Research ArticleMATERIALS SCIENCE

Imaging an unsupported metal–metal bond in dirhenium molecules at the atomic scale

See allHide authors and affiliations

Science Advances  17 Jan 2020:
Vol. 6, no. 3, eaay5849
DOI: 10.1126/sciadv.aay5849
  • Fig. 1 Diatomic molecule Re2 trapped in carbon nano–test tube.

    (A) Schematic illustration of the preparation of dirhenium molecule confined in SWNT by eliminating CO groups from Re2(CO)10 precursor. Three dirhenium molecules in two SWNTs can be observed in the AC-HRTEM images [two dirhenium molecules imaged at 80 kV with Cs-corrected (top image) and one dirhenium molecule Cc/Cs-corrected (bottom two images) TEM, unprocessed data]. (B) Time-series AC-HRTEM images (80 kV) from movie S1 acquired by Titan CS-corrected TEM showing the characteristic states of the dirhenium molecule changing under e-beam irradiation. This dirhenium molecule is the right one in the SWNT of the top AC-HRTEM image in (A) named “Titan Re2 A.” The corrected Re–Re bond length of each frame is presented; error is ±0.015 nm. N/A is the standing state with unknown bond length.

  • Fig. 2 Changes in Re–Re bond length over time.

    (A) Time-series AC-HRTEM images (80 kV) (unprocessed data) of the first stage of movie S2 acquired by the SALVE TEM. At this stage, the dirhenium molecule moves at a defect site on the SWNT, climbs out from the defect, and then slides into the vdW gap between two parallel SWNTs. The corrected Re–Re bond length of each frame is presented; error is ±0.010 nm. (B) Selected frames with adjusted high contrast from movie S2 for analyzing the atomically precise position of the dirhenium molecule when it is drifting along the outer surface of host SWNT. The position of the Re atoms are indicated by yellow arrows. The AC-HRTEM images are partially covered by the model of an SWNT with chirality of (10, 10). The simulated structure shows the position of dirhenium molecule in the frame of 82 s. (C) Corrected bond length changing of the right dirhenium molecule in movie S1 (Titan Re2 A); error is ±0.015 nm. (D) Corrected bond length of the dirhenium molecule drifting along the outer wall of SWNT in movie S2 (SALVE Re2); error is ±0.010 nm. (E) The histogram shows the count frequencies of the different bond lengths of Titan Re2 A (0 to 553 s).

  • Fig. 3 Atomic-scale dynamics of Re–Re bond dissociation.

    (A) Time-series AC-HRTEM images (80 kV) (unprocessed data) of the second stage of movie S2 acquired by the SALVE TEM. At this stage, the dirhenium molecule confined in the vdW gap shows various dynamic processes. The metallic bonds between two Re atoms break and rebind twice. The dirhenium molecule also stands and lies down in the gap. (B) In the first row, false-color images of the red dashed line framed areas in the AC-HRTEM images of 89, 94, and 132 s in (A). The second row shows the intensity profiles of the corresponding black dashed line in the false-color images of the same column. The distances between two Re atoms are measured with an error of ±0.010 nm. The third row shows the possible state of the two Re atoms in each image of the first row.

  • Fig. 4 Interactions of Re2 with carbon nanotube.

    (A) Comparison of the spatial extent of the Re2 HOMO (SOMO) viewed end-on and side-on; the overlap with electron density of the SWNT LUMO sufficient for bonding is only achieved when Re2 approaches the nanotube wall in the end-on orientation. (B) Side-on and end-on views of the HOMO (SOMO) of the bound configuration, showing the contraction of the (blue) orbital lobes that maximizes bonding overlap (in the end-on view, some carbon atoms have been removed and the electron density isovalue has been increased to aid visualization). (C) Illustration of the dynamics of the dirhenium molecule in the SWNT, with the associated calculated energies relative to the separated molecule and SWNT (left), and front and side views of each state.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/6/3/eaay5849/DC1

    Section S1. Re2 electronic structure and choice of functional

    Fig. S1. Infrared spectra of Re2 precursor before and after removal of CO ligands.

    Fig. S2. Analysis of a typical migration process repeatedly observed in our TEM experiment.

    Fig. S3. Schematic diagram explaining the method for calculating the real bond length between two Re atoms in Re2 by correcting the measured projected bond length.

    Fig. S4. Shapes and energies of Re2 orbitals.

    Fig. S5. Possible configurations of Re2 lying on the graphitic structure.

    Fig. S6. The model SWNT system used in the DFT calculations discussed in the text.

    Fig. S7. Configurations of Re2 outside SWNT with respect to the nanotube lattice.

    Fig. S8. The Mulliken charge distribution of the bonded standing state found in the DFT calculations.

    Movie S1. Dynamics of two Re2 molecules confined in SWNT stimulated and imaged by electron beam in Titan TEM at 80 kV.

    Movie S2. Dynamics of one Re2 molecule stimulated and imaged by electron beam in SALVE TEM at 80 kV.

    References (2839)

  • Supplementary Materials

    The PDFset includes:

    • Section S1. Re2 electronic structure and choice of functional
    • Fig. S1. Infrared spectra of Re2 precursor before and after removal of CO ligands.
    • Fig. S2. Analysis of a typical migration process repeatedly observed in our TEM experiment.
    • Fig. S3. Schematic diagram explaining the method for calculating the real bond length between two Re atoms in Re2 by correcting the measured projected bond length.
    • Fig. S4. Shapes and energies of Re2 orbitals.
    • Fig. S5. Possible configurations of Re2 lying on the graphitic structure.
    • Fig. S6. The model SWNT system used in the DFT calculations discussed in the text.
    • Fig. S7. Configurations of Re2 outside SWNT with respect to the nanotube lattice.
    • Fig. S8. The Mulliken charge distribution of the bonded standing state found in the DFT calculations.
    • Legends for movies S1 and S2
    • References (2839)

    Download PDF

    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mp4 format). Dynamics of two Re2 molecules confined in SWNT stimulated and imaged by electron beam in Titan TEM at 80 kV.
    • Movie S2 (.mp4 format). Dynamics of one Re2 molecule stimulated and imaged by electron beam in SALVE TEM at 80 kV.

    Files in this Data Supplement:

Stay Connected to Science Advances

Navigate This Article