Quantifying reversible nitrogenous ligand binding to Co(<scp>ii</scp>) porphyrin receptors at the solution/solid interface and in solution

Johnson, Kristen N.; Hipps, K. W.; Mazur, Ursula

doi:10.1039/d0cp04109b

Cited by 7 publications

(7 citation statements)

References 56 publications

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“…However, we have shown (1) surface reactions can proceed orders of magnitude slower than expected based on solution phase kinetic measurement and (2) it is possible to correct rate constants for the effects of missed dwells due to low temporal resolution, thereby extending the range of rates that can be measured. Lest one assume that the O 2 -CoOEP/HOPG system is unique; we have tracked adsorption and desorption events in time for several systems including 1-phenylimidazole−CoOEP/HOPG, 38 4-methoxypyridine−CoOEP/ HOPG, 39 and imidazole−NiOEP/HOPG. 17 Thus, these systems are excellent candidates for stochastic analysis, and that work is underway.…”

Section: Table 1 Results Of Dwell Time Analysismentioning

confidence: 99%

Single-Molecule Kinetic Analysis of Oxygenation of Co(II) Porphyrin at the Solution/Solid Interface

Johnson

Mazur

Hipps

2022

J. Phys. Chem. Lett.

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Kinetic analysis of surface reactions at the single molecule level is important for understanding the influence of the substrate and solvent on reaction dynamics and mechanisms, but it is difficult with current methods. Here we present a stochastic kinetic analysis of the oxygenation of cobalt octaethylporphyrin (CoOEP) at the solution/solid interface by monitoring fluctuations from equilibrium using scanning tunneling microscopy (STM) imaging. Image movies were used to monitor the oxygenated and deoxygenated state dwell times. The rate constants for CoOEP oxygenation are k a = 4.9 × 10 −6 s −1 •Torr −1 and k d = 0.018 s −1 . This is the first use of stochastic dwell time analysis with STM to study a chemical reaction, and the results suggest that it has great potential for application to a wide range of surface reactions. Expanding these stochastic studies to further systems is key to unlocking kinetic information for surface-confined reactions at the molecular level, especially at the solution/solid interface.

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Section: Table 1 Results Of Dwell Time Analysismentioning

confidence: 99%

Single-Molecule Kinetic Analysis of Oxygenation of Co(II) Porphyrin at the Solution/Solid Interface

Johnson

Mazur

Hipps

2022

J. Phys. Chem. Lett.

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“…The π–π structure seen in Figure c is significantly different from metal bonded ligands we have previously studied. − To ascertain the role of the crown configuration of the ethyl groups in stabilizing the π–π structure, we also performed PW-DFT calculations on the PhThCoP-HOPG system. This allows us to ascertain the importance of the eight ethyl groups.…”

Section: Resultsmentioning

confidence: 99%

“…Several STM studies reported by us and others have effectively demonstrated in situ chemistry and reaction dynamics of heterocyclic ligand coordination to metal complexes (porphyrins and phthalocyanines , ) adsorbed on solid supports at the solution/solid interface. Some of these reports confirmed that axial ligation can be reversible, and, furthermore, that the electronic properties, reactivity, and cooperativity (nonadditive interactions) of the adsorbed complex can be modulated by the underlying substrate. − The binding reactions of imidazole to NiOEP and 1-phenylimidazole (PhIm) to CoOEP proceeded at room temperature because of charge donation from the underlying graphite substrate to porphyrin . The presence of highly ordered pyrolytic graphite (HOPG) was also crucial to observe positive cooperativity for both 4-methoxypyridine and PhIm binding to CoOEP at the solution/solid interface.…”

Section: Introductionmentioning

confidence: 89%

In Situ Imaging and Computational Modeling Reveal That Thiophene Complexation with Co(II)porphyrin/Graphite Is Highly Cooperative

