Molecular Modeling of the Physical Properties for Aqueous Amine Solution Containing a CO₂ Hydration Catalyst

The effects of an amphiphilic CO₂ hydration catalyst (C3P) on the physical properties of aqueous monoethanolamine (MEA) solutions were studied using molecular simulations and verified experimentally. Adding 2.7–27.7 g/L of C3P in 30 wt % MEA aqueous solution did not significantly affect the solution viscosity, surface tension, or CO₂ diffusivity. These results confirm that the previously reported increase in CO₂ mass transfer by C3P is due to CO₂ hydration catalysis and not due to changes in the physical properties of the MEA solution. Additional simulations indicate that the catalyst molecules tend to aggregate in MEA solution and are preferentially adsorbed at the gas–liquid interface region. For the catalyst molecules remaining in the bulk solution, the local concentrations of CO₂ and MEA in the area immediately around the catalyst are increased while the local water concentration is decreased, relative to their concentrations in the rest of the bulk MEA solution

Synthesis and Ligand Non-Innocence of Thiolate-Ligated (N₄S) Iron(II) and Nickel(II) Bis(imino)pyridine Complexes

The known iron­(II) complex [Fe^II(LN₃S)­(OTf)] (<b>1</b>) was used as starting material to prepare the new biomimetic (N₄S­(thiolate)) iron­(II) complexes [Fe^II(LN₃S)­(py)]­(OTf) (<b>2</b>) and [Fe^II(LN₃S)­(DMAP)]­(OTf) (<b>3</b>), where LN₃S is a tetradentate bis­(imino)­pyridine (BIP) derivative with a covalently tethered phenylthiolate donor. These complexes were characterized by X-ray crystallography, ultraviolet–visible (UV-vis) spectroscopic analysis, ¹H nuclear magnetic resonance (NMR), and Mössbauer spectroscopy, as well as electrochemistry. A nickel­(II) analogue, [Ni^II(LN₃S)]­(BF₄) (<b>5</b>), was also synthesized and characterized by structural and spectroscopic methods. Cyclic voltammetric studies showed <b>1</b>–<b>3</b> and <b>5</b> undergo a single reduction process with <i>E</i>_1/2 between −0.9 V to −1.2 V versus Fc⁺/Fc. Treatment of <b>3</b> with 0.5% Na/Hg amalgam gave the monoreduced complex [Fe­(LN₃S)­(DMAP)]⁰ (<b>4</b>), which was characterized by X-ray crystallography, UV-vis spectroscopic analysis, electron paramagnetic resonance (EPR) spectroscopy (<i>g =</i> [2.155, 2.057, 2.038]), and Mössbauer (δ = 0.33 mm s^–1; Δ<i>E</i>_Q = 2.04 mm s^–1) spectroscopy. Computational methods (DFT) were employed to model complexes <b>3</b>–<b>5</b>. The combined experimental and computational studies show that <b>1</b>–<b>3</b> are 5-coordinate, high-spin (<i>S</i> = 2) Fe^II complexes, whereas <b>4</b> is best described as a 5-coordinate, intermediate-spin (<i>S</i> = 1) Fe^II complex antiferromagnetically coupled to a ligand radical. This unique electronic configuration leads to an overall doublet spin (<i>S</i>_total = 1/2) ground state. Complexes <b>2</b> and <b>3</b> are shown to react with O₂ to give S-oxygenated products, as previously reported for <b>1</b>. In contrast, the monoreduced <b>4</b> appears to react with O₂ to give a mixture of sulfur oxygenates and iron oxygenates. The nickel­(II) complex <b>5</b> does not react with O₂, and even when the monoreduced nickel complex is produced, it appears to undergo only outer-sphere oxidation with O₂

Secondary Coordination Sphere Influence on the Reactivity of Nonheme Iron(II) Complexes: An Experimental and DFT Approach

