ChemInform Abstract: Electronic Structure and Spectra of Uranocene.

Abstract

The wave functions and energy levels for uranocene, U(C{sub 8}H{sub 8}){sub 2}, have been computed using ab initio techniques including the spin-orbit interaction and relativistic core potentials. The results give detailed information on the bonding in the ground state and on the assignment of the visible spectrum. A large amount of mixing of the ligand {pi} orbitals with the uranium 6d (and 5f) orbitals was found, confirming expectations of sizable covalent bonding. The symmetry of the ground state was found to be E{sub 3g}, in agreement with some previous experimental and theoretical results. There are many low-lying 5f{sup 2} excited states, only two of which have been observed, as well as 5f {yields} 6d, {pi} {yields} 6d, and {pi} {yields} 5f excited states. The visible bands, which give uranocene its green color, previously thought to be ligand-to-metal bands, are found to be primarily due to 5f {yields} 6d excitations. The basis set of 208 generally contracted Gaussian symmetry orbitals is of slightly better than double-{xi} quality, and 32 carbon core electrons and 78 uranium core electrons were replaced by relativistic core potentials. Double-group symmetry-adapted configuration-interaction expansions up to 31,000 in length were used. Spin-orbit matrix elements were included in themore » Hamiltonian matrices.« less