A sui generis electrode-driven spatial confinement effect responsible for strong twisting enhancement of floppy molecules in closely packed self-assembled monolayers

Abstract

At present, it is widely accepted that properties (e.g., molecular conformation) of molecules adsorbed to form self-assembled monolayers (SAMs) on electrodes can be very different from isolated species because of a substantial charge transfer or specific chemical bonding at the interface. Contrary to this view, the theoretical results presented here predict that the strong twisting angle (φ) enhancement of floppy molecules adsorbed to form densely packed SAMs on most common electrodes (Pt, Au, Ag, and Cu) is neither due to charge transfer nor to specific bonding but rather to a sui generis electrode-driven spatial confinement effect that can be quantitatively described within an electrode-free two-dimensional model. We predict a logistic ("Fermi-Dirac") growth pattern of φ as the coverage approaches the value characteristic of a herringbone arrangement, which is twice the value for isolated molecules or low-coverage SAMs.

Density Functional Theory Study of Pd Aggregation on a Pyridine‐Terminated Self‐Assembled Monolayer

“…SAM on Au(111)s urface structure Beforea ddressing Pd adsorption on the PyP1 SAM, we discuss structurald etails of the native monolayer.S canning tunnelling microscope (STM) studies proposed a( 2 p 3 p 3) R308 structure of the monolayer on Au(111)w ith ah erringbone packing of the pyridine-based molecules, [43,44] corresponding to the structurally analogous w-biphenyl-alkanethiols with an odd number of methylene spacers on Au(111). [41] Like biphenylthiolates, [45][46][47][48] PyP1 can exhibit coplanar or twisted conformations of the pyridine-benzenemoiety and the rotational freedom between the aromatic rings is ac lears ource for structural variations. Unfortunately,t his twist angle is, in general, difficult to accesse xperimentally.…”

Suppression of Groups Intermingling as an Appealing Option for Flattening and Delaying the Epidemiological Curve While Allowing Economic and Social Life at a Bearable Level during the COVID‐19 Pandemic

“…The results reported below were obtained by means of the logistic model [21][22][23][24][25][26][27][28] extended (see Equation (16)) to allow treatment of infection propagation in a network consisting of groups in interaction. To fix the ideas and to make the paper self-contained, in Section 3.1 we will first review the main aspects related to the logistic model applied to an isolated group using a terminology adapted to the specific subject under consideration.…”

“…Therefore, to better emphasize this idea, instead of a SIR-based approach (which would pose no special problem), in this paper we prefer to adopt the simpler logistic growth framework. The logistic model is particularly appealing in view of its simplicity and versatility demonstrated in approaching a broad variety of real systems with very different nature, [21][22][23][24][25][26][27][28] including population dynamics of epidemic states. [29][30][31][32] Prior to this study, results based on the logistic model were presented for COVID-19 time evolution in China and the United States.…”

Suppression of Groups Intermingling as Appealing Option For Flattening and Delaying the Epidemiologic Curve While Allowing Economic and Social Life at Bearable Level During COVID-19 Pandemic

“…The results reported below were obtained by means of the logistic model [21][22][23][24][25][26][27][28] extended (see equation (16)) to allow treatment of infection propagation in a network consisting of groups in interaction. To fix the ideas and to make the paper self-contained, in Section 3.1 we will first review the main aspects related to the logistic model applied to an isolated group using 3 a terminology adapted to the specific subject under consideration.…”

“…Therefore, to better emphasize this idea, instead of a SIR-based approach (which would pose no special problem), in this paper we prefer to adopt the simpler logistic growth framework. The logistic model is particularly appealing in view of its simplicity and versatility demonstrated in approaching a broad variety of real systems with very different nature, [21][22][23][24][25][26][27][28] including population dynamics of epidemic states. [29][30][31][32] Prior to this study, results based on the logistic model were presented for COVID-19 time evolution in China and USA.…”