PDOS of the donor-acceptor dyad in ConB. (a) CBHP in the gas phase. (c) CBHP-Pt in the gas phase. (e) CBHP-Pt adsorbed on Pt(111) (color code as in Fig. 3a, in addition Pt-adatom in turquoise). (b and d) Relevant frontier molecular orbitals marked by black lines in (a) and (c). (f) LDOS plots at selected energies marked by black lines in (e).

Contexts in source publication

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... simulations of the CBHP molecule without the Pt adatom were conducted and are given in ESI Fig. S4. † While in the experimental STM images one bright, distinct spot is observed on the edge of the HP acceptor, two smaller spots appear in the simulated constant-current image for the CBHP molecule, which can be assigned to the two oxygen atoms of HP. Thus, DFT calculations strongly suggest the formation of the CBHP-Pt complexes, as ...

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... sequentially by calculating the isolated CBHP molecule, the isolated CBHP-Pt complex, and the CBHP-Pt complex adsorbed on the Pt(111) surface. Throughout, the positions of all atoms were kept frozen at the values of the metal-molecule junction, thus allowing us to disentangle electronic from geometric effects and analyze the former ones alone. Fig. 4 shows the results of this analysis for ...

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... CBHP molecule in the gas phase (Fig. 4a) exhibits discrete molecular orbitals shown by well-separated PDOS peaks. The DOS projected over different donor and acceptor subunits are represented in different colors, like dened in Fig. 3. The calculated HOMO-LUMO gap of the molecule in the ConB geometry is 1.23 eV, close to the value of 1.37 eV in the ConA geometry and 1.40 eV in ...

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... gap values, calculated with the vdW-DF exchange-correlation functional, are smaller than with other functionals which feature a more accurate description of electron-electron interaction (Fig. S8, ESI †) but which cannot be applied to the metal-molecule interface. The donor-acceptor character of the isolated dyad in geometry ConB can be seen in Fig. 4a, where PDOS peaks projected over the inner and outer donor regions are predominant at negative energies (green and orange lines), while the HP acceptor states abound in the unoccupied part of the spectrum. Bridge states are found mostly far from the gap for the unoccupied states. Fig. 4b illustrates the donor-acceptor character of the ...

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... of the isolated dyad in geometry ConB can be seen in Fig. 4a, where PDOS peaks projected over the inner and outer donor regions are predominant at negative energies (green and orange lines), while the HP acceptor states abound in the unoccupied part of the spectrum. Bridge states are found mostly far from the gap for the unoccupied states. Fig. 4b illustrates the donor-acceptor character of the isolated molecule by plotting selected molecular orbitals, whose energies are indicated in panel (a) with vertical lines. The HOMO is localized over the donor rings and the bridge phenylene and methylene units. In contrast, the LUMO is delocalized on the HP acceptor unit but has no ...

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... bridge phenylene and methylene units. In contrast, the LUMO is delocalized on the HP acceptor unit but has no signicant amplitude on the phenylene bridge group or the CB acceptor. This is consistent with the donor-acceptor character of the CBHP dyad, which is clearly manifested in the gas phase, even in the somewhat constrained geometry ConB. Fig. 4c shows the calculated PDOS aer bond formation between a Pt atom (turquoise PDOS) and one of the HP oxygen atoms of CBHP, while keeping the geometry frozen to that of the ConB/Pt(111) interface. Additional features appear near the HOMO-LUMO gap due to the mixing of molecular states located at the HP acceptor with the states of this Pt ...

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... complex have appreciable Pt PDOS contribution (turquoise line). In particular, the buildup slightly below the Fermi level leads to the edge of the Pt band in the slab. Many wave functions of the CBHP-Pt complex are delocalized over both species. However, the gas-phase orbitals selected in panel (b) still retain their characteristic nodal patterns (Fig. 4d) even though their ordering in the spectrum has changed as they are now HOMOÀ2 and LUMO+1, respectively. Thus, despite the mixing and rearranging introduced by the states of the Pt atom, the CBHP-Pt complex largely preserves the donor-acceptor characteristics of the isolated dyad (see ESI, Fig. S9 and S10 ...

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... situation, however, is signicantly changed when the complex is adsorbed on the Pt(111) surface. Fig. 4e shows the calculated DOS projected onto the different donor and acceptor regions when CBHP-Pt is adsorbed on Pt(111). Molecular states are signicantly broadened due to the strong hybridization with the Pt substrate. This is expected from the multiple bond formation established between C atoms of the CB and HP units and the Pt surface, ...

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... a wide range of energies above and below the Fermi level, calculated LDOS features are spread to some extent over donor, bridge, and acceptor units. We found no energies at which the distinctive localization and nodal patterns of panels (b) and (d) were preserved. Fig. 4f shows the calculated LDOS at two energies above and below the Fermi level. Electronic states at À1.18 eV involve dominantly the bridge and donor parts of the molecule, but also the Pt adatom bound to the HP unit and the HP unit. At 1.18 eV, there is no signicant LDOS on the bridge group, however, it is spread over the HP acceptor ...

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... the donor-acceptor character of CBHP for both congurations in the gas phase. Binding of the complex to the Pt adatom ( Fig. 5b and e) introduces changes in the O-Pt region but the potential in other parts of the molecule remains almost unchanged, thus the donor-acceptor character is maintained. This is consistent with the ndings shown in Fig. 4, which indicate the introduction of Pt-related states but otherwise the preservation of the character of isolated molecular orbitals. Adsorption onto the Pt(111) substrate, however, leads to an increase of the electrostatic potential throughout the molecule. Negative values are only retained near the HP O atoms in both conformations, ...