The new biomimetic ligands N4Py^2Ph (<b>1</b>) and N4Py^2Ph,amide (<b>2</b>) were synthesized and yield the iron­(II) complexes [Fe^II(N4Py^2Ph)­(NCCH₃)]­(BF₄)₂ (<b>3</b>) and [Fe^II(N4Py^2Ph,amide)]­(BF₄)₂ (<b>5</b>). Controlled orientation of the Ph substituents in <b>3</b> leads to facile triplet spin reactivity for a putative Fe^IV(O) intermediate, resulting in rapid arene hydroxylation. Addition of a peripheral amide substituent within hydrogen-bond distance of the iron first coordination sphere leads to stabilization of a high-spin Fe^IIIOOR species which decays without arene hydroxylation. These results provide new insights regarding the impact of secondary coordination sphere effects at nonheme iron centers

Synthesis and Ligand Non-Innocence of Thiolate-Ligated (N₄S) Iron(II) and Nickel(II) Bis(imino)pyridine Complexes

The known iron­(II) complex [Fe^II(LN₃S)­(OTf)] (<b>1</b>) was used as starting material to prepare the new biomimetic (N₄S­(thiolate)) iron­(II) complexes [Fe^II(LN₃S)­(py)]­(OTf) (<b>2</b>) and [Fe^II(LN₃S)­(DMAP)]­(OTf) (<b>3</b>), where LN₃S is a tetradentate bis­(imino)­pyridine (BIP) derivative with a covalently tethered phenylthiolate donor. These complexes were characterized by X-ray crystallography, ultraviolet–visible (UV-vis) spectroscopic analysis, ¹H nuclear magnetic resonance (NMR), and Mössbauer spectroscopy, as well as electrochemistry. A nickel­(II) analogue, [Ni^II(LN₃S)]­(BF₄) (<b>5</b>), was also synthesized and characterized by structural and spectroscopic methods. Cyclic voltammetric studies showed <b>1</b>–<b>3</b> and <b>5</b> undergo a single reduction process with <i>E</i>_1/2 between −0.9 V to −1.2 V versus Fc⁺/Fc. Treatment of <b>3</b> with 0.5% Na/Hg amalgam gave the monoreduced complex [Fe­(LN₃S)­(DMAP)]⁰ (<b>4</b>), which was characterized by X-ray crystallography, UV-vis spectroscopic analysis, electron paramagnetic resonance (EPR) spectroscopy (<i>g =</i> [2.155, 2.057, 2.038]), and Mössbauer (δ = 0.33 mm s^–1; Δ<i>E</i>_Q = 2.04 mm s^–1) spectroscopy. Computational methods (DFT) were employed to model complexes <b>3</b>–<b>5</b>. The combined experimental and computational studies show that <b>1</b>–<b>3</b> are 5-coordinate, high-spin (<i>S</i> = 2) Fe^II complexes, whereas <b>4</b> is best described as a 5-coordinate, intermediate-spin (<i>S</i> = 1) Fe^II complex antiferromagnetically coupled to a ligand radical. This unique electronic configuration leads to an overall doublet spin (<i>S</i>_total = 1/2) ground state. Complexes <b>2</b> and <b>3</b> are shown to react with O₂ to give S-oxygenated products, as previously reported for <b>1</b>. In contrast, the monoreduced <b>4</b> appears to react with O₂ to give a mixture of sulfur oxygenates and iron oxygenates. The nickel­(II) complex <b>5</b> does not react with O₂, and even when the monoreduced nickel complex is produced, it appears to undergo only outer-sphere oxidation with O₂

Synthesis and Ligand Non-Innocence of Thiolate-Ligated (N₄S) Iron(II) and Nickel(II) Bis(imino)pyridine Complexes

