Single Molecule Imaging of Oxygenation of Cobalt Octaethylporphyrin at the Solution/Solid Interface: Thermodynamics from Microscopy

Friesen, Benjamin A.; Bhattarai, Ashish; Mazur, Ursula; Hipps, K. W.

doi:10.1021/ja304431b

Cited by 84 publications

(167 citation statements)

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“…Such investigations are immensely important from a commercial point of view owing to their relevance to heterogeneous catalysis. In a recent study, Hipps and co-workers [64] studied the thermodynamics of the reversible binding of oxygen to cobalt (II) octaethylporphyrin (CoOEP; figure 9a) adsorbed at the 1-phenyloctane/HOPG interface. The monolayer of CoOEP adsorbed at 25 • C in equilibrium with pure O 2 shows varying STM contrast (figure 9c).…”

Section: Thermodynamics Of Reactions and Catalysis In Two-dimensionalmentioning

confidence: 99%

“…By carrying out STM measurements at different temperatures and at 100% O 2 saturation, the authors obtained a plot of the free energy change versus the temperature, the slope of which corresponds to the entropy change of the process relative to the standard state. From this value of entropy, it was possible to calculate the enthalpy changes associated with the process [64].…”

Section: Thermodynamics Of Reactions and Catalysis In Two-dimensionalmentioning

confidence: 99%

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Principles of molecular assemblies leading to molecular nanostructures

Mali

Feyter

2013

Phil. Trans. R. Soc. A.

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Self-assembled physisorbed monolayers consist of regular two-dimensional arrays of molecules. Two-dimensional self-assembly of organic and metal–organic building blocks is a widely used strategy for nanoscale functionalization of surfaces. These supramolecular nanostructures are typically sustained by weak non-covalent forces such as van der Waals, electrostatic, metal–ligand, dipole–dipole and hydrogen bonding interactions. A wide variety of structurally very diverse monolayers have been fabricated under ambient conditions at the liquid–solid and air–solid interface or under ultra-high-vacuum (UHV) conditions at the UHV–solid interface. The outcome of the molecular self-assembly process depends on a variety of factors such as the nature of functional groups present on assembling molecules, the type of solvent, the temperature at which the molecules assemble and the concentration of the building blocks. The objective of this review is to provide a brief account of the progress in understanding various parameters affecting two-dimensional molecular self-assembly through illustration of some key examples from contemporary literature.

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Section: Thermodynamics Of Reactions and Catalysis In Two-dimensionalmentioning

confidence: 99%

Section: Thermodynamics Of Reactions and Catalysis In Two-dimensionalmentioning

confidence: 99%

Principles of molecular assemblies leading to molecular nanostructures

Mali

Feyter

2013

Phil. Trans. R. Soc. A.

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“…Indeed, in total, only a few studies of SAM temperature dependence have ever been performed, as recently reviewed (12,34,35). An important conclusion drawn is that the nature of observed SAM composition can be controlled by either kinetic and/or thermodynamic effects (9,12,14,15,(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44). SAMs in thermodynamic equilibrium can have free energies determined directly from dynamics observed in the STM (17).…”

mentioning

confidence: 99%

A priori calculations of the free energy of formation from solution of polymorphic self-assembled monolayers

Reimers

Panduwinata

Visser

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

110

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Modern quantum chemical electronic structure methods typically applied to localized chemical bonding are developed to predict atomic structures and free energies for meso-tetraalkylporphyrin self-assembled monolayer (SAM) polymorph formation from organic solution on highly ordered pyrolytic graphite surfaces. Large polymorphdependent dispersion-induced substrate−molecule interactions (e.g., −100 kcal mol −1 to −150 kcal mol −1 for tetratrisdecylporphyrin) are found to drive SAM formation, opposed nearly completely by large polymorph-dependent dispersion-induced solvent interactions (70-110 kcal mol −1 ) and entropy effects (25-40 kcal mol −1 at 298 K) favoring dissolution. Dielectric continuum models of the solvent are used, facilitating consideration of many possible SAM polymorphs, along with quantum mechanical/molecular mechanical and dispersion-corrected density functional theory calculations. These predict and interpret newly measured and existing high-resolution scanning tunnelling microscopy images of SAM structure, rationalizing polymorph formation conditions. A wide range of molecular condensed matter properties at room temperature now appear suitable for prediction and analysis using electronic structure calculations.self-assembled monolayers | density functional theory | dispersion | free energy | polymorphism A priori calculations of the free energies of chemical reactions using density functional theory (DFT) and/or ab initio methods are now well established for gas-phase processes (1, 2), gas surface reactions (3), and, using continuum self-consistent reaction field (SCRF) methods, for condensed phase processes also (4). Over the last few years, a major advance in computational methods has occurred, however, allowing for rapid and accurate evaluation of intermolecular dispersion interactions. This makes feasible similar SCRF calculations for physisorption, macromolecule structuring, and other self-assembly processes in condensed phases. We present the first application of this type, to our knowledge, considering the free energy of formation of various polymorphs of tetraalkylporphyrin self-assembled monolayers (SAMs) at solid/liquid interfaces on highly ordered pyrolytic graphite (HOPG) surfaces. Calculated structures and free energies are used to interpret new and existing high-resolution scanning tunneling microscopy (STM) images, focusing on the critical roles played by the dispersion interaction in driving SAM formation and by entropy and dispersion-based desolvation effects that oppose it.Calculating a priori free energies for SAM formation from solution is a significant challenge. Accurate representations of the substrate−molecule energies, the intermolecular energies, the solvent interaction energies, and the effects of solvent structure are required, a set of tasks that, with a few exceptions (see e.g., refs. 5 and 6), has remained prohibitive a priori. Alternatively, model calculations have been useful for identifying key qualitative features (7-11), whereas some full molecular dynamics si...

