A C2-symmetric, basic Fe(iii) carboxylate complex derived from a novel triptycene-based chelating carboxylate ligand

Li, Yang; Wilson, Justin J.; H., Loi; Apfel, Ulf‐Peter; Lippard, Stephen J.

doi:10.1039/c2dt31260c

Cited by 7 publications

(7 citation statements)

References 18 publications

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“…This was consistent with a limited amount of PNFs in the 30 mM iron sample, or complete absence of PNFs in the other iron containing samples ( Figure S5 ), which suggests that the iron may have interacted with the carboxylic acid groups on the protein chains. These interactions could include the formation of tri/pentanuclear carboxylate complexes with low charge, 52 , 53 which have been reported to be stable at low pH values (< 2). 54 , 55 The explanation is in agreement with the result that no Fe 2/3+ ions, in the form of chloride salts, or formed oxides, could be observed in the X-ray diffraction patterns ( Figure S1 ).…”

Section: Resultsmentioning

confidence: 99%

Protein Nanofibrils and Their Hydrogel Formation with Metal Ions

Capezza

Xiao

et al. 2021

ACS Nano

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Protein nanofibrils (PNFs) have been prepared by whey protein fibrillation at low pH and in the presence of different metal ions. The effect of the metal ions was systematically studied both in terms of PNF suspension gelation behavior and fibrillation kinetics. A high valence state and a small ionic radius ( e.g ., Sn 4+ ) of the metal ion resulted in the formation of hydrogels already at a metal ion concentration of 30 mM, whereas an intermediate valence state and larger ionic radius (Co 2+ , Ni 2+ , Al 3+ ) resulted in the hydrogel formation occurring at 60 mM. A concentration of 120 mM of Na + was needed to form a PNF hydrogel, while lower concentrations showed liquid behaviors similar to the reference PNF solution where no metal ions had been introduced. The hydrogel mechanics were investigated at steady-state conditions after 24 h of incubation/gelation, revealing that more acidic (smaller and more charged) metal ions induced ca . 2 orders of magnitude higher storage modulus as compared to the less acidic metal ions (with smaller charge and larger radius) for the same concentration of metal ions. The viscoelastic nature of the hydrogels was attributed to the ability of the metal ions to coordinate water molecules in the vicinity of the PNFs. The presence of metal ions in the solutions during the growth of the PNFs typically resulted in curved fibrils, whereas an upper limit of the concentration existed when oxides/hydroxides were formed, and the hydrogels lost their gel properties due to phase separation. Thioflavin T (ThT) fluorescence was used to determine the rate of the fibrillation to form 50% of the total PNFs ( t 1/2 ), which decreased from 2.3 to ca . 0.5 h depending on the specific metal ions added.

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Section: Resultsmentioning

confidence: 99%

Protein Nanofibrils and Their Hydrogel Formation with Metal Ions

Capezza

Xiao

et al. 2021

ACS Nano

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“…The structure of the central Fe 3 (μ 3 -O) core resembles that of the trinuclear oxo-centered iron complexes of the general formula [Fe 3 (μ 3 -O)(O 3 CR) 6 L 3 ] z ( z = 1+ and 0 and L = neutral monodentate ligand), known as “basic carboxylates”, which have been studied intensively . The widespread occurrence of the {Fe 3 O(O 2 CR) 6 } + motif is most likely a consequence of its thermodynamic stability . Attempts to obtain 2 in a controlled way by adding Fe III or an excess of Fe II in the syntheses were unsuccessful.…”

Section: Results and Discussionmentioning

confidence: 99%

Nonanuclear Spin-Crossover Complex Containing Iron(II) and Iron(III) Based on a 2,6-Bis(pyrazol-1-yl)pyridine Ligand Functionalized with a Carboxylate Group

et al. 2016

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The synthesis and magnetostructural characterization of [Fe(III)3(μ3-O)(H2O)3[Fe(II)(bppCOOH)(bppCOO)]6](ClO4)13·(CH3)2CO)6·(solvate) (2) are reported. This compound is obtained as a secondary product during synthesis of the mononuclear complex [Fe(II)(bppCOOH)2](ClO4)2 (1). The single-crystal X-ray diffraction structure of 2 shows that it contains the nonanuclear cluster of the formula [Fe(III)3(μ3-O)(H2O)3[Fe(II)(bppCOOH)(bppCOO)]6](13+), which is formed by a central Fe(III)3O core coordinated to six partially deprotonated [Fe(II)(bppCOOH)(bppCOO)](+) complexes. Raman spectroscopy studies on single crystals of 1 and 2 have been performed to elucidate the spin and oxidation states of iron in 2. These studies and magnetic characterization indicate that most of the iron(II) complexes of 2 remain in the low-spin (LS) state and present a gradual and incomplete spin crossover above 300 K. On the other hand, the Fe(III) trimer shows the expected antiferromagnetic behavior. From the structural point of view, 2 represents the first example in which bppCOO(-) acts as a bridging ligand, thus forming a polynuclear magnetic complex.

