Infrared spectra and quantum chemical calculations of the uranium carbide molecules UC and CUC with triple bonds.
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.
Wang
Xuefeng
X
Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904-4319, USA.
Andrews
Lester
L
Malmqvist
Per-Ake
PA
Roos
Björn O
BO
Gonçalves
António P
AP
Pereira
Cláudia C L
CC
Marçalo
Joaquim
J
Godart
Claude
C
Villeroy
Benjamin
B