An Iron-Based Molecular Redox Switch as a Model for Iron Release from Enterobactin via the Salicylate Binding Mode

Ward, Thomas R.; Lutz, Andreas; Parel, Serge P.; Ensling, Jürgen; Gütlich, Philipp; Buglyó, Péter; Orvig, Chris

doi:10.1021/ic990225e

“…Here we brie¯y describe some interesting molecules that exhibit linkage isomerizations induced by electrochemical processes. Shanzer et al [8] and Ward et al [9] studied examples of linkage isomerizations of Fe 2+/3+ between two binding sites in a three-stranded ligand twisting into a helix, as shown in Fig. 2A.…”

Section: Linkage Isomerizations Induced By Electrochemical Processesmentioning

confidence: 99%

Molecular Hysteresis by Linkage Isomerizations Induced by Electrochemical Processes

Sano

¹

2001

Molecular Machines and Motors

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The redox behavior of [Ru(NH 3 ) 5 S ® O induced by electrochemical processes are reviewed. The properties of molecules speci®cally designed to exhibit a hysteresis loop on being addressed electrochemically are described. These molecules comprise a combination of two Ru 3+ /Ru 2+ couples, one with the metal attached to an electrochemically reversible group and the other with the metal attached to the sulfoxide by a bridging ligand. Their redox and kinetic behaviors are presented and their memory lives are determined as the rates of the conversions between two isomeric intermediate states. Reading out the memory by intervalence bands is also discussed. Some considerations are also presented for linkage isomerizations and molecular hysteresis.

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“…[3,4] Movement of metal ions, which takes place following a predetermined pathway, can be induced by different stimuli, such as a variation of the redox potential, [5,6] or a pH change. [1] This possibility gives rise to a new class of potential artificial molecular machines, [2] thus adding to the possibilities based on rotaxanes and catenanes.…”

mentioning

confidence: 99%

Untitled

Amendola¹,

Fabbrizzi²,

Mangano³

et al. 2002

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The translocation of a metal ion in a reversible and repeatable manner from one compartment to the other within a ditopic ligand could lead to mechanical work at the molecular level. [1] This possibility gives rise to a new class of potential artificial molecular machines, [2] thus adding to the possibilities based on rotaxanes and catenanes. [3,4] Movement of metal ions, which takes place following a predetermined pathway, can be induced by different stimuli, such as a variation of the redox potential, [5,6] or a pH change. [7] The use of pH as the stimulus is especially convenient as it involves a rather mild perturbation and does not cause degradation of the system, and hence its operation can be repeated at will, indefinitely. This situation is not always the case with the more drastic and destructive processes which involve an auxiliary oxidation and reduction reaction. The essential requirements for the occurrence of a pH-driven metal translocation process are that 1) one of the two coordinating compartments (A) also shows a distinct acid ± base behavior (for example, through the AH n >A nÀ nH equilibrium), and that 2) the coordinating tendencies of the two compartments decrease along the series A nÀ ) B ) AH n , where B is the second compartment that does not display acid ± base behavior, at least in the investigated pH interval. Thus, at a pH value in which AH n dominates, the metal ion stays in compartment B. On the other hand, when the pH value is increased and AH n deprotonates, the metal ion moves to the more appealing compartment A nÀ . The metal ion moves back to B on decreasing the pH value. In the case of transition metal ions, a change in the compartment typically modifies the stereochemistry and the ligand field experienced by the cation, thus altering its electronic structure and spectral features. Ultimately, the displacement of the metal ion is signaled by a color change of the solution. We show here that the position of the metal ion in the ditopic system can be determined by the powerful signal of a fluorescent indicator (which is present at a very low concentration) provided that the indicator is able to interact selectively with the metal ion.The envisaged ditopic ligand 1 contains two distinct tetradentate compartments: A and B. The donor set of A consists of two secondary amine and two secondary amide nitrogen atoms. As the amide group itself possesses poor or no coordinating tendencies, the neutral form AH 2 is expected to display minimum binding tendencies towards the chosen metal ion, Cu II . On the other hand, at neutral or slightly alkaline pH values, the amide group deprotonates in the presence of divalent late-transition-metal ions to give rise to a very strong donor group: thus, the doubly deprotonated A 2À compartment is expected to establish especially intense metal ± ligand interactions and give rise to a very stable complex with a square geometry. Compartment B is constituted by two 2,2'-bipyridine (bpy) fragments, which display fairly good binding tendencies towards Cu II...

