Insights into the Solution Structure of Polyoxoaurates: UV-Vis Spectral Simulations by TD-DFT
Aleksandar
Kondinski, Nina Vankova*,
Thomas Heine
School of
Engineering and Science, Jacobs University, Campus Ring 1, 28759 Bremen,
Germany, E-Mail: a.kondinski@jacobs-university.de
The quest for new structural architectures in metal-oxo nanocluster
chemistry has led to the recent discovery of noble metal based polyoxoanions
(Pd, Au and Pt). These new materials exhibit potential to serve as
well-characterizable models for understanding industrially important noble
metal catalyzed oxidation processes including molecular oxygen.[1]
In this contribution we report a de
novo approach for correlating structural to spectroscopic properties of the
two hitherto known polyoxoaurates [Au4As4O20]8-
(Au4As4)[2a]
and [Au4Se4O16]4- (Au4Se4)[2b].
Our approach combines time-dependent density functional theory (TD-DFT)
calculations, experimental UV-Vis spectroscopy and electrospray ionization mass
spectrometry (ESI-MS).[3] The TD-DFT calculated excitation spectra
can describe well the observed spectra of Au4Se4,
while in the case of Au4As4
it reveals strong UV-Vis spectra dependence on the polyanion–cation
interactions. Good agreement between theory and experiment is obtained for the
dimeric assemblies of Na5Au8As8,
clarifying the perceptible differences in the experimental UV-Vis spectra of
the two polyoxoaurates. The existence of the Na5Au8As8 assemblies in the
solutions of Au4As4
is corroborated by an ESI-MS study.
Accurate predictions of the UV-Vis spectra of metal-oxo clusters by
TD-DFT are currently beyond routine. The approach presented in this study can
be extended to other systems as an alternative for understanding the structural
properties in solution, especially in systems where conventional techniques
such as NMR and ESR are not applicable.
[1] J.C. Goloboy, W. G. Klemperer, Angew. Chem. Int. Ed. 2009, 48, 3562.
[2] (a) N. V. Izarova, N. Vankova, T.
Heine, R. Ngo Biboum, B. Keita, L. Nadjo, U. Kortz, Angew. Chem. Int. Ed. 2010,
49, 1886. (b) Y. Xiang, N. V. Izarova, F.
Schinle, O. Hampe, B. Keita and U. Kortz, Chem. Commun. 2012, 48,
9849.
[3] A. Kondinski, N.
Vankova, F. Schinle, P. Jäger, O.
Hampe, U. Kortz, T. Heine, Eur. J. Inorg.
Chem. 2014 (accepted for
publication).
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