The electronic structures of tetrahedral oxo-complexes. The nature of the “charge transfer” transitions |
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Authors: | T Ziegler A Rauk EJ Baerends |
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Institution: | Department of Chemistry, University of Calgary, Calgary, Alberta, Canada T2N 1N4;Scheikundig Laboratorium der Vrije Universiteir, De Boelelaan 1083, Amsterdam, The Netherlands |
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Abstract: | The electronic structures of MnO?4, MnO2?4, MnO3?4, CrO2?4, CrO3?4, VO3?4, RuO4, RuO?4, RuO2?4, TcO?4 and MoO2?4 have been investigated using the Hartree-Fock-Slater Discrete Variational Method. The calculated ordering of the valence orbitals of all the comlexes is: t1, 4t2, 3a1, 1c, 3t2, with t1 the orbital of highest energy. The calculated single transition energies are in good agreement with experimental values and indicate the uniform assignment: t1 → 2e(v1), 4t2 → 2e(v2). t1 → 5t2(v3), and 4t2 → 5t2(v4). A/D values, calculated from the theory of magnetic circular dichroism (MDC) also support this assignment.Population analyses reveal that all complexes, whether d0, d1 or d2, have d-orbital populations close to those of the corresponding M2+ ions in which two electrons have been removed from the (n + 1)s orbital of M. This is also true of the excited states, such as t1 → 2e and 4t2 → 2e, where a transfer of charge from the ligands to the metal has previously been assumed. It is shown that, instead of a transfer of charge from ligands to metal, electronic excitation consists of a rearrangement of electron density both at the ligands and at the metal. |
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