Matrix Isolation and Solvation of the Benzonitrile Radical Anion

Area of Science:

• Physical Chemistry
• Materials Science
• Spectroscopy

Background:

• Solvated electrons are potent reducing agents with typically short lifetimes (picoseconds to milliseconds) in solution.
• Long-lived solvated electrons, stable for days, are achievable using sodium metal in liquid ammonia, a method established in synthetic chemistry.
• Trapping short-lived species in matrices is crucial for studying their properties and reactivity.

Purpose of the Study:

• To investigate the possibility of trapping solvated electrons in low-density amorphous (LDA) water ice matrices.
• To determine the lifetime and reactivity of solvated electrons generated using sodium atoms in LDA water ice.
• To explore the formation and properties of benzonitrile radical anion in different matrix environments.

Main Methods:

• Generation of solvated electrons using sodium atoms as the electron source.
• Trapping of solvated electrons in low-density amorphous (LDA) water ice and solid argon matrices.
• Doping matrices with benzonitrile to study electron reactions.
• Photoexcitation of radical anions to observe electron transfer reversal.
• Annealing of matrices to study complex formation.

Main Results:

• Solvated electrons were successfully trapped in LDA water ice with lifetimes of several days.
• In LDA matrices, solvated electrons reacted with benzonitrile to form the benzonitrile radical anion.
• Higher yields of the benzonitrile radical anion were observed in water ice compared to argon matrices.
• Photoexcitation reversed the electron transfer, regenerating benzonitrile.
• Annealing argon matrices with water led to hydrogen-bonded complexes between water and the radical anion.

Conclusions:

• Low-density amorphous water ice can stabilize solvated electrons for extended periods, enabling their use as reducing reagents.
• The presence of water is crucial for efficient trapping and reaction of solvated electrons with benzonitrile.
• The study demonstrates a novel method for generating and utilizing long-lived solvated electrons in a solid-state matrix.