## 3 Results and Discussion
### Calculated Core-Level Binding Energies, XP Spectra, and Work Function Changes  
#### 3.3.1 Energetic Shifts Due to Variations in the Interface Dipole  
In Figure 3, we show the core level binding energies and XP spectra of systems I, III, V, and VIa as prototypical examples for the impact of the docking groups on the core level binding energies. In the following, the \"vacuum level alignment\" system VIa was used as an energy reference for the work function as well as for the core level binding energies (for the absolute values of the reference energies see the Methods Section). This directly yields \(\Delta\)E\({}_{\text{CIs}}\) and \(\Delta\Phi\) (i.e., the quantities shown in Figure 1). As far as the systems not displayed in Figure 3 are concerned, the data points for II essentially coincide with those of I and (apart from chemical shifts for the carbon atoms directly bonded to nitrogen atoms) the binding energies of III and V are also similar. System VI is similar to VIa with binding energies shifted to higher values by 0.34 eV. The corresponding data can be seen in the Supplementary Materials, where we show a (somewhat busy) plot analogous to Figure 3 containing values for all investigated systems. Compared to System VIa, the core level binding energies in all chemically bonded SAMs are shifted to higher (more negative) binding energies by several electronvolts. The effect is largest for III, for which the shift amounts to 2.8 eV (see black arrow). Even between docked systems, the peak positions vary by 1.6 eV with the smallest value (\(-265.2\) eV) for the methyl thiolate and the largest (\(-266.8\) eV) for the pyridine. This is exactly the situation one would expect according to Figure 1 for varying interface dipoles as a consequence of collective electrostatic effects [31; 40; 45; 46; 63]. In passing we note that, to the best of our knowledge, there is no systematic experimental study of docking group induced shifts in a series of well-ordered monolayers, but there are examples comparing thiols and isocyanides: [PERSON] et al. compared 4,4'-ethynylphenyl-I-benzetchiols on polycrystalline Au bonded either by thiols or by isocyanides and for the isocyanide-docked SAMs they observed a C1s peak at 0.6 eV higher binding energy than for the thiol case [138]. There is also indirect evidence that such shifts occur in other types of SAMs: when comparing thiolate and isocyanide bonded acene SAMs, [PERSON] et al. measured a distinctly larger ionization energy of the isocyanide-bonded system with the shift between the valence orbitals amounting to 0.7 eV [139]. Unfortunately, they did not report corresponding C1s core level spectra, but, as discussed above, the shifts of valence and core levels have the same physical origin. Overall, the results in [138; 139] are well in line with the data for systems I and IV in Figure 3, where the somewhat larger shift in the simulations is presumably due to assumed perfect ordering of the SAMs. Superimposed on the electrostatic shifts of the XPS peaks, one can also identify the chemical shifts due to the differently bonded carbon atoms (cf. Figure 3a). For example, the carbon atoms connecting the two benzene rings are shifted by 0.5 eV relative to the other carbon atoms of the rings. Additionally, the carbon atoms attached to the docking groups are chemically shifted, resulting in distinct variations of the binding energies. This is, however, rather inconsequential for the positions and shapes of the XP spectra as a consequence of the finite escape depth of the photoelectrons. This is well visible, for example, for the isocyanide-docked SAM (system IV), where the lowest carbon atoms are shifted by 2 eV relative to the ones in the rings. The latter still rather exclusively determine the position of the peak in the corresponding XP spectrum. Provided that the primary core level shifts are truly a consequence of collective electrostatic effects caused by interface dipoles they should directly correlate with the SAM-induced changes in the work function for systems I to VIa.