Adamantanes as white-light emitters: Controlling arrangement and functionality by external Coulomb forces

TL;DR

This study investigates how external Coulomb forces influence the structure and nonlinear optical properties of functionalized adamantane molecular clusters, revealing mechanisms for controlling white-light emission and photochemical effects.

Contribution

It demonstrates that transient Coulomb forces can induce structural transformations affecting optical properties, and explores how bromine functionalization enables control over photochemical and emission behaviors.

Findings

Coulomb forces lead to intramolecular and intermolecular structural changes.

Bromine functionalization triggers photochemical rearrangements.

Structural changes correlate with enhanced optical properties.

Abstract

Functionalized adamantane molecular cluster materials show highly transient nonlinear optical properties of currently unclear structural origin. Several interaction mechanisms in compounds comprising molecular clusters, their inter- and intramolecular interactions as well as the interplay of their electronic systems and vibrations of their backbone are viable concepts to explain these nonlinear optical properties. We show that transient Coulomb forces also have to be considered as they can lead to intramolecular structure transformations and intermolecular rearrangements in the crystal. Both strongly influence the nonlinear optical properties. Moreover, selective bromine functionalization can trigger a photochemical rearrangement of the molecules. The structure and chemical bonding within the compounds are investigated in dependence on the laser irradiation at different stages of their nonlinear emission by electron diffraction and electron energy loss spectroscopy. The transient structural and chemical states observed are benchmarked by similar observations during electron irradiation, which makes quantification of structural changes possible and allows the correlation with first principles calculations. The functionalization and its subsequent usage to exploit photochemical effects can either enhance two-photon absorption or facilitate white-light emission rather than second-harmonic generation.