# Matrix Isolation and Solvation of the Benzonitrile Radical Anion

## TL;DR

This paper shows that solvated electrons can be trapped in water ice and used to form a stable radical anion of benzonitrile, which is relevant for understanding chemical processes in space.

## Contribution

The study demonstrates the formation and stabilization of the benzonitrile radical anion in amorphous water ice matrices using solvated electrons.

## Key findings

- Solvated electrons in amorphous water ice matrices form the benzonitrile radical anion with high yield.
- Hydrogen-bonded complexes between water and the radical anion are observed after annealing.
- Photoexcitation reverses electron transfer, reforming benzonitrile in both argon and water ice matrices.

## Abstract

Solvated electrons, one of the strongest reducing agents, exhibit short lifetimes in the range of pico‐ to milliseconds when generated photochemically or by radiolysis in solution. In contrast, solvated electrons produced using sodium metal in liquid ammonia are stable for days and have long been used in synthetic chemistry. Using sodium atoms as an electron source, we were able to trap solvated electrons in low‐density amorphous (LDA) water ice matrices with lifetimes of several days and use these electrons as reducing reagents. In LDA matrices doped with benzonitrile 1, these electrons react with 1 to form the benzonitrile radical anion 2. In argon matrices, in the absence of water, only small amounts of 2 were observed after deposition, and most of the sodium and 1 remained unreacted. The yield of radical anion 2 is significantly higher in amorphous water ice than in solid argon. The photoexcitation of radical anion 2 in both argon and LDA water ice matrices resulted in a reversal of the electron transfer under back formation of benzonitrile 1. Annealing of argon matrices doped with small amounts of water containing 2 resulted in the formation of 1:1 and 2:1 hydrogen‐bonded complexes between water and radical anion 2.

Hydrated electrons are potent reducing agents that may play significant roles in chemical evolution within astrochemical and prebiotic environments. Benzonitrile, a molecule present in the interstellar medium (ISM), can capture electrons in amorphous water ice at cryogenic temperatures, forming a radical anion. This radical anion engages in hydrogen bonding with surrounding water molecules, interactions that can be characterized using infrared (IR) spectroscopy.