ISBN: 978-83-60043-10-3 - eurobic9

Eurobic9, 2-6 September, 2008, Wrocław, Poland
KL26. Accurate Spin State Energies for First-row Transition Metal
Compounds
M. Swart a , M. Güell b , J.M. Luis b , M. Solà b
a Institució Catalana de Recerca i Estudis Avançat, (ICREA), and Universitat de Girona, Institut de Química
Computacional, Campus Montili, 17071, Girona, Spain,
b Institut de Química Computacional, Dept. de Química, Universitat de Girona, Campus Montilivi, 17071,
Girona, Spain
e-mail: marcel.swart@icrea.es
An accurate theoretical description of the spinground state of transition-metal complexes is vital for the
elucidation ofreaction mechanisms of metalloenzymatic reactions.[1] For instance, thecatalytic cycle of
cytochrome P450 goes from a doublet in the resting state, toa sextet after substrate binding, to a singlet after the
firstelectron-reduction and binding of molecular oxygen. The subsequent steps, leading to product formation, are
still being debated, both experimentally andcomputationally. Therefore, to be able to discriminate between e.g. a
doubletor a quartet pathway, one should be able to trust the methodology to give thecorrect spin ground state.
In this respect, the OPBE functional has shown promisingresults, [2, 3, 4] unlike other DFT functionals that fail
for either high or lowspin states. This good performance of OPBE concurs with recent benchmark studiesfor
reaction barriers [5] and NMR chemical shifts.[6] Moreover, withthe OPBE functional, the spin ground state of
transition-metal compounds can beeasily understood as a delicate compromise between metal-ligand bonding
andHund’s rule.[3] Furthermore, not only the functional, also the basis set usedis of the utmost importance.[4]
Here we will show results for spin-stateenergies of several iron complexes [7], computed with a range of
computationalmethods, both for vertical and relaxed spin-state splittings. The OPBE results are reliable and
consistent, in contrast to the other DFT functionals. Alsofor spin-crossover compounds and compounds with
other first-row transition-metalsdoes OPBE give good results.[8]
References:
[1] See e.g.: Groenhof, A.R.; Ehlers, A.W.; Lammertsma, K. J. Am. Chem. Soc. 2007, 129, 6204.
[2] Swart, M.; Groenhof, A.R.; Ehlers, A.W.; Lammertsma, K. J. Phys. Chem. A 2004, 108, 5479.
[3] Swart, M. Inorg. Chim. Acta (“The Next Generation” issue) 2007, 360, 179.
[4] Güell, M.; Luis, J.M.; Solà, M.; Swart, M. J. Phys. Chem. A 2008, accepted.
[5] Swart, M.; Solà, M.; Bickelhaupt, F.M. J. Comput. Chem. 2007, 28, 1551.
[6] Wu, A.; Zhang, Y.; Xu, X.; Yan, Y. J. Comput. Chem. 2007, 28, 2431.
[7] Swart, M. submitted.
[8] Güell, M.; Luis, J.M.; Solà, M.; Swart, M. in preparation.
_____________________________________________________________________
45