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“…Because the active site of sMMOH utilizes carboxylate rather than ester groups, the analogous ligand, H 2 L2 Ph4 , which bears sterically protected bis(benzoxazole) diacid ligands, was synthesized. 47 The coordination of H 2 L2 Ph4 to iron in the presence of an external carboxylate afforded the unanticipated triiron complex, [NaFe 3 ( L2 Ph4 ) 2 (μ 3 -O)(μ-O 2 CCPh 3 ) 2 (H 2 O) 3 ](OTf) 2 , having a “basic iron acetate” core. 47 A noteworthy feature of the [NaFe 3 ( L2 Ph4 ) 2 (μ 3 -O)(μ-O 2 CCPh 3 ) 2 (H 2 O) 3 ](OTf) 2 structure is the lack of iron coordination at the nitrogen atoms of the benzoxazole arms.…”

Section: Resultsmentioning

confidence: 99%

“…47 The coordination of H 2 L2 Ph4 to iron in the presence of an external carboxylate afforded the unanticipated triiron complex, [NaFe 3 ( L2 Ph4 ) 2 (μ 3 -O)(μ-O 2 CCPh 3 ) 2 (H 2 O) 3 ](OTf) 2 , having a “basic iron acetate” core. 47 A noteworthy feature of the [NaFe 3 ( L2 Ph4 ) 2 (μ 3 -O)(μ-O 2 CCPh 3 ) 2 (H 2 O) 3 ](OTf) 2 structure is the lack of iron coordination at the nitrogen atoms of the benzoxazole arms. We hypothesized that these N atoms do not bind to the iron centers because of the low basicity of the benzoxazole moiety (pK b = 13.2).…”

Section: Resultsmentioning

confidence: 99%

Triptycene‐Based, Carboxylate‐Bridged Biomimetic Diiron(II) Complexes

Soe

Wilson

et al. 2013

Eur J Inorg Chem

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A triptycene-based bis(benzimidazole) ester ligand, L3, was designed to enhance the electron donating ability of the heterocyclic nitrogen atoms relative to those of the first generation bis(benzoxazole) analogs, L1 and L2. A convergent synthesis of L3 was designed and executed. Three-component titration experiments using UV-visible spectroscopy revealed that the desired diiron(II) complex could be obtained with a 1:2:1 ratio of L3:Fe(OTf)2(MeCN)2:external carboxylate reactants. X-ray crystallographic studies of two diiron complexes derived in this manner from L3 revealed their formulas to be [Fe2L3(μ-OH)(μ-O2CR)(OTf)2], where R = 2,6-bis(p-tolyl)benzoate (7) or triphenylacetate (8). The structures are similar to that of a diiron complex derived from L1, [Fe2L1(μ-OH)(μ-O2CArTol)(OTf)2] (9) with a notable difference being that, in 7 and 8, the geometry at iron more closely resembles square-pyramidal than trigonal-bipyramidal. Mössbauer spectroscopic analyses of 7 and 8 indicate the presence of high-spin diiron(II) cores. These results demonstrate the importance of substituting benzimidazole for benzoxazole for assembling biomimetic diiron complexes with syn disposition of two N-donor ligands, as found in O2-activating carboxylate-bridged diiron centers in biology.

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A C2-symmetric, basic Fe(iii) carboxylate complex derived from a novel triptycene-based chelating carboxylate ligand

Cited by 7 publications

References 18 publications

Protein Nanofibrils and Their Hydrogel Formation with Metal Ions

Protein Nanofibrils and Their Hydrogel Formation with Metal Ions

Nonanuclear Spin-Crossover Complex Containing Iron(II) and Iron(III) Based on a 2,6-Bis(pyrazol-1-yl)pyridine Ligand Functionalized with a Carboxylate Group

Triptycene‐Based, Carboxylate‐Bridged Biomimetic Diiron(II) Complexes

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