et al. 2022

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Scanning tunneling microscopy (STM) was employed to quantitively investigate in situ binding of 3-phenyl thiophene (PhTh) to Co(II)octaethyl porphyrin (CoOEP) supported on highly ordered pyrolytic graphite (HOPG) in fluid solution. To our knowledge, this is the first single-molecule level study of a complexation reaction between a metalloporphyrin and a sulfur base at the solution/solid interface and one of the few examples of thiophene coordination with a d7 transition metal. Real-time imaging experiments revealed that PhTh binds reversibly to HOPG-supported CoOEP at room temperature. The coordination process increases with increasing PhTh concentration. The nearest-neighbor analysis of STM images indicates that the complexation reaction is cooperative. Because PhTh does not bind to CoOEP in solution, the STM results strongly suggest that the presence of HOPG is crucial to observe ligand binding and cooperativity in this system. Periodic plane-wave density functional theory (DFT) computations corroborate that PhTh has low binding affinity toward CoOEP in solution but predict that the ligand can adsorb to CoOEP/HOPG through coordination with S atoms or interact through noncovalent π–π bonding with the porphyrin chromophore. Three possible structures were considered, and DFT theory was used to calculate binding energies and free energies. In solution and on the HOPG surface both a π–π configuration and a η1(S) configuration have similar computed energies. The η1(S) structure shows the largest stabilization in going from the vapor to adsorbed on HOPG. We also show that statistical analysis of nearest neighbors is more sensitive to cooperative binding than is fitting with the Temkin or Langmuir isotherm. The implication is that isotherm fitting alone is insufficient for identifying cooperative binding on surfaces.

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“…Not only do the molecules adsorb on the surface (molecule–surface interactions), but they also do so in a highly nonrandom and programmed fashion by achieving supramolecular interactions between themselves (molecule–molecule interactions). While the Langmuir adsorption isotherm holds true for the self-assembly of several systems such as in the cases of small molecule binding on metalloporphyrins, , the assumption of noninteracting molecules makes it unsuitable for application to systems where molecules interact. Clearly, this simplest analytical thermodynamic model fails to explain experimentally observed behavior in the studied ISA systems.…”

Section: Discussionmentioning

confidence: 99%

“…The adapted Born–Haber cycle approach combines experimental results with computations to derive the enthalpy change upon self-assembly for hydrogen- and halogen-bonded systems, while the entropic contributions are mainly calculated based on statistical mechanics. ,, Additionally, the same group expanded the possibilities for studying these systems by STM with the development of an immersion-type STM that has, among other things, allowed the quantitative study of ultraslow kinetic processes at the liquid/solid interface. , Hipps et al have mainly focused on the investigations of porphyrin systems. They have been able to compare ligand binding in solution to on-surface binding, observed cooperative effects in ligand binding to the porphyrin monolayers, and successfully evaluated thermodynamic parameters for several systems. − In a recent publication, Hipps et al reported a detailed study exploring the effects of solvent on the structure, stability, and dynamics of a physisorbed porphyrin SAMN. They have additionally been able to use STM to observe and monitor the initial stages of adlayer formation and growth, which provided insight into the mechanism and rates of self-assembly on surfaces …”

Section: Introductionmentioning

confidence: 99%

Quantifying the Cooperative Process of Molecular Self-Assembly on Surfaces: A Case Study of Isophthalic Acids

et al. 2023

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Molecular self-assembly, a promising strategy for modifying surfaces on the nanometer scale, is essential for developing functional materials in electronics, catalysis, or twodimensional (2D) crystal engineering. In this work, we are shifting attention to the physical chemistry of the process at a molecular level through a study of the effect of concentration on the overall process of self-assembled molecular network formation using scanning tunneling microscopy. The overarching idea is to correlate experimental results with analytical thermodynamic models to improve the understanding of supramolecular chemistry in two dimensions by obtaining quantitative data. For this purpose, a series of isophthalic acids have been chosen as a model system. The effect of the concentration on the adsorption behavior, focusing on the surface coverage, has been evaluated at the nanoscale. Our results confirm the existence of a critical concentration above which self-assembly occurs and that a change in the molecular structure (the length of the alkyl chain) has a remarkable impact on the value of this critical threshold. Finally, we report highly cooperative behavior in studied systems, which presents one of the rare examples of quantitative measurement of cooperative phenomena at the liquid/solid interface.

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Quantifying reversible nitrogenous ligand binding to Co(ii) porphyrin receptors at the solution/solid interface and in solution

Abstract: Single molecule microscopy can quantifiably probe the dynamics of reversible ligand binding to metalloporphyrin receptors at the solution/solid interface.

Cited by 7 publications

References 56 publications

Single-Molecule Kinetic Analysis of Oxygenation of Co(II) Porphyrin at the Solution/Solid Interface

Single-Molecule Kinetic Analysis of Oxygenation of Co(II) Porphyrin at the Solution/Solid Interface

In Situ Imaging and Computational Modeling Reveal That Thiophene Complexation with Co(II)porphyrin/Graphite Is Highly Cooperative

Quantifying the Cooperative Process of Molecular Self-Assembly on Surfaces: A Case Study of Isophthalic Acids

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