# Collective Electrostatics vs through-Space Interactions: Electronic Properties of Molecules with Multiple Polar Substituents

## TL;DR

The paper investigates how collective electrostatic effects influence electronic properties of molecules with multiple polar substituents, comparing them to through-space interactions.

## Contribution

The study introduces a model system to distinguish through-space interactions from collective electrostatic effects in molecules with multiple polar substituents.

## Key findings

- Through-space interactions significantly alter molecular electronic properties via cumulative electric fields of substituents.
- Distinct deviations from collective electrostatic behavior are observed in molecules with multiple polar substituents.
- The study highlights the role of cumulative local-field electrostatic effects in molecular systems.

## Abstract

Collective electrostatic
has been identified as the single most
important factor determining the electronic structure and (electronic)
functionality of heterogeneous interfaces. It changes spectroscopically
determined quantities like electron binding energies and core-level
shifts. Additionally, it results in massive changes of surface potentials
and injection barriers in conventional and molecular electronic devices
and shifts the electrostatic potential within the channels of porous
materials. Collective electrostatics is triggered by the superposition
of the electric fields of dipoles, which are arranged in a (semi)­periodic
fashion. This raises the questions, which role it plays in individual
molecules comprising multiple polar substituents and how collective
electrostatics is related to the widely discussed through-space interactions
between molecular backbones and polar substituents. Thus, the current
manuscript will specifically address the question, whether through-space
interactions can be regarded as yet another manifestation of collective
electrostatics. To that aim, first a model-system is designed in which
through-bond interactions with substituents are essentially eliminated.
Subsequently, the localization of the encountered frontier orbitals
and charging induced polarization effects are studied. Additionally,
the evolution of ionization energies, electron affinities and the
local distribution of the potential shifts with the number of polar
substituents are analyzed. The data as a whole suggest that through
space interactions can massively change the electronic properties
of molecules due to the combined electric field of the polar substituents;
still, distinct deviations from the typical characteristics of systems
dominated by collective electrostatics are observed. This shows that
in molecules one is rather in the realm of cumulative local-field
electrostatic effects.