show abstract

“…[1] This possibility gives rise to a new class of potential artificial molecular machines, [2] thus adding to the possibilities based on rotaxanes and catenanes. [3,4] Movement of metal ions, which takes place following a predetermined pathway, can be induced by different stimuli, such as a variation of the redox potential, [5,6] or a pH change. [7] The use of pH as the stimulus is especially convenient as it involves a rather mild perturbation and does not cause degradation of the system, and hence its operation can be repeated at will, indefinitely.…”

mentioning

confidence: 99%

“…Concentration of the species present at the equilibrium in a solution containing equimolar amounts of 1 ( LH 2 ) and Cu 2 ions; profiles a, b, c, and d refer to the variously protonated forms of LH 2 (from LH6 4 to LH 3 ). Profile e refers to the metal-containing protonated species [Cu II (LH 3 )] 3 .…”

mentioning

confidence: 99%

“…[3] The endothermic nature of the overall process has been invoked to explain the failure of a radicalchain approach to accomplish this reaction. [4,5] While performing b-scission reactions of cycloalkanols, [6] we noticed that (diacetoxyiodo)benzene [PhI(OAc) 2 ] [7] gave rise to a mixture of compounds, where iodocyclohexane (2 b) was found as the major product, resulting from an activation of the cyclohexane used as solvent.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Signal Amplification by a Fluorescent Indicator of a pH-Driven Intramolecular Translocation of a Copper(II) Ion

Amendola

¹

,

Fabbrizzi

²

,

Mangano

³

et al. 2002

Angew. Chem. Int. Ed.

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The translocation of a metal ion in a reversible and repeatable manner from one compartment to the other within a ditopic ligand could lead to mechanical work at the molecular level. [1] This possibility gives rise to a new class of potential artificial molecular machines, [2] thus adding to the possibilities based on rotaxanes and catenanes. [3,4] Movement of metal ions, which takes place following a predetermined pathway, can be induced by different stimuli, such as a variation of the redox potential, [5,6] or a pH change. [7] The use of pH as the stimulus is especially convenient as it involves a rather mild perturbation and does not cause degradation of the system, and hence its operation can be repeated at will, indefinitely. This situation is not always the case with the more drastic and destructive processes which involve an auxiliary oxidation and reduction reaction. The essential requirements for the occurrence of a pH-driven metal translocation process are that 1) one of the two coordinating compartments (A) also shows a distinct acid ± base behavior (for example, through the AH n >A nÀ nH equilibrium), and that 2) the coordinating tendencies of the two compartments decrease along the series A nÀ ) B ) AH n , where B is the second compartment that does not display acid ± base behavior, at least in the investigated pH interval. Thus, at a pH value in which AH n dominates, the metal ion stays in compartment B. On the other hand, when the pH value is increased and AH n deprotonates, the metal ion moves to the more appealing compartment A nÀ . The metal ion moves back to B on decreasing the pH value. In the case of transition metal ions, a change in the compartment typically modifies the stereochemistry and the ligand field experienced by the cation, thus altering its electronic structure and spectral features. Ultimately, the displacement of the metal ion is signaled by a color change of the solution. We show here that the position of the metal ion in the ditopic system can be determined by the powerful signal of a fluorescent indicator (which is present at a very low concentration) provided that the indicator is able to interact selectively with the metal ion.The envisaged ditopic ligand 1 contains two distinct tetradentate compartments: A and B. The donor set of A consists of two secondary amine and two secondary amide nitrogen atoms. As the amide group itself possesses poor or no coordinating tendencies, the neutral form AH 2 is expected to display minimum binding tendencies towards the chosen metal ion, Cu II . On the other hand, at neutral or slightly alkaline pH values, the amide group deprotonates in the presence of divalent late-transition-metal ions to give rise to a very strong donor group: thus, the doubly deprotonated A 2À compartment is expected to establish especially intense metal ± ligand interactions and give rise to a very stable complex with a square geometry. Compartment B is constituted by two 2,2'-bipyridine (bpy) fragments, which display fairly good binding tendencies towards Cu II...

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An Iron-Based Molecular Redox Switch as a Model for Iron Release from Enterobactin via the Salicylate Binding Mode

Cited by 48 publications

References 42 publications

Molecular Hysteresis by Linkage Isomerizations Induced by Electrochemical Processes

Molecular Hysteresis by Linkage Isomerizations Induced by Electrochemical Processes

Untitled

Signal Amplification by a Fluorescent Indicator of a pH-Driven Intramolecular Translocation of a Copper(II) Ion

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