Binding of a Co(III) Metalloporphyrin to Amines in Water: Influence of the pKa and Aromaticity of the Ligand, and pH-Modulated Allosteric Effect

IF 4.3 2区 化学 Q1 CHEMISTRY, INORGANIC & NUCLEAR Inorganic Chemistry Pub Date : 2024-12-21 DOI:10.1021/acs.inorgchem.4c04183
Lilia Milanesi, Rosa M. Gomila, Antonio Frontera, Salvador Tomas
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Abstract

Metalloporphyrins have been widely utilized as building blocks for molecular self-assembly in organic solvents, but their application in water is less common due to competition from water molecules for the metal center. However, Co(III) metalloporphyrins are notable for their strong binding to two aromatic amine ligands in aqueous buffers. In this study, we present a comprehensive investigation of the binding behavior of Co(III) tetraphenyl sulfonic acid porphyrin with selected aromatic and aliphatic amines in aqueous solution. Our findings reveal that the ligand affinity is influenced by the pKa values of both the ligand and the porphyrin, as well as the hybridization state of the nitrogen atom, with binding to sp3-hybridized nitrogen being significantly weaker than to sp2-hybridized nitrogen. DFT calculations further suggest that the variations in binding affinities are due to differences in the electrostatic potential at the nitrogen atoms, with aromatic ligands generally exhibiting stronger Co–N coordination due to greater electrostatic attraction. Moreover, our study and the binding model we developed demonstrate that changes in pH affect the affinity for each ligand to varying degrees, sometimes resulting in an allosteric cooperative effect. This effect is linked to electronic changes introduced by the binding of the first ligand. Our model provides a predictive tool for understanding the assembly behavior of these porphyrins in aqueous buffers, with potential applications in developing more efficient catalysts and in the creation of smart materials for fields ranging from catalysis to nanomedicine and optoelectronics

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来源期刊
Inorganic Chemistry
Inorganic Chemistry 化学-无机化学与核化学
CiteScore
7.60
自引率
13.00%
发文量
1960
审稿时长
1.9 months
期刊介绍: Inorganic Chemistry publishes fundamental studies in all phases of inorganic chemistry. Coverage includes experimental and theoretical reports on quantitative studies of structure and thermodynamics, kinetics, mechanisms of inorganic reactions, bioinorganic chemistry, and relevant aspects of organometallic chemistry, solid-state phenomena, and chemical bonding theory. Emphasis is placed on the synthesis, structure, thermodynamics, reactivity, spectroscopy, and bonding properties of significant new and known compounds.
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