Ionization potentials of ferrocene and Koopmans' theorem. Anab initio LCAO-MO-SCF calculation

The Electronic Structure of Closed Shell Metallocenes in the Ground State and in the Cationic Hole-States

“…[17] derived the sequence 6eiu on top of 4eig while Rabalais et al [18] favoured the opposite sequence. The first assignment was in line with a near minimal basis ZlSCF study while double-zeta calculations predicted the latter one [2], The results of Evans et al [17] have been corroborated unequivocally by a very recent study under He (I) and He (II) radiation conditions [49]. The remaining IP's of 3 in the lower energy region are found between 11.8 and 14 eV with maxima at 12.3, 13.0 and 13.49 eV and with a weak shoulder (11.9 eV) at the lower energy side.…”

“…E^ (co) vanishes in the case of canonical MO's and E (2) (co) is the leading term of the perturbational series. In accordance with our previous studies [10,11,21,22] we have employed an effective renormalized self-energy approximation where the second order contributions of the E(co) expansion are scaled by a single third order element (D4).…”

“…Ferrocene was one of the first examples in the class of transition metal compounds where the nonvalidity of Koopmans' theorem [1] (7^ = -£;) for ionization events in the outer valence region had been demonstrated [2]. The sequence of the canonical molecular orbital energies in the electronic ground state differed from the sequence of the calculated ionization potentials derived in an ab initio zlSCF framework.…”

“…We have chosen bis (jr-cylopentadienyl)magnesium (1) as a representative example of a closed shell metallocene with outer valence MO's that are prevailingly localized in the Cp rings. Three complexes with occupied 3d orbitals have been considered: bisbenzene chromium (2), ferrocene (3) and the mixed sandwich cyclopentadienyl benzene manganese (4). The PE spectra of these compounds have been measured by several groups (1: [13], 2: [14][15][16], 3: [13,17,18] and 4: [16]).…”

“…The PE spectra of these compounds have been measured by several groups (1: [13], 2: [14][15][16], 3: [13,17,18] and 4: [16]). Within the series 1-4 only the PE spectra of 2 [14] and 3 [2,19,20] have been discussed on the basis of computational results (zlSCF calculations), the PE data of 1 and 4 have 0340-4811 / 82 / 1000-1193 $ 01.30/0. -Please order a reprint rather than making your own copy.…”