The known iron­(II) complex [Fe^II(LN₃S)­(OTf)] (<b>1</b>) was used as starting material to prepare the new biomimetic (N₄S­(thiolate)) iron­(II) complexes [Fe^II(LN₃S)­(py)]­(OTf) (<b>2</b>) and [Fe^II(LN₃S)­(DMAP)]­(OTf) (<b>3</b>), where LN₃S is a tetradentate bis­(imino)­pyridine (BIP) derivative with a covalently tethered phenylthiolate donor. These complexes were characterized by X-ray crystallography, ultraviolet–visible (UV-vis) spectroscopic analysis, ¹H nuclear magnetic resonance (NMR), and Mössbauer spectroscopy, as well as electrochemistry. A nickel­(II) analogue, [Ni^II(LN₃S)]­(BF₄) (<b>5</b>), was also synthesized and characterized by structural and spectroscopic methods. Cyclic voltammetric studies showed <b>1</b>–<b>3</b> and <b>5</b> undergo a single reduction process with <i>E</i>_1/2 between −0.9 V to −1.2 V versus Fc⁺/Fc. Treatment of <b>3</b> with 0.5% Na/Hg amalgam gave the monoreduced complex [Fe­(LN₃S)­(DMAP)]⁰ (<b>4</b>), which was characterized by X-ray crystallography, UV-vis spectroscopic analysis, electron paramagnetic resonance (EPR) spectroscopy (<i>g =</i> [2.155, 2.057, 2.038]), and Mössbauer (δ = 0.33 mm s^–1; Δ<i>E</i>_Q = 2.04 mm s^–1) spectroscopy. Computational methods (DFT) were employed to model complexes <b>3</b>–<b>5</b>. The combined experimental and computational studies show that <b>1</b>–<b>3</b> are 5-coordinate, high-spin (<i>S</i> = 2) Fe^II complexes, whereas <b>4</b> is best described as a 5-coordinate, intermediate-spin (<i>S</i> = 1) Fe^II complex antiferromagnetically coupled to a ligand radical. This unique electronic configuration leads to an overall doublet spin (<i>S</i>_total = 1/2) ground state. Complexes <b>2</b> and <b>3</b> are shown to react with O₂ to give S-oxygenated products, as previously reported for <b>1</b>. In contrast, the monoreduced <b>4</b> appears to react with O₂ to give a mixture of sulfur oxygenates and iron oxygenates. The nickel­(II) complex <b>5</b> does not react with O₂, and even when the monoreduced nickel complex is produced, it appears to undergo only outer-sphere oxidation with O₂

Synthesis and Ligand Non-Innocence of Thiolate-Ligated (N₄S) Iron(II) and Nickel(II) Bis(imino)pyridine Complexes

The known iron­(II) complex [Fe^II(LN₃S)­(OTf)] (<b>1</b>) was used as starting material to prepare the new biomimetic (N₄S­(thiolate)) iron­(II) complexes [Fe^II(LN₃S)­(py)]­(OTf) (<b>2</b>) and [Fe^II(LN₃S)­(DMAP)]­(OTf) (<b>3</b>), where LN₃S is a tetradentate bis­(imino)­pyridine (BIP) derivative with a covalently tethered phenylthiolate donor. These complexes were characterized by X-ray crystallography, ultraviolet–visible (UV-vis) spectroscopic analysis, ¹H nuclear magnetic resonance (NMR), and Mössbauer spectroscopy, as well as electrochemistry. A nickel­(II) analogue, [Ni^II(LN₃S)]­(BF₄) (<b>5</b>), was also synthesized and characterized by structural and spectroscopic methods. Cyclic voltammetric studies showed <b>1</b>–<b>3</b> and <b>5</b> undergo a single reduction process with <i>E</i>_1/2 between −0.9 V to −1.2 V versus Fc⁺/Fc. Treatment of <b>3</b> with 0.5% Na/Hg amalgam gave the monoreduced complex [Fe­(LN₃S)­(DMAP)]⁰ (<b>4</b>), which was characterized by X-ray crystallography, UV-vis spectroscopic analysis, electron paramagnetic resonance (EPR) spectroscopy (<i>g =</i> [2.155, 2.057, 2.038]), and Mössbauer (δ = 0.33 mm s^–1; Δ<i>E</i>_Q = 2.04 mm s^–1) spectroscopy. Computational methods (DFT) were employed to model complexes <b>3</b>–<b>5</b>. The combined experimental and computational studies show that <b>1</b>–<b>3</b> are 5-coordinate, high-spin (<i>S</i> = 2) Fe^II complexes, whereas <b>4</b> is best described as a 5-coordinate, intermediate-spin (<i>S</i> = 1) Fe^II complex antiferromagnetically coupled to a ligand radical. This unique electronic configuration leads to an overall doublet spin (<i>S</i>_total = 1/2) ground state. Complexes <b>2</b> and <b>3</b> are shown to react with O₂ to give S-oxygenated products, as previously reported for <b>1</b>. In contrast, the monoreduced <b>4</b> appears to react with O₂ to give a mixture of sulfur oxygenates and iron oxygenates. The nickel­(II) complex <b>5</b> does not react with O₂, and even when the monoreduced nickel complex is produced, it appears to undergo only outer-sphere oxidation with O₂

