Spectroscopy of CrO 4- 4 , MnO 3- 4 and FeO 2- 4 : New (3d) 2 luminophores in the NIR

Brunold, Thomas C.; Herren, Markus; Oetliker, Ueli; ̈del, Hans-Ueli Gu; Kesper, U.; Albrecht, Ch.; Reinen, D.

doi:10.1016/0022-2313(94)90114-7

Cited by 22 publications

(11 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The bonding and spectroscopic properties of the tetraoxoferrate͑VI͒ ion, FeO 4 2Ϫ , have been studied in this work by means of Restricted Active Space Self-Consistent-Field ͑RASSCF͒ calculations. The five molecular orbitals of main character Fe(3d) constitute a complete active space and the twelve orbitals of main character O 4 (2p) constitute a restricted active space from which all single, double, triple, and quadruple O 4 (2p)→Fe(3d) excitations are allowed.…”

Section: Discussionmentioning

confidence: 99%

“…In the present case, however, the demands of the FeO 4 2Ϫ cluster turned out to be very different. In effect, when the CASSCF(3d) wavefunction for FeO 4 2Ϫ is being calculated, the multiconfigurational space appears to be insufficient: The MCSCF procedure, if convergent at all, clearly shows that some molecular orbitals of main character ligands-2 p appear in the final natural orbital active space. The need to enlarge the CAS to include ligand orbitals is evident and it is associated to the fact that all the Fe(3d) and O 4 (2p) orbitals are close in energy.…”

Section: The Feo 4 2؊ Wavefunctionsmentioning

confidence: 99%

“…In order to compare our results with measured absorption spectra, we have also included in Table III experimental data corresponding to the polarized absorption spectra of Fe͑VI͒ doped in K 2 CrO 4 7,9 and in isomorphous K 2 SO 4 8 ͑see also Table IV͒ and to unpolarized absorption spectra of FeO 4 2Ϫ in 9 M KOH solution. 9,39 We have summarized the complex experimental data in the following way: In Table III the band maxima are tabulated and the maximum absorbance is indicated in squared parentheses, when available.…”

Section: A Vertical Absorption Spectramentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…[4][5][6] The d 2 spin-flip transition energies are expected to be slightly reduced with respect to the corresponding 1 D→ 3 F free ion values due to the so called nephelauxetic effect, 1 which has been interpreted as a consequence of the radial expansion of the 3d orbitals in the crystal field; however, Brunold et al 4 have observed a very irregular trend of this reduction at the end of the mentioned Ti͑III͒-Fe͑VI͒ series, together with a very unusual, tremendous decrease observed in K 2 CrO 4 :Fe 6ϩ , where the 1 E -3 A 2 energy difference is shown to be less than 40% of the 1 D -3 F free Fe͑VI͒ value. 4 These experimental results deserve some explanation. Moreover, Fe͑VI͒-doped K 2 CrO 4 and Fe͑VI͒-doped K 2 SO 4 ͓where Fe͑VI͒ is in the center of a slightly distorted tetrahedron͔ must exhibit, according to the Ligand Field Theory for d 2 ions in high field materials, two narrow spinforbidden and two broad spin-allowed bands in the low energy absorption spectrum, associated to d→d electronic transitions from the 3 A 2 ground state to 1 E, 1 A 1 , 3 T 2 , and 3 T 1 excited states, respectively, which should be seen in the polarized absorption spectra, splitted according to the actual T d →C s distortion in the crystals.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

A new interpretation of the bonding and spectroscopy of the tetraoxoferrate(VI) FeO42− ion

Al-Abdalla¹,

Seijo²,

Barandiarán³

1998

The Journal of Chemical Physics

View full text Add to dashboard Cite

In this paper we present an ab initio study of the absorption spectrum of the FeO 4 2Ϫ ion. The wavefunctions and energies of the ground and excited states of the FeO 4 2Ϫ cluster are calculated by means of the Restricted Active Space self-consistent-field method ͑RASSCF͒. The molecular orbitals of the cluster with main character Fe(3d) define a complete active space; all single, double, triple, and quadruple excitations from the molecular orbitals of main character O(2p) to those of main character Fe(3d) are allowed. The multiconfigurational expansions resulting from these ligands-to-metal excitations include between 50000 to 100000 configuration state functions. The results of the calculations lead to a new interpretation of the bonding and of the absorption spectra of FeO 4 2Ϫ ͑which were observed in the solid state and in solution͒, both of them stem from the near degeneracy between Fe(3d) and O(2 p) levels, which is ultimately due to the high and unstable oxidation state of Fe͑VI͒ in the FeO 4 2Ϫ complex. The analysis of the ground and excited state wavefunctions reveals that the electronic structure of FeO 4 2Ϫ does not correspond to the ionic image of Ligand Field Theory ͓d 2 -Fe͑VI͒ϩclosed-shell O 2Ϫ ions͔, nor does it correspond to simple extensions of it which take into account ligands-to-metal 2 p→3d single excitations, nor to any other simple image; on the contrary, it corresponds to the superposition of a large number of configurations with a very large weight of high-order ligands-to-metal excitations, which indicates a remarkable intra-cluster inwards delocalization of electron density away from the closed-shell ligands, impelled by the unstable high formal charge of Fe͑VI͒. The calculated absorption spectrum allows for a thorough interpretation of the features observed in the experimental spectra measured in Fe͑VI͒-doped K 2 MO 4 ͑MϭS, Cr͒ and in 9 M KOH solution ͑absorption maxima, intensities, electronic origins, band shapes͒, which implies completely new assignments. This is particularly so for the broad intense bands observed between 10000-25000 cm Ϫ1 , which, according to our calculations, are found to be associated to electronic transitions from the 3 A 2 ground state to increasingly dense sets of excited states that include not only spin singlet and triplet states ͑as expected for a d 2 configuration from Ligand Field Theory͒, but also spin quintet electronic states, all of which can be understood as direct effects of the above-mentioned oxygens(2p)-iron(3d) near degeneracy.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: The Feo 4 2؊ Wavefunctionsmentioning

confidence: 99%