Understanding the Effect of Internal Electrostatic Fields Created by Alkaline Earth Metal Ions Poised over Secondary Coordination Sphere of Molecular Iron Complexes

Inorganic Chemistry, Год журнала: 2023, Номер 62(25), С. 9818 - 9826

Опубликована: Июнь 13, 2023

Understanding the effect of local electrical field around reaction center in enzymes and molecular catalysis is an important topic research. Herein, we explored electrostatic exerted by alkaline earth metal ions (M2+ = Mg2+, Ca2+, Sr2+, Ba2+) Fe FeIII(Cl) complexes experimental computational investigations. M2+ coordinated dinuclear (12M) were synthesized characterized X-ray crystallography different spectroscopic techniques. EPR magnetic moment measurements exhibited presence high-spin FeIII centers 12M complexes. Electrochemical investigations revealed FeIII/FeII reduction potential values shifted anodically compared to 1. Likewise, 2p3/2 2p1/2 peaks XPS data found shift positively complexes, demonstrating that redox-inactive make more electropositive. However, nearly similar λmax UV–vis spectra observed 1 The first-principles-based simulations further impact on stabilizing 3d-orbitals Fe. distortion Laplacian distribution (∇2ρ(r)) electron density also indicates possibility having Fe–M interactions these absence a bond critical point between dominant through-space interaction centers. Experimental studies collectively imply installation internal fields alters electronic structure FeIII.

Язык: Английский

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A tetraanionic diphosphine borate ligand: Complexation with platinum

Polyhedron, Год журнала: 2024, Номер 253, С. 116904 - 116904

Опубликована: Фев. 19, 2024

Charge is a property that inherent to most chemical phenomena. In coordination chemistry, charge can be conferred through targeted ligand design. Notwithstanding, examples of ligands containing greater than single pendant point remain sparse. This report describes new diphosphine framework hosts four tetraborate units, accessed from borane alkylation 1,2-bis(di(3-dicyclohexylpropylboranyl)phosphino)ethane (P2BCy4) using alkyllithium reagents. The chemistry this was developed the platinum(II) starting material, [Pt(COD)(CH3)2] (COD = 1,5-cyclooctadiene) providing corresponding tetraanionic Pt(II) compound. Despite its high negative 4- charge, species (and ligand) are soluble in common non-polar organic solvents such as pentane and toluene, complementing previously examined sulfonate or carboxylate-containing ligands, for aqueous media. work additionally outlines effect state on spectroscopic observables, NMR shift, coupling constant, infrared stretching frequency.

Язык: Английский

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Thermochemical Studies of Nickel Hydride Complexes with Cationic Ligands in Aqueous and Organic Solvents

Organometallics, Год журнала: 2022, Номер 41(18), С. 2605 - 2611

Опубликована: Сен. 13, 2022

Transition metal hydride complexes are key intermediates in a variety of catalytic processes. Transfer hydride, hydrogen atom, or proton is defined by the thermochemical parameters hydricity, bond dissociation free energy (BDFE), and pKa, respectively. These values have been studied primarily organic solvents to predict understand reactivity. Despite growing interest development aqueous catalysis, BDFE measurements transition hydrides water rare. Herein, we report two nickel with one cationic ligands that enable measurement both using their reduction potential pKa values. The Ni(I/0) potentials increase anodically as more charged groups introduced into ligand framework among most positive measured for Ni complexes. complex ligands, 2-Ni(II)–H, displays exceptional stability no evidence decomposition at pH 1 least 2 weeks. 2-Ni(II)–H was be 53.6 kcal/mol between 50.9 56.2 acetonitrile, consistent prior work indicates minimal solvent dependence BDFEs O–H N–H bonds. results indicate do not change drastically inform future studies on highly

Язык: Английский

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Catalyst Self-Assembly Accelerates Bimetallic Light-Driven Electrocatalytic H2 Evolution in Water

Опубликована: Апрель 10, 2023

Hydrogen evolution is an important fuel-generating reaction that has been subject to mechanistic debate about the roles of monometallic and bimetallic pathways. In this study, molecular iridium catalysts undergo photoelectrochemical dihydrogen afford a rare opportunity systematically understand factors promote H–H coupling. Covalently tethered diiridium evolve H2 from neutral water faster than catalysts, even at lower overpotential. The origin improvement noncovalent supramolecular self-assembly into “all-catalyst” nanoscale aggregates efficiently harvest light form bonds. New containing long-chain alkane substituents leverage self-assemly close expected maximum rate for light-driven splitting with activity below 100 mV Design parameters holding multiple catalytic sites in proximity tuning catalyst microenvironment emerge work.

Язык: Английский

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Electric fields imbue enzyme reactivity by aligning active site fragment orbitals

Опубликована: Июнь 17, 2024

It is broadly recognized that intramolecular electric fields, produced by the protein scaffold and acting on active site, facilitate enzymatic catalysis. This field effect can be described several theoretical models, each of which intuitive to varying degrees. In this contribution, we show a fundamental fields generate electrostatic potentials energetic alignment reactant frontier orbitals. We apply model demystify impact high-valent iron-oxo heme proteins: catalases, peroxidases, peroxygenases/monooxygenases. Specifically, easily accounts for observed field-induced changes spin distribution within peroxidase sites explains transition between epoxidation hydroxylation pathways seen in Cytochrome P450 site models. Thus, interpretation chemical field, strategy involves analyzing response orbitals fragments, their alignment. note energy difference fragment involved charge redistribution acts as measure hardness/softness reactive complex. measure, its sensitivity offers single parameter from quantitatively assess effects reactivity selectivity. provides an additional perspective describe preorganization offer ways manipulation.

Язык: Английский

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