Monoligated Monovalent Ni: the 3dNi9 Manifold of States of NiCu and Comparison to the 3d9 States of AlNi, NiH, NiCl, and NiF†

A dispersed fluorescence investigation of the low-lying electronic states of NiCu has allowed the observation of four out of the five states that derive from the 3dNi9 3dCu10 ó2 manifold. Vibrational levels of the ground X2¢5/2 state corresponding to V) 0-11 are observed and are fit to provide öe) 275.93 ( 1.06 cm-1 and öexe) 1.44 ( 0.11 cm-1. The V) 0 levels of the higher lying states deriving from the 3dNi9 3dCu10 ó2 manifold are located at 912, 1466, and 1734 cm-1, and these states are assigned to ¿ values of 3/2, 1/2, and 3/2, respectively. The last of these assignments is based on selection rules and is unequivocal; the first two are based on a comparison to ab initio and ligand field calculations and could conceivably be in error. It is also possible that the V) 0 level of the state found at 912 cm-1 is not observed, so that T0 for the lowest excited state actually lies near 658 cm-1. These results are modeled using a matrix Hamiltonian based on the existence of a ground manifold of states deriving from the 3d9 configuration on nickel. This matrix Hamiltonian is also applied to the spectroscopically well-known molecules AlNi, NiH, NiCl, and NiF. The term energies of the 2“+, 2ƒ, and 2 ¢ states of these molecules, which all derive from a 3d9 configuration on the nickel atom, display a clear and understandable trend as a function of the electronegativity of the ligands. I