Noble gas–uranium coordination and intersystem crossing for the CUO(Ne)x(Ng)n (Ng = Ar, Kr, Xe) complexes in solid neon

Abstract

Atomic uranium excited by laser ablation reacts with CO in excess neon to produce the novel CUO molecule, which forms weak complexes CUO(Ne)_m with neon and stronger complexes CUO(Ne)_x(Ng)_n (Ng = Ar, Kr, Xe) when the heavier noble gas atoms are present. The heavier CUO(Ne)_m − 1(Ng) complexes are identified through the effects of CO isotopic and Ng substitution on the neon matrix infrared spectra and by comparison to DFT frequency calculations on the model complexes CUO(Ng) (Ng = Ne, Ar, Kr, Xe). The U–C and U–O stretching frequencies of CUO(Ne)_m − 1(Ng) complexes are slightly red shifted from the 1047 and 872 cm⁻¹ frequencies for the ¹Σ⁺ CUO ground state neon complex, which identifies singlet ground state CUO(Ne)_m − 1(Ng) complexes in solid neon. The next singlet CUO(Ne)_x(Ng)₂ complexes in excess neon follow in like manner. However, stretching modes and the isotopic shifts of the higher CUO(Ne)_x(Ng)_n complexes approach those of the pure argon matrix CUO(Ar)_n complex, which characterizes triplet ground state complexes by comparison to DFT frequency calculations.