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The Crucial Role of Solvation Forces in the Steric Stabilization of Nanoplatelets.

ABSTRACT: The steric stability of inorganic colloidal particles in an apolar solvent is usually described in terms of the balance between three contributions: the van der Waals attraction, the free energy of mixing, and the ligand compression. However, in the case of nanoparticles, the discrete nature of the ligand shell and the solvent has to be taken into account. Cadmium selenide nanoplatelets are a special case. They combine a weak van der Waals attraction and a large facet to particle size ratio. We use coarse grained molecular dynamics simulations of nanoplatelets in octane to demonstrate that solvation forces are strong enough to induce the formation of nanoplatelet stacks and by that have a crucial impact on the steric stability. In particular, we demonstrate that for sufficiently large nanoplatelets, solvation forces are proportional to the interacting facet area, and their strength is intrinsically tied to the softness of the ligand shell.

SUBMITTER: Petersen N

PROVIDER: S-EPMC9801426 | biostudies-literature | 2022 Dec

REPOSITORIES: biostudies-literature

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The Crucial Role of Solvation Forces in the Steric Stabilization of Nanoplatelets.

Petersen Nanning N Girard Martin M Riedinger Andreas A Valsson Omar O

Nano letters 20221209 24

The steric stability of inorganic colloidal particles in an apolar solvent is usually described in terms of the balance between three contributions: the van der Waals attraction, the free energy of mixing, and the ligand compression. However, in the case of nanoparticles, the discrete nature of the ligand shell and the solvent has to be taken into account. Cadmium selenide nanoplatelets are a special case. They combine a weak van der Waals attraction and a large facet to particle size ratio. We ...[more]

PMID: 36493312

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Project description:Catalytic asymmetric hydrogenation of ketones is an important approach to prepare valuable chiral alcohols. Understanding how transition metals promote these reactions is key to the rational design of more active, selective and sustainable catalysts. A highly unusual mechanism for asymmetric hydrogenation of acetophenone catalysed by an anionic IrIII hydride system, including a strong counterion dependence on catalyst activity, is explored and rationalised here. The active catalyst, generated in situ from [IrCl(COD)]2 and a bidentate ligand (P,SR) under H2 in the presence of a strong base (M+iPrO- in isopropanol, M = Li, Na, K), is the solvated M+[Ir(H)4(P,SR)] salt (P,SR = CpFe[1,2-C5H3(PPh2)(CH2SR)], with R = iPr, Ph, Bz and Cy). Catalyst activity increases, for all R derivatives, significantly as the counterion is varied in the order Li < Na < K. For the most active K system, the addition of 18-crown-6 drastically reduces the activity. While the cation strongly affects catalyst activity, it does not significantly affect enantioselectivity. DFT calculations explored these effects in detail and showed that the solvation model used in the calculations is critical. Only a hybrid implicit/explicit solvent model including sufficient explicit solvent molecules to properly describe the first solvation shell of the cation is able to reproduce the experimental observations. This model revealed the fundamental importance of the alkali-metal cation coordination sphere in understanding the counterion effects. The turnover-determining states in the catalytic cycle are those involved in outer-sphere hydride transfer to the substrate. This step leads to coordination of the alkoxide product to the alkali-metal cation, with a significant rearrangement of the coordination sphere of M, whereas there is little change in the geometrical parameters around Ir or the alkoxide. The DFT calculations also pinpointed the major enantio-discriminating interactions and rationalised the insensitivity of the enantioselectivity on the alkali metal cation placement.

Dataset Information

The Crucial Role of Solvation Forces in the Steric Stabilization of Nanoplatelets.

Publications

The Crucial Role of Solvation Forces in the Steric Stabilization of Nanoplatelets.

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