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High-energy-resolution-fluorescence-detected X-ray absorption near-edge structure (HERFD-XANES) spectroscopy is shown to be a sensitive tool to investigate the electronic changes of copper complexes induced by geometric distortions caused by the ligand backbone as a model for the entatic state. To fully exploit the information contained in the spectra gained by the high-energy-resolution technique, (time-dependent) density functional theory calculations based on plane-wave and localized orbital basis sets are performed, which in combination allow the complete spectral range from the prepeak to the first resonances above the edge step to be covered. Thus, spectral changes upon oxidation and geometry distortion in the copper N-(1,3-dimethylimidazolidin-2-ylidene)quinolin-8-amine (DMEGqu) complexes [CuI(DMEGqu)2](PF6) and [CuII(DMEGqu)2](OTf)2·MeCN can be accessed.

Department of Chemistry, University of California, One Shields Avenue, Davis, CA 95616, USAReceived 20 July 2011, revised 16 September 2011, accepted 26 September 2011Published online 28 December 2011Dedicated to Thomas Frauenheim on the occasion of his 60th birthdayKeywords charge-density wave, electron transport, entropy, in adsorption, nanowire, Peierls transition, Si(111) surface

Ab initio calculations of the electronic g-tensor of paramagnetic states at surfaces and solar cells are presented, whereby special emphasis is given onto the influence of relativistic effects. After discussing the numerical requirements for such calculations, we show that for silicon surfaces the g-tensor varies critically with the hydrogen coverage, and provides an exceptionally characteristic property. This holds also in the case of powder spectra where only the isotropic part g av is available from experiments. Extending our calculations onto microcrystalline 3C-SiC, our study explains why sol-gel grown undoped material can serve as an excellent acceptor material for an effective charge separation in organic solar cells: Due to an auto-doping mechanism by surface-induced states it fits excellently into the energy level scheme of this kind of solar cell and has the potential to replace the usually used rather expensive fullerenes.