Lawrence Berkeley National Laboratory

The electronic structure of Th(Cp″)3 (Cp″ = η5-C5H3(SiMe3-1,3), a molecule which has a 6d1 ground configuration and an excited 5f1 configuration beginning approximately 14,000 cm−1 higher, is reexamined. The ground state of the 6d1 configuration in a crystal field of D3h symmetry is shown to be an orbitally quenched 2A1ʹ state, best described as a pure 2D1/2 state. Electric dipole selection rules from this state to the states for the 5f1 configuration in a D3h crystal field result in the 5f1 truncated optical spectrum observed. The optical spectrum of the square planar Th3+ compound [Li(THF)4][Th(OAr′)4], where (OAr′ = OC6 H2tBu2-2,6-Me-4), is discussed.