Orbital analysis of metal-to-ligand charge transfer and oxidation in (NH3)5RuL2+ complexes: Effective t2g orbital ordering and the role of ligand π and π* orbitals

Journal of Physical Chemistry

Volumn 100, Issue 4, 1996, Pages 1104-1110

  Shin, Yeung Gyo K ^a   Brunschwig, Bruce S ^a   Creutz, Carol ^a   Newton, Marshall D ^a   Sutin, Norman ^a  

^a BROOKHAVEN NATIONAL LABORATORY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 33751123246     PISSN: 00223654     EISSN: None     Source Type: Journal    
DOI: 10.1021/jp9517817     Document Type: Article

References (53)

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12. Since the HF orbital energy e/ includes the interaction of the electron in the ith orbital with all of the other electrons, the energy of a particular electronic configuration is not simply equal to the sum of the individual orbital energies because each electron-electron interaction would be included twice. Furthermore, the orbital energies will depend upon the electronic configuration considered.10'"'
13. Even in the case of ionization, Koopmans' theorem is not necessarily obeyed by alternative orbital models; for example, those obtained from density functional theory calculations do not obey Koopmans' theorem.
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35. AGMi = -14.4(1 - l/Ds)/2r (eV) where q is the charge (au) on the complex, r is the effective radius (A) of the unhydrated or hydrated complex, and Ds is the static dielectric constant. The effective radii, obtained by taking the geometric mean of the three mutually perpendicular molecular radii (r = (n/)"3),35 are 4.49,4.41, and 4.49 A for the py, pz, and pzH+ complexes, respectively, and 5.4, 5.6, and 5.6 A for the corresponding hydrated complexes.
36. Brunschwig, B. S.; Ehrenson, S.; Sutin, N. J. Phys. Chem. 1986, 90, 3657-3668.
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42. If, as an alternative, the Mulliken population analysis is adopted,26 the 5s, 5p populations are considerably smaller, but the 4d populations differ by <5% from the ZDO values given in Table 3.
43. Shin, Y.-g.; Brunschwig, B. S.; Creutz, C.; Sutin, N. To be published.
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48. In the case of centrosymmetric binuclear complexes, where the two metal centers are symmetry equivalent, the L and L°4 MO's of pyrazine belong to different irreducible representations, so they occur in different MO's (those involving, respectively, the antisymmetric and symmetric combinations of d.T and d.i- orbitals).
49. In the ZINDO calculations a molecular exchange integral K(iJ) is nonzero only if MO's i,j have contributions from the same atomic orbitals, as occurs when the localized M and L orbitals are mixed via ligand field coupling. In a similar fashion, the Coulomb integral J(ij) tends to increase in magnitude with increasing M-L delocalization since this increases the contribution from the relatively large one-center atomic Coulomb integrals.
50. Note that exchange contributions are absent for the MLCT triplet state. Consequently, the lowest energy transition to the triplet is always from the ground state HOMO, and the orbital ordering is the same for spectroscopic excitation and for ionization.
51. The d.T hole represents the lowest energy configuration of the Ru(III) charge state over a range of Ru-N(pz) bond lengths, including the equilibrium values for the Ru(II) and Ru(III) complexes, 2.006 and 2.08 A,28 respectively.
52. Generalizing slightly the treatment given in ref 6, we find that the superexchange coupling element, //d,d, for a d, -d.T MMCT transition (d, = d.T- or da) is given by (Ad,.i7,.)('L,.,d,VAE'cT, where /,> is the metalto-ligand coupling element (linking orbitals / and J) and AEcr is the appropriate energy gap. Since the oscillator strengths (and hence the coupling element h) for the dy -L.-i and da -La- transitions are so low, //dyjt, will be negligible. Note that the d.y -d.T and dt -d.T MMCT transitions produce an electronically excited Ru(III) center and that the superexchange coupling only pertains to the component of the MLCT transition that is polarized parallel to the M-L axis. Although the d-T- -L.7. transition is allowed, it is polarized perpendicular to the M-L axis while the da -<, transition is totally forbidden in Ci symmetry.
53. In the case where A£MLcr(d) > 0 but AEMLcKd,) < AIP(d,), as in the case of L = py, eq A6 can be replaced by the weaker condition 2|AK(d,)| - fJ(d,) > 0.