(μ-O)} core motif, charge-compensated by two protonated mdeaH cations. 2 comprises a [FeO(OH)(teda)(N)(MeO)] cation with a {FeO(OH)} core, whereas 3 contains a charge-neutral [FeO(teda)(Cl)] complex with an {FeO} core. Finally, employing flexible bdeaH or mdeaH ligands under soft reaction conditions afforded giant {Fe} oxo-hydroxo complexes (4 and 5) with a central {Fe} layer sandwiched between two outer {Fe} groups. Magnetic studies of 1-5 revealed strong antiferromagnetic coupling between the Fe spin centers in all clusters.

A high-nuclearity complex containing a decanuclear iron(iii)/oxo cage in a football-like structure and rare (R-/S)-hemiacetalate ligands in a butterfly-like format

“…[23][24][25] Although, there are many reports about high nuclearity iron(III)-oxo clusters with beautiful structures, such as high nuclearity iron(III)-oxo cages and wheels, and useful magnetic properties, a challenge in the eld of high nuclearity Fe(III)/oxo cluster chemistry remains the development of new synthetic methods to such molecules through the employment of new chelating or bridging organic ligands. [20][21][22][23][24][25][26] This investigation reports a 10-nuclear iron(III)/oxo cage with unusual (R-/S)hemiacetalate ligands ((R-/S)-py-hemi) by the employment of pyridine-2-carboxaldehyde (py-2-al), which displays football-like iron(III)/oxo cage, buttery-like structure and antiferromagnetism. The synthesis, proposed mechanism and the physical characterization are described in this contribution.…”

“…18,19 The high nuclearity iron(III)-oxo chemistry has being developed over many years by virtue of their important role in bioinorganic chemistry, molecular magnetism and so on. [20][21][22] The high charge and Lewis acidity of Fe III strongly favor formation of oxide bridges from water molecules and thus foster formation of higher-nuclearity clusters. [23][24][25] Although, there are many reports about high nuclearity iron(III)-oxo clusters with beautiful structures, such as high nuclearity iron(III)-oxo cages and wheels, and useful magnetic properties, a challenge in the eld of high nuclearity Fe(III)/oxo cluster chemistry remains the development of new synthetic methods to such molecules through the employment of new chelating or bridging organic ligands.…”

The Influence of Halide Substituents on the Structural and Magnetic Properties of Fe6Dy3 Rings

“…Cyclic 3d/4f clusters where 3d = Fe(III) offer new opportunities in chiral separation (Baniodeh et al, 2013), magnetic resonance imaging (MRI) (Guthausen et al, 2015;Ranzinger et al, 2016) and the magnetocaloric effect (Botezat et al, 2017;Schmidt et al, 2017b). The Fe/4f cyclic coordination clusters show perhaps the most exotic behavior and can be produced in different nuclearities, such as [Fe 2 Ln 2 ] (Song et al, 2013;Pugh et al, 2016;Alexandru et al, 2018), [Fe 3 Ln 2 ] (Baniodeh et al, 2013), [Fe 4 Dy 4 ] (Schray et al, 2010;Chen et al, 2015), [Fe 4 Ln 2 ] (Schmidt et al, 2012(Schmidt et al, , 2017aBaniodeh et al, 2013;Botezat et al, 2017Botezat et al, , 2019bChen et al, 2017), [Fe 5 Ln 3 ] (Baniodeh et al, 2013), [Fe 6 Ln 3 ] (Kühne et al, 2016;Botezat et al, 2019a), [Fe 6 Ln 4 ] (Botezat et al, 2019b), [Fe 8 Ln 8 ] (Zhang et al, 2020), [Fe 10 Ln 10 ] (Baniodeh et al, 2013(Baniodeh et al, , 2014, [Fe 16 Ln 4 ] (Baniodeh et al, 2011), and [Fe 18 Ln 6 ] (Botezat et al, 2017). The Fe 10 Gd 10 system demonstrated the potential of cyclized systems to show solid state properties on a molecular length scale-in this case, a quantum critical point tipping the system toward a ferromagnetic ultra-high spin state of S = 60 with a choice of at least 10,000 ground state configurations, making this a system with polynary rather than binary prospects (Baniodeh et al, 2018).…”

“…The Fe 10 Gd 10 system demonstrated the potential of cyclized systems to show solid state properties on a molecular length scale-in this case, a quantum critical point tipping the system toward a ferromagnetic ultra-high spin state of S = 60 with a choice of at least 10,000 ground state configurations, making this a system with polynary rather than binary prospects (Baniodeh et al, 2018). A particularly fascinating aspect to these systems is provided by examples where the components of the chain are not simply alternating iron and 4f ions (Schmidt et al, 2012(Schmidt et al, , 2017aBaniodeh et al, 2013;Botezat et al, 2017Botezat et al, , 2019b. This behavior was recently reported for the family of Fe 6 Ln 3 clusters (Kühne et al, 2016) where the repeating unit can be regarded as {Fe 2 Ln} 3 and three of these give an {Fe 6 Ln 3 } cycle.…”

“…The repeating units within big clusters can vary, but it is also possible to have a situation where there is no true cyclisation of a fundamental building block. This can be seen for example in the arrangement within [Fe 4 Ln 2 ] clusters where some structures can be described in terms of a {FeLn 2 } 2 cycle as shown by Schmidt et al (2012), Botezat et al (2019b), and Schmidt et al (2017a) which is very different from the cyclized strand of {FeLn 4 Fe} described in Baniodeh et al (2013). Other repeating units, such as {Fe 3 Dy} have been reported in the largest example of Fe/4f coordination cluster where the basic unit is repeated six times to give an {Fe 18 Dy 6 } cycle (Botezat et al, 2017).…”