Infrared Spectroscopy of Size-Selected Hydrated Carbon Dioxide Radical Anions CO2 .- (H2 O)n (n=2-61) in the C-O Stretch Region.

Andreas Herburger,Wai Kit Tang,Martin K Beyer,Chi‐Kit Siu,Jakob Heller,Milan Ončák,Ephrem G Demissie

doi:10.1002/chem.201901650

Andreas Herburger, Wai Kit Tang + Show 5 more

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https://doi.org/10.1002/chem.201901650

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Abstract

Understanding the intrinsic properties of the hydrated carbon dioxide radical anions CO2 .−(H2O)n is relevant for electrochemical carbon dioxide functionalization. CO2 .−(H2O)n (n=2–61) is investigated by using infrared action spectroscopy in the 1150–2220 cm−1 region in an ICR (ion cyclotron resonance) cell cooled to T=80 K. The spectra show an absorption band around 1280 cm−1, which is assigned to the symmetric C−O stretching vibration ν s. It blueshifts with increasing cluster size, reaching the bulk value, within the experimental linewidth, for n=20. The antisymmetric C−O vibration ν as is strongly coupled with the water bending mode ν 2, causing a broad feature at approximately 1650 cm−1. For larger clusters, an additional broad and weak band appears above 1900 cm−1 similar to bulk water, which is assigned to a combination band of water bending and libration modes. Quantum chemical calculations provide insight into the interaction of CO2 .− with the hydrogen‐bonding network.

Highlights

The carbon dioxide radical anion CO2CÀ is a key intermediate in the electrochemical as well as catalytic activation of carbon dioxide, which is relevant for using CO2 as a C1 building block.[1]
We investigate size-selected CO2CÀ(H2O)n clusters, n 61, by using infrared photodissociation spectroscopy in the range 1150–2220 cmÀ1 at T = 80 K
This is correct only for those clusters with a relatively high internal energy, which decay upon absorption of a single photon

Summary

Introduction

The carbon dioxide radical anion CO2CÀ is a key intermediate in the electrochemical as well as catalytic activation of carbon dioxide, which is relevant for using CO2 as a C1 building block.[1]. Williams and co-workers investigated how different core ions influence the hydrogen-bond network in large water clusters up to n % 550, far beyond the first solvation shell.[44,45,46,47,48,49,50,51] They found that the free OÀH band, resulting from the vibration of water molecules with at least one hydrogen atom not involved in hydrogen bonding, redshifts and increases in intensity with increasing positive charge.[44] Their work demonstrates long-range solvation effects upon hydration of different ions.

Results

Conclusion