Synthesis and Ligand Non-Innocence of Thiolate-Ligated (N₄S) Iron(II) and Nickel(II) Bis(imino)pyridine Complexes

The known iron­(II) complex [Fe^II(LN₃S)­(OTf)] (<b>1</b>) was used as starting material to prepare the new biomimetic (N₄S­(thiolate)) iron­(II) complexes [Fe^II(LN₃S)­(py)]­(OTf) (<b>2</b>) and [Fe^II(LN₃S)­(DMAP)]­(OTf) (<b>3</b>), where LN₃S is a tetradentate bis­(imino)­pyridine (BIP) derivative with a covalently tethered phenylthiolate donor. These complexes were characterized by X-ray crystallography, ultraviolet–visible (UV-vis) spectroscopic analysis, ¹H nuclear magnetic resonance (NMR), and Mössbauer spectroscopy, as well as electrochemistry. A nickel­(II) analogue, [Ni^II(LN₃S)]­(BF₄) (<b>5</b>), was also synthesized and characterized by structural and spectroscopic methods. Cyclic voltammetric studies showed <b>1</b>–<b>3</b> and <b>5</b> undergo a single reduction process with <i>E</i>_1/2 between −0.9 V to −1.2 V versus Fc⁺/Fc. Treatment of <b>3</b> with 0.5% Na/Hg amalgam gave the monoreduced complex [Fe­(LN₃S)­(DMAP)]⁰ (<b>4</b>), which was characterized by X-ray crystallography, UV-vis spectroscopic analysis, electron paramagnetic resonance (EPR) spectroscopy (<i>g =</i> [2.155, 2.057, 2.038]), and Mössbauer (δ = 0.33 mm s^–1; Δ<i>E</i>_Q = 2.04 mm s^–1) spectroscopy. Computational methods (DFT) were employed to model complexes <b>3</b>–<b>5</b>. The combined experimental and computational studies show that <b>1</b>–<b>3</b> are 5-coordinate, high-spin (<i>S</i> = 2) Fe^II complexes, whereas <b>4</b> is best described as a 5-coordinate, intermediate-spin (<i>S</i> = 1) Fe^II complex antiferromagnetically coupled to a ligand radical. This unique electronic configuration leads to an overall doublet spin (<i>S</i>_total = 1/2) ground state. Complexes <b>2</b> and <b>3</b> are shown to react with O₂ to give S-oxygenated products, as previously reported for <b>1</b>. In contrast, the monoreduced <b>4</b> appears to react with O₂ to give a mixture of sulfur oxygenates and iron oxygenates. The nickel­(II) complex <b>5</b> does not react with O₂, and even when the monoreduced nickel complex is produced, it appears to undergo only outer-sphere oxidation with O₂