Valence Stabilization, Mixed Crystal Chemistry, and Electronic Transitions in Tetrahedral Oxo and Hydroxo Cr(IV), Mn(V), and Fe(VI) Clusters: A Theoretic Investigation

Atanasov, Mihail; Adamsky, H.; Eifert, K.

doi:10.1006/jssc.1996.7092

Cited by 20 publications

(7 citation statements)

References 37 publications

(42 reference statements)

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“…13 By measurement of the electric conductivity, Seebeck coefficient and magnetic susceptibility, and from ab initio molecular orbital (MO) calculations, RECrO 4 (RE~La, Nd and Eu) was found to be an n-type semiconductor having a unique conduction band of antibonding ps* states (O 2p origin) arising from the intermixing of Ligand to Metal Charge Transfer (LMCT) states. [13][14][15][16][17] In the course of further investigations on RECrO 4 containing smaller RE III ions than Eu III , however, we found that these compounds were never obtained as the stoichiometric ones reported so far. When we started the synthesis from the precursor of stoichiometric composition, it always produced a mixed phase.…”

Section: Introductionmentioning

confidence: 77%

Synthesis, structure and defects of rare earth chromates(V), RE0.9CrO3.85 (RE = Gd, Yb and Y)

Aoki

Konno

2001

J. Mater. Chem.

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Section: Introductionmentioning

confidence: 77%

Synthesis, structure and defects of rare earth chromates(V), RE0.9CrO3.85 (RE = Gd, Yb and Y)

Aoki

Konno

2001

J. Mater. Chem.

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“…For the three states it can be observed that ͑i͒ the weight of the d 2 (e 2 ) Ligand Field configuration in the RASSCF wavefunction is very small (р0.5%); ͑ii͒ the ligands-to-metal 2p→3d single excitations, usually called ligand-to-metal charge transfer configurations, amount to some 7%; ͑iii͒ ligands-to-metal double and triple excitations are very important, their accumulated weight being about 50%; ͑iv͒ a large number of configurations ͑some 70͒, contribute to the wavefunction with C i у0.05, however, their total weight is only about 60%. All these observations lead to the following conclusions: The electronic structure of FeO 4 2Ϫ does not correspond to the d 2 ionic image of Ligand Field Theory, 1 nor it does correspond to simple extensions of it which only take into account ligands-to-metal 2p→3d single excitations, 36,37 nor to any other simple image. On the contrary, it corresponds to the superposition of a large number of configurations, which represents a remarkable intracluster delocalization of electron density inwards, away from the closed shell ligands, impelled by the unstable high oxidation state of Fe͑VI͒.…”

Section: The Feo 4 2؊ Wavefunctionsmentioning

confidence: 98%

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

Al-Abdalla¹,

Seijo²,

Barandiarán³

1998

The Journal of Chemical Physics

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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.

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“…While orbital contributions from 3d (TM) and ligand (L) 2p functions to the bonding and antibonding orbitals may vary in a wide range, depending on the TM-ligand covalency and ionicity, transfer of electrons from the nonbonding (L, 2p) to the antibonding t 2 and e orbitals can take place either in the ground or in the excited state and reduce by one the TM oxidation state. 5 In a recent study using charge-transfer (CT) spectra, we have been able to recognize many peculiarities of the electronic and geometric structures of the lower oxidation states of TM such as V IV , Cr V , and Mn VI (d 1 ) by analyzing the ligand-to-metal charge-transfer (LMCT) spectra of the corresponding V V , Cr VI , and Mn VII (d 0 ) TM tetrahedral oxo anions. 6 The electron flow from fully occupied nonbonding (ligand) MOs to empty or partly occupied antibonding orbitals is enhanced by interelectronic repulsion, which destabilizes these orbitals to a larger extent than the energetically close lying antibonding MOs.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Studies on the Higher Oxidation States of Iron

Atanasov

1999

Inorg. Chem.

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Density functional theory (DFT) and multiconfiguration self-consistent field (MCSCF) calculations on the oxo FeO(4)(2)(-) (Fe(VI)) and the hypothetical oxo FeO(4)(-) (Fe(VII)), and FeO(4) (Fe(VIII)) and peroxo FeO(2)(O-O)(z)() [z = -2 (Fe(IV)), z = -1 (Fe(V)), z = 0 (Fe(VI))], Fe(O-O)(2)(z)() [z = -2 (Fe(II)), z = -1 (Fe(III)), z = 0 (Fe(IV))], and FeO(O-O)(2)(z)() [z = -2 (Fe(IV)), z = -1 (Fe(V)), z = 0 (Fe(VI))] clusters are presented and discussed. The results show the potential of stabilizing Fe(VII) and Fe(VIII) in tetrahedral oxo coordination. On the basis of absolute electronegativities calculated using DFT, it is predicted that FeO(4) will be rather oxidizing, even stronger than Cl(2) and O(2). On the basis of a comparison between total bonding energies of M(1)M(2)Fe(VI)O(4) (M(1), M(2) = Li, K), MFe(VII)O(4) (M = Li, K), and Fe(VI)O(4) clusters, possible synthetic routes for electrochemical preparation of FeO(4)(-) and FeO(4) species are discussed.

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Valence Stabilization, Mixed Crystal Chemistry, and Electronic Transitions in Tetrahedral Oxo and Hydroxo Cr(IV), Mn(V), and Fe(VI) Clusters: A Theoretic Investigation

Cited by 20 publications

References 37 publications

Synthesis, structure and defects of rare earth chromates(V), RE0.9CrO3.85 (RE = Gd, Yb and Y)

Synthesis, structure and defects of rare earth chromates(V), RE0.9CrO3.85 (RE = Gd, Yb and Y)

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

Theoretical Studies on the Higher Oxidation States of Iron

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