Theoretical study of the photoelectron spectrum of (n5-C5H5)Ni(NO)

Abstract

The valence photoelectron spectrum of cyclopentadienyl nickel nitrosyl (CpNiNO) was computed to determine the ion state orbital ordering of the 5e1, 7a1, and 3e2 bands. Calculations were performed with Hartree-Fock theory, density functional theory, M[]ller-Plesset perturbation theory, and configuration interaction theory and, in all cases, utilized a triple-z basis set including polarization and diffuse functions (6-311+G*). Density functional theory was also used with the same basis set to calculate the ion state orbital ordering of the lowest energy e1, a1, and e2 bands in pentamethylcyclopentadienyl nickel nitrosyl (Cp*NiNO). Recent experimental studies have proposed the conflicting ion state orbital orderings of 5e1(l),5e1(2)<7a1†3e2(3) (band numbers are in parentheses) and 5e1(1)<7a1(2)<3e2(3) for CpNiNO. In this study, the ordering concluded from calculated energy differences between the neutral ground state and the cationic states is 5e1( 1 )<:7a1(2)<3e2(3), while comparison of the calculated band shifts between the CpNiNO and CP*NiNO spectra support the assignment of 5e1 (1 ),5e1 (2)<7a1 †3e2(3).