Selective molecular recognition by nanoscale environments in a supported iridium cluster catalyst

Okrut, Alexander; Runnebaum, Ron C.; Ouyang, Xiaoying; Lu, Jichang; Aydin, Ceren; Hwang, Son‐Jong; Zhang, Shengjie; Olatunji-Ojo, Olayinka; Durkin, Kathleen A.; Dixon, David A.; Gates, Bruce C.; Katz, Alexander

doi:10.1038/nnano.2014.72

Cited by 54 publications

(103 citation statements)

References 34 publications

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“…This inference is consistent with the experimental result that bridging carbonyls dissociate more readily in thermal decarbonylation [42]. Because bri CO ligands and eq, ax CO ligands can be readily interconverted [40], substitution with a new ligand can take place at any basal position determined by its bulk and orbital direction; api substitutions are rare except through some selectively reactive decarbonylations that lower the activation energy, as they are not readily interconverted [43].…”

Section: Ir 4 (Ph 3 ) Y (Co) Z Structures Relative Energies and Dissupporting

confidence: 86%

“…We were particularly motivated to investigate tetrairidium clusters with combinations of carbonyl and phosphine ligands, having recently demonstrated an on-off switch for the bonding and catalytic conversion of ethylene at single iridium sites on the tetrairidium frame, as triggered by a sheath of organic ligands bonded at neighboring iridium sites that control the electronic properties of the active site [43]. Ethylene binding and activation in a supported tetrairidium cluster catalyst were shown to be controlled by selective nanoenvironments at the metal surface, which are formed by three bulky calixarene-phosphine ligands surrounding and bonding to the cluster at sites neighboring the site where reactivity is switched off and on.…”

Section: Introductionmentioning

confidence: 99%

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Structures, relative energies, and ligand dissociation energies of iridium carbonyl phosphine clusters

Zhang

Katz

Gates

et al. 2015

Computational and Theoretical Chemistry

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a b s t r a c tThere is significant interest in the catalytic properties of substituted iridium carbonyl clusters but little thermodynamic information available characterizing them. The low-energy isomers of Ir x (PH 3 ) y (CO) z (x = 1, 2, 4) were investigated with density functional theory and correlated molecular orbital theory at the coupled cluster CCSD(T) level. The relative energies and ligand dissociation energies were calculated. Differences in relative energies are consequences of both electronic and steric effects of the phosphines and carbonyls. The calculations predict three fundamental structural types for Ir 2 (PH 3 ) y (CO) z : C 2v , C 2 , and D 3d . Ten exchange-correlation functionals were used for the ligand dissociation energy calculations in addition to CCSD(T) for the smaller clusters. The xB97X-D functional gave the most consistent ligand dissociation energies as compared with the CCSD(T) benchmark calculations, and, so it was used to predict the dissociation energies for larger clusters when CCSD(T) calculations were infeasible. The dissociation energies characteristic of Ir 4 (PH 3 ) y (CO) z were in the range of $30 to $60 kcal/mol. Dissociation of a bridging ligand often involved a hydrogen atom transfer from a phosphine to a coordinatively unsaturated iridium atom and a phosphine converting from a bridging site to an equatorial site. The products of such reactions are predicted to have lower relative energies than other isomers.Phosphines act as r-electron donors, and there is a trend of an increase in carbonyl ligand dissociation energies as more phosphines are substituted in the small clusters.

