Theoretical investigation of the cyclopropene radical cation c-C₃H^+•₄: structure, energetics and spectroscopic properties^†

Abstract

The structure and properties of the cyclopropene radical cation c-C₃H^+• ₄ are investigated by means of quantum chemical methods. The equilibrium geometry of c-C₃H^+• ₄ is found to have C ₂ symmetry and a low barrier of 470 cm⁻¹ for stereomutation (around 700 cm⁻¹, including ZPVE corrections) with a transition state of C _2v symmetry. The adiabatic ionisation potential is estimated to be 77,800 cm⁻¹ with respect to c-C₃H₄. Vertical ionisation potential energies of c-C₃H₄, and vertical excitation energies to low-lying excited states of c-C₃H^+• ₄ are presented.

Keywords:

• cyclopropene
• cyclopropene radical cation
• C3H+•4
• ionisation potential
• vibrational frequencies
• transition states
• tunnelling splitting
• potential energy surface
• excitation energies
• ccsd(t)
• correlation consistent basis sets

Acknowledgements

Our work is financially supported by ETH Zürich. The Brutus cluster of ETH Zürich is acknowledged for computational resources. H.F. Schaefer was supported by the US Department of Energy. We would like to thank Dr K. Vasilatou, Dr J. Michaud, Dr F. Mariotti and Professor Dr F. Merkt, for stimulating and productive discussions.

We would like to congratulate Professor Dr Dr h.c. Martin Quack on his jubilee. We greatly acknowledge his scientific stimulus and numerous fruitful discussions on many fundamental questions of physical chemistry; primary kinetic processes and spectroscopy in particular.

Dedicated to Professor Martin Quack on the occasion of his 65th birthday.

Notes

^a Ref. [9].