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“…The majority of these studies use ensemble techniques in solution, such as electrochemistry and absorption, electron paramagnetic resonance and nuclear magnetic resonance spectroscopy. The scanning tunneling microscope (STM) has proven to be a promising tool to study reactions at the molecular level [8][9][10][11][12] , and initial experiments have been reported in which the reactive properties of metal porphyrins were studied on a surface at the single molecule level by STM in ultrahigh vacuum (UHV) [13][14][15][16][17] and under ambient conditions 18,19 .Here we report detailed STM studies of the complex redox chemistry of reactions between 10,15,R,R,porphyrin manganese(III) chloride (Mn1Cl, Fig. 2a) and different oxygen donors at a solid/liquid interface.…”

mentioning

confidence: 99%

“…44 But also in the absence of a direct chemical bond a surface like graphite can activate a metal centre, as was demonstrated in a recent STM study of the oxygenation of cobalt porphyrins at the graphite/1-phenyloctane interface. 19 In that case the graphite surface was proposed to stabilise the polarised porphyrin Co−O2 complex by means of charge donation. …”

mentioning

confidence: 99%

Detection of different oxidation states of individual manganese porphyrins during their reaction with oxygen at a solid/liquid interface

et al. 2013

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[4][5][6][7] . The majority of these studies use ensemble techniques in solution, such as electrochemistry and absorption, electron paramagnetic resonance and nuclear magnetic resonance spectroscopy. The scanning tunneling microscope (STM) has proven to be a promising tool to study reactions at the molecular level [8][9][10][11][12] , and initial experiments have been reported in which the reactive properties of metal porphyrins were studied on a surface at the single molecule level by STM in ultrahigh vacuum (UHV) [13][14][15][16][17] and under ambient conditions 18,19 .Here we report detailed STM studies of the complex redox chemistry of reactions between 10,15,R,R,porphyrin manganese(III) chloride (Mn1Cl, Fig. 2a) and different oxygen donors at a solid/liquid interface. Although the dynamic nature of the molecules at this interface complicates the use of techniques that are typically being used under UHV conditions, such as X-ray 3 Photoelectron Spectroscopy (XPS), STM can provide extremely high spatial resolution and insight into changes in the electronic properties of molecules with a liquid medium over them.These liquid conditions make the system far more comparable with processes taking place in biological systems than the UHV conditions, where solvent-mediated factors such as the diffusion and concentration of reactants are fully absent. It is in principle possible with STM to monitor single molecules at the highest detail while they are involved in multistep chemical reactions with STM, and to image and identify reactants, intermediates and products in the most direct way, i.e. by imaging. This approach allows the study of reaction dynamics in realspace and real-time, which may provide unique information about reaction mechanisms that remains hidden in ensemble measurements at the macroscopic scale. STM may reveal variations in reactivity of single molecules, the relation of these variations to molecular adsorption geometry, and cooperativity effects at the nanometre scale.An overview of the possible reaction pathways involving manganese porphyrins and oxygen, based on the literature 1-3,18,20-29 and the observations described here, is depicted in Figure 1 In a first experiment we deposited a droplet of a ~10 −5 M solution of Mn1Cl in 1-octanoic acid at the basal plane of a freshly cleaved highly oriented pyrolytic graphite (HOPG) sample under ambient conditions. Related alkyl-functionalised free base porphyrin molecules are known to form well-ordered monolayers on the same substrate 30,31 . STM revealed the 5 instantaneous self-assembly of the molecules of Mn1Cl in extended lamellar arrays, in which the porphyrin planes are adsorbed parallel to the surface and the alkyl chains interdigitated (Fig. 2B). The orientation of the lamellae and the alkyl chains with respect to the main crystallographic directions of the graphite surface is identical to that observed for the corresponding free base derivative. 30 When the surface was scanned under ambient conditions at a negative bias voltage of −800 mV and ...

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Single Molecule Imaging of Oxygenation of Cobalt Octaethylporphyrin at the Solution/Solid Interface: Thermodynamics from Microscopy

Cited by 84 publications

References 72 publications

Principles of molecular assemblies leading to molecular nanostructures

Principles of molecular assemblies leading to molecular nanostructures

A priori calculations of the free energy of formation from solution of polymorphic self-assembled monolayers

Detection of different oxidation states of individual manganese porphyrins during their reaction with oxygen at a solid/liquid interface

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