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Mapping the d-d Excited-State Manifolds of Transition Metal beta-Diiminato-Imido Complexes. Comparison of Density Functional Theory and CASPT2 Energetics

Ghosh, Abhik; Gonzalez, Emmanuel; Tangen, Espen and Roos, Björn LU (2008) In The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory 112(50). p.12792-12798
Abstract
Trigonal-planar, middle transition metal diiminato-imido complexes do not exhibit high-spin states, as might be naively expected on the basis of their low coordination numbers. Instead, the known Fe(III), Co(III), and Ni(III) complexes exhibit S = (3)/(2), S = 0, and S = (1)/(2), ground states, respectively. Kohn-Sham DFT calculations have provided a basic molecular orbital picture of these compounds as well as a qualitative rationale for the observed spin states. Reported herein are ab initio multiconfiguration second-order perturbation theory (CASPT2) calculations, which provide a relatively detailed picture of the d-d excited-state manifolds of these complexes. Thus, for a C-2v Fe-III(diiminato)(NPh) model complex, two near-degenerate... (More)
Trigonal-planar, middle transition metal diiminato-imido complexes do not exhibit high-spin states, as might be naively expected on the basis of their low coordination numbers. Instead, the known Fe(III), Co(III), and Ni(III) complexes exhibit S = (3)/(2), S = 0, and S = (1)/(2), ground states, respectively. Kohn-Sham DFT calculations have provided a basic molecular orbital picture of these compounds as well as a qualitative rationale for the observed spin states. Reported herein are ab initio multiconfiguration second-order perturbation theory (CASPT2) calculations, which provide a relatively detailed picture of the d-d excited-state manifolds of these complexes. Thus, for a C-2v Fe-III(diiminato)(NPh) model complex, two near-degenerate states (B-4(2) and B-4(1)) compete as contenders for the ground state. Moreover, the high-spin sextet, two additional quartets and even a low-spin doublet all occur at <0.5 eV, relative to the ground state. For the Co(III) system, although CASPT2 reproduces an S = 0 ground state, as observed experimentally for a related complex, the calculations also predict two exceedingly low-energy triplet states; there are, however, no other particularly low-energy d-d excited states. In contrast to the Fe(III) and Co(III) cases, the Ni(III) complex has a clearly nondegenerate B-2(2) ground state. The CASPT2 energetics provide benchmarks against which we can evaluate the performance of several common DFT methods. Although none of the functionals examined perform entirely satisfactorily, the B3LYP hybrid functional provides the best overall spin-state energetics. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory
volume
112
issue
50
pages
12792 - 12798
publisher
The American Chemical Society
external identifiers
  • wos:000261652800009
  • scopus:58149234955
ISSN
1520-5215
DOI
10.1021/jp711159h
language
English
LU publication?
yes
id
15c81ce0-6fe1-4763-95a8-cf4d7bd9b6de (old id 1379243)
date added to LUP
2009-04-24 09:34:44
date last changed
2017-05-28 03:52:37
@article{15c81ce0-6fe1-4763-95a8-cf4d7bd9b6de,
  abstract     = {Trigonal-planar, middle transition metal diiminato-imido complexes do not exhibit high-spin states, as might be naively expected on the basis of their low coordination numbers. Instead, the known Fe(III), Co(III), and Ni(III) complexes exhibit S = (3)/(2), S = 0, and S = (1)/(2), ground states, respectively. Kohn-Sham DFT calculations have provided a basic molecular orbital picture of these compounds as well as a qualitative rationale for the observed spin states. Reported herein are ab initio multiconfiguration second-order perturbation theory (CASPT2) calculations, which provide a relatively detailed picture of the d-d excited-state manifolds of these complexes. Thus, for a C-2v Fe-III(diiminato)(NPh) model complex, two near-degenerate states (B-4(2) and B-4(1)) compete as contenders for the ground state. Moreover, the high-spin sextet, two additional quartets and even a low-spin doublet all occur at &lt;0.5 eV, relative to the ground state. For the Co(III) system, although CASPT2 reproduces an S = 0 ground state, as observed experimentally for a related complex, the calculations also predict two exceedingly low-energy triplet states; there are, however, no other particularly low-energy d-d excited states. In contrast to the Fe(III) and Co(III) cases, the Ni(III) complex has a clearly nondegenerate B-2(2) ground state. The CASPT2 energetics provide benchmarks against which we can evaluate the performance of several common DFT methods. Although none of the functionals examined perform entirely satisfactorily, the B3LYP hybrid functional provides the best overall spin-state energetics.},
  author       = {Ghosh, Abhik and Gonzalez, Emmanuel and Tangen, Espen and Roos, Björn},
  issn         = {1520-5215},
  language     = {eng},
  number       = {50},
  pages        = {12792--12798},
  publisher    = {The American Chemical Society},
  series       = {The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory},
  title        = {Mapping the d-d Excited-State Manifolds of Transition Metal beta-Diiminato-Imido Complexes. Comparison of Density Functional Theory and CASPT2 Energetics},
  url          = {http://dx.doi.org/10.1021/jp711159h},
  volume       = {112},
  year         = {2008},
}