Precise Chemical, Electronic, and Magnetic Structure of Binuclear Complexes Studied by Means of X-ray Spectroscopies and Theoretical Methods

• Published in: Journal of physical chemistry. C Vol. 115; no. 50; pp. 25030 - 25039
• Main Authors: Kuepper, Karsten, Benoit, David M, Wiedwald, Ulf, Mögele, Florian, Meyering, Andreas, Neumann, Manfred, Kappler, Jean-Paul, Joly, Loïc, Weidle, Stefan, Rieger, Bernhard, Ziemann, Paul
• Format: Journal Article
• Language: English
• Published: American Chemical Society 22.12.2011
• Subjects: C: Electron Transport, Optical and Electronic Devices, Hard Matter
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp2069804

We investigate two planar complexes MnNi and CoNi (see Scheme 1) by X-ray photoelectron spectroscopy (XPS) and ultralow-temperature X-ray magnetic circular dichroism (XMCD). In this way the valence states as well as the presence of uncompensated magnetic moments are obtained. The magnetism has been probed at a temperature of 0.6 K in order to reveal the magnetic ground state properties. We find that divalent Ni ions are in a diamagnetic low spin ground state in both complexes; however, in MnNi a small fraction of divalent nickel high-spin ions leads to a residual XMCD signal, indicating parallel spin alignment with the Mn spins. Mn and Co are found to be in a divalent high-spin configuration in both compounds. Theoretically, we address the energetic ordering of the different possible spin states of the binuclear complexes using (zeroth-order) relativistic approximation density functional calculations and a triple-ζ quality basis set. These results show that intermediate-spin states are often favored over low-spin states for most both metal combinations, in qualitative agreement with our experimental observations.