Infrared spectra and quantum chemical calculations of the uranium carbide molecules UC and CUC with triple bonds

Xuefeng Wang; Lester Andrews; Per-Ake Malmqvist; Björn O Roos; António P Gonçalves; Cláudia C L Pereira; Joaquim Marçalo; Claude Godart; Benjamin Villeroy

doi:10.1021/ja102475t

Infrared spectra and quantum chemical calculations of the uranium carbide molecules UC and CUC with triple bonds

J Am Chem Soc. 2010 Jun 23;132(24):8484-8. doi: 10.1021/ja102475t.

Authors

Xuefeng Wang¹, Lester Andrews, Per-Ake Malmqvist, Björn O Roos, António P Gonçalves, Cláudia C L Pereira, Joaquim Marçalo, Claude Godart, Benjamin Villeroy

Affiliation

¹ Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904-4319, USA.

PMID: 20504028
DOI: 10.1021/ja102475t

Abstract

Laser evaporation of carbon-rich uranium/carbon alloys followed by atom reactions in a solid argon matrix and trapping at 8 K gives weak infrared absorptions for CUO at 852 and 804 cm(-1). A new band at 827 cm(-1) becomes a doublet with mixed carbon 12 and 13 isotopes and exhibits the 1.0381 isotopic frequency ratio, which is appropriate for the UC diatomic molecule, and another new band at 891 cm(-1) gives a three-band mixed isotopic spectrum with the 1.0366 isotopic frequency ratio, which is characteristic of the linear CUC molecule. CASPT2 calculations with dynamical correlation find the C[triple bond]U[triple bond]C ground state as linear 3Sigma(u)+ with 1.840 A bond length and molecular orbital occupancies for an effective bond order of 2.83. Similar calculations with spin-orbit coupling show that the U[triple bond]C diatomic molecule has a quintet (Lambda = 5, Omega = 3) ground state, a similar 1.855 A bond length, and a fully developed triple bond of 2.82 effective bond order.