Are the Ground States of the Later Actinocenes Multiconfigurational? All-Electron Spin−Orbit Coupled CASPT2 Calculations on An(η8-C8H8)2 (An = Th, U, Pu, Cm)

2009-07-30T00:00:00Z (GMT) by Andrew Kerridge Nikolas Kaltsoyannis
Spin−orbit free and spin−orbit coupled CASPT2 wave functions and energies are presented for the ground and low-lying excited states of four actinide element sandwich molecules; thorocene (ThCOT2), uranocene (UCOT2), plutonocene (PuCOT2), and curocene (CmCOT2). Spin−orbit coupling is found to make little difference to the equilibrium geometry of uranocene and plutonocene but has a significant effect on the energy spectrum of all the systems considered here other than thorocene. In all cases, however, the spin−orbit free ground states make the dominant contribution to their spin−orbit coupled counterparts. Following work presented in J. Phys. Chem. A 2009, 113, 2896, the variation in the multiconfigurational character of the ground-state wave functions as the 5f series is crossed is quantified via the occupation of the au/b1u (e2u) metal-ring bonding and antibonding natural orbitals. The ground state of plutonocene is found to be nondegenerate with |MJ| = 0, in agreement with its temperature-independent paramagnetism.