# Formation of the Long-Lived Parent Anion upon Electron Attachment to Menadione

## TL;DR

This study explores how menadione forms a stable anion when electrons attach to it, revealing insights into its behavior in biological systems.

## Contribution

The study identifies the formation of a long-lived parent anion of menadione through electron attachment.

## Key findings

- The parent molecular anion of menadione forms efficiently with electron attachment.
- Fragment anions C2H2– and CH3– form at higher electron energies.
- The parent anion is structurally stable and has a long lifetime.

## Abstract

Menadione is a multifunctional molecule involved in critical
biological
processes such as blood coagulation, redox regulation, and cellular
metabolism. Understanding its electron attachment properties and capacity
to form stable anions is essential for elucidating its function in
biological environments. In this study, we investigated electron attachment
to menadione using a crossed electron-molecular beam experiment, complemented
by quantum chemical and electron scattering calculations. Upon electron
attachment, the efficient formation of the parent molecular anion
is observed. Its signal extends from 0 to 2.5 eV, with pronounced
peaks at ∼0 and 0.7 eV, assigned to the formation of different
precursor anion states. Two fragment anions, namely, C2H2
– and CH3
–, were also detected. In contrast to the parent anion, their formation
occurs with significantly lower efficiency and only at higher electron
energies, above 4 eV, consistent with the higher energy thresholds
required for dissociative electron attachment. Our findings show,
on the one hand, that the metastable parent anion of menadione has
a relatively long lifetime, which may be further extended in biological
environments due to solvent effects, and, on the other hand, that
it is structurally stable in the interaction with low-energy electrons.