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Section: Ir 4 (Ph 3 ) Y (Co) Z Structures Relative Energies and Dissupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Structures, relative energies, and ligand dissociation energies of iridium carbonyl phosphine clusters

Zhang

Katz

Gates

et al. 2015

Computational and Theoretical Chemistry

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“…[1][2][3][4][5] The energy level quantization in metal clusters of small atomicity triggers the emergence of promising luminescent, magnetic and catalytic properties. 3,4,[6][7][8][9][10] The recent advances in surface passivation and templated synthesis (e.g. mercapto derivatives, DNA, polymers, polyelectrolytes, proteins, dendrimers, etc.)…”

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confidence: 99%

Self-Assembly of Silver Metal Clusters of Small Atomicity on Cyclic Peptide Nanotubes

et al. 2015

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Subnanometric noble metal clusters, composed by only a few atoms, behave like molecular entities and display magnetic, luminescent and catalytic activities. However, noncovalent interactions of molecular metal clusters, lacking of any ligand or surfactant, have not been seen at work. Theoretically attractive and experimentally discernible, van der Waals forces and noncovalent interactions at the metal/organic interfaces will be crucial to understand and develop the next generation of hybrid nanomaterials. Here, we present experimental and theoretical evidence of noncovalent interactions between subnanometric metal (0) silver clusters and aromatic rings and their application in the preparation of 1D self-assembled hybrid architectures with ditopic peptide nanotubes. Atomic force microscopy, fluorescence experiments, circular dichroism and computational simulations verified the occurrence of these interactions in the clean and mild formation of a novel peptide nanotube and metal cluster hybrid material. The findings reported here confirmed the sensitivity of silver metal clusters of small atomicity toward noncovalent interactions, a concept that could find multiple applications in nanotechnology. We conclude that induced supramolecular forces are optimal candidates for the precise spatial positioning and properties modulation of molecular metal clusters. The reported results herein outline and generalize the possibilities that noncovalent interactions will have in this emerging field.

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“…Such organicinorganic systems are also encountered in technological environments, particularly selective catalysis (6)(7)(8), enhanced oil recovery (9), self-assembly of colloidal NPs (10-13), and CO 2 capture and sequestration (14). Despite being well-documented qualitatively, the magnitudes of such interactions and their impact on the interface molecular configurations have barely been directly identified.…”

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confidence: 99%

Probing the energetics of organic–nanoparticle interactions of ethanol on calcite

Navrotsky

2015

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

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Knowing the nature of interactions between small organic molecules and surfaces of nanoparticles (NP) is crucial for fundamental understanding of natural phenomena and engineering processes. Herein, we report direct adsorption enthalpy measurement of ethanol on a series of calcite nanocrystals, with the aim of mimicking organic-NP interactions in various environments. The energetics suggests a spectrum of adsorption events as a function of coverage: strongest initial chemisorption on active sites on fresh calcite surfaces, followed by major chemical binding to form an ethanol monolayer and, subsequently, very weak, near-zero energy, physisorption. These thermochemical observations directly support a structure where the ethanol monolayer is bonded to the calcite surface through its polar hydroxyl group, leaving the hydrophobic ends of the ethanol molecules to interact only weakly with the next layer of adsorbing ethanol and resulting in a spatial gap with low ethanol density between the monolayer and subsequent added ethanol molecules, as predicted by molecular dynamics and density functional calculations. Such an ordered assembly of ethanol on calcite NP is analogous to, although less strongly bonded than, a capping layer of organics intentionally introduced during NP synthesis, and suggests a continuous variation of surface structure depending on molecular chemistry, ranging from largely disordered surface layers to ordered layers that nevertheless are mobile and can rearrange or be displaced by other molecules to strongly bonded immobile organic capping layers. These differences in surface structure will affect chemical reactions, including the further nucleation and growth of nanocrystals on organic ligand-capped surfaces.thermodynamics | adsorption calorimetry | ligand-capped nanocrystal | biomineralization | carbonate formation

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Selective molecular recognition by nanoscale environments in a supported iridium cluster catalyst

Cited by 54 publications

References 34 publications

Structures, relative energies, and ligand dissociation energies of iridium carbonyl phosphine clusters

Structures, relative energies, and ligand dissociation energies of iridium carbonyl phosphine clusters

Self-Assembly of Silver Metal Clusters of Small Atomicity on Cyclic Peptide Nanotubes

Probing the energetics of organic–nanoparticle interactions of ethanol on calcite

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