Ferrocene, ionization energy

Table II also shows the calculated ionization energies for ferrocene based on the SCF-SW-A"a procedure. The Xa calculation gives a better quantitative account of the observed photoelectron spectrum than the ab initio calculations of Veillard et al. (58). Whether the Xa technique is generally more reliable remains to be established.

Ab initio Eigenvalues for the Ground State of Ferrocene, Computed Ionization Energies (eV) and Experimental Ionization Energies (eV)... 

In systems where the molecular orbitals have a similar atomic basis, as in the molecules discussed in this review, it is usually found that the sequence of ionization energies and orbital energies is the same although the absolute values do not agree, as for example in Table 1. Should there be a discrepancy in sequence there is said to be a failure of Koopmans theorem , examples of which are common especially for molecules where the atomic bases differ as, for instance, in organometallic compounds like ferrocene and bis-(7i-allyl)nickeP . Further examples can be found in Refs 38-44. 

Table 1. Comparison of theoretical estimates of ionization energies (eV) of ferrocene...

Some related ruthenocene species have also been investigated [117], almost always showing lower quadratic hyperpolarizabihties, in accordance with the higher ionization energy of the ruthenocene vs ferrocene moiety [115]. 

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