Oscillations in the Stability of Consecutive Chemical Bonds Revealed by Ion‐Induced Desorption

Abstract

While it is a common concept in chemistry that strengthening of one bond results in weakening of the adjacent ones, no results have been published on if and how this effect protrudes further into the molecular backbone. By binding molecules to a surface in the form of a self-assembled monolayer, the strength of a primary bond can be selectively altered. Herein, we report that by using secondary-ion mass spectrometry, we are able to detect for the first time positional oscillations in the stability of consecutive bonds along the adsorbed molecule, with the amplitudes diminishing with increasing distance from the molecule-metal interface. To explain these observations, we have performed molecular dynamics simulations and DFT calculations. These show that the oscillation effects in chemical-bond stability have a very general nature and break the translational symmetry in molecules.

Thiolate versus Selenolate: Structure, Stability, and Charge Transfer Properties

“…This suggests a smaller molecular inclination, even at the same twist angle as for the nitrile- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 is static SIMS (S-SIMS). 86 As documented in Figure S6 in the Supporting Information, both negative and positive ion mass spectra of the NC-NapS and the NC-NapSe SAMs were 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 19 recorded. These spectra exhibit secondary ion signals typical of SAMs on gold, viz.…”

“…C−S bond breaks more easily as the sulfur-metal bond gets stronger. 91,92 Summarizing this part and 26taking into account the literature data for the BPnS(Se) monolayers,86 we can conclude that, independent of the character of the molecular backbone (aliphatic or aromatic), the Se−Au bond is more stable as compared to S−Au one, with, however, lower stability of the adjacent C−Se bond as compared to C−S.A reasonable question at this point is why, despite the stronger binding to the substrate in the case of Se headgroup, the respective SAMs adopt a structure dictated mostly by the intermolecular interaction, with a very simple unit cell which is very similar to the molecular arrangement in crystalline napthalene. This unit cell involves different adsorption sites for the identical molecules (seeFigure 3e), thus indicating a presumably lower involvement of the molecule-substrate energetics into the 2D ordering.…”

Core-level spectra and molecular deformation in adsorption: V-shaped pentacene on Al(001)

“…Due to the strong coupling between C1 and the underlying Al atom at the B site the C1–C2 bond experiences the highest variation in length, which increases by 0.07 Å from g to B. Such an elongation occurs because the C1 orbital modifies from sp 2 to sp 3 hybridization, which results in a displacement of the valence electron density of C1 from the C1–C2 bond to the newly formed C1–Al bond, as recently discussed for self-assembled monolayers [ 28 ]. This further affects the delicate electron density balance within the molecule, i.e., while the C1–C2 bond length increases (decreasing π-character), the C2–C2’ bond length decreases (increasing π-character) at the B site.…”

Engineering a Poly(3,4-ethylenedioxythiophene):(Polystyrene Sulfonate) Surface Using Self-Assembling Molecules—A Chemical Library Approach

“…Typically, in SIMS spectra of SAM adsorbed on solid surfaces, signals corresponding to characteristic fragments of the molecule are visible along with the others corresponding to whole molecules, clusters of molecules and atoms of the substrate. 23 For silane adsorbed on a soft PEDOT:PSS substrate, the SIMS spectra also contain fragments of the polymer that often interfere with the signals coming from the SAM. In the present study, two fragments derived from 3FS molecules were tracked, F 3 C 3 H 4 SiO 3 – and CF – , as presented in Figure 1A.…”