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

Eurobic9, 2-6 September, 2008, Wrocław, Poland
P168. A Versatile Electronic Hole in One-electron Oxidized Ni II bissalicylidene
Phenylenediamine Complexes
O. Rotthaus a , O. Jarjayes a , C. Perez Del Valle b , C. Philouze a , F. Thomas a
a
Département de Chimie Moléculaire - Chimie Inorganique Redox Biomimétique (CIRE) – UMR-5250,
Université Joseph Fourier, Grenoble, France
e-mail: Fabrice.Thomas@ujf-grenoble.fr; Olivier.Jarjayes@ujf-grenoble.fr
b
Département de Chimie Moléculaire - Chimie Théorique – UMR-5250, Université Joseph Fourier, Grenoble,
France.
Phenoxyl radicals coordinated to divalent or trivalent metal ions are the focus of a considerable interest since the
discovery of a Cu II -tyrosyl radical entity in the active site of Galactose Oxidase. Several Cu II -coordinated
phenoxyl radicals have been characterized during the last decade in order to mimic the enzyme active site.
Recently, nickel complexes of pro-phenoxyl ligands (the phenolate moiety is substituted by electron-donating
groups) have emerged in literature. Compared to Cu II -phenoxyl complexes, they exhibit ligand and metal redox
active orbitals closer in energy. Consequently, either Ni II -phenoxyl or Ni III -phenolate redox state are expected to
be reached upon one-electron oxidation, making these compounds particularly interesting. We present in this
poster a series of one-electron oxidized nickel salen complexes that exhibit a radical character with partial
delocalization of the spin density onto the orbital of the nickel ion. We show that the degree of delocalization
could be modulated by the electron-donating properties of phenolate para substituent R (Fig. 1-3). In addition,
we found that it greatly influences the affinity of exogenous ligands for the metal, and thus the ability of the
complexes to exhibit valence tautomerism properties (tetracoordinated Ni II -phenoxyl to octahedral Ni III -
phenolate transformation in the presence of exogenous ligands).
N
Ni
R O O
R
N
R = t-Bu: 1
R = OMe: 2
R = NMe 2: 3
(R = NHMe 2 + : 3H2 2+ )
Figure 1 Formula of the neutral phenolate-nickel
complexes
dX''
dB
1 +
2 +
3 +
g = 2.034
g = 2.017
g = 2.006
320 325 330 335 340 345
B / mT
Figure 3 X-Band EPR spectra of CH2Cl2 solutions
(anhydrous + 0.1 M TBAP) of 1 + (1mM), 2 + (0.5 mM)
and 3 + (1 mM) at 233 K. Microwave Freq : 9.42 GHz,
power: 20 mW, Mod. Freq: 100 KHz, Amp. 0.4 mT
(1 + ), 0.05 mT (2 + , 3 + ).
Figure 2 Optimized structures and calculated SOMO
for 1 + , 2 + and 3 + ; The Mulliken contribution of the
nickel orbitals (mainly the dyz) to the total spin density
is indicated.
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