Matrix Isolation and Solvation of the Benzonitrile Radical Anion.

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 reagent. 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.